Study of photocatalytic and antimicrobial activities of TiO₂/ZnO/graphene oxide nanocomposites

A simple and easy route was employed to synthesize TiO₂/ZnO (TZ) and TiO₂/ZnO/Graphene oxide (TZG) nanocomposites (NCs) followed by various characterizations using Powder X- Ray Diffraction (P-XRD), Field Emission Scanning Microscopy (FE-SEM), Energy dispersive X-Ray analysis (EDS), High-Resolution Transmission Electron Microscopy (HR-TEM), Raman and Ultraviolet-Visible Diffuse reflectance spectroscopy (UV–Vis-DRS) spectrophotometer. The P-XRD confirmed the formation of the anatase and zincite phases of TiO₂ and ZnO, respectively. The TZG NCs were evaluated for the removal of two antibiotics Amoxicillin (AMX) and Azithromycin (AZI) and two organic dyes Methyl Orange (MO) and Malachite Green (MG) via adsorption and photocatalytic degradation under solar-simulated light, achieving degradation efficiencies of 88 %, 50 %, 50.06 %, and 99.99 %, respectively. The degradation kinetics followed to the pseudo-second-order (PSO) kinetics model, with rate constant (k₂) 0.603 × 10⁻²,0.066 × 10⁻² mol⁻¹ L min⁻¹ for AMX and AZI, respectively, while pseudo-first order (PFO) kinetics model with rate constant (k₁) 0.252 × 10⁻² and 35.4 × 10⁻² min⁻¹ for MO and MG dyes, respectively. Antimicrobial activity tests of TZG NCs against bacteria Gram (+ve) Staphylococcus aureus, Streptococcus sp., Gram (−ve) Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Salmonella typhi showed good results for both Gram (+ve) and Gram (−ve) bacteria with Chloramphenicol antibiotic as a control drug. Among all tested bacteria, it showed a maximum inhibition zone for P. aeruginosa (23.0 ± 0.42 mm) among all tested microbial strains. These results indicated the remarkable advantages of TZG NCs for the degradation of antibiotics, dyes and antibacterial activity applications in wastewater treatment.