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 H 2 SO 4 with organic compound-free Na 2 SO 4 wastewater has been known for many years, but actually, lots of Na 2 SO 4 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 Na 2 SO 4 into H 2 SO 4 and NaOH from these wastewaters. RESULTS Co-electrolysis of Na 2 SO4 (1.13 mol L −1 ) and AO7 (50 ∼ 500 mg L −1 ) was investigated in a diaphragm cell with IrO 2 -coated Ti electrodes. It was found that the concentrations of the resulting NaOH and H 2 SO 4 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 diaphragm cell with IrO 2 -coated Ti electrodes, NaOH and H 2 SO 4 could be effectively generated, and simultaneously, AO7 could also be degraded for the wastewater containing Na 2 SO 4 and AO7. Interestingly, the electro-generation of NaOH and H 2 SO 4 was not significantly affected by the occurrence and degradation of AO7 in 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. © 2016 Society of Chemical Industry
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