Adsorption Characteristics of Phosphate Based on Al-Doped Waste Ceramsite: Batch and Column Experiments

Phosphorus widely existing in rainfall and wastewater impacts the water environment. In this study, sludge, cement block, and coal fly ash were employed as ceramsite material to synthesize Al-doped waste ceramsite (Al-ceramsite) for removing phosphate (PO43--P) from aqueous solutions. Batch static adsorption-desorption experiments were designed to investigate the effect of various parameters such as Al-ceramsite dosage, PO43--P concentration, temperature, initial pH, coexisting ions, and desorbents on the removal of PO43--P. Also, the fate of PO43--P removal efficiency in actual rainwater was studied through dynamic adsorption column experiments using Al-ceramsite. Results showed that Al-ceramsite could remove PO43--P efficiently under the optimum parameters as follows: Al-ceramsite dosage of 40 g/L, initial PO43--P concentration of 10 mg/L, temperature of 25 degrees C, and pH of 5. Besides that, the Al-ceramsite could completely remove PO43--P in actual rainwater, and the effluent PO43--P concentration was lower than the environmental quality standards for surface water Class I (0.02 mg/L). The adsorption characteristics of Al-ceramsite on PO43--P by X-ray photoelectron spectroscopy (XPS) were further explained. As a result, ligand exchange and complexation were confirmed as the main PO43--P removal mechanism of Al-ceramsite. Thus, Al-ceramsite was prepared from industrial waste and has shown excellent potential for phosphorus removal in practical applications.