Fabrication, performance and mechanism of MgO meso-/macroporous nanostructures for simultaneous removal of As(iii) and F in a groundwater system

The coexistence of arsenic and fluoride in groundwater has attracted extensive attention worldwide, and it is of crucial importance to efficiently remove them. In this study, hierarchically meso-/macroporous MgO using nanosheets as building blocks and with pore size distribution in the range of 10 to 150 nm was synthesized. The maximum adsorption capacities for As(iii) and F were found to be about 540.9 mg g^-1 (7.22 mmol g^-1) and 290.67 mg g^-1 (15.30 mmol g^-1), respectively. Research indicated that a broad and multimodal pore size distribution provided suitable channels for ion diffusion, which were conducive to the proximity of contaminants to the internal surfaces of the adsorbent. Thermodynamic adsorption models demonstrated that two types of active sites coexisted on the MgO surface. The adsorption mechanisms of As(iii) and F were proposed to include surface complexation as well as exchanges with hydroxyl and carbonate groups. Moreover, the removal rates of As(iii) and F for a co-contaminated groundwater sample were determined to be 98.9% and 95%, respectively.