Improved hydrodynamic cavitation device with expanded orifice plate for effective chlorotetracycline degradation: Optimization of device and operation parameters

Hydrodynamic cavitation (HC) is a promising technology for the degradation of organic pollutants. In this work, the degradation of chlorotetracycline in aqueous solution is performed by using an improved HC device with expanded orifice plate in three-dimension. Different instrument parameters in the improved HC device such as the diameter (X) of orifice distribution region, the length (Y) of orifice plate inlet region and the length (Z) of orifice plate outlet region are optimized. The influences of some operating parameters including inlet pressure, solution pH and initial chlorotetracycline concentration on the HC degradation of chlorotetracycline are investigated by using response surface methodology (RSM). Besides, the effects of inorganic anions, metal ions and H 2 O 2 on the degradation of chlorotetracycline by using HC are explored. The formed intermediate products during the chlorotetracycline degradation are detected by using LC-MS. The results manifested that the chlorotetracycline molecules can be degraded into some organic compounds with low molecular weight in HC degradation process. And that, these intermediate products can be further oxidized into CO 2 , H 2 O and some inorganic ions with the extension of treatment time in the HC + H 2 O 2 system. The experimental results indicated that, for optimized device parameters (X = 32 mm, Y = 100 mm and Z = 200 mm), the degradation ratios can reach 78.53% and 94.65%, respectively, in HC and HC + H 2 O 2 systems under 3.0 bar inlet pressure, 10 mg/L initial chlorotetracycline concentration and pH = 7.0. And the mineralization ratio can reach 60.77% in the HC + H 2 O 2 system for 60 min treatment time, demonstrating that chlorotetracycline can be mineralized effectively. The existences of the inorganic anions and the metal ions show a certain inhibition effect for the chlorotetracycline degradation reactions by using HC. Overall, the work revealed that the HC is a potential technology for a large-scale treatment of antibiotics contaminated water.