Decontamination of Arsenic in Actual Water Samples by Calcium Containing Layered Double Hydroxides from a Convenient Synthesis Method

Abstract

A series of calcium-containing layered double hydroxides (LDHs) and calcined product (CLDH) were synthesized using a comparative simple synthesis method (without using organic solvents and with a shortened reaction time) and applied in the adsorption of arsenic in water. The adsorption performance of arsenate on these LDHs and CLDH were studied using batch tests. The effects of various factors during the adsorption process, such as pH of the solution, dosage of materials, coexisting ions, contact time, and initial arsenate concentration, were evaluated. The maximum adsorption capacity of arsenate on three materials (CaFe-CLDH, CaFe-Cl-LDH, CaFe-NO3-LDH) were 156.0 mg·g−1, 150.5 mg·g−1, and 148.0 mg·g−1, respectively. When the concentration of CaFe-CLDH was 0.5 g·L−1, the concentration of arsenate was reduced from 5000 μg·L−1 to 10 μg·L−1 after adsorption. Moreover, when the CaFe-NO3-LDH or CaFe-Cl-LDH dosage was 1.0 g·L−1, a similar decontamination result could be achieved. The synthesized CaFe-CLDH was used to treat actual contaminated water samples from a river in a mining area north of Lengshuijiang City in Hunan Province, China. After treating using CaFe-CLDH, the residual arsenic concentration of actual water samples can fully meet the requirements for arsenic in the drinking water standards of the World Health Organization and China. This indicates that synthetic CaFe-CLDH has the potential to serve as an effective adsorbent for the removal of arsenic contamination.