Dávila-Jiménez M M, Elizalde-González M P, Mattusch J, Morgenstern P, Pérez-Cruz M A, Reyes-Ortega Y, Wennrich R, Yee-Madeira H
Facultad de Cs. Químicas, Universidad Autónoma de Puebla, Apdo. Postal J-55, 72571 Puebla, Mexico.
J Colloid Interface Sci. 2008 Jun 15;322(2):527-36. doi: 10.1016/j.jcis.2008.03.042. Epub 2008 Mar 29.
Adsorption methods have been developed for the removal of arsenic from solution motivated by the adverse health effects of this naturally occurring element. Iron exchanged natural zeolites are promising materials for this application. In this study we introduced iron species into a clinoptilolite-rich zeolitic tuff by the liquid exchange method using different organic and inorganic iron salts after pretreatment with NaCl and quantified the iron content in all trials by XRF spectroscopy. The materials were characterized by XRD, FTIR, FTIR-DR, UV-vis, cyclic voltammetry, ESR and Mössbauer spectroscopies before and after adsorption of arsenite and arsenate. The reached iron load in the sample T+Fe was %Fe(2)O(3)-2.462, n(Fe)/n(Al)=0.19, n(Si)/n(Fe)=30.9 using FeCl(3), whereby the iron leachability was 0.1-0.2%. The introduced iron corresponded to four coordinated species with tetrahedral geometry, primarily low spin ferric iron adsorbing almost 12 mug g(-1) arsenite (99% removal) from a 360 mug(As(III)) L(-1) and 6 mug g(-1) arsenate from a 230 mug(As(V)) L(-1). Adsorption of arsenite and arsenate reached practically a plateau at n(Fe)/n(Si)=0.1 in the series of exchanged tuffs. The oxidation of arsenite to arsenate in the solution in contact with iron modified tuff during adsorption was observed by speciation. The reduction of ferric iron to ferrous iron could be detected in the electrochemical system comprising an iron-clinoptilolite impregnated electrode and was not observed in the dried tuff after adsorption.
由于这种天然存在的元素对健康有不利影响，人们已经开发出吸附方法用于从溶液中去除砷。铁交换天然沸石是用于此应用的有前途的材料。在本研究中，我们在使用NaCl预处理后，通过液体交换法使用不同的有机和无机铁盐将铁物种引入富含斜发沸石的沸石凝灰岩中，并通过XRF光谱对所有试验中的铁含量进行了定量。在吸附亚砷酸盐和砷酸盐之前和之后，通过XRD、FTIR、FTIR-DR、UV-vis、循环伏安法、ESR和穆斯堡尔光谱对材料进行了表征。使用FeCl₃时，样品T + Fe中的铁负载量为%Fe₂O₃ - 2.462，n(Fe)/n(Al)=0.19，n(Si)/n(Fe)=30.9，铁的浸出率为0.1 - 0.2%。引入的铁对应于具有四面体几何结构的四配位物种，主要是低自旋铁离子，从360μg(As(III))L⁻¹溶液中吸附了近12μg g⁻¹亚砷酸盐（去除率99%），从230μg(As(V))L⁻¹溶液中吸附了约6μg g⁻¹砷酸盐。在一系列交换凝灰岩中，当n(Fe)/n(Si)=0.1时，亚砷酸盐和砷酸盐的吸附实际上达到了平台期。通过形态分析观察到，在吸附过程中与铁改性凝灰岩接触的溶液中亚砷酸盐氧化为砷酸盐。在包含铁斜发沸石浸渍电极的电化学系统中可以检测到三价铁还原为二价铁，而在吸附后的干燥凝灰岩中未观察到这种情况。
