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Rapid Removal of Carbofuran from Aqueous Solution by Pulsed Corona Discharge Treatment: Kinetic Study, Oxidative, Reductive Degradation Pathway, and Toxicity Assay

Singh, Raj Kamal, Philip, Ligy, Ramanujam, Sarathi
Industrial & Engineering Chemistry Research 2016 v.55 no.26 pp. 7201-7209
aqueous solutions, bicarbonates, carbofuran, ecotoxicology, electric power, engineering, free radical scavengers, humic acids, microalgae, oxidation, pH, toxicity
This work demonstrates the application of plasma generated by pulsed corona discharge for the rapid degradation of carbofuran from aqueous solution. Carbofuran with a concentration of 0.5 mg/L to 30 mg/L was effectively removed within 4 to 10 min of treatment time, at 101.5 W input power. Degradation yield (2.95 g/kWh) was much higher for 10 mg/L carbofuran concentration compared to degradation yield (0.37 g/kWh) for 0.5 mg/L carbofuran. The effect of pulsed voltage, pulsed frequency, initial pesticide concentration, pH, and effect of radical scavengers (HCO₃–, CO₃²–, and humic acid) was also investigated in detail. Appearance of some key intermediates confirmed the possibility of formation of some demethylated products due to direct electron impaction during degradation process. Seven intermediates were identified, and possible oxidation and reduction mechanism of carbofuran degradation pathway was proposed. Microalgae ecotoxicity study confirmed the complete detoxification of carbofuran after 14 min corona discharge.