Characterization of phosphate adsorption on goethite macroscopic and spectroscopic analyses

The present study describes phosphate adsorption on goethite. macroscopic experiments were carried out in order to study the effects of contact time,ph,phosphate concentration and competitive ions. infrared analyses were performed to characterize the phosphate interaction with the goethite surface in the absence and in the presence of competitive ions. the evolution of phosphate sorption with time is characterized by two steps. in first,the rate of phosphate removal is rapid then,a slower process is observed. the kinetics can be described by the pseudo second order model. the presence of oxalate ions implies a decrease in phosphate sorption in acidic ph. however,no competitive effect is observed in the presence of sulfate ions. phosphate removal increases in the presence of lead and decreases in the presence of cadmium and copper. at ph > 4,spectroscopic analyses show the formation of monodentate inner sphere surface complex in the absence of competitive ions and in the presence of lead,chromate and sulfate. however,in the presence of oxalate,copper and cadmium,the phosphate surface complex converts to outer sphere complex.