Enhanced removal of As(iii) by manganese-doped defective UiO-66 coupled peroxymonosulfate: multiple reactive oxygen species and system stability

Abstract

Structurally defective UiO-66 has garnered significant interest due to its remarkable performance in the domains of adsorption and catalysis. In this research, the successful synthesis of Mn-doped defective UiO-66 (Mn₁D₄₀UiO-66) was confirmed by XRD and FTIR characterization. More than 95% of As(III) (C₀ = 1.1 mg L⁻¹) was removed in 1 h (C_catalyst = 0.2 g L⁻¹, C_PMS = 0.1 mM). Compared with the original UiO-66, when coupled with peroxymonosulfate (PMS), Mn₁D₄₀UiO-66 accelerated the generation of reactive oxygen species (ROS), resulting in an increase in As(III) removal efficiency by about 50%. XPS spectra and EXAFS spectra indicated that As(III) adsorbed in the Mn₁D₄₀UiO-66/PMS system was fully oxidized to As(V) and the adsorption was attributed to As–O–Zr coordination. Several types of ROS (·OH, SO₄˙⁻, and O₂˙⁻) generated by PMS activation acted collectively on As(III) oxidation, so a single ROS scavenger did not have a marked inhibitory effect on As(III) removal. In addition, the system maintained efficiency over a broad pH range (3–11), and retained an arsenic removal rate higher than 89.8% even in the presence of high concentrations of several anions (SO₄²⁻/Cl⁻/NO₃⁻, 10 mM). Meanwhile, 99.3% of the As(III) could be removed by Mn₁D₄₀UiO-66 at extremely high humic acid concentrations (100 mg L⁻¹). Due to the excellent stability of the material, only trace amounts of metal leaching were detected (Mn ion ≤ 3 μg L⁻¹) during the whole experiment. The whole oxidation and adsorption process demonstrated excellent anti-interference ability and stability. This study shows the great potential of transition metal doped defective metal–organic frameworks in the field of adsorption and catalysis and provides a novel idea for the high-efficiency management of As(III) pollution in water environments.