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

• Published in: Journal of chemical technology and biotechnology (1986) 2017-04, Vol.92 (4), p.827-833
• Main Authors: Feng, Jinxi, Lan, Shenyu, Yao, Chunyang, Xiong, Ya, Tian, Shuanghong
• Format: Article
• Language: English
• Subjects: AO7; electrolysis; IrO2; sulfate
• ISSN: 0268-2575; 1097-4660
• DOI: 10.1002/jctb.5066

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 ∼ 500 mg L−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 diaphragm cell 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 AO7. Interestingly, the electro‐generation of NaOH and H2SO4 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