Phosphate adsorption using calcium aluminate decahydrate to achieve low phosphate concentrations: Batch and fixed-bed column studies

In the wastewater treatment, achieving low phosphate concentrations is important to meet the increasingly stringent discharge requirements and alleviate eutrophication. Calcium aluminate decahydrate (CAH10) was prepared by a facile hydration method as a novel phosphate adsorbent. CAH10 exhibited a maximum adsorption capacity of 89.58 mg P/g at 25 degrees C in batch experiments. The phosphate adsorption followed the Elovich kinetic model and Freundlich isotherm model. The adsorption capacity at the equilibrium concentration of 0.1 mg P/L reached 3.27 mg P/g. High adsorption selectivity was obtained in the presence of common anions and humic acid. The phosphate adsorption mechanism mainly involved inner-sphere complexation and surface precipita-tion, which were supported by the SEM-EDS, FTIR and XPS results. The fixed-bed column adsorption perfor-mance demonstrated that CAH10 could effectively remove phosphate from real secondary effluent and achieve a low concentration of 0.1 mg P/L. The study indicated that CAH10 is a suitable adsorbent to remove phosphate in the context of secondary effluent polishing in wastewater treatment plants.