Phosphate removal from industrial wastewaters using layered double hydroxides.

In the present study, Mg–Al and Zn–Al layered double hydroxides (LDH) were synthesized by the co–precipitation method and employed to remove phosphate from synthetic aqueous solutions and industrial wastewaters. LDH were characterized by X–ray diffraction (XRD), N₂ adsorption/desorption isotherms (BET method), thermal analyses (TG–DTA) and Fourier transform infrared spectroscopy (FTIR). XRD and TG–DTA analysis showed that Mg–Al and Zn–Al formed the LDH structure. Experimental adsorption data indicated that pseudo–second order model best described phosphate adsorption kinetics. Data of equilibrium experiments fitted well to Sips and Freundlich models for Mg–Al and Zn–Al, respectively. The effect of co–existing anions on the phosphate adsorption capacity was analyzed by utilizing industrial wastewater. The results showed that the phosphate removal decreases in the presence of other anions. Mg–Al adsorbent exhibited 74% removal of phosphate with a dosage of 5 g/L in industrial wastewater. [ABSTRACT FROM AUTHOR]