硫化协同老化零价铁增效去除水中Cr(Ⅵ)的作用机制

Sulfidation couples with aging to enhance the reactivity of zerovalent iron toward Cr(Ⅵ)in water

为缓解零价铁(AZVI)的老化失活,考察了硫化对老化零价铁去除水中Cr(Ⅵ)性能的影响,并借助拉曼光谱、X射线光电子能谱(XPS)以及电化学等方法探究了硫化对老化零价铁除污增效的作用机制。以水中Cr(Ⅵ)为目标污染物,研究结果表明,AZVI在老化周期为0.5~1 d内反应速率从0.0024 min^(-1)降低至失活,而硫化的AZVI(AZVIS)在0.5~14 d内仍能维持高反应活性。基于结构表征技术手段以及相关性分析,明确了空间硫(S^(2-)/S_(2)^(2-))能够改善AZVI的电子转移能力以实现Cr(Ⅵ)的增效去除,解析了反应前后Fe和Cr的价态及含量变化,进一步揭示了表层Fe3O4耦合嵌层FeS/FeS2介导内核Fe0电子传递以实现AZVIS高效还原除污的反应机理。

To resolve the deactivation of zero-valent iron(ZVI)by aging effect,the sulfidation was proposed in this work to improve the reactivity of aged ZVI(AZVI).In addition,the coupled effects of sulfidation and aging on the improved performance of ZVI were explored with the help of Raman spectroscopy,X-ray photoelectron spectroscopy(XPS)and electrochemistry.Taking the Cr(Ⅵ)as the targeted contaminant,the results showed that the reaction rate of AZVI decreased from 0.0024 min-1 to 0 within an aging period of 0.5—1 d,while the sulfated AZVI(AZVIS)maintained the high reactivity within 0.5—14 d.Based on structural characterization techniques and correlation analysis,it is clear that steric sulfur(S^(2-)/S_(2)^(2-))can improve the electron transfer ability of AZVI to achieve the synergistic removal of Cr(Ⅵ),and analyze the valence states of Fe and Cr before and after the reaction.In the subshell of AZVIS at 20 nm,the correlation coefficients of S^(2-)/S_(2)^(2-)with lgk_(SA)were greater than 0.63,further demonstrating that sulfidation can modulate the reactivity of AZVI through the roles of spatial sulfurs(S^(2-)/S_(2)^(2-)).In addition,this work further revealed that the surface Fe3O4 could couple the embedded FeS/FeS2 to mediate the electron transfer from Fe0 core for efficient reduction of Cr(Ⅵ)by AZVIS.In general,this study not only helps to guide the interface reconstruction of ZVI,but also is expected to provide theoretical support for the development of ZVI-based technology for water treatment.