Investigating the influence of CuS ratio on sun light - Driven photocatalytic performance of ZnS:CuS nanocomposites and reusability of PVA/ZnS: CuS polymer membrane

In this study, ZnS and CuS nanocomposites (NCs) were synthesized using a simple and cost-effective co-precipitation method. These NCs were evaluated for their photocatalytic activity in degrading Crystal Violet dye under sunlight. ZnS:CuS nanocomposites were created using QDs in ratios of 4:1, 1:1, and 1:4. The synthesized NCs were analyzed for structural, morphological, chemical purity, and optical properties using XRD, TEM, EDAX, and UV-Vis spectroscopy. Structural analysis revealed phase-pure cubic and hexagonal structures for ZnS and CuS nanoparticles, respectively. The average crystallite sizes of the pure ZnS and CuS and their composites (4:1, 1:1 and 1:4) ratios are 1.66, 14.7, 1.90, 11.2 and 12.1 nm, respectively. TEM analysis confirmed aggregated and isolated particles, matching the SAED pattern and d-spacing values from XRD analysis. Increasing the CuS ratio in the composites enhanced absorption due to a bandgap reduction from 3.99 eV to 3.35 eV. The pure ZnS and CuS NPs and their composites in ratios of 4:1, 1:1, and 1:4 exhibited degradation efficiency of approximately 89 %, 87 %, 99 %, 97 %, and 96 % respectively over a period of 180 min. ZnS:CuS (4:1) exhibited outstanding photocatalytic activity, achieving 90 % degradation in 80 min under sunlight. Detailed discussions included the proposed photocatalytic mechanism, scavenging activity, and dosage effect. Hemolytic activity assays indicated that the synthesized NCs are nonhemolytic. The PVA and PVA/ZnS:CuS (4:1) composite membrane exhibited degradation efficiency of 63 % and 92 % respectively. ZnS:CuS (4:1) NCs, with their superior capacity for wastewater treatment, were incorporated into a PVA polymer membrane to enhance reusability and prevent photo-corrosion.