An internal circulation iron-carbon micro-electrolysis reactor for aniline wastewater treatment: Parameter optimization, degradation pathways and mechanism

Aniline is a vital industrial raw material. However, highly-toxic aniline wastewater usually deteriorated effluent quality, posed a threat to human health and ecosystem safety. Therefore, this study reported a novel internal circulation iron-carbon micro-electrolysis (ICE) reactor to treat aniline wastewater. The effects of reaction time, pH, aeration rate and iron-carbon (Fe/C) ratio on the removal rate of aniline and the chemical oxygen demand were investigated using single-factor experiments. This process exhib-ited high aniline degradation performance of approximately 99.86% under optimal operating conditions (reaction time = 20 min, pH = 3, aeration rate = 0.5 m3 center dot h-1, and Fe/C = 1:2). Based on the experimental results, the response surface method was applied to optimize the aniline removal rate. The Box- Behnken method was used to obtain the interaction effects of three main factors. The result showed that the reaction time had a dominant effect on the removal rate of aniline. The highest aniline removal rate was obtained at pH of 2, aeration rate of 0.5 m3 center dot h-1 and reaction time of 30 min. Under optional exper-imental conditions, the aniline content of effluent was reduced to 3 mg center dot L-1 and the removal rate was as high as 98.24%, within the 95% confidence interval (97.84%-99.32%) of the predicted values. The solution was treated and the reaction intermediates were identified by high-performance liquid chromatography, ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, gas chromatography-mass spectrometry, and ion chromatography. The main intermediates were phenol, benzoquinone, and car-boxylic acid. These were used to propose the potential mechanism of aniline degradation in the ICE reac-tor. The results obtained in this study provide optimized conditions for the treatment of industrial wastewater containing aniline and can strengthen the understanding of the degradation mechanism of iron-carbon micro-electrolysis.(c) 2023 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.