Herein, we report the synthesis of Mg/Al-CO₃ layered double hydroxides (LDHs) by the urea hydrolysis method under hydrothermal conditions at different aging times. The LDHs were characterized by different microscopic, spectroscopic, diffractometric, and thermal analysis techniques. The as-prepared LDHs were then used as adsorbents for the removal of fluoride ions from water. The adsorption process was systematically studied in terms of influences of pH, interaction time, temperature, adsorbent loading, fluoride ion concentration, and the effect of coexisting anions to understand the ideal conditions for adsorption. The adsorption process primarily followed pseudo-second-order kinetics. The Langmuir monolayer adsorption capacities of different adsorbents are in the range of 15.13–27.03 mg g^–1 at 303 K. The hydrothermal aging time has a negative impact on the adsorption capacities of the LDHs. The as-prepared LDHs are reusable up to five cycles of the fluoride ion adsorption–desorption process.

中文翻译：

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Mg / Al层状双金属氢氧化物的合成，用于吸附去除水中的氟：机理和动力学研究

本文中，我们报道了在水热条件下，在不同的老化时间下，通过尿素水解法合成的Mg / Al-CO ₃层状双氢氧化物（LDHs）。通过不同的显微镜，光谱，衍射和热分析技术对LDHs进行表征。然后将所制备的LDH用作吸附剂，用于从水中去除氟离子。从pH，相互作用时间，温度，吸附剂负载量，氟离子浓度和共存阴离子的影响等方面对吸附过程进行了系统研究，以了解理想的吸附条件。吸附过程主要遵循拟二级动力学。不同吸附剂的Langmuir单层吸附能力在15.13–27.03 mg g ^–1的范围内在303K。水热老化时间对LDHs的吸附能力有负面影响。所制备的LDH最多可重复使用五个氟离子吸附-解吸过程。