State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China.
J Hazard Mater. 2010 Jul 15;179(1-3):208-14. doi: 10.1016/j.jhazmat.2010.02.081. Epub 2010 Mar 3.
The Langmuir two-site equation, X-ray photoelectron spectroscopy, and extended X-ray absorption fine structure spectroscopy have been employed to study the competitive behaviors of fluoride (F) and phosphate (P) in relation to arsenate adsorption on an Fe-Ce adsorbent as well as the mechanisms involved. The two-site isotherm revealed the presence of two kinds of adsorption sites with different binding affinities for arsenate. Both the total and low-binding-energy maximum adsorption capacities (Q and Q(1)) of arsenate decreased significantly even at a molar ratio of As/P=1:0.1. The coexistence of F, only influenced the total Q of arsenate at high simultaneous F concentrations. The fact that Fe-Ce released 0.15-0.24 mmol sulfate for every mmol arsenate adsorbed suggested that, while sulfate groups might have played a role for adsorption, surface hydroxyl groups should be the major active sites. The XPS results indicated that arsenate and P are mainly adsorbed through the substitution of Fe surface active sites, while F is mainly adsorbed through substitution of Ce surface active sites. The As k-edge EXAFS data show that the second peak of Fe-Ce after arsenate adsorption is As-Fe shell, which further supported that arsenate adsorption occurs mainly at the Fe surface active sites.
采用 Langmuir 双位方程、X 射线光电子能谱和扩展 X 射线吸收精细结构光谱研究了氟化物 (F) 和磷酸盐 (P) 与砷酸盐在 Fe-Ce 吸附剂上的吸附竞争行为及相关机理。双位等温线表明，砷酸盐存在两种具有不同结合亲和力的吸附位。即使在砷/磷摩尔比为 1:0.1 的情况下，砷酸盐的总最大吸附量 (Q) 和低结合能最大吸附量 (Q(1)) 也显著降低。F 的共存仅在高同时 F 浓度下影响砷酸盐的总 Q。Fe-Ce 每吸附 1mmol 砷酸盐就释放 0.15-0.24mmol 硫酸盐这一事实表明，虽然硫酸盐基团可能在吸附中起作用，但表面羟基基团应该是主要的活性位点。XPS 结果表明，砷酸盐和 P 主要通过取代 Fe 表面活性位点进行吸附，而 F 主要通过取代 Ce 表面活性位点进行吸附。砷 K 边 EXAFS 数据表明，砷酸盐吸附后 Fe-Ce 的第二个峰是 As-Fe 壳，这进一步证实了砷酸盐主要在 Fe 表面活性位点上吸附。
