PREPARATION OF METAL MODIFIED BIOCHAR FOR PHOSPHORUS REMOVAL BY ADSORPTION AND ITS MECHANISM

With the improvement of the coverage of domestic sewage network and the successive control of point source discharge of industrial wastewater, agricultural non-point source pollution has become the main problem affecting the improvement of surface water quality. In this study, a control technology for phosphate, a key pollutant in the P River of Shenzhen was proposed, by adsorption of metal modified biochar. Common local abundant biomass of landscape plants was used as the raw material, and Ca, Fe and Mg, which are non-toxic to plants, were selected as the modifier. The optimal pyrolysis temperatures were determined to be 500 ℃, 400 ℃ and 600 ℃, and three kinds of metal modified biochar (CaBC500, FeBC400, and MgBC600) were prepared. The results showed that under the condition of phosphate concentration of 14 mg/L and an initial pH of 8, the optimal dosage of CaBC500, FeBC400 and MgBC600 was 0.8 g, 0.8 g and 1.0 g, respectively. The highest phosphorus removal rates were 84%, 92% and 97%, respectively. The static phosphate adsorption capacities of CaBC500, FeBC400 and MgBC600 were 65.5 mg/g, 69.3 mg/g and 49.3 mg/g, respectively. Through SEM, EDS, BET, FITR and XRD characterization, as well as the construction of adsorption kinetics, thermodynamics and isothermal curve models, it can be found that the adsorption process accords with the pseudo-second-order and Langmuir models, and the phosphorus adsorption mechanisms includes surface precipitation, complex crystallization, ligand exchange and electrostatic attraction. The adsorption and removal of phosphorus can be effectively achieved by using metal modified biochar, indicating its practical application potential.