3种吸附剂对污水磷污染去除性能与机制比较

为探索高效利用膨润土、红壤和炉渣去除农业污水磷污染的可行性,对比分析了3种吸附剂对人工合成含磷污水的吸附去除特性,结合SEM、XDS和BET等测试结果以及等温吸附、吸附动力学及Ca2+释放量探讨了3种材料对磷的吸附机制.结果表明,炉渣对磷的吸附能力高于膨润土和红壤,吸附过程均适合Langmuir等温吸附方程(R2 0. 96),对磷的理论饱和吸附量为:炉渣(16. 87 mg·g~(-1))红壤(1. 21 mg·g~(-1))膨润土(0. 92 mg·g~(-1)).炉渣对磷的吸附动力学特征符合Elovich方程(R2=0. 966),而膨润土和红壤对磷的吸附特征则更适合准二级动力学方程(R2为0. 982和0. 959).炉渣的Ca2+释放量(10. 46 mg·g~(-1))显著大于膨润土(0. 31 mg·g~(-1))和红壤(0. 03 mg·g~(-1))(P 0. 05).红壤对磷的吸附量随着p H的升高而降低;膨润土在初始p H为7. 0时,吸附量最低;但初始p H值对炉渣去除磷的影响不大.相比红壤和炉渣,膨润土解吸较快,易于进行重复利用.综上所述,吸附材料的磷吸附能力主要与其结构、化学组成、Ca2+释放能力及溶液初始p H值等有关,炉渣较膨润土和红壤对磷酸盐有着更强的去除能力,适合处理农村污水磷污染.

Removal Performance and Mechanism for Treating Phosphorus in Agricultural Wastewater by Three Adsorbents

To screen the optimal absorbents for P removal from agricultural wastewater, the P adsorption capacity of bentonite, red soil, and slag was studied using synthetic wastewater. Combing the properties of three adsorbents measured by SEM, XDS, and BET methods, the isothermal adsorption, adsorption kinetics, and Ca²⁺ release capacity were analyzed to elucidate the mechanisms of P adsorption. The results showed that the P adsorption capacity of slag was higher than that of bentonite and red soil, and the Langmuir isotherm model was able to better fit the adsorption data (R²>0.96). The P theoretical saturation sorption capacity of slag was higher (16.87 mg·g^-1) than that of bentonite (1.21 mg·g^-1) and red soil (0.92 mg·g^-1) (P<0.05). The results for adsorption kinetics indicated that slag rapidly removed 95.6% of P from 10 mg·L^-1 solution, and the Elovich equation fit the data well (R²=0.812). The adsorption kinetics of P on bentonite and red soil were better described by the pseudo-second-order kinetic equation (R²=0.982 and 0.959, respectively). The Ca²⁺ release capacity of slag (10.46 mg·g^-1) was significantly higher compared to bentonite (0.31 mg·g^-1) and red soil (0.03 mg·g^-1) (P<0.05). The P adsorption capacity of red soil was 0.26 mg·g^-1 when the pH value was 3, and it decreased as the pH values increased. At the initial pH of 7.0, the P adsorption capacity of bentonite was about 0.01 mg·g^-1, lower than 0.04 mg·g^-1 at pH 3, and 0.05 mg·g^-1 at pH 11. The initial pH value had little effect on the P adsorption capacity of slag. The P-loaded bentonite, red soil, and slag were effectively regenerated by using CaCl₂ solution, and bentonite was easier to reuse compared to red soil and slag. The key factors affecting the P adsorption capacity of the three adsorbents were physical and chemical properties, such as crystal structure and the content of metal ions, Ca²⁺ release capacity, and initial pH. These findings demonstrated that slag was a better choice for P removal compared to bentonite and red soil and could be used as an effective P adsorbent for agricultural wastewater treatment.