Synthesis, Characterization, and Photocatalytic Application of Iron Oxalate Capped Fe, Fe-Cu, Fe-Co, and Fe-Mn Oxide Nanomaterial

A major challenge in the field of dye degradation and its remediation is the scarcity of active catalysts that are inexpensive, easily accessible, suitable for large-scale applications, and able to complete mineralization of dyes. In this regard, an easy, sustainable, scalable, and environmentally benign chemical method has been developed to synthesize four different selective orthorhombic iron (oxalate) capped Fe, Cu, Co, and Mn doped heterobimetallic-10 oxide nanomaterials from the redox reaction between [Fe(ox)-Fe(0)] and the corresponding CuSO4, CoNO3, and KMnO4 in water. The variable band gaps, morphologies, surface charges, and surface areas of the four synthesized materials have been successfully utilized for large scale visible light promoted complete mineralization of various dyes into the corresponding CO2, NO3-, and SO42-. The photodegradation mechanism by taking methylene blue as a representative dye suggested that photogenerated holes and free hydroxyl radicals (OH degrees) are mainly responsible for its skeletal decomposition. DFT study further suggested that the protonated species of MB, which have lower HOMO LUMO energy gap and more surface absorption affinity compared to its neutral species, will favor the degradation process and thus is evidence of its peak shifting and enhanced photodegradation rate in acidic pH. The photocatalytic activities of four synthesized materials were checked with phenol and observed degradation rate decreases in the order of UV > yellow LED > visible light. Toward the large scale degradation of dyes, iron(oxalate) capped Fe-Mn oxide [Fe(ox)Fe-MnOx] nanomaterials show the highest activity among the four synthesized materials. Finally, aqueous reaction medium, easy and scalable synthesis, large scale photodegradation of various dyes and their removal via complete mineralization, and efficient recycling of the catalyst make the protocol economical and sustainable.