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2022 Vol. 40, No. 11
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2022, 40(11): 1-12.
doi: 10.13205/j.hjgc.202211001
Abstract:
In the context of circular economy, energy and resource utilization have become an effective way to dispose of municipal solid waste in China. However, the wide range of sources, complex types and variable compositions of municipal solid waste affected the stable operation of equipment. In this paper, the current situation of boiler and industrial kiln disposal of municipal solid waste, the corrosion phenomenon, mechanism and influencing factors during operation, were reviewed. The current targeted anti-corrosion measures were summarized, and the influence of sulfur, chlorine, and alkali metal elements during collaborative disposal was investigated. Moreover, the lack of current research was discussed, and the directions of further exploration were proposed. This study was hoped to provide a basis for the recycling of municipal solid waste.
In the context of circular economy, energy and resource utilization have become an effective way to dispose of municipal solid waste in China. However, the wide range of sources, complex types and variable compositions of municipal solid waste affected the stable operation of equipment. In this paper, the current situation of boiler and industrial kiln disposal of municipal solid waste, the corrosion phenomenon, mechanism and influencing factors during operation, were reviewed. The current targeted anti-corrosion measures were summarized, and the influence of sulfur, chlorine, and alkali metal elements during collaborative disposal was investigated. Moreover, the lack of current research was discussed, and the directions of further exploration were proposed. This study was hoped to provide a basis for the recycling of municipal solid waste.
2022, 40(11): 13-18.
doi: 10.13205/j.hjgc.202211002
Abstract:
The low C/N domestic sewage was treated by a step-feed continuous flow partial denitrification-anaerobic ammonium oxidation (PD-Anammox) process coupled with denitrification, the pollutants' removal characteristics, pollutants' concentrations in different stages of the system at a typical operation cycle, and total nitrogen(TN) removal contribute efficiencies of PD-anammox and denitrification were studied. The results showed that when the average influent concentrations of COD, NH4+-N, and TN were 193.1, 58.6 and 60.3 mg/L respectively, their effluent concentrations were 46.3, 1.5, and 13.4 mg/L respectively, complying with the first level A criteria specified in the Discharge Standard of Pollution for Municipal Wastewater Treatment Plants (GB 18918-2002). The nitrate transformed to nitrite in anoxic by nitrate pre-starvation and post-inlet to provide the anammox matrix of nitrite and ammonium. The TN efficiency got improved by setting anammox filler in the anoxic zones. The average PD-Anammox process's contribution rates to TN removal of anoxic zone Ⅰ and Ⅱ were 54.37% and 64.17% respectively, through mass balance calculation at the anoxic zones.
The low C/N domestic sewage was treated by a step-feed continuous flow partial denitrification-anaerobic ammonium oxidation (PD-Anammox) process coupled with denitrification, the pollutants' removal characteristics, pollutants' concentrations in different stages of the system at a typical operation cycle, and total nitrogen(TN) removal contribute efficiencies of PD-anammox and denitrification were studied. The results showed that when the average influent concentrations of COD, NH4+-N, and TN were 193.1, 58.6 and 60.3 mg/L respectively, their effluent concentrations were 46.3, 1.5, and 13.4 mg/L respectively, complying with the first level A criteria specified in the Discharge Standard of Pollution for Municipal Wastewater Treatment Plants (GB 18918-2002). The nitrate transformed to nitrite in anoxic by nitrate pre-starvation and post-inlet to provide the anammox matrix of nitrite and ammonium. The TN efficiency got improved by setting anammox filler in the anoxic zones. The average PD-Anammox process's contribution rates to TN removal of anoxic zone Ⅰ and Ⅱ were 54.37% and 64.17% respectively, through mass balance calculation at the anoxic zones.
2022, 40(11): 19-25.
doi: 10.13205/j.hjgc.202211003
Abstract:
Quartz sand filtration is the most commonly used technology to remove particulates in water. Among them, uniform gradation filter media is widely used because of its strong dirt holding capacity and long filtration cycle. However, in the current engineering design standard, the effective particle size (d10) and uniformity coefficient (K60) of the uniformly graded filter media are broadly defined. The experiments investigated the turbidity removal and operating characteristics of two uniformly graded filter columns with different ratios of fine sand (<0.9 mm, 0.9~1.0 mm), used powdered activated carbon with different surface potentials and particle sizes as tracer particles, and then studied the retention characteristics of two kinds of filter media for particulate matters. The results showed that:compared with the filter column with a lower proportion of fine sand (16%), the filter column with a higher proportion of fine sand (29%) had a lower turbidity of about 0.2 NTU, and the average increase rate of head loss rose by 8.7%~31.6%, the filter layer had a high mud content of 12%~27%, and the running cycle was 7 h when the filtered water turbidity was used as the control index; in terms of particle retention, the retention of particles by the two filter media decreased as the electronegativity of the particle surface increased and the particle size decreased, among them, the filter media with a higher proportion of fine sand had less impact on particle retention by the nature of the particles, showing a stable retention effect. Therefore, appropriately increasing the proportion of fine sand in the uniformly graded quartz sand filter material may slightly increase the filter head loss, but obtain lower effluent turbidity and a more stable particle retention effect.
Quartz sand filtration is the most commonly used technology to remove particulates in water. Among them, uniform gradation filter media is widely used because of its strong dirt holding capacity and long filtration cycle. However, in the current engineering design standard, the effective particle size (d10) and uniformity coefficient (K60) of the uniformly graded filter media are broadly defined. The experiments investigated the turbidity removal and operating characteristics of two uniformly graded filter columns with different ratios of fine sand (<0.9 mm, 0.9~1.0 mm), used powdered activated carbon with different surface potentials and particle sizes as tracer particles, and then studied the retention characteristics of two kinds of filter media for particulate matters. The results showed that:compared with the filter column with a lower proportion of fine sand (16%), the filter column with a higher proportion of fine sand (29%) had a lower turbidity of about 0.2 NTU, and the average increase rate of head loss rose by 8.7%~31.6%, the filter layer had a high mud content of 12%~27%, and the running cycle was 7 h when the filtered water turbidity was used as the control index; in terms of particle retention, the retention of particles by the two filter media decreased as the electronegativity of the particle surface increased and the particle size decreased, among them, the filter media with a higher proportion of fine sand had less impact on particle retention by the nature of the particles, showing a stable retention effect. Therefore, appropriately increasing the proportion of fine sand in the uniformly graded quartz sand filter material may slightly increase the filter head loss, but obtain lower effluent turbidity and a more stable particle retention effect.
2022, 40(11): 26-31.
doi: 10.13205/j.hjgc.202211004
Abstract:
Buoy-bead flotation is a new microalgae harvesting method at present. The bead material has an important effect on harvesting efficiency. In order to achieve a high-efficiency bead material and mechanism during flotation, the study chose Chlorella vulgaris as the flotation microalgae and sodium borosilicate, hollow glass, fly ash and latex as the bead material. The experimental results showed that the harvesting efficiency of sodium borosilicate could achieve 63.24% without flotation reagent. The sodium silicate borate material could achieve high harvesting efficiency, because there was a secondary minimum at 16.6 nm during adhesion with microalgae. Sodium silicate had a strong hydrophobicity, which was easy to adhere to Chlorella vulgaris. Sodium silicate also had high surface roughness, which provided more binding sites. The two reasons were also important factors of high Chlorella vulgaris harvesting efficiency
Buoy-bead flotation is a new microalgae harvesting method at present. The bead material has an important effect on harvesting efficiency. In order to achieve a high-efficiency bead material and mechanism during flotation, the study chose Chlorella vulgaris as the flotation microalgae and sodium borosilicate, hollow glass, fly ash and latex as the bead material. The experimental results showed that the harvesting efficiency of sodium borosilicate could achieve 63.24% without flotation reagent. The sodium silicate borate material could achieve high harvesting efficiency, because there was a secondary minimum at 16.6 nm during adhesion with microalgae. Sodium silicate had a strong hydrophobicity, which was easy to adhere to Chlorella vulgaris. Sodium silicate also had high surface roughness, which provided more binding sites. The two reasons were also important factors of high Chlorella vulgaris harvesting efficiency
2022, 40(11): 32-40.
doi: 10.13205/j.hjgc.202211005
Abstract:
Enhancing the separation and recycling of magnetic particles or agglomerates in fluid by the applied magnetic field is a key problem in the open gradient magnetic separation technology. By establishing a numerical model, the effects of four arrangement modes of strip magnets (the axial alternating arrangement, the axial concurrent arrangement, the transverse alternating arrangement, and the transverse concurrent arrangement) and different magnetic end spacings on the particle capture rate were studied, and also the particle capture results were analyzed, in combination with the particle trajectory and the magnetic force distribution. At the same time, the ratio of magnet length to width, the effects of particle susceptibility, the fluid flow velocity, and the magnet magnetization on particle capture rate were studied. The results showed that, for strip magnets, when the magnetic end spacing was far enough, the axial placement was better than the transverse placement; for a low magnetic end spacing, the axial alternating arrangement was the best; for the rectangular magnets with the same magnetic flux and cross-sectional area, the square magnet with the aspect ratio of 1:1 had the best trapping effect on the particles. The results could provide theoretical guidance for the design of a multi-magnet magnetic separator.
Enhancing the separation and recycling of magnetic particles or agglomerates in fluid by the applied magnetic field is a key problem in the open gradient magnetic separation technology. By establishing a numerical model, the effects of four arrangement modes of strip magnets (the axial alternating arrangement, the axial concurrent arrangement, the transverse alternating arrangement, and the transverse concurrent arrangement) and different magnetic end spacings on the particle capture rate were studied, and also the particle capture results were analyzed, in combination with the particle trajectory and the magnetic force distribution. At the same time, the ratio of magnet length to width, the effects of particle susceptibility, the fluid flow velocity, and the magnet magnetization on particle capture rate were studied. The results showed that, for strip magnets, when the magnetic end spacing was far enough, the axial placement was better than the transverse placement; for a low magnetic end spacing, the axial alternating arrangement was the best; for the rectangular magnets with the same magnetic flux and cross-sectional area, the square magnet with the aspect ratio of 1:1 had the best trapping effect on the particles. The results could provide theoretical guidance for the design of a multi-magnet magnetic separator.
2022, 40(11): 41-46.
doi: 10.13205/j.hjgc.202211006
Abstract:
Global climate variation leads to frequent urban flood disasters. Extreme rainfall has the characteristics of short duration and rapid disaster, which is the major cause of urban inundation. The study on the changing trend of extreme rainfall can provide a reference for cities to deal with inundation. To analyze the temporal evolution characteristics of extreme rainfall events in Xi'an, this paper analyzed the rainfall data of Xi'an from 1990 to 2020 by using the methods of moving average, linear regression, M-K mutation test, and Hurst index analysis. After that, the change characteristics of rainfall events in Xi'an over the past 30 years were obtained, and the future change trend was predicted and analyzed. The results showed that:1) there was no obvious change trend of annual rainfall in Xi'an, however, the extreme rainfall showed an increasing trend at the rate of 29 mm/10 a, and the trend had an increasing mutation in 2002; 2) the frequency of extreme rainfall showed an increasing trend of 0.85 times/10 a, however, the frequency of extreme rainfall had an increasing mutation in 2014; 3) the H values of extreme rainfall and extreme rainfall frequency were 0.974 and 0.893 respectively, and both had strong sustainability. This showed that the change trends of both were consistent with the past, and the extreme rainfall events in Xi'an would continue to increase in the future.
Global climate variation leads to frequent urban flood disasters. Extreme rainfall has the characteristics of short duration and rapid disaster, which is the major cause of urban inundation. The study on the changing trend of extreme rainfall can provide a reference for cities to deal with inundation. To analyze the temporal evolution characteristics of extreme rainfall events in Xi'an, this paper analyzed the rainfall data of Xi'an from 1990 to 2020 by using the methods of moving average, linear regression, M-K mutation test, and Hurst index analysis. After that, the change characteristics of rainfall events in Xi'an over the past 30 years were obtained, and the future change trend was predicted and analyzed. The results showed that:1) there was no obvious change trend of annual rainfall in Xi'an, however, the extreme rainfall showed an increasing trend at the rate of 29 mm/10 a, and the trend had an increasing mutation in 2002; 2) the frequency of extreme rainfall showed an increasing trend of 0.85 times/10 a, however, the frequency of extreme rainfall had an increasing mutation in 2014; 3) the H values of extreme rainfall and extreme rainfall frequency were 0.974 and 0.893 respectively, and both had strong sustainability. This showed that the change trends of both were consistent with the past, and the extreme rainfall events in Xi'an would continue to increase in the future.
2022, 40(11): 47-53,68.
doi: 10.13205/j.hjgc.202211007
Abstract:
The Chahannur lake Basin was taken as the research object of this paper. By extracting the lake areas of the Chahannur during the wet season of 31 years from 1990 to 2020 using Landsat images by modified normalized difference water index (MNDWI) combined with the method of visual interpretation, the evolution law of the lake area was obtained. Based on the monthly temperature, precipitation, evaporation and relative humidity data of Huade, Shangyi and Shangdu meteorological stations, the linear trend estimation method and Mann-Kendall test method were used to analyze the changing trend of climate factors. Principal component analysis and correlation analysis were used to explain the response of the lake area to climate factors. The results showed that:1) In the past 31 years, the Chahannur lake Basin has presented a warming and drying trend of rising temperature, decreasing precipitation and increasing evaporation; 2) the area of the Chahannur lake experienced four stages of stability, decrease, increase, and decrease again, and the water surface area of the Chahannur lake showed a downward trend as a whole between 1990 to 2020. During the 31 years, the lake area was 49.72 square kilometers at its maximum and 0.074 square kilometers at its minimum; 3) lake area respond quickly to climate. The increase of evaporation and decrease of precipitation in summer resulted in a significant decrease in relative humidity, which was the main factor affecting the lake area in the wet season and causing the obvious seasonal variation of the Chahannur lake.
The Chahannur lake Basin was taken as the research object of this paper. By extracting the lake areas of the Chahannur during the wet season of 31 years from 1990 to 2020 using Landsat images by modified normalized difference water index (MNDWI) combined with the method of visual interpretation, the evolution law of the lake area was obtained. Based on the monthly temperature, precipitation, evaporation and relative humidity data of Huade, Shangyi and Shangdu meteorological stations, the linear trend estimation method and Mann-Kendall test method were used to analyze the changing trend of climate factors. Principal component analysis and correlation analysis were used to explain the response of the lake area to climate factors. The results showed that:1) In the past 31 years, the Chahannur lake Basin has presented a warming and drying trend of rising temperature, decreasing precipitation and increasing evaporation; 2) the area of the Chahannur lake experienced four stages of stability, decrease, increase, and decrease again, and the water surface area of the Chahannur lake showed a downward trend as a whole between 1990 to 2020. During the 31 years, the lake area was 49.72 square kilometers at its maximum and 0.074 square kilometers at its minimum; 3) lake area respond quickly to climate. The increase of evaporation and decrease of precipitation in summer resulted in a significant decrease in relative humidity, which was the main factor affecting the lake area in the wet season and causing the obvious seasonal variation of the Chahannur lake.
2022, 40(11): 54-60.
doi: 10.13205/j.hjgc.202211008
Abstract:
The accumulation of nitrogen and phosphorus elements in rural river sediments in China is serious, and the existing physical and chemical remediation technology has some problems, such as incomplete removal of pollutants and easy destruction of the aquatic ecosystem. The adoption of biological ecological remediation technology can not only inhibit the release of sediment pollution, but also restore the aquatic ecosystem and strengthen the self-purification function of water bodies. In this paper, a sediment-water interface micro-ecosystem with corn straw biochar immobilizing denitrification bacteria, Vallisneria natans and Elodea nuttallii-snail was constructed, and the removal effect of pollutants in sediment and overlying water, and the effect on the microbial community structure of sediment were investigated. The results showed that the composite micro-ecosystem could effectively remove nitrogen and phosphorus pollution from the sediment. After 62 days of operation, the removal efficiencies of TN and TP from the sediment were 77.40% and 54.98%, respectively. The sediment with severe pollution level of TN, TP, and organic matters could be restored to the level of mild, moderate and clean, respectively. At the same time, the micro-ecosystem had a good removal effect on nitrogen in overlying water, and the concentration of NH4+-N and TN in overlying water reached the class Ⅲ of Environmental Quality Standard for Surface Water. The construction of the micro-ecosystem improved the biodiversity of the river sediment system, and the relative abundance of Chloroflexi, which indicates the pollution of sediment, got decreased, while the relative abundance of Proteobacteria, which is capable of degrading pollutants, got increased.
The accumulation of nitrogen and phosphorus elements in rural river sediments in China is serious, and the existing physical and chemical remediation technology has some problems, such as incomplete removal of pollutants and easy destruction of the aquatic ecosystem. The adoption of biological ecological remediation technology can not only inhibit the release of sediment pollution, but also restore the aquatic ecosystem and strengthen the self-purification function of water bodies. In this paper, a sediment-water interface micro-ecosystem with corn straw biochar immobilizing denitrification bacteria, Vallisneria natans and Elodea nuttallii-snail was constructed, and the removal effect of pollutants in sediment and overlying water, and the effect on the microbial community structure of sediment were investigated. The results showed that the composite micro-ecosystem could effectively remove nitrogen and phosphorus pollution from the sediment. After 62 days of operation, the removal efficiencies of TN and TP from the sediment were 77.40% and 54.98%, respectively. The sediment with severe pollution level of TN, TP, and organic matters could be restored to the level of mild, moderate and clean, respectively. At the same time, the micro-ecosystem had a good removal effect on nitrogen in overlying water, and the concentration of NH4+-N and TN in overlying water reached the class Ⅲ of Environmental Quality Standard for Surface Water. The construction of the micro-ecosystem improved the biodiversity of the river sediment system, and the relative abundance of Chloroflexi, which indicates the pollution of sediment, got decreased, while the relative abundance of Proteobacteria, which is capable of degrading pollutants, got increased.
2022, 40(11): 61-68.
doi: 10.13205/j.hjgc.202211009
Abstract:
Diatomite/MnFe2O4 composite catalyst (DMF) was rationally synthesized by sol-gel method. The performance and reaction mechanism of DMF activated peroxymonosulfate (PMS) were degraded with orange Ⅱ as the target pollutant. The results showed that:1) MnFe2O4 particles were uniformly loaded on diatomite and DMF had better dispersion and stability; 2) DMF had a better catalytic activity to PMS than MnFe2O4 so that the degradation rate of DMF/PMS system for orange Ⅱ removal was 2.16 times that of MnFe2O4 system, the reaction process could be fitted by the pseudo-first-order kinetic pattern. A degradation rate of 93.1% could be achieved within 40 min for 50 mg/L AO2 by 0.5 g/L DMF and 0.5 mmol/L PMS; 3) there were four active radicals ·OH、SO4-·、1O2 and ·O2- in the reaction system, and OH and SO4- play the main role; 4) DMF had better structural stability and its metal ion dissolution was much lower than MnFe2O4. This study paved a way for the practical application of the new PMS activators in industrial wastewater treatment.
Diatomite/MnFe2O4 composite catalyst (DMF) was rationally synthesized by sol-gel method. The performance and reaction mechanism of DMF activated peroxymonosulfate (PMS) were degraded with orange Ⅱ as the target pollutant. The results showed that:1) MnFe2O4 particles were uniformly loaded on diatomite and DMF had better dispersion and stability; 2) DMF had a better catalytic activity to PMS than MnFe2O4 so that the degradation rate of DMF/PMS system for orange Ⅱ removal was 2.16 times that of MnFe2O4 system, the reaction process could be fitted by the pseudo-first-order kinetic pattern. A degradation rate of 93.1% could be achieved within 40 min for 50 mg/L AO2 by 0.5 g/L DMF and 0.5 mmol/L PMS; 3) there were four active radicals ·OH、SO4-·、1O2 and ·O2- in the reaction system, and OH and SO4- play the main role; 4) DMF had better structural stability and its metal ion dissolution was much lower than MnFe2O4. This study paved a way for the practical application of the new PMS activators in industrial wastewater treatment.
2022, 40(11): 69-77.
doi: 10.13205/j.hjgc.202211010
Abstract:
In this study, the combustion experiments of three kinds of coal at 1200℃ were implemented by using a drop-tube furnace and tubular furnace experimental devices respectively, to explore the effect of cchlorine-containing desulfurization wastewater addition on mercury release characteristics during coal combustion. In the experiment, the content of chlorine in coal was controlled by changing the mass fraction of simulated desulfurization wastewater solution to 0.00%, 0.02%, 0.04% and 0.06% respectively. Then by analysing the change of mercury concentration in flue gas, absorption solution, fly ash and coal ash after coal combustion, it was found that with the increase of chlorine dosage, the concentration of Hg0 in flue gas gradually decreased, while the concentrations of Hg2+ gradually increased. However, the effect of Hgt concentration was subtle. When the chlorine dosage was 0.06%, the Hg0 concentration in the flue gas after coal type B was burned in the drop-tube furnace decreased by about 2.3 μg/m3, but the concentrations of Hg2+ increased by about 2.6 μg/m3, but the concentration of Hgt only increased by 0.3 μg/m3. The addition of chlorine not only increased the mercury content in fly ash but also decreased the mercury content in coal ash. Through a comprehensive comparative analysis of the experimental results of drop-tube furnace and tubular furnace, it was found that the Hg0 ratio in the flue gas after coal combustion in drop-tube furnace was less than in tubular furnace, whether chlorine was added or not. When the chlorination amount of coal type B was 0.06%, the proportion of Hg0 after combustion in drop-tube furnace and tubular furnace was 50.6% and 67.8% respectively. In addition, it was also found that the mercury release rate of the three kinds of coal combustion after added chlorine in the tubular furnace was more obvious than that in drop-tube furnace. Therefore, the addition of chlorine-containing desulfurization wastewater solution could not only change the release characteristics of mercury during coal combustion, but also promoted the oxidation of Hg0 in flue gas, which played an important role in mercury removal from coal-fired flue gas.
In this study, the combustion experiments of three kinds of coal at 1200℃ were implemented by using a drop-tube furnace and tubular furnace experimental devices respectively, to explore the effect of cchlorine-containing desulfurization wastewater addition on mercury release characteristics during coal combustion. In the experiment, the content of chlorine in coal was controlled by changing the mass fraction of simulated desulfurization wastewater solution to 0.00%, 0.02%, 0.04% and 0.06% respectively. Then by analysing the change of mercury concentration in flue gas, absorption solution, fly ash and coal ash after coal combustion, it was found that with the increase of chlorine dosage, the concentration of Hg0 in flue gas gradually decreased, while the concentrations of Hg2+ gradually increased. However, the effect of Hgt concentration was subtle. When the chlorine dosage was 0.06%, the Hg0 concentration in the flue gas after coal type B was burned in the drop-tube furnace decreased by about 2.3 μg/m3, but the concentrations of Hg2+ increased by about 2.6 μg/m3, but the concentration of Hgt only increased by 0.3 μg/m3. The addition of chlorine not only increased the mercury content in fly ash but also decreased the mercury content in coal ash. Through a comprehensive comparative analysis of the experimental results of drop-tube furnace and tubular furnace, it was found that the Hg0 ratio in the flue gas after coal combustion in drop-tube furnace was less than in tubular furnace, whether chlorine was added or not. When the chlorination amount of coal type B was 0.06%, the proportion of Hg0 after combustion in drop-tube furnace and tubular furnace was 50.6% and 67.8% respectively. In addition, it was also found that the mercury release rate of the three kinds of coal combustion after added chlorine in the tubular furnace was more obvious than that in drop-tube furnace. Therefore, the addition of chlorine-containing desulfurization wastewater solution could not only change the release characteristics of mercury during coal combustion, but also promoted the oxidation of Hg0 in flue gas, which played an important role in mercury removal from coal-fired flue gas.
2022, 40(11): 78-83.
doi: 10.13205/j.hjgc.202211011
Abstract:
[TETA] [L] ionic liquid was synthesized by the acid-base neutralization reaction of triethylenetetramine and L-lactic acid, and different mass fractions of ionic liquid were loaded into coconut shell activated carbon. The effects of ionic liquid impregnation on the microstructure and CO2 adsorption performance of coconut shell activated carbon were investigated by FTIR, XRD and automatic specific surface and pore size distribution analyzer. The results showed that the interaction between ionic liquid and activated carbon led to the fine crystallization of graphitized microcrystals, which adversely affected the structural stability of activated carbon, while the "plugging" filling of the pore structure of coconut shell activated carbon by ionic liquid led to the significant decrease of CO2 physical adsorption performance, and limited the increase of CO2 chemisorption performance of the composite, which was the root cause of the significant decrease in the total CO2 absorption performance of the composite. And ionic liquid in activated carbon showed a "step" filling behavior from small pore size to large pore size.
[TETA] [L] ionic liquid was synthesized by the acid-base neutralization reaction of triethylenetetramine and L-lactic acid, and different mass fractions of ionic liquid were loaded into coconut shell activated carbon. The effects of ionic liquid impregnation on the microstructure and CO2 adsorption performance of coconut shell activated carbon were investigated by FTIR, XRD and automatic specific surface and pore size distribution analyzer. The results showed that the interaction between ionic liquid and activated carbon led to the fine crystallization of graphitized microcrystals, which adversely affected the structural stability of activated carbon, while the "plugging" filling of the pore structure of coconut shell activated carbon by ionic liquid led to the significant decrease of CO2 physical adsorption performance, and limited the increase of CO2 chemisorption performance of the composite, which was the root cause of the significant decrease in the total CO2 absorption performance of the composite. And ionic liquid in activated carbon showed a "step" filling behavior from small pore size to large pore size.
2022, 40(11): 84-91,142.
doi: 10.13205/j.hjgc.202211012
Abstract:
Based on computational fluid dynamics (CFD), the flow field simulation results of four schemes of a Suzhou environmental protection company's experimental downdraft fabric baghouse filter were analyzed and compared, in no deflector (scheme 1), straight plate with isotropic wing plate (scheme 2), straight plate with anisotropic wing plate (scheme 3), and vertical deflector with rectifier grille (scheme 4). The relative standard deviation of cross-sectional velocity at the first 100 mm of the bag inlet was selected as the evaluation index. The feasibility of differential pressure, flow velocity and concentration as the characteristic factors for leak detection was studied by numerical simulation of bag breakage in different areas. The results showed that the flow field distribution of scheme 4 was the most uniformed, better than schemes 2 and 3; scheme 2 had the smallest resistance increase, significantly lower than schemes 3 and 4. The study verified that the small-scale broken bag outlet concentration was linearly positively correlated with the broken bag area through simulation, and found that the pressure difference and flow rate, as the characteristic factors of leak detection, had no significant effect, and the concentration change was the most sensitive. Combined with the two important evaluation indicators of airflow distribution uniformity and resistance, the speed uniformity index of scheme 2 was 0.36, the speed uniformity index of scheme 4 was 0.2, the increase of resistance of scheme 2 was much smaller than that of scheme 4, and scheme 2 was more practical. The numerical simulation scheme provided in this paper could provide a certain reference for the distribution of the deflector plate of the lower intake bag filter and the selection of the monitoring sensor.
Based on computational fluid dynamics (CFD), the flow field simulation results of four schemes of a Suzhou environmental protection company's experimental downdraft fabric baghouse filter were analyzed and compared, in no deflector (scheme 1), straight plate with isotropic wing plate (scheme 2), straight plate with anisotropic wing plate (scheme 3), and vertical deflector with rectifier grille (scheme 4). The relative standard deviation of cross-sectional velocity at the first 100 mm of the bag inlet was selected as the evaluation index. The feasibility of differential pressure, flow velocity and concentration as the characteristic factors for leak detection was studied by numerical simulation of bag breakage in different areas. The results showed that the flow field distribution of scheme 4 was the most uniformed, better than schemes 2 and 3; scheme 2 had the smallest resistance increase, significantly lower than schemes 3 and 4. The study verified that the small-scale broken bag outlet concentration was linearly positively correlated with the broken bag area through simulation, and found that the pressure difference and flow rate, as the characteristic factors of leak detection, had no significant effect, and the concentration change was the most sensitive. Combined with the two important evaluation indicators of airflow distribution uniformity and resistance, the speed uniformity index of scheme 2 was 0.36, the speed uniformity index of scheme 4 was 0.2, the increase of resistance of scheme 2 was much smaller than that of scheme 4, and scheme 2 was more practical. The numerical simulation scheme provided in this paper could provide a certain reference for the distribution of the deflector plate of the lower intake bag filter and the selection of the monitoring sensor.
2022, 40(11): 92-97,158.
doi: 10.13205/j.hjgc.202211013
Abstract:
Based on the analysis of solubility of sodium thiocyanate (NaSCN) and sodium thiosulfate (Na2S2O3) under a water-ethanol system, two types of desulfurization mixed salts in the coking plant were chosen for further purification and separation through decolorization and water-ethanol system separation method. NaSCN products with a purity of 94% to 96%, and Na2S2O3 products with a purity of 95% to 98% were obtained respectively. Among them, the recoveries of NaSCN and Na2S2O3 in the first type of waste salt (white, improved ADA desulfurization method) were 90.8% and 68.3%, respectively, and the recoveries of them in the other waste salt (green, PDS desulfurization method) were 91.3% and 81.8%, respectively. Besides, desulphurization waste salt and products were detected and analyzed by XRD, TG-DSC and FT-IR, which showed that the quality of the products by the water-ethanol system separation method was similar to that of commercially available NaSCN and Na2S2O3. Hence, instead of absolute ethyl alcohol, carbinol and other pure solvents, the water-ethanol system made the operational process relatively safer. In addition, compared with the step crystallization process, the method had the advantages of high purity of products, less energy consumption. Therefore, the water-ethanol system separation method had certain theoretical value and practical significance for the resource utilization of coking desulfurization waste salt.
Based on the analysis of solubility of sodium thiocyanate (NaSCN) and sodium thiosulfate (Na2S2O3) under a water-ethanol system, two types of desulfurization mixed salts in the coking plant were chosen for further purification and separation through decolorization and water-ethanol system separation method. NaSCN products with a purity of 94% to 96%, and Na2S2O3 products with a purity of 95% to 98% were obtained respectively. Among them, the recoveries of NaSCN and Na2S2O3 in the first type of waste salt (white, improved ADA desulfurization method) were 90.8% and 68.3%, respectively, and the recoveries of them in the other waste salt (green, PDS desulfurization method) were 91.3% and 81.8%, respectively. Besides, desulphurization waste salt and products were detected and analyzed by XRD, TG-DSC and FT-IR, which showed that the quality of the products by the water-ethanol system separation method was similar to that of commercially available NaSCN and Na2S2O3. Hence, instead of absolute ethyl alcohol, carbinol and other pure solvents, the water-ethanol system made the operational process relatively safer. In addition, compared with the step crystallization process, the method had the advantages of high purity of products, less energy consumption. Therefore, the water-ethanol system separation method had certain theoretical value and practical significance for the resource utilization of coking desulfurization waste salt.
2022, 40(11): 98-104.
doi: 10.13205/j.hjgc.202211014
Abstract:
Goethite-modified biochar (GMB) was prepared by hydrolytic co-precipitation under different pyrolysis temperatures and raw material ratios, characterized by SEM-EDS, XRD, FTIR and XPS. Adsorption experiments of Cr(Ⅵ) for exploring the adsorption performance and mechanism were carried out. The results showed that:1) modification with goethite formed iron hydroxyl oxide (FeOOH) on the surface of biochar and greatly improved its adsorption capacity; 2) the best adsorption capacity of 20.67 mg/g was performed by modified biochar GMB600-12 with pyrolysis temperature at 600℃ and mass ratio of biochar and Fe(NO3)3·9H2O at 1:12; 3) the adsorption of Cr(Ⅵ) was mainly chemisorption as revealed by quasi-second-order kinetics, and both Langmuir model and Freundlich model could well describe the adsorption characteristics of Cr(Ⅵ) by GMB; 4) the removal of Cr(Ⅵ) from aqueous solution by GMB is a synergistic effect of redox and surface adsorption.
Goethite-modified biochar (GMB) was prepared by hydrolytic co-precipitation under different pyrolysis temperatures and raw material ratios, characterized by SEM-EDS, XRD, FTIR and XPS. Adsorption experiments of Cr(Ⅵ) for exploring the adsorption performance and mechanism were carried out. The results showed that:1) modification with goethite formed iron hydroxyl oxide (FeOOH) on the surface of biochar and greatly improved its adsorption capacity; 2) the best adsorption capacity of 20.67 mg/g was performed by modified biochar GMB600-12 with pyrolysis temperature at 600℃ and mass ratio of biochar and Fe(NO3)3·9H2O at 1:12; 3) the adsorption of Cr(Ⅵ) was mainly chemisorption as revealed by quasi-second-order kinetics, and both Langmuir model and Freundlich model could well describe the adsorption characteristics of Cr(Ⅵ) by GMB; 4) the removal of Cr(Ⅵ) from aqueous solution by GMB is a synergistic effect of redox and surface adsorption.
2022, 40(11): 105-112,119.
doi: 10.13205/j.hjgc.202211015
Abstract:
In view of high moisture content of classified kitchen waste in Beijing, and the problems with serious acidification, slow temperature rise and high leachate yield in the kitchen waste composting process, leading to lower quality of final compost and a large amount of odorous gas emission. This study investigated the influence of agricultural and forestry wastes with different carbon sources (cornstalk, garden waste and watermelon seedling waste) on the maturity and odor gas emissions during kitchen waste composting. The proportion of bulking agents added was 15%, and mechanical forced continuous ventilation rate was 0.5 L/(kg DM·min). The composting cycle was 16 d, and the pile was turned over every 4 d. The result showed that kitchen waste composted alone had serious acidification, temperature startup was failing, and the duration of the high temperature period (>55℃) of the added bulking agents exceeded 10 d. Different carbon source bulking agents affected the degree of difficulty of degradation of organic matter, watermelon stalks increased rapidly in the early stage of composting, garden waste was warmer in the middle of composting, and corn straw was warmer in the middle and late stages of composting. The addition of corn stalks, garden waste and watermelon stalks reduced leachate by 95%, 39% and 17%, respectively. Germination index (GI) of cornstalk and watermelon seedling waste amendment treatments exceeded 100% on day 12, and the GI of final compost for garden waste treatment had a delay of 4 days. Compared with the watermelon seedling waste treatment, the addition of cornstalk reduced H2S and Me2S by 66.6% and 86.3%, respectively; garden waste treatment decreased Me2S emission by 82.3%. The main physicochemical factors affecting the compost humility and odor emission of kitchen waste were pH and temperature.
In view of high moisture content of classified kitchen waste in Beijing, and the problems with serious acidification, slow temperature rise and high leachate yield in the kitchen waste composting process, leading to lower quality of final compost and a large amount of odorous gas emission. This study investigated the influence of agricultural and forestry wastes with different carbon sources (cornstalk, garden waste and watermelon seedling waste) on the maturity and odor gas emissions during kitchen waste composting. The proportion of bulking agents added was 15%, and mechanical forced continuous ventilation rate was 0.5 L/(kg DM·min). The composting cycle was 16 d, and the pile was turned over every 4 d. The result showed that kitchen waste composted alone had serious acidification, temperature startup was failing, and the duration of the high temperature period (>55℃) of the added bulking agents exceeded 10 d. Different carbon source bulking agents affected the degree of difficulty of degradation of organic matter, watermelon stalks increased rapidly in the early stage of composting, garden waste was warmer in the middle of composting, and corn straw was warmer in the middle and late stages of composting. The addition of corn stalks, garden waste and watermelon stalks reduced leachate by 95%, 39% and 17%, respectively. Germination index (GI) of cornstalk and watermelon seedling waste amendment treatments exceeded 100% on day 12, and the GI of final compost for garden waste treatment had a delay of 4 days. Compared with the watermelon seedling waste treatment, the addition of cornstalk reduced H2S and Me2S by 66.6% and 86.3%, respectively; garden waste treatment decreased Me2S emission by 82.3%. The main physicochemical factors affecting the compost humility and odor emission of kitchen waste were pH and temperature.
2022, 40(11): 113-119.
doi: 10.13205/j.hjgc.202211016
Abstract:
The effects of mixed combustion of municipal solid waste (MSW) with aged refuse in landfills and different air distribution schemes on combustion process flow field distribution and NOx emission in a 350 t/d furnace were studied by CFD simulation. The results showed that adding aged refuse delayed the combustion process of char on the bed, which was conducive to the release of volatiles, so that the gas phase combustion in the combustion zone and flue became more intense. And the overall temperature of the furnace was increased, which also caused local overtemperature. At the same time, the NOx concentration at the first flue outlet decreased from 247.85 mg/Nm3 to 198.75 mg/Nm3. In working condition 4, the upper and lower secondary air was increased, so that the fluid in the combustion zone was fully mixed and burned. And the increased degree of fluid turbulence in the flue made the temperature in the furnace more uniform, which was beneficial to relieve the phenomenon of high-temperature corrosion in the first flue. An appropriate air distribution ratio could greatly reduce the NOx concentration at the flue outlet from 198.75 mg/Nm3 to 89.80 mg/Nm3, and also prolonged the residence time of flue gas in the furnace. The results could provide a reference for improving the mixing ratio of aged refuse and air distribution ratio of the refuse incinerator.
The effects of mixed combustion of municipal solid waste (MSW) with aged refuse in landfills and different air distribution schemes on combustion process flow field distribution and NOx emission in a 350 t/d furnace were studied by CFD simulation. The results showed that adding aged refuse delayed the combustion process of char on the bed, which was conducive to the release of volatiles, so that the gas phase combustion in the combustion zone and flue became more intense. And the overall temperature of the furnace was increased, which also caused local overtemperature. At the same time, the NOx concentration at the first flue outlet decreased from 247.85 mg/Nm3 to 198.75 mg/Nm3. In working condition 4, the upper and lower secondary air was increased, so that the fluid in the combustion zone was fully mixed and burned. And the increased degree of fluid turbulence in the flue made the temperature in the furnace more uniform, which was beneficial to relieve the phenomenon of high-temperature corrosion in the first flue. An appropriate air distribution ratio could greatly reduce the NOx concentration at the flue outlet from 198.75 mg/Nm3 to 89.80 mg/Nm3, and also prolonged the residence time of flue gas in the furnace. The results could provide a reference for improving the mixing ratio of aged refuse and air distribution ratio of the refuse incinerator.
2022, 40(11): 120-126.
doi: 10.13205/j.hjgc.202211017
Abstract:
The study investigated the effects of organic loading rate (OLR), stirring rate and material retention time on methane production in semi-continuous dry anaerobic fermentation, and used a structural equation model to discuss the dynamics of the regulating factors on the intermediate products and methane production in the anaerobic system. The results showed that when the OLR was increased to 5.5 g VS/(L·d), the methane production reached the peak, and the average daily methane production reached 3084.40 mL/(L·d). Increasing the stirring rate and material retention time could promote methane production, but a lower or higher material retention time led to the accumulation of NH4+-N and VFAs, and inhibited the anaerobic methanogenesis process. The stirring rate of 20 r/min and solid retention time of 1 d were synthetically considered as the most favorable condition for methane synthesis. The structural equation model results revealed that the influence of stirring rate and material retention time on methane production in semi-continuous dry anaerobic fermentation of kitchen waste was greater than that of OLR, and the standardized total effect were 0.435, 0.370 and -0.04, respectively, mainly because the rise of stirring rate effectively relieved the inhibition effect of VFAs on methane production in dry anaerobic fermentation.
The study investigated the effects of organic loading rate (OLR), stirring rate and material retention time on methane production in semi-continuous dry anaerobic fermentation, and used a structural equation model to discuss the dynamics of the regulating factors on the intermediate products and methane production in the anaerobic system. The results showed that when the OLR was increased to 5.5 g VS/(L·d), the methane production reached the peak, and the average daily methane production reached 3084.40 mL/(L·d). Increasing the stirring rate and material retention time could promote methane production, but a lower or higher material retention time led to the accumulation of NH4+-N and VFAs, and inhibited the anaerobic methanogenesis process. The stirring rate of 20 r/min and solid retention time of 1 d were synthetically considered as the most favorable condition for methane synthesis. The structural equation model results revealed that the influence of stirring rate and material retention time on methane production in semi-continuous dry anaerobic fermentation of kitchen waste was greater than that of OLR, and the standardized total effect were 0.435, 0.370 and -0.04, respectively, mainly because the rise of stirring rate effectively relieved the inhibition effect of VFAs on methane production in dry anaerobic fermentation.
2022, 40(11): 127-133,151.
doi: 10.13205/j.hjgc.202211018
Abstract:
Laboratory-based incubation experiments were carried out to study the effectiveness of readily available materials on the deactivation of sediment arsenic (As) using micro-electrode technology and micro-interface analysis technology (e.g. HR-Peeper). Group experiments (i.e. lanthanum modified bentonite group (LMB) and oxygenate group (CaO2+CaCO3)) were carried out to test the reduction of the dissolved As in sediment interstitial water via adding LMB or CaO2+CaCO3 to the sediments after 4, 30, 90, and 150 day, and compared with control group. The results showed that both LMB and oxygenate could effectively decrease As pollution in sediments. The addition of LMB caused 50.86% reduction in the dissolved As content in sediment interstitial water with the influencing depth of -100 mm and duration of 150 d, while the addition of CaO2+CaCO3 caused 55.52% reduction in the dissolved As content in sediment interstitial water with the influencing depth of -100 mm and duration of 90 d. Both additions could dramatically decrease the internal dissolved As release. This could be explained by that the lanthanum ion on LMB had a strong affinity for arsenate and could remove the arsenate from sediment interstitial water. Moreover, the addition of LMB or oxygenate increased the Eh value of the sediments, and further led to the absorption of As by Fe (Ⅲ) oxidized from Fe (Ⅱ). Dissolved As contents along the sediment profile had a positive correlation with Fe (Ⅱ) contents (P<0.001). This study could be helpful for As pollution control in sediment in freshwater ecosystems.
Laboratory-based incubation experiments were carried out to study the effectiveness of readily available materials on the deactivation of sediment arsenic (As) using micro-electrode technology and micro-interface analysis technology (e.g. HR-Peeper). Group experiments (i.e. lanthanum modified bentonite group (LMB) and oxygenate group (CaO2+CaCO3)) were carried out to test the reduction of the dissolved As in sediment interstitial water via adding LMB or CaO2+CaCO3 to the sediments after 4, 30, 90, and 150 day, and compared with control group. The results showed that both LMB and oxygenate could effectively decrease As pollution in sediments. The addition of LMB caused 50.86% reduction in the dissolved As content in sediment interstitial water with the influencing depth of -100 mm and duration of 150 d, while the addition of CaO2+CaCO3 caused 55.52% reduction in the dissolved As content in sediment interstitial water with the influencing depth of -100 mm and duration of 90 d. Both additions could dramatically decrease the internal dissolved As release. This could be explained by that the lanthanum ion on LMB had a strong affinity for arsenate and could remove the arsenate from sediment interstitial water. Moreover, the addition of LMB or oxygenate increased the Eh value of the sediments, and further led to the absorption of As by Fe (Ⅲ) oxidized from Fe (Ⅱ). Dissolved As contents along the sediment profile had a positive correlation with Fe (Ⅱ) contents (P<0.001). This study could be helpful for As pollution control in sediment in freshwater ecosystems.
2022, 40(11): 134-142.
doi: 10.13205/j.hjgc.202211019
Abstract:
Metal pollution in soils is an issue of global concern, and lead (Pb) pollution is considered to be the most serious type. In this study, five native crops[wormwood (Artemisia capillaris), dandelion (Taraxacum mongolicum), alfalfa (Medicago sativa), sauce (Lxeris chinensis), and plantain (Plantago asiatica L.)] that grow naturally around the tailings slag in a mining area in Northwest China were selected to test their ecological restoration impacts on Pb-contaminated soil. In pot experiments, different metal lead pollution gradients (0, 2‰, 3‰, and 5‰, w/w) were set, the changes of soil Pb content in different tissues and organs before and after planting were analyzed. The results showed that wormwood and plantain were suitable for planting under various soil Pb pollution levels, and the removal rate was 12%~32%. The accumulation of Pb in the roots of plantain and the stems of dandelion was more advantageous than in other plants, up to 3617,720 mg/kg respectively. These two crops had great potential as remediation plants for soil Pb pollution. The content of microbial biomass carbon in rhizosphere soil was 2.37%~13.89% higher than that in bulk soil. The catalase activity of rhizosphere and bulk soil was inhibited by soil Pb, which was 0.44%~22.3% lower than that of the control, and the catalase activity of rhizosphere soil was 0.89%~8.09% higher than that of bulk soil. The results can provide a theoretical basis for phytoremediation and soil environmental quality evaluation of Pb contaminated wasteland in mining areas.
Metal pollution in soils is an issue of global concern, and lead (Pb) pollution is considered to be the most serious type. In this study, five native crops[wormwood (Artemisia capillaris), dandelion (Taraxacum mongolicum), alfalfa (Medicago sativa), sauce (Lxeris chinensis), and plantain (Plantago asiatica L.)] that grow naturally around the tailings slag in a mining area in Northwest China were selected to test their ecological restoration impacts on Pb-contaminated soil. In pot experiments, different metal lead pollution gradients (0, 2‰, 3‰, and 5‰, w/w) were set, the changes of soil Pb content in different tissues and organs before and after planting were analyzed. The results showed that wormwood and plantain were suitable for planting under various soil Pb pollution levels, and the removal rate was 12%~32%. The accumulation of Pb in the roots of plantain and the stems of dandelion was more advantageous than in other plants, up to 3617,720 mg/kg respectively. These two crops had great potential as remediation plants for soil Pb pollution. The content of microbial biomass carbon in rhizosphere soil was 2.37%~13.89% higher than that in bulk soil. The catalase activity of rhizosphere and bulk soil was inhibited by soil Pb, which was 0.44%~22.3% lower than that of the control, and the catalase activity of rhizosphere soil was 0.89%~8.09% higher than that of bulk soil. The results can provide a theoretical basis for phytoremediation and soil environmental quality evaluation of Pb contaminated wasteland in mining areas.
2022, 40(11): 143-151.
doi: 10.13205/j.hjgc.202211020
Abstract:
As the only legal method for the determination of hexavalent chromium[Cr(Ⅵ)] in soils and sediments, alkaline digestion/flame atomic absorption spectrometry (specified in China's national standard, HJ 1082-2019) was implemented in China in June 2020. However, false positive and negative deviation were reported by some researchers and engineering projects for Cr(Ⅵ)-contaminated soils. The positive and negative biases caused by dissolved Cr(Ⅲ), flushing agent (citrate) and reductants (FeSO4, Na2S2O5, Na2S and CaSx) were investigated in this study. Experimental results showed that Cr(Ⅲ) produced during remediation was supersaturated over the remediation and determination process, resulting in small positive biases which may cause erroneous judgment. The adsorption effect of soil to the Cr(Ⅲ) played a crucial role in mitigating the positive bias to below the determination limit. Citrate could significantly enhance the dissolution of Cr(Ⅲ) to a level resulting in positive bias. When a large number of residual reductants remained in soils after remediation, they could reduce the extracted Cr(Ⅵ) into Cr(Ⅲ) during alkaline digestion or pH adjustment, resulting in significant negative bias. This negative bias couldn't be offset by the positive bias of FAAS, due to the uncertainty and small amplitude of the positive biases.
As the only legal method for the determination of hexavalent chromium[Cr(Ⅵ)] in soils and sediments, alkaline digestion/flame atomic absorption spectrometry (specified in China's national standard, HJ 1082-2019) was implemented in China in June 2020. However, false positive and negative deviation were reported by some researchers and engineering projects for Cr(Ⅵ)-contaminated soils. The positive and negative biases caused by dissolved Cr(Ⅲ), flushing agent (citrate) and reductants (FeSO4, Na2S2O5, Na2S and CaSx) were investigated in this study. Experimental results showed that Cr(Ⅲ) produced during remediation was supersaturated over the remediation and determination process, resulting in small positive biases which may cause erroneous judgment. The adsorption effect of soil to the Cr(Ⅲ) played a crucial role in mitigating the positive bias to below the determination limit. Citrate could significantly enhance the dissolution of Cr(Ⅲ) to a level resulting in positive bias. When a large number of residual reductants remained in soils after remediation, they could reduce the extracted Cr(Ⅵ) into Cr(Ⅲ) during alkaline digestion or pH adjustment, resulting in significant negative bias. This negative bias couldn't be offset by the positive bias of FAAS, due to the uncertainty and small amplitude of the positive biases.
2022, 40(11): 152-158.
doi: 10.13205/j.hjgc.202211021
Abstract:
The remediation process of heavy metal contaminated soil in tailings ponds is complicated and slow. To reduce the remediation cycle and accelerate the development of intelligence and refinement of soil remediation technology, the mechanism and law of the phyto-electrokinetic method were used, and the evaluation index system of soil remediation variables was established flexibly. A new GRA-RF model for soil simulated remediation was established by combining a random forest classifier and GRA simulation algorithm, and then the simulated remediation and experimental repair were compared. The results showed that:1) the highest grade value in remediation variables was the voltage gradient (0.092), followed successively by current value (0.078), soil humidity (0.074), power-on time (0.069), dynamic pH level of the soil (0.066), electrode space (0.063), electrode arrangement way (0.06), additive type (0.057), and electrode material (0.053). The weight values of the other variables were lower than the average. The size of the remediation variables would be changed following the importance order of the variables until the optimal repair effect was obtained; 2) the remediation efficiency of the simulation was higher than that of the experiment for 8 samples. The relative errors of remediation environment, for A1 to A4 were 2.22%, 4.72%, 8.75%, 3.89% and from B1 to B4 were 9.91%, 8.28%, 6.74% and 5.63% respectively. The remediation effect of Cd, Cu and Pb in environment A were better than Cd, Cu and Pb, while Zn had an opposite remediation effect; 3) by comparing the error rate of the algorithm, it was found that GRA-RF model was better than Random-RF. This method more precisely simulated the process of enhanced remediation of contaminated soil. The efficiency of soil remediation was improved by optimizing the remediation variables, it laid a foundation for making and improving soil remediation schemes.
The remediation process of heavy metal contaminated soil in tailings ponds is complicated and slow. To reduce the remediation cycle and accelerate the development of intelligence and refinement of soil remediation technology, the mechanism and law of the phyto-electrokinetic method were used, and the evaluation index system of soil remediation variables was established flexibly. A new GRA-RF model for soil simulated remediation was established by combining a random forest classifier and GRA simulation algorithm, and then the simulated remediation and experimental repair were compared. The results showed that:1) the highest grade value in remediation variables was the voltage gradient (0.092), followed successively by current value (0.078), soil humidity (0.074), power-on time (0.069), dynamic pH level of the soil (0.066), electrode space (0.063), electrode arrangement way (0.06), additive type (0.057), and electrode material (0.053). The weight values of the other variables were lower than the average. The size of the remediation variables would be changed following the importance order of the variables until the optimal repair effect was obtained; 2) the remediation efficiency of the simulation was higher than that of the experiment for 8 samples. The relative errors of remediation environment, for A1 to A4 were 2.22%, 4.72%, 8.75%, 3.89% and from B1 to B4 were 9.91%, 8.28%, 6.74% and 5.63% respectively. The remediation effect of Cd, Cu and Pb in environment A were better than Cd, Cu and Pb, while Zn had an opposite remediation effect; 3) by comparing the error rate of the algorithm, it was found that GRA-RF model was better than Random-RF. This method more precisely simulated the process of enhanced remediation of contaminated soil. The efficiency of soil remediation was improved by optimizing the remediation variables, it laid a foundation for making and improving soil remediation schemes.
2022, 40(11): 159-164.
doi: 10.13205/j.hjgc.202211022
Abstract:
Aiming at the difficult problems of determining the target value of groundwater risk management and control, this article took an abandoned ferroalloy plant as the research object, and discussed the environmental impact of hexavalent chromium pollution in groundwater on the downstream sensitive target rivers. Numerical simulation methods were used to determine the pollution under hydraulic interception conditions, the target value of groundwater risk management and control of the plot. The results showed that:under natural conditions, after 2500 days, the pollution plume with hexavalent chromium concentration greater than 0.5 mg/L will migrate to the river; under hydraulic interception condition, when the hydraulic interception of the hexavalent chromium concentration was above 10 mg/L of the pollution plume, the highest concentration of hexavalent chromium discharged to the river was 0.46 mg/L, achieving the purpose of groundwater risk management and control. It's finally determined that the groundwater risk control value of this site was 10 mg/L, which reduced the area of groundwater risk control by about 9.45 m2 and saved the cost of sewage treatment. This study provides support for determining the target value of groundwater risk management and control, and preparation of groundwater remediation plans for contaminated land in China.
Aiming at the difficult problems of determining the target value of groundwater risk management and control, this article took an abandoned ferroalloy plant as the research object, and discussed the environmental impact of hexavalent chromium pollution in groundwater on the downstream sensitive target rivers. Numerical simulation methods were used to determine the pollution under hydraulic interception conditions, the target value of groundwater risk management and control of the plot. The results showed that:under natural conditions, after 2500 days, the pollution plume with hexavalent chromium concentration greater than 0.5 mg/L will migrate to the river; under hydraulic interception condition, when the hydraulic interception of the hexavalent chromium concentration was above 10 mg/L of the pollution plume, the highest concentration of hexavalent chromium discharged to the river was 0.46 mg/L, achieving the purpose of groundwater risk management and control. It's finally determined that the groundwater risk control value of this site was 10 mg/L, which reduced the area of groundwater risk control by about 9.45 m2 and saved the cost of sewage treatment. This study provides support for determining the target value of groundwater risk management and control, and preparation of groundwater remediation plans for contaminated land in China.
2022, 40(11): 165-170,181.
doi: 10.13205/j.hjgc.202211023
Abstract:
Given the shortage of freshwater resources and conventional energy resources in remote islands, it is practical to research and develop a solar desalination device for islands. In this paper, a new seawater desalination device was developed through a procedure of technical design, mathematical calculation, heat and mass transfer, simulation test and performance analysis, etc. And its performance was tested under three working modes, photothermal mode, photothermal photovoltaic mode, and electric heating mode. The experimental results showed that:1) the water production rate of the desalination device was 225 mL/h in photothermal mode, 332 mL/h in photothermal photovoltaic mode (47.6% higher than that of photothermal mode), and 1910 mL/h in electric heating mode, reflecting the importance of medium and high temperature solar collector; 2) the optimal experimental conditions of desalination device were as follows:the temperature of evaporation chamber was 103℃, the temperature of cooling water was 41℃, and the ambient temperature was 30℃, then the instantaneous water yield was as high as 2389 mL/h, and the influence degree of various factors were in the sequence of evaporation chamber temperature>cooling water temperature>ambient temperature; 3) the water yield per unit area of the desalination device under the photothermal mode and photothermal photovoltaic mode was 2172, 1167 mL/(m2·d), when the minimum heat consumption of the solar distillation process was 2.03 kW·h/m3.
Given the shortage of freshwater resources and conventional energy resources in remote islands, it is practical to research and develop a solar desalination device for islands. In this paper, a new seawater desalination device was developed through a procedure of technical design, mathematical calculation, heat and mass transfer, simulation test and performance analysis, etc. And its performance was tested under three working modes, photothermal mode, photothermal photovoltaic mode, and electric heating mode. The experimental results showed that:1) the water production rate of the desalination device was 225 mL/h in photothermal mode, 332 mL/h in photothermal photovoltaic mode (47.6% higher than that of photothermal mode), and 1910 mL/h in electric heating mode, reflecting the importance of medium and high temperature solar collector; 2) the optimal experimental conditions of desalination device were as follows:the temperature of evaporation chamber was 103℃, the temperature of cooling water was 41℃, and the ambient temperature was 30℃, then the instantaneous water yield was as high as 2389 mL/h, and the influence degree of various factors were in the sequence of evaporation chamber temperature>cooling water temperature>ambient temperature; 3) the water yield per unit area of the desalination device under the photothermal mode and photothermal photovoltaic mode was 2172, 1167 mL/(m2·d), when the minimum heat consumption of the solar distillation process was 2.03 kW·h/m3.
2022, 40(11): 171-176.
doi: 10.13205/j.hjgc.202211024
Abstract:
The denitrification technology using ozone oxidation combined with wet absorption can be used in the purification of flue gas with relatively low temperature (<150℃) and NOx concentration (<400 mg/m3), such as the flue gas from steel sintering, coke oven and ceramics industries. The technology has the advantages of higher SO2 and NOx removal efficiency, simpler equipment, relatively lower construction and operation cost. The physicochemical behaviors of ozone oxidation combined with the liquid phase absorption denitrification process was firstly analyzed. The distribution of nitrogen products from both gas-phase NO oxidation and gas-phase oxidation combined with wet absorption were investigated by Fourier infrared spectroscopy and ion chromatography, and the nitrogen conversion was calculated. The results showed that the O3/NO molar ratio and water solubility were the key factors affecting the degree of NO oxidation and NOx removal efficiency. When the O3/NO molar ratio was higher than 1.5, NO oxidation products were mainly N2O5 and HNO3, and their water solubility was equivalent to SO2. Thus, NOx could be effectively removed in the traditional desulfurization absorber, and the product was NO3- with good stability. The nitrogen conversion rate was close to 99%, and the undetectable nitrogen components could be ignored or never exist.
The denitrification technology using ozone oxidation combined with wet absorption can be used in the purification of flue gas with relatively low temperature (<150℃) and NOx concentration (<400 mg/m3), such as the flue gas from steel sintering, coke oven and ceramics industries. The technology has the advantages of higher SO2 and NOx removal efficiency, simpler equipment, relatively lower construction and operation cost. The physicochemical behaviors of ozone oxidation combined with the liquid phase absorption denitrification process was firstly analyzed. The distribution of nitrogen products from both gas-phase NO oxidation and gas-phase oxidation combined with wet absorption were investigated by Fourier infrared spectroscopy and ion chromatography, and the nitrogen conversion was calculated. The results showed that the O3/NO molar ratio and water solubility were the key factors affecting the degree of NO oxidation and NOx removal efficiency. When the O3/NO molar ratio was higher than 1.5, NO oxidation products were mainly N2O5 and HNO3, and their water solubility was equivalent to SO2. Thus, NOx could be effectively removed in the traditional desulfurization absorber, and the product was NO3- with good stability. The nitrogen conversion rate was close to 99%, and the undetectable nitrogen components could be ignored or never exist.
2022, 40(11): 177-181.
doi: 10.13205/j.hjgc.202211025
Abstract:
Jiangsu promulgated a new regional standard, "Emission Limits for Major Water Pollutants from Urban Sewage Treatment Plants and Key Industrial Industries in the Taihu Basin" (DB32/1072-2018) in June 2018. Urban sewage treatment plants in the Taihu Basin are facing a new round of upgrading and reconstruction. Regarding a municipal sewage treatment plant in the Taihu Basin as the research object, the whole process analysis was applied to evaluate the main problems in the actual operation of the Orbal oxidation ditch. The results showed that the rate of denitrification potential and rate of activated sludge were 8.0 and 2.24 mg NO3--N/(g VSS·h) respectively. Regarding the analysis of the whole process of chemical oxygen demand (COD) and total nitrogen (TN), it revealed that the lack of carbon source, low internal reflux ratio, and siltation limited the further improvement of nitrogen removal efficiency, so there was still a certain potential for nitrogen removal after the optimized operation. This paper provided a basis for the actual operation of the plant and the design of the subsequent upgrade, and also offered a reference for the similar urban sewage treatment plants that had the need for upgrade and renovation.
Jiangsu promulgated a new regional standard, "Emission Limits for Major Water Pollutants from Urban Sewage Treatment Plants and Key Industrial Industries in the Taihu Basin" (DB32/1072-2018) in June 2018. Urban sewage treatment plants in the Taihu Basin are facing a new round of upgrading and reconstruction. Regarding a municipal sewage treatment plant in the Taihu Basin as the research object, the whole process analysis was applied to evaluate the main problems in the actual operation of the Orbal oxidation ditch. The results showed that the rate of denitrification potential and rate of activated sludge were 8.0 and 2.24 mg NO3--N/(g VSS·h) respectively. Regarding the analysis of the whole process of chemical oxygen demand (COD) and total nitrogen (TN), it revealed that the lack of carbon source, low internal reflux ratio, and siltation limited the further improvement of nitrogen removal efficiency, so there was still a certain potential for nitrogen removal after the optimized operation. This paper provided a basis for the actual operation of the plant and the design of the subsequent upgrade, and also offered a reference for the similar urban sewage treatment plants that had the need for upgrade and renovation.
2022, 40(11): 182-188,198.
doi: 10.13205/j.hjgc.202211026
Abstract:
After leaching calcium from fly ash of municipal solid waste incineration with ammonium chloride solution, the carbonization method was used to recover calcium carbonate from the leaching solution. The optimal conditions for leaching calcium ion after single factor experiment and response surface design were as follows:ammonium chloride concentration=3.9 mol/L, reaction time=64 min, liquid-solid ratio=5.6 mL/g; the degree of influence of the three factors on the leaching of calcium ions was in the order of liquid-solid ratio>ammonium chloride concentration>reaction time.The results of metal toxicity leaching from fly ash residues showed that the leaching concentration of Pb、Cu、Zn、Cd、Ni were 0.0929,0.0012,0.0054,0.0017, 0.0002 mg/L, respectively, which were significantly lower than the maximum permissible emission concentration limit stipulated in GB 8978-1996 Integrated Wastewater Discharge Standard. And the heavy metal toxicity leaching results of fly ash residues met the comprehensive utilization requirements of Term 6.3 in HJ 1134-2020 Technical Specification for Pollution Control of Fly-ash from Municipal Solid Waste Incineration. After using homemade PAN-PEI to adsorb heavy metals in the salt wash, the recycled calcium carbonate was of excellent quality. Its main crystal type is vaterite, and the contents of Pb, Cd, and Fe were 0.0009%, 0.0002%, and 0.0103%, respectively, in line with HG/T 2776-2010 Fine Precipitated Calcium Carbonate and Fine Activated Precipitated Calcium Carbonate for Industrial Use standard requirements, showing a wide range of application potential.
After leaching calcium from fly ash of municipal solid waste incineration with ammonium chloride solution, the carbonization method was used to recover calcium carbonate from the leaching solution. The optimal conditions for leaching calcium ion after single factor experiment and response surface design were as follows:ammonium chloride concentration=3.9 mol/L, reaction time=64 min, liquid-solid ratio=5.6 mL/g; the degree of influence of the three factors on the leaching of calcium ions was in the order of liquid-solid ratio>ammonium chloride concentration>reaction time.The results of metal toxicity leaching from fly ash residues showed that the leaching concentration of Pb、Cu、Zn、Cd、Ni were 0.0929,0.0012,0.0054,0.0017, 0.0002 mg/L, respectively, which were significantly lower than the maximum permissible emission concentration limit stipulated in GB 8978-1996 Integrated Wastewater Discharge Standard. And the heavy metal toxicity leaching results of fly ash residues met the comprehensive utilization requirements of Term 6.3 in HJ 1134-2020 Technical Specification for Pollution Control of Fly-ash from Municipal Solid Waste Incineration. After using homemade PAN-PEI to adsorb heavy metals in the salt wash, the recycled calcium carbonate was of excellent quality. Its main crystal type is vaterite, and the contents of Pb, Cd, and Fe were 0.0009%, 0.0002%, and 0.0103%, respectively, in line with HG/T 2776-2010 Fine Precipitated Calcium Carbonate and Fine Activated Precipitated Calcium Carbonate for Industrial Use standard requirements, showing a wide range of application potential.
2022, 40(11): 189-198.
doi: 10.13205/j.hjgc.202211027
Abstract:
With an abandoned land area after an explosion accident in an organic chemical plant as the research subject, the soils at different depths were evaluated using the single-factor pollution index, and comprehensive pollution index, as well as the risk assessment model recommended in the Technical Guidelines for Soil Pollution Risk Assessment of Construction Land, HJ 25.3-2019. Further, we evaluated the pollution degree and health risk of the site, and proposed risk control values of pollutants based on human health risk assessment. The results showed that excessive pollutants in the soil comprised 1,1,2-trichloroethane, chlorobenzene and 1,4-dichlorobenzene, which were mainly concentrated in the central and northwest subsoil (2 to 8 meters deep) of the study area. The results of the single-factor pollution index assessment showed that these three organic compounds displayed different degrees of pollution in the subsoil, with chlorobenzene as the most serious pollutant. The results of the comprehensive pollution index assessment showed that the topsoil was not polluted, whereas the comprehensive pollution degree of some areas in the subsoil was severe. The health risk assessment results showed that the cancer risks and hazard quotient in the central and northwest subsoil of the study area exceeded the acceptable threshold. The primary exposure risk came from the indoor inhalation pathway of gaseous pollutants, such as chlorobenzene and 1,4-dichlorobene. The calculation results of the risk control value showed that the risk control value of pollutants was far lower than the maximum detection value. When the risk control value calculated by layers was selected as the repair target value, the amount of pollution could be effectively reduced.
With an abandoned land area after an explosion accident in an organic chemical plant as the research subject, the soils at different depths were evaluated using the single-factor pollution index, and comprehensive pollution index, as well as the risk assessment model recommended in the Technical Guidelines for Soil Pollution Risk Assessment of Construction Land, HJ 25.3-2019. Further, we evaluated the pollution degree and health risk of the site, and proposed risk control values of pollutants based on human health risk assessment. The results showed that excessive pollutants in the soil comprised 1,1,2-trichloroethane, chlorobenzene and 1,4-dichlorobenzene, which were mainly concentrated in the central and northwest subsoil (2 to 8 meters deep) of the study area. The results of the single-factor pollution index assessment showed that these three organic compounds displayed different degrees of pollution in the subsoil, with chlorobenzene as the most serious pollutant. The results of the comprehensive pollution index assessment showed that the topsoil was not polluted, whereas the comprehensive pollution degree of some areas in the subsoil was severe. The health risk assessment results showed that the cancer risks and hazard quotient in the central and northwest subsoil of the study area exceeded the acceptable threshold. The primary exposure risk came from the indoor inhalation pathway of gaseous pollutants, such as chlorobenzene and 1,4-dichlorobene. The calculation results of the risk control value showed that the risk control value of pollutants was far lower than the maximum detection value. When the risk control value calculated by layers was selected as the repair target value, the amount of pollution could be effectively reduced.
2022, 40(11): 199-210.
doi: 10.13205/j.hjgc.202211028
Abstract:
The process flow simulation of imidazolium-based ionic liquids (ILs) used for natural gas (NG) dehydration was established by Aspen Plus. Technological and environmental impacts of different ILs in the NG dehydration process were compared by using the sensitivity analysis and life cycle assessment (LCA), and the IL structural effect on techno-environmental assessment in NG dehydration was evaluated. The results demonstrated that the ILs with[BF4]- combined with the cation possessing the shorter alkyl chain exhibited better dehydration performance (the order following[EMIM] [BF4]>[BMIM] [BF4]>[OMIM] [BF4]). For producing 1 kg methane, the largest environmental impact lay in the[BMIM] [PF6] based dehydration process, and its impact was 5 times the lowest scenario using[OMIM] [BF4] on average. Furthermore, for the dehydration scenarios with same anions[BF4]-, the impact order was[OMIM] [BF4]<[BMIM] [BF4]<[EMIM] [BF4]. The results can serve as a significant guidance strategy from both the technical and environmental assessment on screening or developing proper IL candidates for NG dehydration processes.
The process flow simulation of imidazolium-based ionic liquids (ILs) used for natural gas (NG) dehydration was established by Aspen Plus. Technological and environmental impacts of different ILs in the NG dehydration process were compared by using the sensitivity analysis and life cycle assessment (LCA), and the IL structural effect on techno-environmental assessment in NG dehydration was evaluated. The results demonstrated that the ILs with[BF4]- combined with the cation possessing the shorter alkyl chain exhibited better dehydration performance (the order following[EMIM] [BF4]>[BMIM] [BF4]>[OMIM] [BF4]). For producing 1 kg methane, the largest environmental impact lay in the[BMIM] [PF6] based dehydration process, and its impact was 5 times the lowest scenario using[OMIM] [BF4] on average. Furthermore, for the dehydration scenarios with same anions[BF4]-, the impact order was[OMIM] [BF4]<[BMIM] [BF4]<[EMIM] [BF4]. The results can serve as a significant guidance strategy from both the technical and environmental assessment on screening or developing proper IL candidates for NG dehydration processes.
2022, 40(11): 211-221.
doi: 10.13205/j.hjgc.202211029
Abstract:
Composting is an important way of resource utilization of organic solid waste. The development and application of composting are limited by the odor produced in the composting process. To understand the research trend and focus in the field of compost odor control, the literature on compost odor research in CNKI and Web of ScienceTM core collection database in 2001-2020, was visually analyzed by CiteSpace software. The results showed that the number of documents issued in the field of compost odor control keep increasing in recent 20 years. The core research team is Li Guoxue from China Agricultural University. Research hotspots mainly focus on composting materials rich in protein or carbohydrate and easy to produce odor, such as livestock manure, sludge and kitchen waste, odor components such as ammonia and volatile organic compounds, and deodorization means such as adding external regulators and biological effects. The treatment of odor produced by food waste composting, the mechanism of odor emission reduction under the action of microorganisms, and the collaborative control of odor, heavy metals, and antibiotic resistance genes should be research frontier in the future. In conclusion, the field of compost odor research is in an active development state, and the perspectives of future research will be more diverse.
Composting is an important way of resource utilization of organic solid waste. The development and application of composting are limited by the odor produced in the composting process. To understand the research trend and focus in the field of compost odor control, the literature on compost odor research in CNKI and Web of ScienceTM core collection database in 2001-2020, was visually analyzed by CiteSpace software. The results showed that the number of documents issued in the field of compost odor control keep increasing in recent 20 years. The core research team is Li Guoxue from China Agricultural University. Research hotspots mainly focus on composting materials rich in protein or carbohydrate and easy to produce odor, such as livestock manure, sludge and kitchen waste, odor components such as ammonia and volatile organic compounds, and deodorization means such as adding external regulators and biological effects. The treatment of odor produced by food waste composting, the mechanism of odor emission reduction under the action of microorganisms, and the collaborative control of odor, heavy metals, and antibiotic resistance genes should be research frontier in the future. In conclusion, the field of compost odor research is in an active development state, and the perspectives of future research will be more diverse.
2022, 40(11): 222-230.
doi: 10.13205/j.hjgc.202211030
Abstract:
The reduction of CO2 into high-energy chemicals by electrical energy to achieve carbon reduction has received global attention, and the advent of the Big Data era provided a new research platform. This paper investigated and summarized 4089 papers on electro-catalytic reduction of CO2 in the Web of Science core database during 2012-2021, and used the citation analysis software VOSviewer for metric statistics and visual analysis. The research development trends in this field were analyzed from several perspectives and future development trends were predicted. The results showed that the number of articles published in the field of electro-catalytic reduction of CO2 had been steadily increasing during 2012-2021; China and the USA were the leaders in the field of electro-catalytic reduction of CO2, and the scientific achievements of them were also relatively outstanding; the research focus in the field of electro-catalytic reduction of CO2 had changed from the preparation of single metal and alloy catalyst materials to non-metallic nanostructured catalysts, precise regulation of catalyst performance and mechanism revealing of electro-catalytic reaction, etc.
The reduction of CO2 into high-energy chemicals by electrical energy to achieve carbon reduction has received global attention, and the advent of the Big Data era provided a new research platform. This paper investigated and summarized 4089 papers on electro-catalytic reduction of CO2 in the Web of Science core database during 2012-2021, and used the citation analysis software VOSviewer for metric statistics and visual analysis. The research development trends in this field were analyzed from several perspectives and future development trends were predicted. The results showed that the number of articles published in the field of electro-catalytic reduction of CO2 had been steadily increasing during 2012-2021; China and the USA were the leaders in the field of electro-catalytic reduction of CO2, and the scientific achievements of them were also relatively outstanding; the research focus in the field of electro-catalytic reduction of CO2 had changed from the preparation of single metal and alloy catalyst materials to non-metallic nanostructured catalysts, precise regulation of catalyst performance and mechanism revealing of electro-catalytic reaction, etc.
2022, 40(11): 231-236,250.
doi: 10.13205/j.hjgc.202211031
Abstract:
The Chinese baijiu industry is facing a challenge in recycling the distiller's grain, which is featured by large yield, rich organic matters, short-lived storage, and high cost of treatment. This study reviewed new research progress on technologies of distiller's grains processing and utilization, with an emphasis on academic articles published between year 2017 and 2021. Animal feeding is still the mainstream of distiller's grains reutilization. The characteristics of processing technologies development are twofold. The microbial processing technique has been extensively employed with the benefit of balancing nutrients in grain-derived animal fodders by degrading cellulose with a rate of 24% to 42%, and increasing crude protein with a rate of 21% to 60%. Carbonization and pyrolysis of distiller grains to produce biochar is currently a hot topic with great promise, and the rate of biochar production is kept between 33% and 43%. At last, this study proposes a new technology paradigm for large-scale treatment of distiller's grains, in conjunction with baijiu production, biochar production and crop planting, to construct a holistic reutilization.
The Chinese baijiu industry is facing a challenge in recycling the distiller's grain, which is featured by large yield, rich organic matters, short-lived storage, and high cost of treatment. This study reviewed new research progress on technologies of distiller's grains processing and utilization, with an emphasis on academic articles published between year 2017 and 2021. Animal feeding is still the mainstream of distiller's grains reutilization. The characteristics of processing technologies development are twofold. The microbial processing technique has been extensively employed with the benefit of balancing nutrients in grain-derived animal fodders by degrading cellulose with a rate of 24% to 42%, and increasing crude protein with a rate of 21% to 60%. Carbonization and pyrolysis of distiller grains to produce biochar is currently a hot topic with great promise, and the rate of biochar production is kept between 33% and 43%. At last, this study proposes a new technology paradigm for large-scale treatment of distiller's grains, in conjunction with baijiu production, biochar production and crop planting, to construct a holistic reutilization.
2022, 40(11): 237-250.
doi: 10.13205/j.hjgc.202211032
Abstract:
Volatile organic compounds (VOCs) in the atmosphere are harmful to the ecological environment and human health, and need urgent treatment. The adsorption method has become one of the most economical and effective methods for VOCs removal, due to its advantages of simple operation, high efficiency, and low energy consumption. Traditional adsorption materials such as molecular sieve, activated carbon, and diatomite are limited by small adsorption capacity, easy plugging, low selectivity, difficult regeneration, etc. Therefore, it is still a current research hotspot to develop efficient and stable VOCs adsorption materials. Metal-organic frameworks (MOFs), as a new type of porous material, have shown good performance in VOCs adsorption due to their high specific surface area, abundant pore structures, and adjustable chemical characters. This review focused on the studies of VOCs adsorption using MOFs-based porous materials in the past 10 years. Starting from the structures and characteristics of MOFs, the classification of MOFs and types of their composites were described in detail. Based on the influential factors and adsorption mechanisms in the adsorption process of VOCs on MOFs-based porous materials, the research progress of MOFs-based porous materials in the application of VOCs adsorption was summarized and its future development in this field was looked forward.
Volatile organic compounds (VOCs) in the atmosphere are harmful to the ecological environment and human health, and need urgent treatment. The adsorption method has become one of the most economical and effective methods for VOCs removal, due to its advantages of simple operation, high efficiency, and low energy consumption. Traditional adsorption materials such as molecular sieve, activated carbon, and diatomite are limited by small adsorption capacity, easy plugging, low selectivity, difficult regeneration, etc. Therefore, it is still a current research hotspot to develop efficient and stable VOCs adsorption materials. Metal-organic frameworks (MOFs), as a new type of porous material, have shown good performance in VOCs adsorption due to their high specific surface area, abundant pore structures, and adjustable chemical characters. This review focused on the studies of VOCs adsorption using MOFs-based porous materials in the past 10 years. Starting from the structures and characteristics of MOFs, the classification of MOFs and types of their composites were described in detail. Based on the influential factors and adsorption mechanisms in the adsorption process of VOCs on MOFs-based porous materials, the research progress of MOFs-based porous materials in the application of VOCs adsorption was summarized and its future development in this field was looked forward.
2022, 40(11): 251-259.
doi: 10.13205/j.hjgc.202211033
Abstract:
Biofouling is a critical challenge in the membrane-based water treatment process. Biofilm formation is regulated by bacterial quorum sensing. Inhibition of quorum sensing is an emerging technology for membrane biofouling control. Mechanism of quorum sensing and research on biofilm formation involving quorum sensing was introduced in this work. By interfering with and blocking the circuits of cell-cell communication, expression of the target quorum-sensing-controlled gene can be prevented, and the specific group behavior of bacteria can be inhibited. Research on biofouling control of water treatment membranes based on quorum sensing and quorum quenching is reviewed. The application of quorum sensing inhibitors in membrane-based water treatment systems, and studies on the immobilization of inhibitors as well as membrane modification are overviewed. An outlook of future research on membrane biofouling control based on quorum sensing tactics is proposed.
Biofouling is a critical challenge in the membrane-based water treatment process. Biofilm formation is regulated by bacterial quorum sensing. Inhibition of quorum sensing is an emerging technology for membrane biofouling control. Mechanism of quorum sensing and research on biofilm formation involving quorum sensing was introduced in this work. By interfering with and blocking the circuits of cell-cell communication, expression of the target quorum-sensing-controlled gene can be prevented, and the specific group behavior of bacteria can be inhibited. Research on biofouling control of water treatment membranes based on quorum sensing and quorum quenching is reviewed. The application of quorum sensing inhibitors in membrane-based water treatment systems, and studies on the immobilization of inhibitors as well as membrane modification are overviewed. An outlook of future research on membrane biofouling control based on quorum sensing tactics is proposed.
