Characterization and toxicity evaluation of chitosan/ZnO nanocompoite as promising nano-biopolymer for treatment of synthetic wastewater

Nanotechnology advances wastewater treatment through the application of Nano entities that optimize contaminant removal and enhance water purification efficacy. In this study, ZnO nanoparticles (ZnO NPs) were synthesized using Klebsiella pneumoniae, subsequently, a chitosan/ZnO nanocomposite (CS/ZnO NC) was prepared for removing reactive black 5 (RB-5) dye from synthetic wastewater. The biosynthesized nanomaterials were characterized using UV–VIS, FTIR, XRD, SEM and TEM techniques. The UV–Vis absorbance peaks at 370 nm and 350 nm corresponded to the characteristic surface plasmon resonance of ZnO NPs and the CS/ZnO NC, respectively. Additionally, FTIR analysis identified the various functional groups associated with ZnO NPs and the CS/ZnO NC. XRD analysis revealed their crystallinity to be approximately 22.44 and 25.76, respectively. The SEM images of ZnO NPs and the CS/ZnO NC show hexagonal plate-like particles with sizes of 33.66 nm and 38.64 nm, respectively. Four concentrations of ZnO NPs and CS/ZnO NC (0.25, 0.5, 1, and 2 mg/mL) were evaluated for RB-5 degradation at three different levels (25, 50, and 100 mg/L). Statistical analysis showed that chitosan/ZnO NC achieved 95 % dye degradation, compared to 81 % degradation with the same amount of ZnO nanoparticles. Furthermore, a pot experiment was carried out to evaluate the phytotoxicity effects of treated wastewater on wheat (Triticum aestivum L.). Both ZnO NPs and CS/ZnO NC did not significantly affect the viability of epithelial retinal cell lines at concentrations up to 100 µg/mL, suggesting a safe cytotoxic profile within this dosage range.