Preparation of layered double hydroxides (LDHS) for arsenate and chromate removal

Abstract

Layer double hydroxides (LDHs) including MgFe-Cl (2:1), MgAl-Cl (2:1), ZnFe-Cl (2:1) and ZnAl-Cl (2:1) were synthesized by co-precipitation followed by calcination in air at 400 ^oC. The as-synthesized LDHs were characterized by powder X-Ray Diffraction, Scanning Electron Microscopy, Fourrier Transform Infrared spectroscopy and Brunauer Emmett Teller nitrogen adsorption method and tested for adsorption of arsenate (AsO₄^3-) and chromate (CrO₄^2-). The powder X-Ray Diffraction and Scanning Electron Microscopy revealed that the synthesized LDHs possess high crystallinity and hierarchical structure. At initial concentration ([AsO₄^3-] or [CrO₄^2-] = 100 mg/L), more than 99 % of AsO₄^3- and CrO₄^2- were removed by MgFe-Cl and MgAl-Cl. Approximately 71.62 % of AsO₄^3-and 86.54 % of CrO₄^2- were removed by ZnAl-Cl. While the removal of AsO₄^3- and CrO₄^2- by ZnFe-Cl were 78.33 % and 90.7 %,  respectively. Thus, present work has demonstrated that MgFe-Cl and MgAl-Cl is an interesting potential adsorbent application for AsO₄^3- and CrO₄^2- decontamination technology.

Keywords. Layered double hydroxides, arsenate, chromate, removal.