Visible Light-Induced Photocatalytic Degradation of Toxic Dyes Using Bromine-Treated TiO ₂ Nanotubes

A serious environmental threat is posed by the discharge of organic pollutants into water bodies, necessitating the development of sustainable remediation technologies. This paper discusses the effectiveness of bromine-treated titanium dioxide (TiO₂) nanotubes, synthesized by a cost-effective and scalable electrochemical method, for the photocatalytic degradation of three highly toxic dyes: crystal violet (100% at pH 10) in 120 min and methylene blue (96.8% at pH 10) and methyl orange (98.6% at pH 3) within 180 min of irradiation. The photodegradation rate constants for the bromine-treated photocatalysts exhibited a remarkable increase compared to the untreated samples. The photocatalytic mechanism was systematically investigated through radical scavenger experiments and pH-dependent zeta potential analysis. Bromine treatment significantly modified the electronic structure of TiO₂, leading to a reduction in the band gap from 3.00 to 2.48 eV, the formation of abundant oxygen vacancies, and the partial reduction of Ti⁴⁺ to Ti³⁺ and Ti²⁺, as confirmed by X-ray photoelectron spectroscopy. Structural, morphological, and optical properties were characterized by using X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and diffuse reflectance spectroscopy. Cyclic stability tests demonstrated the excellent reusability of the photocatalyst. These findings highlight bromine-treated TiO₂ nanotubes as a promising and efficient photocatalyst for wastewater treatment and environmental remediation applications.