Goh Kok-Hui, Lim Teik-Thye, Dong Zhili
Nanyang Technological University, Singapore.
Water Res. 2008 Mar;42(6-7):1343-68. doi: 10.1016/j.watres.2007.10.043. Epub 2007 Nov 7.
Layered double hydroxides (LDHs) are lamellar mixed hydroxides containing positively charged main layers and undergoing anion exchange chemistry. In recent years, many studies have been devoted to investigating the ability of LDHs to remove harmful oxyanions such as arsenate, chromate, phosphate, etc. from contaminated waters by both surface adsorption and anion exchange of the oxyanions for interlayer anions in the LDH structure. This review article provides an overview of the LDH synthesis methods, the LDH characterization techniques, and the recent advancement that has been achieved in oxyanion removal using LDHs, highlighting areas of consensus and currently unresolved issues. Experimental studies relating to the sorption behaviors of LDHs with various oxyanions, and the kinetic models adopted to explain the adsorption rate of oxyanions from aqueous solution onto LDHs, have been comprehensively reviewed. This review discusses several key factors such as pH, competitive anions, temperature, etc., that influence the oxyanion adsorption on LDHs. The reusability of LDHs is discussed and some mechanistic studies of oxyanion adsorption on LDHs are highlighted. The sorption capacities of LDHs for various oxyanions are also compared with those of other adsorbents. In addition, this review critically identifies the shortcomings in current research on LDHs, such as the common weaknesses in the adopted methodology, discrepancies among reported results and ambiguous conclusions. Possible improvement of LDHs and potential areas for future application of LDHs are also proposed.
层状双氢氧化物（LDHs）是含有带正电荷主层并进行阴离子交换化学的层状混合氢氧化物。近年来，许多研究致力于研究LDHs通过表面吸附以及将有害含氧阴离子（如砷酸根、铬酸根、磷酸根等）与LDH结构中的层间阴离子进行阴离子交换，从受污染水体中去除这些有害含氧阴离子的能力。这篇综述文章概述了LDH的合成方法、LDH的表征技术以及在使用LDHs去除含氧阴离子方面取得的最新进展，突出了共识领域和当前未解决的问题。与LDHs对各种含氧阴离子的吸附行为相关的实验研究以及用于解释含氧阴离子从水溶液吸附到LDHs上的吸附速率所采用的动力学模型已得到全面综述。本综述讨论了影响LDHs对含氧阴离子吸附的几个关键因素，如pH值、竞争性阴离子、温度等。讨论了LDHs的可重复使用性，并突出了一些关于含氧阴离子在LDHs上吸附的机理研究。还将LDHs对各种含氧阴离子的吸附容量与其他吸附剂的吸附容量进行了比较。此外，本综述批判性地指出了当前LDHs研究中的不足之处，如所采用方法的常见弱点、报告结果之间的差异以及模糊的结论。还提出了LDHs可能的改进方向以及未来应用的潜在领域。
