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

Abstract

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.