Synergistic Electro-Photocatalytic Degradation of Organic Dyes Using Nanostructured Semiconductors: A Dual-Action Approach for Wastewater Treatment

Abstract

Background The organic dyes in industrial wastewater constitute a risk to the ecology and the human health manly because of their toxicity, persistence and inadequate elimination by the traditional methods of water treatment. It would be very promising to exploit a dual-action strategy such as synergistic electro-photocatalytic degradation by nanostructured semiconductors to fulfill spectroscopic degradation of these pollutants.

Objective: The objective of this work is to explore the effectiveness and mechanism of organic dye removal by using new nanostructured semiconductor composites in an integrated electrochemical/photocatalytic process, while developing a powerful approach for the treatment of wastewater.

Method: The nanostructured materials, LaFeO₃-MoS₂, α-Fe₂O₃/ZnO-MoS₂ and NiFe₂O₄/CeO₂/GO were prepared and characterized by XRD, SEM, BET and UV-vis spectroscopy. Visible light and applied bias electro-photocatalytic degradation of model dyes (methylene blue, rhodamine B) were performed. Degradation kinetics, total organic carbon elimination, stability of the catalyst, degradation intermediates, were studied on the basis of UV-Vis spectroscopy, TQ anal., cyclic reuse tests and LC-MS, respectively.

Results The NiFe₂O₄/CeO₂/GO composite displayed the highest efficiency of dye removal (96.4%) and the fastest of kinetic rate constants under dual-action operation well as beyond single acts of photocatalytic or electrochemical. TOC degradation was proved to be substantial mineralization. The catalysts achieved remarkable stability over five cycles, while LC-MS demonstrated intermediate compounds and indicated successive degradation pathways.

Conclusions: The process can be considered as an efficient, reversible, and environmentally friendly alternative for the treatment of the dye contaminated wastewater. This synergistic route leads to the separation of charge and generation of more reactive species, which could overcome the shortage of single method and provide an alternative for decontamination in environmental field.

Keywords: Electro-photo-catalysis, nanostructured semiconductors, organic dyes, wastewater treatment, degradation kinetics, catalyst stability