Sequestration of naturally abundant seawater calcium and magnesium to enhance the adsorption capacity of bentonite toward environmental phosphate

Abstract

The consideration of the water energy nexus inspires environmental engineers to pursue a more sustainable remediation method for pollution control and resource recovery. In this study, a cost-effective strategy is proposed to enhance the adsorption capacity of bentonite toward environmental phosphate by sequestrating naturally abundant seawater calcium and magnesium. By adopting this method, the adsorption capacity of modified bentonite toward phosphate is enhanced by two orders of magnitude (11.45 vs. 0.11 mg g⁻¹). This achievement can be realized as a result of the intercalated seawater Ca²⁺/Mg²⁺ to screen the negative charge of aluminum phyllosilicate sheets of bentonite. The results from an additional SEM/EDX analysis and FTIR characterization imply that adsorbed phosphate is strongly associated with the intercalated Ca²⁺/Mg²⁺ in a configuration similar to that of hydroxyapatite. Moreover, our results demonstrate that the acquisition of ocean resources would be a promising and green strategy for the perspective of environmental remediation.