PVDF/SiO2-g-CDs blended membrane for fluorescence detection and adsorption of metal ions

The preparation method of PVDF/SiO2-g-CDs blended membrane was that the silanized modified carbon dots (CDs) were grafted onto the PVDF/SiO2 blended membrane surface. The surface composition, morphology, hydrophilicity, fluorescence performance and metal ions adsorption performance of PVDF/SiO2-g-CDs blended membrane were studied. The fluorescence quenching effect of the membrane with Hg2+ and Fe3+ was obvious. The quenching mechanism was the complexation of metal ions with the functional groups of CDs including -NH2, -OH and -COOH. The optical detection limits of PVDF/SiO2-g-CDs blended membrane for Hg2+ was 1.6 nM in the linear range of 0.0025–20 μM, and the optical detection limits for Fe3+ was 2.1 μM in the linear range of 0.5–5000 μM. The maximum adsorption capacity of PVDF/SiO2-g-CDs blended membrane for Fe3+ was 47.04 mg·g−1. The adsorption of the membrane conformed to the pseudo-second-order kinetics and Langumir model, and belonged to monolayer chemical adsorption on the membrane surface. Through adsorption thermodynamic analysis, adsorption was a spontaneous endothermic process. The recovery rate of fluorescence and adsorption capacity could still be maintained above 82% after five cycles. The PVDF/SiO2-g-CDs blended membrane had the ability to regenerate. In summary, the PVDF/SiO2-g-CDs blended membrane had the dual functions of detecting and adsorbing metal ions, and had broad application prospects in sewage treatment.