双表面活性剂修饰下纳米零价铁对水中Cr(Ⅵ)污染去除研究

Removal of Cr(Ⅵ) from water by double-surfactants modified nanoscale zero-valent iron

为解决纳米级零价铁(nZVI)在环境中易团聚、易氧化的问题,强化其去除水中Cr(Ⅵ)的能力,选择非离子型表面活性剂聚乙烯吡咯烷酮(PVP)和阴离子表面活性剂油酸钠(NaOA)同时对nZⅥ进行修饰.同时,通过对比不同pH值、材料干湿状态、初始浓度及共存离子条件下的反应效果,结合材料的XRD和XPS表征、动力学实验和25℃等温线的拟合进行机理分析.结果表明:酸性条件有利于Cr(Ⅵ)的去除;材料的干湿状态对去除效率影响较大;材料去除水中Cr(Ⅵ)可在3 h内达到反应平衡,去除效率在90%以上,实验条件下最大去除量为183.1 mg·g^-1,反应过程符合准二级动力学模型及Langmuir模型;反应过程中Cr(Ⅵ)大部分转化为Cr(Ⅲ).

In order to prevent the aggregation and oxidation of nanoscale zero-valent iron(nZVI) and enhance its ability to remove Cr(Ⅵ) from water, non-ionic surfactant polyvinylpyrrolidone(PVP) and anionic surfactant sodium oleate(NaOA) were selected to modify nZⅥ simultaneously. Comparison of removal efficiency was investigated under different pH, materials′ status(dry or wet), initial concentration and coexisting ions. The reaction mechanism was further analyzed through XRD and XPS characterization, kinetics and curve fitting with adsorption isotherm models. It can be found that: ①acidic conditions are conducive to the removal of Cr(Ⅵ);②the materials′ status makes significant difference to removal efficiency;③equilibrium can be reached within 3 h with a removal efficiency above 90% and a maximum removal amount of 183.1 mg·g^-1;④the reaction process is fitted well with pseudo-second-order kinetics and Langmuir model;⑤the process makes a full transformation of Cr(Ⅵ) into Cr(Ⅲ) under the reaction condition.