改性蛇纹石对Pb2+的吸附机理及吸附条件优化

为提升蛇纹石对污染物Pb²⁺的去除效果，实现废水中Pb²⁺的高效去除，本研究将天然蛇纹石矿物高温改性，探究改性后蛇纹石对Pb²⁺的吸附机理、解吸情况及蛇纹石用量、溶液的初始pH、蛇纹石粒径大小和吸附时间对吸附量和Pb²⁺去除率的影响，并通过Box-Behnken响应面法优化改性蛇纹石吸附Pb²⁺的实验条件。结果表明：改性蛇纹石吸附性能明显提升，理论最大饱和吸附容量更高，二者吸附过程均更符合Freundlich等温吸附模型和准二级动力学模型，且吸附过程为自发吸热进行的。改性蛇纹石吸附Pb²⁺的机理主要为蛇纹石裂解产生的Mg²⁺与溶液中溶解的CO₂结合形成MgCO₃，MgCO₃与溶液中的Pb²⁺发生溶积置换生成PbCO₃沉淀；Pb²⁺与改性后蛇纹石表面形成的高能键结合，以Pb（NO₃）₂·Si-O、PbO·O-Si-O配合物的形式吸附在蛇纹石表面。改性蛇纹石在溶液中Pb²⁺的解吸量及解吸率均较低，改性蛇纹石对Pb²⁺的吸附情况较为稳定，Pb²⁺不易被解吸出来。改性蛇纹石对溶液中Pb²⁺最佳吸附条件为固液比为1∶200（m∶V），pH=5.5，粒径为140目，吸附时间为36 h，此时吸附量及Pb²⁺去除率分别为15.26 mg·g^-1、79.89%。研究表明，改性蛇纹石对Pb²⁺吸附性能明显提升，具有较高吸附容量且吸附较为稳定不易解吸，对去除废水中Pb²⁺具有潜在应用价值。

Adsorption mechanism and optimization of the adsorption conditions of modified serpentine for Pb2+ removal

To enhance the removal effect of serpentine on Pb²⁺ pollutants and achieve efficient removal of Pb²⁺ from wastewater, this study modified natural serpentine minerals at high temperature and investigated the adsorption and desorption mechanism of modified serpentine to Pb²⁺. In addition, the effects of the amount of serpentine, initial pH of solution, particle size, and absorption time of serpentine on adsorption amount and Pb²⁺ removal rate were investigated. The experimental conditions for Pb²⁺ adsorption by modified serpentine were optimized using the Box-Behnken response surface method. The results showed that the adsorption performance of modified serpentine was significantly improved. The theoretical maximum saturation capacity was high, and both adsorption processes were more consistent with the Freundlich isothermal adsorption and the Quasi-secondary kinetic models. The adsorption processes were carried out by spontaneous heat absorption. The adsorption mechanism of Pb²⁺ adsorption by modified serpentine was mainly based on the combination of Mg²⁺, generated from the cleavage of serpentine, with dissolved CO₂ in solution to form MgCO₃, and the solvation substitution of MgCO₃ with Pb²⁺ in solution to generate PbCO₃ precipitate. Pb²⁺ binds to the high-energy bonds formed on the surface of modified serpentine and absorbed in the form of Pb(NO₃)₂·Si-O and PbO ·O-Si-O complexes. The modified serpentine was adsorbed on the surface as Pb(NO₃)₂·Si-O and PbO·O-Si-O complexes. The desorption amount and removal rate of Pb²⁺ in solution were low. The adsorption of modified serpentine on Pb²⁺ was relatively stable, and Pb²⁺ was not easily desorbed out. The best adsorption conditions of modified serpentine for Pb²⁺ in solution were 1:200(m:V)solid-liquid ratio, pH=5.5, 140 mesh particle size, and 36 h adsorption time; the adsorption amount and Pb²⁺ removal rate were 15.26 mg·g^-1 and 79.89%, respectively. The present study shows that the adsorption performance of modified serpentine to Pb²⁺ is significantly improved, with high adsorption capacity, more stable adsorption, and less desorption, indicating that serpentine has potential application value for the removal of Pb²⁺ from wastewater.