Selective and Efficient Removal of Toxic Oxoanions of As(III), As(V), and Cr(VI) by Layered Double Hydroxide Intercalated with MoS42–,Chemistry of Materials

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Selective and Efficient Removal of Toxic Oxoanions of As(III), As(V), and Cr(VI) by Layered Double Hydroxide Intercalated with MoS42–
Chemistry of Materials ( IF 7.2 ) Pub Date : 2017-03-30 00:00:00 , DOI: 10.1021/acs.chemmater.7b00618
Lijiao Ma ₁ , Saiful M. Islam ₂ , Hongyun Liu ₁ , Jing Zhao ₂ , Genban Sun ₁ , Huifeng Li ₁ , Shulan Ma _{1,

2} , Mercouri G. Kanatzidis ₂

Affiliation

We demonstrate the highly selective and exceptionally efficient capture of toxic oxoanions of As(III)/As(V) (HAsO₃^2–/HAsO₄^2–) and Cr(VI) (CrO₄^2–) by the Mg/Al layered double hydroxide (Mg/Al-LDH) intercalated with MoS₄^2– (MoS₄-LDH). The MoS₄-LDH exhibits very high removal rates (>99%) of As(III), As(V), and Cr(VI) from complex aqueous solutions. In the presence of many competing nontoxic anions such as SO₄^2–, NO₃^–, and Cl^–, remarkable selectivity for HAsO₃^2–, HAsO₄^2–, and CrO₄^2– is observed. Highly concentrated As(III) and Cr(VI) can be rapidly reduced to <10 ppb, much below the permitted level for drinking water. The maximum adsorption capacities for As(III), As(V), and Cr(VI) are 99, 56, and 130 mg/g, respectively. Sorption isotherms for As(III) and As(V) agree with the Langmuir model, suggesting a monolayer adsorption on the sorbent. The adsorptions of As(V) and Cr(VI) are exceptionally rapid, showing >93% removals within 1 min and >96% removal within 5 min. Sorption kinetics for these oxoanions follows a pseudo-second-order model consistent with a chemisorption involving possible As–S and Cr–S bonding. The Cr(VI) adsorption is accompanied by an oxidation/reduction reaction with MoS₄^2– resulting in Cr(III) species. The order of rate constants (k₂) is Cr(VI) > As(V) > As(III), which reflects their respective adsorption rates. The S–As and S–Cr interactions and the reduction of Cr(VI) to Cr(III) contribute to the effective uptakes. These results make the MoS₄-LDH material a compelling candidate for application in remediation of water polluted with arsenic and hexavalent chromium.

中文翻译：

嵌入MoS ₄^2的层状双氢氧化物选择性高效去除As（III），As（V）和Cr（VI）的有毒氧阴离子

我们证明了通过层状Mg / Al可以高度选择性且异常有效地捕获As（III）/ As（V）（HAsO ₃^2– / HAsO ₄^2–）和Cr（VI）（CrO ₄^2–）的有毒氧阴离子双氢氧化物（Mg / Al-LDH）嵌入MoS ₄^2–（MoS ₄ -LDH）。MoS ₄ -LDH表现出从复杂水溶液中非常高的As（III），As（V）和Cr（VI）去除率（> 99％）。在许多竞争无毒阴离子如SO存在₄^2-，NO ₃^-和Cl ^-，为HAsO显着的选择性₃^2-，HAsO ₄^{2 –}和CrO ₄^2–被观察到。高浓度的As（III）和Cr（VI）可以迅速降低至<10 ppb，远低于饮用水的允许水平。As（III），As（V）和Cr（VI）的最大吸附容量分别为99、56和130 mg / g。As（III）和As（V）的吸附等温线与Langmuir模型一致，表明吸附剂上存在单层吸附。As（V）和Cr（VI）的吸附非常快，在1分钟内显示> 93％的去除，在5分钟内显示> 96％的去除。这些含氧阴离子的吸附动力学遵循伪二级模型，与涉及可能的As-S和Cr-S键的化学吸附相一致。Cr（VI）的吸附伴随着与MoS ₄^2–的氧化/还原反应产生Cr（III）物质。速率常数（k ₂）的顺序为Cr（VI）> As（V）> As（III），反映了它们各自的吸附速率。S–As和S–Cr相互作用以及Cr（VI）还原为Cr（III）有助于有效吸收。这些结果使MoS ₄ -LDH材料成为用于修复被砷和六价铬污染的水的引人注目的候选材料。

更新日期：2017-03-30

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