硫化纳米零价铁(S-nZVI)对水体中镉的去除研究

Removal of cadmium in aquatic environment by sulfidated nanoscale zero-valent iron(S-nZVI)

由于矿山开采、工业废水排放及农业施肥等人类活动,使得我国镉污染日益突出.本研究采用液相还原法制备硫化纳米零价铁(S-nZVI),研究其对Cd的去除行为.考察了不同硫化剂、合成方法、S/Fe比(物质的量比)及pH对Cd去除的影响,并采用扫描电子显微镜(SEM)、拉曼光谱(Raman)、X-射线衍射(XRD)等技术对反应前后的材料进行表征,结合批实验结果探讨Cd的去除机理.结果表明,采用一步法以硫化钠(Na_2S)为硫化剂合成的S-nZVI对Cd的去除效率远高于其它方法,去除容量可达385.6 mg·g^(-1).反应120 min后,S-nZVI对Cd的去除率随S/Fe比的增加而升高,S-nZVI反应体系受pH影响较小.材料表征结果显示,S-nZVI颗粒由Fe^0、Fe_3O_4、FeS组成,其中,FeS的含量随S/Fe比的升高而增加.S-nZVI对Cd的去除机理主要是Cd将FeS中的Fe置换,与S结合形成稳定的CdS.

In China, cadmium pollution has become more and more severe due to human activities such as mining, industrial wastewater discharge, and agricultural fertilization. In this study, various sulfidated nanoscale zero-valent iron(S-nZVI) was synthesized and compared for the performance of Cd removal. The effects of sulfidation reagents, synthesis method, S/Fe molar ratio and pH on Cd removal efficiency were investigated. The removal mechanism of Cd was elucidated based on scanning electron microscopy(SEM), Raman spectroscopy(Raman), X-ray diffraction(XRD), and experimental results. The results showed that the removal efficiency of Cd by presynthesized S-nZVI with Na2S as the sulfidation reagent was much higher than other methods, and the removal capacity reached up to 385.6 mg·g-1. After reaction 120 min, the removal efficiency of Cd increased with the increase of S/Fe molar ratio. pH had little effect on the S-nZVI reaction with Cd. Characterization of S-nZVI showed that the particles were composed of Fe0, Fe3O4 and FeS. FeS increased with the increase of S/Fe molar ratio. The mechanism of the removal of Cd by S-nZVI was mainly via Cd displacement of Fe in FeS and form stable CdS.