Electro-generation of NaOH-H2SO4 and simultaneous degradation of Acid orange 7 from Na2SO4-containing wastewater by Ti/IrO2 electrodes

BACKGROUND: Electro-generation of NaOH and H2SO4 with organic compound-free Na2SO4 wastewater has been known for many years, but actually, lots of Na2SO4 wastewater contains organic pollutants, such as black liquor, dyeing and sulphonating wastewater etc., therefore, there is a strong demand for investigations on performance and effect of the organic pollutants in electrochemically splitting Na2SO4 into H2SO4 and NaOH from these wastewaters. RESULTS: Co-electrolysis of Na2SO4 (1.13 mol L-1) and AO7 (50 similar to 500 mgL(-1)) was investigated in a diaphragm cell with IrO2-coated Ti electrodes. It was found that the concentrations of the resulting NaOH and H2SO4 could remain at about 0.73 mol L-1 and 0.36 mol L-1, respectively, although the COD removal was increased from 50.3 mg L-1 to 166.3 mg L-1 with the increase of AO7 concentration, for 120 min. CONCLUSION: In a diaphragmcell with IrO2-coated Ti electrodes, NaOH and H2SO4 could be effectively generated, and simultaneously, AO7 could also be degraded for the wastewater containing Na2SO4 and AO(7). Interestingly, the electro-generation of NaOH and H2SO4 was not significantly affected by the occurrence anddegradationofAO7in the range 0-500 mg L-1. The phenomenon of constant acid-base yield contributed to the independence of the main acid-generating reactions on the electro-oxidation of AO7. (c). 2016 Society of Chemical Industry