Microalgae-based bio-fabrication using zinc oxide-chitosan nanocomposite for industrial effluent degradation and pollutant reduction

Abstract

The current study investigates the photocatalytic degradation of harmful pollutants from the textile and pharmaceutical industries. Specifically, a chitosan zinc nanocomposite's high photocatalytic degradation efficiency was demonstrated. Zinc nanoparticles were synthesized using an extract derived from Chlorella sp. as a reducing agent. XRD analysis revealed a crystal size of 21 nm for the nanocomposite, confirming its hexagonal phase with a wurtzite structure. Particle size analysis determined an average particle size of 38.7 nm for the nanocomposite. The nanocomposite's photocatalytic degradation of the textile pollutant (methyl orange) and the pharmaceutical pollutant (metformin) was evaluated, achieving 98.7 % degradation in 90 min and 98.2 % degradation in 120 min, respectively. Notably, chitosan zinc nanocomposite exhibited maximum degradation efficiencies of 99.1 % and 98.9 %, respectively, against methylene blue and rhodamine B dyes after 105 min, whereas congo red and eosin yellow achieved 96.8 % and 95.5 % degradation efficiencies after 120 min, respectively. Following the degradation process, the photocatalyst's stability and reusability were assessed over seven cycles. Furthermore, the antibacterials and antioxidant activity of the nanocomposite were evaluated, demonstrating superior performance compared to standard agents. These results highlight the multifunctional capabilities of chitosan zinc nanocomposite for environmental remediation and biomedical applications.