Mandal Sujata, Tichit Didier, Lerner Dan A, Marcotte Nathalie
Institut Charles Gerhardt UMR 5253 CNRS/UM2/ENSCM/UM1, Matériaux Avancés pour la Catalyse et la Santé, 8 rue Ecole Normale, 34296 Montpellier Cedex 5, France.
Langmuir. 2009 Sep 15;25(18):10980-6. doi: 10.1021/la901201s.
Intercalation compounds were obtained by introduction of guest methyl orange (MO) into the interlayer space of host Mg/Al and Ni/Al layered double hydroxides (LDHs). Three synthesis methods of organic anion-LDH intercalation compounds, i.e., coprecipitation, reconstruction of the MII(Al)O mixed oxides, and anion exchange of LDH, were compared. The former method gives rise to a highly organized MO-intercalated Mg/Al LDH with an interlayer spacing of 2.43 nm and up to seven (00l) reflection orders. Reconstruction of the mixed oxide by intercalation with MO in the restored LDH was only achieved with Mg(Al)O. In this case, a competitive adsorption of MO on the external surface of the crystals was also seen. On the other hand, intercalation compounds exhibiting interlayer spacing of 2.43 nm were obtained with both Mg- and Ni-containing LDH using the anionic exchange method. The equilibrium and kinetic adsorption properties of the compounds were analyzed by UV-visible spectroscopy in anionic exchange experiments. According to the pseudo-second-order adsorption model, the amounts of adsorbed MO reach 3.82 and 2.83 mequiv/g for Mg- and Ni-containing LDHs, respectively, which are close to their respective anionic exchange capacity. The adsorption rates are on the same order of magnitude for the two LDHs (0.10-0.44 g mmol(-1) min(-1)), the equilibrium being reached in less than 60 min. The decomposition of MO by combustion of the organic moieties under an oxidizing atmosphere is delayed in Mg-containing MO-LDH hybrids when compared to the free MO molecule, showing that the thermal stability of MO species is enhanced after intercalation. In Ni-containing LDH, the main decomposition step of MO occurs 300 degrees C below that of Mg-containing LDH. This was rationalized in terms of a catalysis by the Ni-containing oxides formed during the thermal treatment. So these materials exhibit several advantages useful for the development of eco-friendly processes for the removal of dyes from effluents of textile, plastic, and paper industries.
通过将客体甲基橙（MO）引入主体Mg/Al和Ni/Al层状双氢氧化物（LDH）的层间空间，获得了插层化合物。比较了有机阴离子-LDH插层化合物的三种合成方法，即共沉淀法、MII(Al)O混合氧化物的重构法和LDH的阴离子交换法。前一种方法产生了高度有序的MO插层Mg/Al LDH，其层间距为2.43 nm，具有多达七个（00l）反射级。仅用Mg(Al)O通过在恢复的LDH中用MO插层来重构混合氧化物。在这种情况下，还观察到MO在晶体外表面的竞争性吸附。另一方面，使用阴离子交换法，含Mg和含Ni的LDH都获得了层间距为2.43 nm的插层化合物。在阴离子交换实验中，通过紫外可见光谱分析了化合物的平衡和动力学吸附性能。根据准二级吸附模型，含Mg和含Ni的LDH吸附的MO量分别达到3.82和2.83 mequiv/g，接近它们各自的阴离子交换容量。两种LDH的吸附速率处于同一数量级（0.10 - 0.44 g mmol(-1) min(-1)），在不到60分钟内达到平衡。与游离MO分子相比，在氧化气氛下，含Mg的MO-LDH杂化物中有机部分燃烧导致的MO分解延迟，这表明插层后MO物种的热稳定性增强。在含Ni的LDH中，MO的主要分解步骤比含Mg的LDH低300℃。这可以根据热处理过程中形成的含Ni氧化物的催化作用来解释。因此，这些材料具有一些优点，有助于开发用于从纺织、塑料和造纸工业废水中去除染料的环保工艺。
