Abstract The aim of this study was to investigate the effect of different ions in the interlayer spaces of layered double hydroxides (LDHs) with different Mg/Al ratios on the adsorption of aqueous nicotinic acid (NAc). For this purpose, three types of LDHs were synthesized for NAc removal using the co-precipitation method with different Mg/Al ratios to include chloride or nitrate anions between the layers (Cl-LDH2:1, NO3-LDH3:1, and NO3-LDH2:1). The LDHs were characterized with Fourier transform infrared spectroscopy, X-ray diffraction, and inductively coupled plasma mass spectrometry, and the effects of initial acid concentration, time, temperature and adsorbent amount on NAc adsorption were investigated. The results showed that the Langmuir equilibrium isotherm model was the best for all three LDHs, and among the kinetic models, the pseudo-second-order agreed the most with experimental data. ΔG, ΔH, and ΔS were calculated for all LDHs, and according to the data, the adsorption of NAc was endothermic and spontaneous. When all the results were evaluated comparatively, it was found that NO3-LDH2:1, with a 2:1Mg/Al ratio and nitrate ions between the layers, has the best NAc adsorption capacity. Graphical Abstract

中文翻译：

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不同类型的 Mg/Al 层状双氢氧化物增强对烟酸的吸附：合成、平衡、动力学和热力学

摘要 本研究的目的是研究不同Mg/Al 比的层状双氢氧化物(LDHs) 层间空间中不同离子对水性烟酸(NAc) 吸附的影响。为此，使用共沉淀法合成了三种类型的 LDHs 以去除 NAc，在不同的 Mg/Al 比率下包括层间的氯离子或硝酸根阴离子（Cl-LDH2:1、NO3-LDH3:1 和 NO3- LDH2:1)。通过傅里叶变换红外光谱、X射线衍射和电感耦合等离子体质谱对LDHs进行表征，并研究了初始酸浓度、时间、温度和吸附剂用量对NAc吸附的影响。结果表明，Langmuir 平衡等温线模型对于所有三种 LDH 都是最好的，并且在动力学模型中，伪二阶与实验数据最吻合。计算所有 LDH 的 ΔG、ΔH 和 ΔS，根据数据，NAc 的吸附是吸热和自发的。对所有结果进行对比评估，发现NO3-LDH2:1，Mg/Al比为2:1，层间有硝酸根离子，对NAc的吸附能力最好。图形概要