Photocatalytic degradation of malachite green over differently synthesized nano-α-Fe₂O₃: a comprehensive pathway

Nano-sized amorphous Iron (III) oxides have been a fascinating material for the scientific community owing to their widespread promising application in photocatalysis of water decontamination, due to high specific surface area and variable valency. Malachite green dye is a non-biodegradable organic pollutant known for its toxic effects on humans and aquatic organisms. In the present work, Fe₂O₃ was synthesized through Citrate–Nitrate Sol–Gel route and Syzygium cumini leaf extract mediated green method. The composition and physical nature of the synthesized iron oxides were confirmed using p-XRD, SEM-EDAX, XPS techniques. A comparative investigation of visible light degradation of malachite green dye was done using differently synthesized Fe₂O₃ at pH 8. The LCMS study exposed that the sol–gel Fe₂O₃ was highly efficient in transforming Malachite green (MG) into a no. of intermediates of low molecular weights, whereas green Fe₂O₃ revealed formation of both high and low molecular weight metabolites. In the light of the evidence derived from LCMS, a pathway has been proposed to highlight the absolute and sequential transformation of the dye to environmentally benign compounds. The study also disclosed the key role played by Iron oxide nanoparticles (IONPs), in the total mineralization of the dye to carbonates and nitrates that can be assimilated by plants and the decontaminated water can be engaged in agricultural practices.