Enhanced arsenite removal in water using multifunctional UiO-66-NH2 embedded chitosan biocomposite beads: defects, oxidation and adsorption

Water decontamination from arsenic-contaminated groundwater is critical to the health of millions of households worldwide. However, efficiently removing the low-adsorbing As(III) remains challenging. Herein, a multifunctional biocomposite bead UiO-66-NH 2 -Cl@PCB integrating defects, oxidation and adsorption properties was prepared to effectively remove As(III). The N -chlorosulfonamide bound within the embedded UiO-66-NH 2 -Cl oxidizes the lower-adsorbing As(III) to As(V), which could be effectively adsorbed by the defect-rich MOF, while the porous chitosan bead (PCB) host ensures the utilisation of the reactive sites of UiO-66-NH 2 -Cl. Using 1 g/L of UiO-66-NH 2 -Cl@PCB, 1 mg/L of As(III) can be reduced to under 10 μg/L in 300 min. Furthermore, similar As(III) removal efficiencies were achieved across a wide pH spectrum (3–9) or in the presence of interfering substances (anions, cations, organic matter). High concentrations of phosphate will inhibit its performance. As(III) removal followed the Freundlich isotherm modal, and its maximum removal capacity reached 58.09 mg/g at pH 7. Furthermore, at equilibrium concentrations of 10 μg/L, its As(III) removal capacity exceeded 10 mg/g. UiO-66-NH 2 -Cl@PCB can purify the As(III)-spiked groundwater to meet the drinking standard level. Using NaOH solution for regeneration, the removal efficiency maintained above 70 % in the fifth cycle. Additional chlorination treatment can significantly improve reusability. 2.4 g of UiO-66-NH 2 -Cl@PCB packed fixed-bed column was capable of purifying 3820 BV of groundwater containing 100 μg/L of As(III). The proposed UiO-66-NH 2 -Cl@PCB has the potential to be an easy-to-use and reliable material for efficient As(III) removal.