Makris Konstantinos C, Sarkar Dibyendu, Parsons Jason G, Datta Rupali, Gardea-Torresdey Jorge L
Environmental Geochemistry Laboratory, Earth and Environmental Science Department, University of Texas, San Antonio, TX 78249, USA.
J Colloid Interface Sci. 2007 Jul 15;311(2):544-50. doi: 10.1016/j.jcis.2007.02.078. Epub 2007 Apr 19.
Drinking-water treatment residuals (WTRs) present a low-cost geosorbent for As-contaminated waters and soils. Previous work has demonstrated the high affinity of WTRs for As, but data pertaining to the stability of sorbed As is missing. Sorption/desorption and X-ray absorption spectroscopy (XAS), both XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure) studies, were combined to determine the stability of As sorbed by an Fe-based WTR. Arsenic(V) and As(III) sorption kinetics were biphasic in nature, sorbing >90% of the initial added As (15,000 mg kg(-1)) after 48 h of reaction. Subsequent desorption experiments with a high P load (7500 mg kg(-1)) showed negligible As desorption for both As species, approximately <3.5% of sorbed As; the small amount of desorbed As was attributed to the abundance of sorption sites. XANES data showed that sorption kinetics for either As(III) or As(V) initially added to solution had no effect on the sorbed As oxidation state. EXAFS spectroscopy suggested that As added either as As(III) or as As(V) formed inner-sphere mononuclear, bidentate complexes, suggesting the stability of the sorbed As, which was further corroborated by the minimum As desorption from the Fe-WTR.
饮用水处理残余物（WTRs）是一种用于处理受砷污染水体和土壤的低成本地质吸附剂。此前的研究已证明WTRs对砷具有高亲和力，但有关吸附态砷稳定性的数据尚缺。本研究结合了吸附/解吸以及X射线吸收光谱（XAS）（包括X射线吸收近边结构（XANES）和扩展X射线吸收精细结构（EXAFS））研究，以确定铁基WTRs吸附的砷的稳定性。砷（V）和砷（III）的吸附动力学本质上是双相的，反应48小时后吸附了初始添加砷（15,000 mg kg⁻¹）的90%以上。随后在高磷负载（7500 mg kg⁻¹）下进行的解吸实验表明，两种砷形态的砷解吸量均可忽略不计；吸附态砷的解吸量约<3.5%；少量解吸的砷归因于丰富的吸附位点数量。XANES数据表明，最初添加到溶液中的砷（III）或砷（V）的吸附动力学对吸附态砷的氧化态没有影响。EXAFS光谱表明，以砷（III）或砷（V）形式添加的砷形成了内球单核双齿络合物，这表明吸附态砷具有稳定性，铁基WTRs中砷的最低解吸量进一步证实了这一点。
