Development of zinc oxide-charcoal-polyacrylic nanocomposite hydrogels for enhanced dye degradation under direct sunlight irradiation and antibacterial applications

Hydrogels with enhanced photocatalytic activity have emerged as promising materials for wastewater treatment and antimicrobial applications. Nanocomposite hydrogels were synthesized using zinc oxide, charcoal, and polyacrylic acid (PAA) through free radical polymerization. These hydrogels were tested for their photocatalytic activity by degrading rhodamine B under direct sunlight and UV-Vis irradiation. The prepared samples were characterized using various techniques, including X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Thermogravimetric Analysis (TGA), and point of zero charge analysis (pH pzc ). EDX analysis confirmed the presence of elemental components, while the XRD pattern and FTIR spectrum indicated the successful incorporation of zinc oxide and charcoal into the PAA chains. TGA analysis revealed that the hydrogel containing zinc oxide exhibited better thermal stability than the hydrogel composed solely of charcoal and PAA. SEM imaging showed porous network within the hydrogels. The combination of zinc oxide and charcoal improved electron flow under both sunlight and UV-Vis light, significantly enhancing the degradation of dye molecules. Additionally, the surface functional groups present on the charcoal increased the hydrogel’s dye adsorption capacity. The effectiveness of dye degradation was influenced by factors such as pH, initial dye concentration, and the amount of zinc oxide content in the hydrogel. The hydrogel containing 1 gram of zinc oxide achieved a maximum rhodamine B degradation of 78.33% under sunlight and 92.54% under UV-Vis irradiation. Furthermore, the hydrogels containing zinc oxide demonstrated strong antibacterial activity against both Gram-positive ( Staphylococcus aureus ) and Gram-negative ( Escherichia coli ) bacteria. The zinc oxide-charcoal-PAA nanocomposite hydrogels exhibited strong antibacterial properties and effective sunlight-driven photocatalytic degradation of dyes, highlighting their potential application in treating textile wastewater.