Ethylene glycol-induced metal alkoxides via phase-transfer catalyst as multi-talented adsorbents for boosted adsorption performance of toxic anions/oxyanions from waters

An outstanding multi-talented complex material for the removal of several toxic anions is of greater interest than that used for single-pollutant adsorption. Here, we report the synthesis of highly stable lanthanum- and zirconium-alkoxides (La-Alk and Zr-Alk) using a strong‐field ligand and the electron-donating nature of ethylene glycol (EG) through a phase-transfer catalyst, dodecyltrimethylammonium bromide (DTAB), was employed to boost the adsorption densities of various toxic anions, such as arsenate (AsO₄³⁻), arsenite (AsO₃³⁻), dichromate (Cr₂O₇²⁻), phosphate (PO₄³⁻), fluoride (F⁻), and selenate (SeO₄²⁻) in water by the application of the basic concept of the HSAB principle. The adsorbents had been characterized before and after adsorption of highly concentrated toxic anions (each of 1 mM) using XPS, PXRD, FTIR, BET, and SEM, and the possible adsorption mechanism was elucidated. The coordination of EG over La(OH)₃ and ZrO₂ was confirmed by the FTIR and PXRD patterns. The SEM images of La-Alk revealed a regular flower-like structure, whereas the structure of Zr-Alk was spherical, which differs from their precursors or pristine forms. The selectivity and stability of the materials were confirmed by a study on the coexisting anions in a binary mixture solution and reusability studies by repeated use, respectively. We found that La-Alk was more selective for the adsorption of arsenate, dichromate, phosphate, fluoride, and selenate, whereas Zr-Alk was highly selective for arsenite at a concentration of 1 mM. We are certain that the multifunctional La- and Zr-Alk nanocomplexes developed in this study will be useful for practical applications in water and wastewater streams.