Construction of NH ₂ –UiO-66@UiO-67-Decorated Polypropylene Nonwovens for Efficient Removal of Cr (VI) via Synergistic Adsorption and Photocatalytic Reduction

Heavy metal contamination in water poses a serious global environmental challenge. In particular, hexavalent chromium (Cr (VI)) is particularly concerning due to its carcinogenicity and genotoxicity. In this work, core-shell NH₂-UiO-66@UiO-67 nanoparticles (NPs) were in situ stepwise grown on sulfonated polypropylene (PP) nonwoven to fabricate a multifunctional composite (NH₂-UiO-66@UiO-67/PP composite nonwoven) for efficient removal of Cr (VI). As expected, the resulting NH₂-UiO-66@UiO-67/PP composite nonwoven exhibited dual functionality for efficient Cr (VI) remediation: simultaneous adsorption and visible-light-driven photocatalytic reduction, accompanied by effective sequestration of the resulting Cr (III), due to the presence of NH₂-UiO-66@UiO-67 NPs. Under visible light irradiation, the composite achieved exceptional performance, reducing Cr (VI) concentrations from 0.608 mg/L to below 0.004 mg/L and lowering total Cr concentrations from 0.876 mg/L to below 0.004 mg/L, corresponding to a removal efficiency of over 99.6%. The mechanism was elucidated as an integrated adsorption-reduction-fixation process. More importantly, the composite demonstrated outstanding recyclability, retaining 80.0% of its removal efficiency after five regeneration cycles, highlighting its practical potential. Therefore, the as-obtained NH₂-UiO-66@UiO-67/PP composite nonwoven can be viewed as a highly efficient material for treating Cr (VI)-contaminated wastewater through an adsorption-photocatalytic reduction pathway.