Al₂O₃ encapsulated by calcium alginate as composite for efficient removal of phosphate from aqueous solutions: batch...

Activated alumina (Al₂O₃) has been widely used to remove aqueous anionic pollutants such as phosphate for preventing the eutrophication phenomenon. While Al₂O₃, as a fine powder material, cannot be stably packed into continuous flow treatment, which limits its practical applications. Herein, we proposed a new strategy in which Al₂O₃ was encapsulated by calcium alginate (CA) to fabricate Al₂O₃/CA composite, which has relatively large particle size and can be suitable for application in columns. The BET surface area of Al₂O₃/CA increased to 51.73 m²/g compared with 37.31 m²/g of Al₂O₃. The maximum adsorption capacity of phosphate on Al₂O₃/CA was estimated at 1.92-fold compared with that of pure Al₂O₃ by Langmuir fitting. The main mechanism of phosphate adsorption was the formation of aluminum phosphate precipitation. Moreover, the column studies showed that the adsorption of phosphate on Al₂O₃/CA was affected by the amount of outer calcium alginate, bed height, influent flow rates and phosphate concentration. This study demonstrated that Al₂O₃/CA composite has better adsorption capacity and can be used in the dynamic adsorption system as a promising approach for phosphate removal from water.