Visible light induced photocatalytic removal of an organic dye using metal doped iron oxide based catalysts derived from red mud

Abstract

Comprehensive strategies with the development of advanced materials are required for the remediation of water and land pollution to protect the environment and human health. In this regard, iron oxide catalysts are recognized as preferable catalysts for the heterogeneous photo-Fenton process, which is an efficient technique for degrading organic pollutants in waste water. The present study discusses the photocatalytic performance of iron oxide-based catalysts synthesized from industrial waste red mud for methylene blue degradation under visible light irradiation. XRD studies confirmed the formation of a pure α-Fe₂O₃ (hematite) phase, whereas the doping of iron oxide with Mn, Cu, and Ce was ascertained by XPS analysis. 3 wt% Cu doped iron oxide with a TOC value of ∼84.7% showed the best removal efficacy to the tune of ∼91% within 60 min of visible light irradiation. Impedance data supports the enhanced charge separation in metal doped α-Fe₂O₃, which improves the photocatalytic performance. A similar trend was observed in photo-electrochemical (PEC) properties, where Cu doped Fe₂O₃ showed 2 times higher photocurrent than the bare one. Based on scavenging tests, electrons and hydroxyl radicals (˙OH) were shown to be major players in the photodegradation of pollutants under visible light. A probable mechanism explaining the enhanced e⁻/h⁺ pair separation and migration was proposed by examining electrochemical properties. This work has significant implications for wastewater treatment with the efficient use of industrial waste red mud as a cost-effective resource.