N-doped titanium dioxide nanoparticles activated under visible light achieve the photocatalytic degradation of textile azo dye remazol brilliant blue

Abstract

Dyes used in the textile industry have varied and complex structures are designed to resist degradation by external agents. Most are water soluble, resistant to chemical agents and not biodegradable, so they cannot be easily removed by wastewater treatment plants. Remazol Brilliant Blue R (RBBR) is one of the most important colorants in the textile industry, and it is frequently used as a starting material in the production of polymer dyes. This work studied the degradation of a textile dye by a heterogeneous photocatalysis process, using a titanium dioxide catalyst doped with nitrogen from urea, in the presence of visible light irradiation. For the optimization of the process a Box-Benhken experimental design was performed. Where, the TiO 2 was varied from 0.1 gL ⁻¹ (-1) to 1.0 gL ⁻¹ (+1), and the pH between 2.0 (-1) to 11(+1). With the optimal response it was possible to remove 86.3% of the dye (R ² = 0.987 and Q ² = 0.873, p < 0.001). The mineralization grade was determined through TOC analysis, which reached 50%, and the toxicity was evaluated with Daphnia magna nematodes, which was reduced considerably after photocatalytic treatment.