PREPARATION OF METAL MODIFIED BIOCHAR FOR PHOSPHORUS REMOVAL BY ADSORPTION AND ITS MECHANISM
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摘要: 随着生活污水管网覆盖率的提高和工业废水的点源排放逐渐被控制,农业面源污染成为影响地表水水质提升的主要问题。针对深圳市P河流的关键污染物磷酸盐提出控制技术——金属改性生物炭吸附。以当地丰富的景观植物落叶生物质为原材料,使用对植物无毒害性的Ca、Fe、Mg三种金属对其改性,确定其最优热解温度为500,400,600 ℃,制备3种金属改性生物炭(CaBC500、FeBC400、MgBC600),探究其对磷的吸附去除效果。结果表明,在磷酸盐浓度为14 mg/L和初始pH=8的条件下,CaBC500、FeBC400和MgBC600的最佳投加量分别为0.8,0.8,1.0 g,最高磷去除率分别为84%、92%和97%。CaBC500、FeBC400、MgBC600的静态磷酸盐吸附容量分别为65.5,69.3,49.3 mg/g。通过SEM、EDS、BET、FITR和XRD表征以及对吸附动力学、热力学和等温曲线模型的构造,可知吸附过程符合拟二阶与Langmuir模型,推测其磷吸附机制为表面沉淀、络合结晶、配体交换和静电引力。通过研究发现,利用金属改性生物炭可有效实现磷的吸附去除,说明该方法具有实际应用的潜力。Abstract: 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.
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