Organic acids enhanced decoloration of azo dye in gas phase surface discharge plasma system

• Published in: Journal of hazardous materials 2016-01, Vol.302, p.65-71
• Main Authors: Wang, Tiecheng, Qu, Guangzhou, Ren, Jingyu, Sun, Qiuhong, Liang, Dongli, Hu, Shibin
• Format: Article
• Language: English
• Subjects: Acid orange; Azo Compounds - chemistry; Carboxylic Acids - chemistry; Decoloration; Electrochemical Techniques; Naphthalenes - chemistry; Organic acids; Plasma Gases; Surface discharge plasma; Water Pollutants, Chemical - chemistry
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2015.09.051

•Organic acids are used to enhance AO7 removal in a surface discharge plasma system.•The effects of various organic acid additives on AO7 decoloration are evaluated.•The enhancement mechanism on AO7 decoloration efficiency is discussed.•The biodegradability of AO7 wastewater is improved with organic acid addition.•A possible pathway for AO7 decomposition in this system is proposed. A gas phase surface discharge plasma combined with organic acids system was developed to enhance active species mass transfer and dye-containing wastewater treatment efficacy, with Acid Orange II (AO7) as the model pollutant. The effects of discharge voltage and various organic acid additives (acetic acid, lactic acid and nonoic acid) on AO7 decoloration efficiency were evaluated. The experimental results showed that an AO7 decoloration efficiency of approximately 69.0% was obtained within 4min of discharge plasma treatment without organic acid addition, which was improved to 82.8%, 83.5% and 88.6% within the same treatment time with the addition of acetic acid, lactic acid and nonoic acid, respectively. The enhancement effects on AO7 decoloration efficiency could be attributed to the decrease in aqueous surface tension, improvement in bubble distribution and shape, and increase in ozone equivalent concentration. The AO7 wastewater was biodegradable after discharge plasma treatment with the addition of organic acid. AO7 decomposition intermediates were analyzed by UV–vis spectrometry and GC–MS; 2-naphthol, 1,4-benzoquinone, phthalic anhydride, coumarin, 1,2-naphthoquinone, and 2-formyl-benzoic acid were detected. A possible pathway for AO7 decomposition in this system was proposed.