Efficient degradation of benzenamine in high salinity solution by air microbubble jet gas-liquid discharge

The degradation of high salinity benzene-series organic wastewater in fine chemical industry is an environmental protection challenge, mainly due to the negative impacts of high-concentration salt solutions on catalysts, microorganisms, etc. This study developed an air microbubble jet gas-liquid discharge with high-speed microbubbles to degrade benzenamine in 1 % salt solution. The characteristics included voltage-current waveforms, discharge images, and the effects of voltage, initial benzenamine concentration, pH and salt types on degradation efficiency were investigated. Gaseous and aqueous reactive species generated by plasma were characterized by optical emission spectra and the chemical probe method, respectively. The results showed that the degradation efficiency increased with the increase of applied voltage but decreased with the increase of initial concentration. The degradation efficiency increased from 58.67 % to 85 % when the voltage was increased from 16 kV to 24 kV (120 mg/L benzenamine), but decreased from 98.05 % to 79.49 % when the initial concentration was increased from 120 mg/L to 160 mg/L. The degradation efficiency was higher in alkaline condition (pH = 8.60, 99.70 %) than in acidic condition (pH = 3.20, 62.35 %). The degradation efficiency of benzenamine reached the optimum value of 99.70 % after 20 min plasma treatment at an applied voltage of 18 kV, an initial concentration of 120 mg/L, and pH = 8.60 in 1 % salt content wastewater. The degradation mechanism of benzenamine was analyzed by reactive species detection, and the possible reaction pathways of benzenamine degradation were revealed by LC-MS analysis, while the acute toxicity test showed that the toxicity of the treated wastewater was significantly reduced. • Achieved efficient degradation of benzenamine organic pollutants in high salinity solutions by discharge plasma. • Elucidated the contribution of reactive species in air microbubble jet gas-liquid discharge plasma to pollutant degradation. • Analyzed the possible degradation pathways of benzenamine based on the results of LC-MS.