Departamento de Química, Universidad de Guadalajara, Marcelino García Barragán 1421, C.P. 44430, Guadalajara, Jalisco, Mexico.
Universidad Autónoma de Nuevo León, UANL, CICFIM-Facultad de Ciencias Físico Matemáticas, Av. Universidad S/N, San Nicolás de los Garza, 66455, Nuevo León, Mexico.
J Environ Manage. 2021 Jun 15;288:112399. doi: 10.1016/j.jenvman.2021.112399. Epub 2021 Mar 26.
Pharmaceuticals and their by-products are recalcitrant contaminants in water. Moreover, the high consumption of these drugs has many detrimental effects on body waters and ecosystems. In this timely review, the advances in molecular engineering of layered double hydroxides (LDH) that have been used for the removal of pharmaceutical pollutants are discussed. The approach starts from the strategies to obtain homogeneous synthesis of LDH that allow the doping and/or surface functionalization of different metals and oxides, producing heterojunction systems as well as composites with carbon and silica-based materials with high surface area. Adsorption is considered as a traditional removal of pharmaceutical pollutants, so the kinetic and mechanism of this phenomenon are analyzed based on pH, temperature, ionic strength, in order to obtain new insights for the formation of multifunctional LDH. Advanced oxidation methodologies, mainly heterogeneous photocatalysis and Fenton-like processes, stand out as the more efficient even to obtain the mineralization of the drugs. The LDH have the advantage of structural memory that favors regeneration processes. The reconstruction of calcined LDH can be used to improve drug removal, through a combination of adsorption capacity/catalytic activity. A meticulous analysis of the persistence, toxicity and bioaccumulation of the most common pharmaceuticals has allowed us to highlight the ability of the LDH to remove recalcitrant drugs at relatively low concentrations (ppm, ppb), in contrast to other mixed oxide nanostructures and homogeneous oxidation processes. In this sense, the mechanism of drug removal by LDH is discussed based on the importance of the use of composites, scavenger agents, Fenton and electro-Fenton processes, membranes, thin films and coatings, among others. In addition, the ecotoxicity of LDH is also reviewed to indicate that these layered structures can exhibit biocompatibility or high toxicity depending on the adsorbed drug and ions/metals that compose them. Undoubtedly, the LDH have a unique flexible structure with adsorption capacity and catalytic activity, facts that explain the important reasons for their extensive use in the environmental remediation of pharmaceutical pollutants from water.
药品及其副产物是水中难降解的污染物。此外，这些药物的高消耗对体水和生态系统有许多不利影响。在这篇及时的综述中，讨论了用于去除药物污染物的层状双氢氧化物（LDH）的分子工程进展。该方法从获得 LDH 均匀合成的策略开始，这些策略允许掺杂和/或表面功能化不同的金属和氧化物，从而产生具有高表面积的碳和基于硅的材料的异质结系统以及复合材料。吸附被认为是一种传统的去除药物污染物的方法，因此基于 pH、温度、离子强度分析了这种现象的动力学和机制，以便为多功能 LDH 的形成获得新的见解。高级氧化方法，主要是多相光催化和类 Fenton 过程，由于能够获得药物的矿化作用，因此脱颖而出，是更有效的方法。LDH 具有结构记忆的优势，有利于再生过程。煅烧 LDH 的重构可用于通过结合吸附能力/催化活性来提高药物去除率。对最常见药物的持久性、毒性和生物累积性的细致分析使我们能够突出 LDH 在相对较低浓度（ppm、ppb）下去除难降解药物的能力，与其他混合氧化物纳米结构和均相氧化过程形成对比。从这个意义上说，根据使用复合材料、清除剂、Fenton 和电 Fenton 过程、膜、薄膜和涂料等的重要性，讨论了 LDH 去除药物的机制。此外，还回顾了 LDH 的生态毒性，以表明这些层状结构可以表现出生物相容性或高毒性，这取决于吸附的药物和构成它们的离子/金属。毫无疑问，LDH 具有独特的灵活结构，具有吸附能力和催化活性，这两个事实解释了它们在水中药剂污染物的环境修复中广泛应用的重要原因。
