Development of surface modified titanium alloy as a promising photocatalyst for textile waste water treatment

Abstract

TiO2 photocatalyst properties can be enhanced by doping with metals and non-metallic elements or coupling with another semiconductor forming a heterostructure photocatalyst, etc. Doped TiO2 can also be achieved by surface modification of commercially available titanium alloys by plasma electrolytic oxidation (PEO). Herein, Ti-6Al-2Sn-4Zr-6Mo, Ti-10V-2Fe-3Al and Ti-6Al-4V are PEO treated, and the photocatalytic ability of the material was studied. Further, the effect of alpha and beta stabilisers on the polymorphs of TiO2 (anatase and rutile) is investigated. Surface morphology, wettability and optical properties are analysed to determine the material’s photocatalytic ability. All titanium alloys possess a typical PEO porous structure, favouring the adsorption of dyes from the textile wastewater. The EDS and XPS analysis found that the alloying elements such as Fe, V and Mo in the titanium have limited participation in the oxidation reaction. In contrast, Al, Zr, and Sn actively participated in the PEO reaction and doped into the TiO2 lattice. The bandgap of the oxide coatings on Ti-6Al-2Sn-4Zr-6Mo, Ti-10V-2Fe-3Al and Ti-6Al-4 V alloys was found to be 2.92, 2.42 and 2.78 eV, respectively. The charge carrier’s recombination rate and separation efficiency of the PEO-treated Ti-6Al-4V and Ti-10V-2Fe-3Al are better than the PEO-treated pure Ti and Ti-6Al-2Sn-4Zr-6Mo. The PEO-treated Ti-6Al-4V alloy showed the highest MB degradation of 98% under visible light irradiation. The article successfully demonstrated PEO surface-modified commercial titanium alloys as a promising new immobilised photocatalyst for efficient textile wastewater degradation under visible light.