针铁矿和赤铁矿吸附As(V)的EXAFS研究  

EXAFS study on arsenite(V) adsorption onto goethite and hematite

作　　者：杨旺 林金如 姚慧 Yuanming Pan Emilio Heredia Roman Chernikov 张丹妮[2] 王少锋[2] 贾永锋[2] YANG Wang;LIN Jinru;YAO Hui;Yuanming Pan;Emilio Heredia;Roman Chernikov;ZHANG Danni;WANG Shaofeng;JIAYongfeng(College of Applied Chemistry,Shenyang University of Chemical Technology,Shenyang 110142,China;Key Laboratory of Pollution Ecology and Environmental Engineering,Institute of Applied Ecology,Chinese Academy of Sciences,Shenyang 110016,China;Department of Geological Sciences,University of Saskatchewan,Saskatoon SK S7N 5E2,Canada;Canadian Light Source,University of Saskatchewan,Saskatoon SK S7N 0X4,Canada)

机构地区：[1]沈阳化工大学应用化学学院,沈阳110142 [2]中国科学院沈阳应用生态研究所污染生态与环境工程重点实验室,沈阳110016 [3]Department ofGeologicalSciences,University ofSaskatchewan,Saskatoon SKS7N 5E2,Canada [4]Canadian LightSource,University ofSaskatchewan,Saskatoon SKS7N 0X4,Canada

出　　处：《核技术》2021年第12期1-11,共11页Nuclear Techniques

基　　金：辽宁省科学事业公益研究基金(No.20170008);辽宁省"兴辽英才计划"项目(No.XLYC1807025);国家自然科学基金面上项目(No.41877393,No.41673130)资助。

摘　　要：砷是一种有毒污染物,其在铁氧化物表面的吸附是影响其迁移转化行为的重要因素。针铁矿和赤铁矿是自然界中广泛存在的稳定氧化铁矿物,它们具有粒径小、比表面积大、活性基团多等特性,可用做吸附剂。在不同pH和不同铁砷摩尔比的实验条件下,用针铁矿和赤铁矿吸附五价砷As(V),结果表明:实验所用的两种吸附剂均呈现吸附量随铁砷摩尔比升高而降低的现象,而在酸性pH条件下的砷吸附量均大于其在碱性pH条件下的吸附量;在相同的实验条件下,针铁矿对砷的吸附量要大于赤铁矿对砷的吸附量。进一步通过扩展X射线吸收精细结构光谱(Extended X-ray Absorption Fine Structure Spectroscopy,EXAFS)观测砷在针铁矿和赤铁矿上吸附后形成的络合物的分子结构,结果显示:砷与针铁矿和赤铁矿中的铁氧八面体之间的配位数均接近1,不同样品中As-Fe键的长度范围为3.29~3.31?,表明As(V)在针铁矿和赤铁矿表面吸附后主要形成单齿单核络合物,且该结构与吸附p H和铁砷摩尔比无关。[Background] Arsenic(As) is one of the most toxic pollutants in the environment. Its adsorption on the surface of iron oxyhydr(oxides) is an important factor affecting its migration and transformation behavior. Goethite and hematite are ubiquitous in soil, groundwater and aquatic sediments. They all have the characteristics of small particle size, large specific surface area, and many active groups, thus can be used as adsorbents for As. [Purpose]This study aims to investigate the behaviors of As(V) adsorbed on these two minerals, and determine its complex structures by extended X-ray absorption fine structure spectroscopy(EXAFS). [Methods] First of all, adsorbents made from goethite and hematite were prepared for experimental measurement of As adsorption at different pH values and Fe/As molar ratios. Then the content of As in the solid phase after adsorption was measured by X-ray fluorescence spectrometer while the surface morphology of the adsorbent was characterized by scanning electron microscope(SEM). Finally, extended X-ray absorption fine structure spectroscopy(EXAFS), obtained at BioXAS beamline of Canadian synchrotron radiation source, was used to detect the coordination numbers of As and Fe adsorbed on the two adsorbents.[Results] The results show that the adsorption capacity of these two adsorbents for As(V) under acidic pH is greater than that of the adsorbent under alkaline conditions. The adsorption capacity of the two adsorbents decreases with the increase of the Fe/As molar ratio. As(V) adsorption capacity of goethite is larger than that of hematite under the same adsorption pH and Fe/As molar ratio. The EXAFS data shows that the coordination numbers of As-Fe in both goethite and hematite are close to 1, and the distance of As-Fe in different samples is in the range of 3.29~3.31 ?. [Conclusions] Arsenic mainly forms monodentate-mononuclear complexes after adsorption on the surface of goethite and hematite, which is independent of the experimental pH values and the Fe/As molar ratios.

关 键 词：AS(V) 针铁矿 赤铁矿 X射线吸收精细结构光谱 吸附 

分 类 号：TL99[核科学技术—核技术及应用] X53[环境科学与工程—环境工程]