Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, The Key Laboratory for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005, PR China.
Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, The Key Laboratory for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005, PR China; Department of Environment Engineering, College of the Environment and Ecology, and The Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, Xiamen University, Xiamen, 361102, PR China; School of Environmental Science & Engineering, South University of Science and Technology of China, Shenzhen, 518055, PR China.
Chemosphere. 2017 Jun;176:57-66. doi: 10.1016/j.chemosphere.2017.02.100. Epub 2017 Feb 21.
Layered double hydroxides (LDHs) intercalated with amino acids such as methionine (Met) were synthesized as new adsorbents to remediate arsenic-polluted water. This ZnAl-Met-LDHs, identified with the formula of ZnAl(OH)(Met)·0.32HO, has good thermal stability. Adsorption experiments with ZnAl-Met-LDHs showed that the residual arsenic in solution could be reduced below the regulation limit, and this adsorption process fitted Langmuir isotherm and the pseudo-second-order kinetics well. A remarkably high removal efficiency and the maximum adsorption capacity for As(III) were achieved, 96.7% and 94.1 mg/g, respectively, at 298 K. The desorption efficiency of As(III) from the arsenic-saturated ZnAl-Met-LDHs (<8.7%), far less than that of As(V), promises a specific and reliable uptake of As(III) in sorts of solutions. More importantly, a complete and in-depth spectra analysis through FTIR, XPS and NMR was conducted to explain the excellent performance of ZnAl-Met-LDHs in arsenic removal. Herein, two special chemical reactions were proposed as the dominant mechanisms, i.e., hydrogen bonding between the carboxyl group of the host Met and the hydroxyl group of As(III) or As(V), and the formation of a chelate ring between the guest As(III) and the S, N bidentate ligands of the intercalated Met in the LDHs.
层状双氢氧化物（LDHs）中插层氨基酸如蛋氨酸（Met）被合成作为一种新的吸附剂，以修复砷污染的水。这种 ZnAl-Met-LDHs，其化学式为 ZnAl(OH)(Met)·0.32HO，具有良好的热稳定性。ZnAl-Met-LDHs 的吸附实验表明，溶液中的残余砷可以降低到规定的限度以下，并且该吸附过程很好地符合朗缪尔等温线和拟二级动力学。在 298 K 时，对 As(III)的去除效率和最大吸附容量分别达到了 96.7%和 94.1 mg/g。从砷饱和的 ZnAl-Met-LDHs 中解吸 As(III)的效率（<8.7%）远低于 As(V)，这意味着在各种溶液中对 As(III)具有特殊和可靠的吸收能力。更重要的是，通过 FTIR、XPS 和 NMR 进行了全面而深入的光谱分析，以解释 ZnAl-Met-LDHs 在砷去除方面的优异性能。在此，提出了两种特殊的化学反应作为主要机制，即主体 Met 的羧基与 As(III)或 As(V)的羟基之间的氢键，以及客体 As(III)与插层 Met 的 S、N 双齿配体之间形成的螯合环。
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