Ball mill synthesized Fe/ZnO nanostructures for dye degradation, heavy metal extraction and light emission applications: Experimental and DFT Perspectives

Water pollution caused by pollutants like organic dyes and heavy metal ions is accountable for problems related to health, economy, and environmental degradation. Metal oxide nanomaterials such as ZnO have extensive potential to tackle water pollution. In the present study, pure, 3 and 6 at% Fe-doped ZnO nanoparticles were synthesized via high-energy ball mill cum solid-state reaction route. The samples were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, Brunauer–Emmett–Teller (BET) technique, UV–visible and photoluminescence spectroscopies. The crystallite size decreased, whereas structural defects increased with Fe concentration. The band gap narrowing (3.36–3.23 eV) has been observed with an increase in Fe doping. The light-emission properties of samples were analyzed using CIE plots. Also, DFT+U calculations were performed to predict the impact of Fe-doping on the crystal structure and electronic & band structure of ZnO. Photocatalytic degradation ability of the nanostructures towards methylene blue (MB) dye was improved from 59.8 % to 90.7 % with Fe doping, and degradation follows pseudo-1st order kinetics. With Fe-doping, Ni ions removal capability of ZnO from water enhanced from 14.7 % to 48 %, and DFT studies of Ni-adsorption on the pure and Fe-ZnO surfaces also predicted this trend.