Removal of Phosphate from Aqueous Solution Using Iron-Oxide-Coated Sand Filter Media: Batch Studies

Iron-oxide-coated sand (IOCS) filter media was investigated to remove phosphate from aqueous solutions in batch experiments. Adsorbability of phosphate by IOCS-1 and IOCS-2 (prepared by different coating process) was compared in order to gain an available coating process to prepare modified sand filter media for effective removal of phosphate. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were used to investigate the surface properties of the coated layer. An energy dispersive X-ray (EDAX) analysis was also used for characterizing phosphate adsorption on IOCS surface. Effects of initial pH, contact time and dose of IOCS on the removal of phosphate were studied. The results showed that the removal efficiency of phosphate by IOCS-1 was greater than IOCS-2, thus, further experiments was carried out using IOCS-1. The adsorption of phosphate by IOCS-1 can be well described by Langmuir, Freundlich and Temkin isotherm at various temperatures. For IOCS-1, the adsorption followed the pseudo-second-order reaction kinetics model. Moreover, the phosphate adsorbed IOCS-1 could be regenerated by alkali solution. Results of this study can provide an effective technology based on adsorption/filtration using IOCS filter media for phosphate removal from water and wastewater.