Adsorption ability for several harmful anions and thermal behavior of Zn-Fe layered double hydroxide

摘要

A zinc-iron layered double hydroxide(Zn-Fe LDH)with sulfate as the interlayer ainon has been prepared by the coprecipita-tion method.The LDH was dehydrated in three steps below 300°C and transformed to the amorphous phase.The recrystalliza-tion from the amorphous phase to ZnO(zincite),ZnFe2O4(spinel)and Zn3O(SO4)2 occurred at approximately 450 C.Furthermore,Zn3O(SO4)2 decomposed into ZnO,SO2 and O2 above 700°C.The adsorption ability of the Zn-Fe LDH was studied for several harmful anions(phosphate,chromate,borate,fluoride,selenate and arsenate)in aqueous solution,and it showed high selectivity for phosphate,chromate and selenate ions.The Zn-Fe LDH was found to be stable over a wide pH range(pH=2-12).The adsorption ability for phosphate ions depends on the initial pH and it increases with decreasing pH.