纳米零价铁在含Cr(VI)水相中的结构性能演变研究  

Evolution of nanoscale zero valent iron on structure and properties in Cr(VI)-containing aqueous phase

作　　者：刘爱荣 戴雨薇[1,2] 夏泽阳 刘静 LIU Airong;DAI Yuwei;XIA Zeyang;LIU Jing(State Key Laboratory of Pollution Control and Resource Reuse,Shanghai 200092;College of Environmental Science and Engineering,Tongji University,Shanghai 200092)

机构地区：[1]污染控制与资源化研究国家重点实验室,上海200092 [2]同济大学环境科学与工程学院,上海200092

出　　处：《环境科学学报》2022年第9期92-101,共10页Acta Scientiae Circumstantiae

基　　金：国家重点研发计划项目(No.2019YFC1805300);国家自然科学基金项目(No.42073082,41673096)。

摘　　要：纳米零价铁(nZVI)进行土壤及水体中污染物的修复过程中,结构和成分发生演化,生成铁氧化合物对污染物在环境中的迁移、转化和归宿等产生影响.本文研究了nZVI在充氧水介质中与铬酸根(Cr(Ⅵ))的反应,结果表明:nZVI的表面化学及晶相结构随溶液初始pH值、Cr(Ⅵ)浓度和反应时间等变化而变化.低浓度Cr(Ⅵ)(≤20 mg∙L^(-1))的存在使得nZVI的腐蚀加速,单个颗粒由链球状结构演变为片状和针状结构,主要腐蚀产物成为γ-Fe_(2)O_(3)/Fe_(3)O_(4)、γ-FeOOH的混合物.溶液中高浓度Cr(Ⅵ)(≥50 mg∙L^(-1))与nZVI反应前后产物颗粒保持球形,证明其抑制nZI颗粒的腐蚀.这是由于Cr(Ⅵ)在nZVI表面还原产生Cr(OH)_(3)或Cr_(x)Fe_(1-x)(OH)_(3)或Cr_(x)Fe_(1-x)OOH,覆盖在表面阻止进一步的腐蚀.塔菲尔(Tafel)曲线测试发现,Cr(Ⅵ)浓度低于0.1 mg∙L^(-1)时,nZVI反应后固体产物制备的电极腐蚀电压负移,腐蚀电流密度增大;而当Cr(Ⅵ)浓度(≥20 mg∙L^(-1))增高时,腐蚀电位正移,腐蚀电流密度减少;且腐蚀电位随着Cr(Ⅵ)含量的增加而向正向移动,而腐蚀电流密度则减小,证明了腐蚀速率越慢.塔菲尔腐蚀电流测试结合扫描电镜、X-射线电子衍射和X-射线光电子能谱分析,nZVI中Cr(Ⅵ)含量越高抗腐蚀能力越强.本文对研究复杂环境条件nZVI与Cr(Ⅵ)反应后的最终产物以及其环境归趋具有重要意义.When nanocale zero valent iron(nZVI)was used for heavy metals remediation,the structures and properties of nZVIcan be evolved with the environmental conditions.The products,iron oxides,etc.would affect the migration,transformation and fate of nZVI.In this study,the transformation of nZVIparticles in chromate[Cr(Ⅵ)]solution containing oxygen was studied.Results showed that the surface chemistry and crystal structure of nZVItransformed with the initial solution pH,initial concentration of Cr(Ⅵ)and the reaction time.The low concentration of Cr(Ⅵ)(≤20 mg∙L^(-1))promoted continuous corrosion of nZVI,and particles changed from spherical to flaky or needle structure after 6 hours of reaction in aquatic solution.The main corrosion products were made up ofγ-Fe_(2)O_(3)/Fe_(3)O_(4),γ-FeOOH.Reacted with Cr(Ⅵ)(50 mg∙L^(-1))for 6 h,the spent nZVIparticles still remained spherical morphology,which proved that the high concentration of Cr(Ⅵ)inhibited the corrosion of nZVI.And Cr(Ⅵ)was reduced to Cr(OH)_(3),Cr_(x)Fe_(1-x)(OH)_(3)or Cr_(x)Fe_(1-x)OOH on the surface of nZVIto prevent further corrosion.Tafel tests results showed that when Cr(Ⅵ)concentration was lower than 0.1 mg∙L^(-1),the corrosion potentials of the electrode prepared by nZVIreaction was negative and the corrosion current densities increased.With the increase of Cr(Ⅵ)concentration(≥20 mg∙L^(-1)),the corrosion potentials was more positive,and the corrosion current densities decreased,which proved that the corrosion rate was slow.The Tafel test,with scanning electron microscopy,X-ray electron diffraction and X-ray photoelectron spectroscopy analysis,confirmed that the higher concentration of Cr(Ⅵ)enhanced the corrosion resistance of nZVI.This study had important significance for understanding the final product and fate of nZVIunder complex environmental systems.

关 键 词：纳米零价铁 六价铬 水相 表面化学 结构演变 

分 类 号：X703[环境科学与工程—环境工程]