Highly efficient Cd2+ and Cu2+ removal by MgO-modified tobermorite in aqueous solutions

Abstract

In this work, nanosized MgO modified TOB was fabricated through a gelation-calcination method for removing Cd2+ and Cu2+ from aqueous solutions. The modified TOB exhibited superior adsorption performance, adsorption equilibrium could be achieved within 30 min and 60 min for Cd2+ and Cu2+, respectively. The maximum theoretical adsorption capacities of the modified TOB were 1428.57 mg/g for Cd2+ and 909.09 mg/g for Cu2+. Batch adsorption data fitted the pseudo-second-order model and Langmuir isotherm model well, indicating a chemical adsorption was undergoing in the system. The modified TOB could efficiently remove target contaminants over a wide pH of 2.0–8.0. Even at a pH of 2.0, the removal efficiency of Cd2+ and Cu2+ was 95.30% and 99.98%, respectively. XRD, FTIR, XPS, SEM and TEM analyses revealed that surface precipitation in forms of Cd(OH)2, CdCO3 and Cu4(SO4)(OH)6·2 H2O and cation exchange with Mg2+ and Ca2+ were the primary mechanisms of Cd2+ and Cu2+ adsorption. Therefore, it was anticipated that the modified TOB had a promising prospect for the broad application in heavy metal containing wastewater treatment.