Tuning Mg-Al layered double hydroxides synthesized from the novel ionic liquid-based surfactant-free microemulsion for efficiently phosphate removal in aqueous solutions

Abstract

Phosphorus pollution is likely to lead to eutrophication of water bodies and phosphate rock resources shortages. In this work, the 1-butyl-3-dodecylbenzimidazole chloride was employed as nonpolar phase for the preparation of 1-butyl-3-dodecylbenzimidazole chloride-ethylamine nitrate-water ionic liquid-based surfactant-free microemulsion. Ionic liquid-based surfactant-free microemulsion was employed to tune the production of Mg-Al-layered double hydroxides (Mg-Al-LDH) nanosheets. The resulting Mg-Al-LDH displayed an enriched pore structure of 11.31 nm and large BET surface area of 134.4 m2·g−1, it is assumed that the phosphorus was remarkable removal from the aqueous solutions using the prepared Mg-Al-LDH. The impacts of initial concentration of phosphate, initial pH of the solution, adsorbent dosage, contact time as well as temperature on the phosphate adsorption via applying Mg-Al-LDH were examined. The kinetics together with thermodynamics of phosphate adsorption on Mg-Al-LDH can be interpreted utilizing Langmuir and pseudo second-order models. The maximum phosphorus adsorption capacity of Mg-Al-LDH was 147.89 mg·g−1, which proved that phosphorus adsorption capacity employing the as-produced Mg-Al-LDH is 2.34 times higher than conventional LDHs. In addition, a study of its mechanism revealed that its adsorption of phosphate is primarily due to inner-sphere complexation, ligand exchange and electrostatic interaction between the produced Mg-Al-LDH and the phosphate, which was ascribed to its rich pore structure and large specific surface area. In conclusion, the prepared Mg-Al-LDH using the ionic liquid-based surfactant-free microemulsion is a highly promising adsorbent for removing the phosphorus from wastewater.