Treatment of Wastewater Containing Phosphate by Fly Ash Adsorbent Loaded with Ferrihydrite

The characteristics of phosphate adsorption on fly ash loaded with ferrihydrite were investigated. The influential factors such as the dosage of adsorbent, concentration of phosphate, solution pH, co-existing anions in solution on removal of phosphate ion were examined. The adsorption isotherm of phosphate on fly ash loaded with ferrihydrite could be described by the Langmuir and Freundlich equations. The adsorption kinetic data could be described by the Lagergren second-order rate equation. The adsorbent had perfect properties in phosphate adsorption capacity, the results showed that the removal rate of phosphate could be over 97% in the conditions of adsorbent dosage 8.0 g/L, and pH=3. When the concentrations of co-existing anions were 5～30 mg/L, SO42-, NO32-, CO32-and Cl-in the solution had almost no effect on the adsorption of phosphate on fly ash loaded with ferrihydrite, but SiO32-caused greater phosphate removal rate decrease.