Characterization of Phosphate Adsorption on Sediments

Phosphate sorption by sediments sampled downstream of the Béni Haroun water dam was studied. Experiments were conducted to assess the effects of time, phosphate concentration, sediment dose, pH and temperature. Infrared spectroscopic analyses and sequential extractions were performed to characterize the mechanism of phosphate interaction with the sediments. The results of the macroscopic tests indicated that the fixing of phosphate ions is accomplished in two stages: the first rapid and the second slow. The kinetic data corresponded very well to a pseudo second-order equation. The equilibrium data was described by a Freundlich isotherm. The adsorption capacity increased with increasing temperature. It was highest in the pH range 7-8. In the IR spectrum, the adsorbed phosphate was characterized by a peak at approximately 1145 cm-1 indicating relatively strong bonding between the adsorbed phosphate and the sorptive sites on the surface. In the sediments, phosphorus is mainly bound to calcium.