Integration of alumina ultrafiltration membrane and palladium-catalyzed peroxymonosulfate for removal of organic micropollutants

Abstract

Organic micropollutants (OMPs) originate from organic chemicals such as drugs and pesticides that are widely used in human activities. OMPs are difficult to remove by conventional water treatment techniques, and hence continue to accumulate in natural water bodies. More effective methods need to be investigated for the removal of OMPs in drinking water treatment because of their toxicity and carcinogenicity, which may pose potential risks to human health. Previous studies have suggested that the use of activated peroxymonosulfate (PMS) catalyzed by Palladium (Pd) immobilized in ultrafiltration (UF) membranes can effectively degrade 1,4-dioxane and p-nitrophenol, while its removal efficiency for other OMPs, limiting factors and reaction mechanism still require for more research. In this study, PMS-Pd/UF system was established by coating Pd on the surface and 20 nm pores of the ultrafiltration membrane. The effectiveness of PMS-Pd/UF in the removal of OMPs from ultrapure water under various flux, pH, PMS dosages and ions presence was examined, as well as the performance in other water matrices including simulated brackish water, simulated brine water and river water. The results showed that PMS-Pd/UF achieved more than 95% of OMPs removal in 1 and 12-hour filtration tests at a flux of 30 LMH, while removal efficiency decreased with the increased flux due to the reduced contact time. The pH tests indicated that the system was more efficient under a neutral pH environment. The presence of 1 mM of various ions (Cl⁻, HCO3⁻, SO₄²⁻, and ClO⁻) had limited effects on the degradation of OMPs. However, the removal of OMPs was inhibited when OMPs coexisted with NOM in river water and, in combination with high salt concentrations simulated brine water (e.g., with 250mM of total anions). From specific scavenger dosing experiments, it was concluded that SO₄^•–, ^•OH, and O₂^•– were the main reactive species induced from Pd/UF-activated PMS for the removal of OMPs.