A low-voltage pulse electrolysis method for the degradation of anthraquinone and azo dyes in chloride medium by anodic oxidation on Ti/IrO2-RuO2-SnO2 electrodes

Wastewater produced by the textile industry containing azo dyes and anthraquinone dyes is significant source of pollution to the environment and is toxic for aquatic life. To overcome the high-energy cost of traditional electrochemical oxidation, a custom-built power supply device for the degradation of anthraquinone and azo dyes by low voltage of 15.0-20.0 V pulsed discharge was investigated. Titanium coated with mixed oxide (Ti/IrO2-RuO2-SnO2) plates and pure titanium plates were used as the anode and cathode, respectively, for the generation of chlorine in the dye solution. For the anthraquinone dye Reactive Blue 19, 60.0% of the chemical oxygen demand (COD) and 22.0% of the total organic carbon (TOC) were removed using this system. A comparison of the direct current electrolysis and pulsed discharge revealed that using the pulsed discharge method reduced the energy cost by 68.6%. UV-visible, LC-MS, and GC-MS were used to identify the intermediate compounds formed during the degradation of Reactive Blue 19. The results indicate that in the process of oxidation by chlorine/hypochlorite, the chromophore group was first oxidized to -NH2, followed by decolorization via chlorination of the aromatic rings. The results confirm that low-voltage pulse electrolysis can be used for the degradation of industrial dyes in waste effluents. Practitioner points Low-voltage pulse electrolysis can be used for the degradation of industrial dyes and/or dyes in waste effluents. For anionic dye Reactive Blue 19, 60.0% of COD and 22.0% of TOC were removed using low-voltage (20.0 V) pulse electrolysis. The pulsed discharge method reduced the energy cost of this degradation process by 68.6% compared with direct current electrolysis. The intermediate compounds formed during the degradation of Reactive Blue 19 were confirmed by UV-visible spectroscopy, LC-MS, and GC-MS.