Electrochemical oxidation of RB-19 dye using a highly BDD/Ti: Proposed pathway and toxicity

In this work, the electrolysis of Reactive Blue 19 (RB-19, a toxic textile dye with a high half-life) using a highly non-commercial boron-doped diamond film on titanium substrate (BDD/Ti) was studied. The BDD film with a B/C ratio of 15,000 ppm, a doping level around 1019 cm−3 and higher content of sp3 (diamond) than sp2 (graphite) was produced with high quality and stability. Under appropriate conditions, the electrode promoted complete decolorization of RB-19, together with 99% of TOC removal and a significant decrease in toxicity against V. fischeri. Furthermore, benzene rings, aromatic amines and naphthalene could be removed also during the electrodegradation. The decay in dye concentration followed pseudo-first order kinetics and the values of the apparent rate constant increased with increasing current density applied. In addition, the main intermediates compounds of RB-19 degradation on BDD/Ti based on HPLC–MS analysis were amino-anthraquinone, tautomers keto-enolic, hydroquinone and benzoquinone, benzoic acid, phenol and acid aliphatic, such as oxalic acid. It is concluded that electrochemical oxidation using a BDD/Ti anode represents a satisfactorily method for the removal of RB-19 in aqueous solutions.