Abstract:
This research investigated the adsorption of three anions, which are phosphate, chromate, and arsenate by using Mg/Al layered double hydroxides (Mg/Al LDHs) and Mg/Al layered double hydroxides accumulate on magnetite (Mg/Al LDHs-Fe). Adsorption rate of three anions by using Mg/Al LDHs was faster than Mg/Al LDHs-Fe because Mg/Al LDHs had a more positive charge on the surface than Mg/Al LDHs-Fe. Batch adsorption studies revealed that both materials had the same equilibrium time, but Mg/Al LDHs had more adsorption capacity than that for Mg/al LDHs-Fe. Adsorption capacities of three anions were decreased by increasing of pH due to the reducing of positive charge on the materials surface. For mixed anion solution, phosphate can be adsorbed by both materials with the highest adsorption capacity following with arsenate and chromate, respectively. The tri-valence structures of phosphate and arsenate might promote adsorption capacity of those anions, while chromate was di-valance anion. Hence, phosphate and arsenate can interact with protonated metal hydroxide on adsorbent surfaces. For reuse experiment, adsorption capacities of three anions were decreased around 50% compared with virgin adsorbents.