絮凝剂除铅性能及分子动力学模拟吸附机理

Pb removal performance of flocculants and adsorption mechanism simulated by molecular dynamics

针对铅在环境中不断富集后会产生不良影响的问题,基于黄原酸化反应得到的具有螯合作用的絮凝剂成为研究的热点。对聚乙烯亚胺基黄原酸钠(PEX)、二硫代羧基化羟甲基聚丙烯酰胺(DTMPAM)和二硫代羧基化丙烯酰胺(PDTAM)3种絮凝剂进行了性能比较试验,得到3种絮凝剂在不同铅离子(Pb^(2+))质量浓度、不同pH值以及共存阳离子影响的条件下的去除能力由高到低的顺序为PEX、DTMPAM、PDTAM。并运用分子动力学模拟计算出主要发挥螯合作用的基团二硫代羧基和Pb^(2+)之间的相互作用能以及径向分布函数,得到3种絮凝剂和Pb^(2+)间的作用稳定性及强度大小,明确了絮凝剂吸附机理,分析了去除效果存在差异的原因。

In response to the problem of adverse effects caused by the continuous enrichment of Pb in the environment,flocculants with chelating properties obtained based on xanthan acidification reactions have become a hot research topic.A performance comparison experiment is conducted on three flocculants,namely polyethyleneimine-sodium xanthogenat(PEX),dithiocarboxyl hydroxymethypolyacrylamid(DTMPAM),and dithiocarboxyl acrylamide(PDTAM).The order of removal ability of the three flocculants from high to low under different Pb~(2+)mass concentrations,pH values,and coexisting cation influences is determined as PEX,DTMPAM,and PDTAM.Molecular dynamics simulations are used to calculate the interaction energy and radial distribution function between the dithiocarboxyl group and Pb~(2+),which mainly play a chelating role.The stability and strength of the interaction between the three flocculants and Pb~(2+)are obtained,and the adsorption mechanism of the flocculants is clarified.The reasons for the differences in removal efficiency are analyzed.