The adsorptive removal of Cr(VI) ions and antibacterial activity studies on hydrothermally synthesized iron oxide and zinc oxide nanocomposite

Abstract

Abstract The synthesis of a multifunctional composite using Fe2O3 and ZnO endowed with antioxidant and antibacterial properties for the adsorption of chromium(VI) ions was reported. Typical approaches of eliminating metal ions from wastewater focus on removing only the contaminants. In this research, a composite was developed that is not only highly efficient in removing Cr(VI) ions but also imparts antibacterial and antioxidant properties to the treated water. The characterizations of the composite were conducted using powder X-ray diffraction (pXRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy-Energy-dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET). BET surface area revealed that the sheet-like Fe2O3 were present alongside hexagonal ZnO rods. The adsorption data corroborated well with Freundlich isotherm (R2= 0.99844) better than the Langmuir model (R2= 0.97993) indicating the prevalence of multi-layer sorption. Pseudo-second-order kinetics model described the adsorption process well implying chemisorption was the major contributor to the adsorption capacity. The composite exhibited additional useful character by inhibiting up to 12% of 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals when used in the concentration range of 10–50 µL. It also showed antibacterial property by removing more than 99% of Staphylococcus aureus after an exposure time of six hours. It is proposed that Fe2O3–ZnO composite may be highly effective for multi-purpose water treatment.