The simultaneous anionic and cationic dyes removal with Zn-Al layered double hydroxides

ZnAl layered double hydroxides (LDH) as-synthesized and in calcined forms with a cationic ratio of 2-4 were applied for the study of anionic indigo carmine (IC) and cationic methylene blue (MB) dyes removal from aqueous media in batch mode. The highest adsorption of IC was observed for ZnAl LDH calcined at 600 degrees C with Zn: Al ratio 2. The adsorption of IC on calcined ZnAl LDH was accompanied by the reconstruction of the layered structure. The sorption capacity of calcined ZnAl LDH to cationic dye MB was extremely low in single dye solutions. The highly effective removal of MB with calcined ZnAl LDHs was achieved from the solutions that contained MB and IC dyes. The optimal IC: MB molar ratio for the total removal of both dyes was found to be 2:1. IC - modified ZnAl LDH demonstrated high activity for the removal of MB from its solutions. The total removal of both dyes was 930 and 320 mg/g for IC and MB, correspondingly.