Adsorption and recovery of phosphate from aqueous solution by katoite: Performance and mechanism

Abstract

Phosphate removal and recovery from wastewater is an effective approach to alleviate eutrophication and overcome the future scarcity of phosphorus. Katoite, a kind of calcium aluminate hydrate, was synthesized and examined as a novel adsorbent to remove phosphate from aqueous solution and recover phosphate as potential slow-release fertilizer. Batch experiments showed that the maximum phosphate adsorption capacity of katoite reached 111.51 mg P/g. Also, a high equilibrium adsorption capacity of 80.14 mg P/g was obtained at the initial concentration of 10 mg P/L. The adsorption could be well described by the Elovich kinetic model and Redlich-Peterson isotherm model. Thermodynamic study suggested that the adsorption was an endothermic process and occurred favorably and spontaneously. Moreover, the adsorption was almost independent of the ionic strength and showed high selectivity for phosphate in solutions containing common coexisting anions. The phosphate adsorption on katoite could be attributed to inner-sphere complexation and surface precipitation, which were further suggested by the SEM-EDS, FTIR and XPS analysis. Desorption experiments results indicated the possible plant availability and successive release property of the phosphate adsorbed on the surface of katoite. Overall, the study suggested that katoite is a promising candidate for phosphate adsorption and subsequent recovery as a slow-release phosphorus fertilizer.