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

The chlorotetracycline degradation is carried out by using hydrodynamic cavitation (HC) method. The effects of device parameters such as diameter (X) of orifice distribution region, length (Y) of orifice plate inlet region and length (Z) of orifice plate outlet region are investigated to obtain a strong HC effect. The effects of inlet pressure, solution pH, initial chlorotetracycline concentration, inorganic anions, metal ions and added H 2 O 2 on chlorotetracycline HC degradation are also studied. The TOC analysis of treated solution under optimum conditions is performed to identify the mineralization extent. The intermediate products during chlorotetracycline degradation are detected by using LC-MS. For optimized device parameters (X = 32 mm, Y = 100 mm and Z = 200 mm), the degradation ratios of chlorotetracycline can reach up to 78.53% and 94.65%, respectively, in HC and HC + H 2 O 2 systems for 3.0 bar inlet pressure, 10 mg/L initial concentration and pH = 7.0. • The traditional orifice plate HC instrument is improved to obtain a strong HC effect. • X, Y and Z as new parameters in improved HC instrument are introduced and optimized. • The effects of some inorganic and metal ions on the HC degradation were studied. • The addition of H 2 O 2 can enhance HC degradation efficiency of organic pollutants. 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.