Phosphorus removal from wastewater using electric arc furnace slag aggregate

Electric arc furnace (EAF) slag aggregate, a waste by-product of the steel industry, exhibited a high potential for phosphorus (P) removal and had attracted considerable attention. The main objectives of this study were to evaluate the performance of using EAF slag aggregate as an adsorbent for P removal and identify its P removal capacity. A series of batch tests showed that P removal capacity of EAF slag increases gradually with the increase of pH with a range of 2-10, while the highest P removal capacity (1.94 mg/g) can be obtained at pH 12. The adsorption kinetics of P on EAF slag can be described by pseudo-second-order kinetic equations. Isothermal adsorption simulations showed that the best fitted model was the Freundlich model with a correlation coefficient of 0.9825. A continuous flow column experiment feeding a synthetic influent containing 15 mg P/L was operated for 60 days and the P removal efficiency was greater than 95% with a P removal capacity of 1.6 mg P/g slag. The results obtained in this study showed that EAF slag could act as an efficient adsorbent for P removal. Calcium phosphate precipitation depends on the release of Ca²⁺ and OH^- by the dissolution of calcium oxide in EAF slag was found to be the dominant removal mechanism for P removal.