凹凸棒土负载硫化纳米零价铁的制备及其去除水中As(Ⅲ)性能研究

Preparation of attapulgite-loaded sulfide-modified nanoscale zero-valent iron and its adsorption of As(Ⅲ) from aqueous solution

以凹凸棒土为载体,结合硫化改性方法制备了凹凸棒土负载硫化纳米零价铁(S-nZVI@ATP)复合材料,通过As(Ⅲ)静态吸附试验,确定了去除As(Ⅲ)效果最佳的S-nZVI@ATP复合材料制备条件:nZVI/ATP质量比为2∶1、以Na2S2O3为硫化剂、S/Fe摩尔比为1∶4,并考察了As(Ⅲ)溶液初始pH、溶解氧浓度及环境温度对该复合材料去除水中As(Ⅲ)效果的影响。结果表明,经过凹凸棒土负载及硫化改性后,nZVI的颗粒团聚状况明显得到改善。在实验条件范围内,适中的溶液pH值、溶解氧浓度以及较高的环境温度均有利于S-nZVI@ATP复合材料对As(Ⅲ)的去除,该吸附过程为吸热反应,符合拟二级动力学模型,外扩散阶段主要受环境温度影响,吸附过程由颗粒内扩散和膜扩散共同控制。

In this paper,a series of attapulgite-loaded sulfide-modified nanoscale zero-valent iron(S-nZVI@ATP) composites were prepared by using attapulgite carrier and sulfidation reagents.Through static adsorption test, the S-nZVI@ATP composite showing the best removal of As(Ⅲ) from aqueous solution was selected,with the mass ratio of nanoscale zero-valent iron(nZVI) to attapulgite at 2∶1,Na2S2O3 as sulfidation reagent and the S/Fe molar ratio at 1∶4.The effects of initial pH, dissolved oxygen concentration of the As(Ⅲ) solution and ambient temperature on the removal rate of As(Ⅲ) using the as-prepared composites were investigated.The results reveal that by means of attapulgite loading and sulfide modification, the particle agglomeration phenomenon of nZVI is significantly improved.Under the experimental conditions, modest solution pH and dissolved oxygen concentration as well as relatively high temperture are beneficial to the removal of As(Ⅲ) by S-nZVI@ATP composite.The adsorption is an endothermic reaction,and the corresponding process conforms with the pseudo-second-order kinetics. The external diffusion is mainly influenced by ambient temperature,and the adsorption is controlled by both intragranular diffusion and membrane diffusion.