Hydrodynamic cavitation degradation of hydroquinone using swirl-type micro-nano bubble reactor

ABSTRACTThis study reports the degradation of hydroquinone using lab-scale hydrodynamic cavitation approach (aswirl-type micro-nano bubble reactor), which is considered a green and effective method. The effects of inlet pressure, gas flow rate, pH and initial hydroquinone concentration on hydroquinone degradation were analysed based on experimental research. After experiments investigation, it was concluded that with pH 7.38, hydroquinone concentration of 50 mg/L, and int pressure of 0.2 MPa, the degradation efficiency of hydroquinone reached 91.25% in wastewater. Furthermore, this study also investigated the degradation effect of hydroquinone wastewater by hydrodynamic cavitation combined with persulfate oxidation (HC + PS). The kinetics of hydroquinone degradation by HC or PS oxidation alone and HC + PS oxidation were also examined. Compared with the degradation method alone, the degradation of hydroquinone by HC + PS was more pronounced, and the enhancement factor was 4.55, which indicates that HC greatly enhances the oxidation capacity of PS. In additon, from viewpoint of energy consumption and operating cost, the synergy of HC + PS (1.05 mM) is also the most promising combination. Based on the detection results of the Gas chromatography-mass spectrometry (GC-MS) the possible degradation pathways of hydroquinone were analysed: under the action of ·OH and the high temperature and pressure by cavitation process, the hydroquinone molecule undergoes dehydrogenation and ring-opening reaction, demethylation and decarboxylation reaction to produce intermediate products, which are finally converted into CO2 and H2O in micro-nano bubble cavitation process.KEYWORDS: Hydrodynamic cavitationmicro-nano bubbleswirl-type micro-nano bubble reactordegradationhydroquinone AcknowledgementsXuehua Li: analysed the data and revised the draft. Zhongyan Long: performed the experiments and analysed the data and wrote the draft. Xiaobing Li: supervision, conceptualisation, funding acquisition, project administration, writing – review.Disclosure statementNo potential conflict of interest was reported by the authors.Data availability statementAll relevant data are within the manuscript and its Additional files.Additional informationFundingThe authors are grateful to the National Key Research and Development Program of China (No. 2019YFE0115600) and the National Natural Science Foundation of China (No. 52074290).