Degradation of Reactive Black 5 using combined electrochemical degradation-solar-light/immobilized TiO2 film process and toxicity evaluation

The combined electrochemical oxidation-solar-light/immobilized TiO2 film process was conducted to degrade an azo dye, Reactive Black 5 (RB5). The toxicity was also monitored by the Vibrio fischeri light inhibition test. The electrochemical oxidation rapidly decolorized RB5 (55, 110 μM) with a supporting electrolyte of 2 g l−1 NaCl at current density 277 A m−2 and pH 4. However, TOC mineralization and A310 removal were low. Additionally, the treated solution showed high biotoxicity. RB5 at 110 μM significantly retarded the de-colorization efficiency by using the solar-light/immobilized TiO2 film process. The combined electrochemical oxidation-solar-light/immobilized TiO2 process effectively increased the removal of color, A310, and TOC. The toxicity was also significantly reduced after 3 h of solar irradiation. The results indicated that the low-cost combined process is a potential technique for rapid treatment of RB5.