Removal of phosphate from aqueous solutions using calcined metal hydroxides sludge waste generated from electrocoagulation

Removal of heavy metals by electrocoagulation generates substantial amount of electrocoagulated metal hydroxides sludge (EMHS). This paper reports calcined EMHS as an effective adsorbent for removal of PO43− from aqueous solutions. Cumulative % removal of PO43− is investigated in a batch adsorber with different initial adsorbate concentrations, adsorbent dose, pH of the solution and adsorption temperature. Adsorption of PO43− is due to ligand exchange between the OH group on oxide surface and PO43− in the aqueous medium with formation of inner surface complex. Removal of PO43− is found to be high at lower pH values and higher temperatures indicating strong positively charged metal oxide surface at acidic pH (