Microwave-assisted plant-extract-mediated synthesis of S-scheme S-g-C₃N₄/ZnWO₄ nanocomposite for visible-light degradation of dye and antibiotic and antimicrobial activity

This investigation focused on the rapid microwave-assisted synthesis of an environmentally benign ZnWO 4 /S-g-C₃N₄ nanocomposite using a dry date-palm extract. The date palm extract functioned as both a reducing and stabilising agent, while microwave irradiation facilitated efficient composite synthesis and enhanced visible-light absorption. XRD, FTIR, SEM, elemental mapping, EDAX, TGA, XPS, UV-DRS, and UV-Visible Spectroscopy were used to thoroughly examine the heterostructure photocatalyst. The photocatalytic performance of the produced nanocomposite was evaluated by degrading Rose Bengal dye and a commercially available Moxifloxacin tablet under visible-light irradiation. The ZnWO 4 /S-g-C₃N₄ photocatalyst (10 ppm/10 mg) exhibited remarkable efficiency, i.e., 95% in 120 min for dye and 85% in 90 min for drug, compared to its individual constituents. The S-g-C₃N₄ heterojunction with ZnWO 4 significantly increased the visible-light absorption and hence reduced photogenerated electron–hole pair recombination, leading to an increase in photocatalytic efficiency, as supported by scavenger experiments that confirmed the involvement of superoxide radicals (⋅O₂⁻) and hydroxyl radicals (⋅OH) as the primary reactive species, with direct hole-mediated oxidation (h⁺) contributing a secondary role. Additionally, the catalyst exhibited satisfactory stability and reusability over multiple cycles. Moreover, the nanocomposite exhibits antibacterial activity against S. aureus and E. coli bacteria, making it multifunctional in environmental remediation. Therefore, this research presents a sustainable and energy-efficient method that holds considerable promise for wastewater treatment applications and demonstrates that employing S-g-C₃N₄ can enhance charge-carrier separation, producing efficient photocatalyst nanocomposites.