Efficient removal of arsenic (III) from aqueous solutions by new layered hydroxides (Ca–Fe–Cl LDHs)

Abstract

A novel bimetallic layered hydroxide (Ca–Fe–Cl LDHs) was prepared for the removal of arsenic (III) (As (III)) from an aqueous solution. The materials were characterized by SEM, XPS, TGA, and FTIR to analyze this removal mechanism. The effects of pH, contact time, dosage, initial concentration, and coexisting anions on the removal of As (III) by Ca–Fe–Cl LDHs were explored. The results demonstrated that Ca–Fe–Cl LDHs exhibited good performance with a maximum adsorption capacity of 22.1 mg/g, and adding 1.26 g/L Ca–Fe–Cl LDHs can reduce the concentration of arsenic solution (0.4 mg/L) to below 0.01 mg/L, and the removal rate of As (III) was not affected within the pH range of 2 − 12. The Langmuir model and the pseudo second-order dynamics model could better fit the experimental data with R2 equal to 0.969 and 0.885, respectively. Coexisting ions, such as HPO4 2−, SO4 2−, CO3 2−, and NO3 −could inhibit material adsorption and reduce the removal efficiency of As (III). Under experimental conditions, the concentration of 0.01 M Na2CO3 solution was used for regeneration, and the efficiency of As (III) removal was maintained above 90% after 5 regenerations.