Study On The Removal Effect And Mechanism Of Ofloxacin By Combined Technology Of Hydrodynamic Cavitation And Photocatalytic

Ofloxacin is widely used as a bactericide and antiinfection because of its good antimicrobial effect and lower side effects,thus generating large amounts of wastewater containing ofloxacin.If untreated or incompletely treated ofloxacin wastewater is released into the environment,it can pose a threat to the ecosystem and human health.Many methods have been used to treat ofloxacin wastewater,but the low bio-absorption and refractory nature of ofloxacin has resulted in traditional methods not being effective in degrading ofloxacin.Therefore,it is crucial to explore an efficient and green method for treating ofloxacin wastewater.Photocatalytic degradation of organic matter using Ti O₂ is widely used as an environmentally friendly technology for wastewater treatment.However,photocatalytic oxidation technology is limited by the small volume of water to be treated,the long reaction time and the tendency of the catalyst to agglomerate,and cannot be implemented for large-scale industrial wastewater treatment.Hydro-cavitation is a new advanced oxidation technology with the advantages of simple operation and no secondary pollution.Therefore,hydro-cavitation can be used in combination with photocatalytic technology to improve the efficiency of pollutant degradation.In this study,the effect of hydro-cavitation-photocatalysis technology on the degradation ofloxacin in solution was investigated using a home-made hydro-cavitation-photocatalysis plant.The factors affecting the degradation ofloxacin were examined to provide a new method for the effective treatment ofloxacin wastewater.（1）Zn-doped Ti O₂ catalysts were prepared by the sol-gel method and characterized by X-ray diffraction（XRD）,scanning/transmission electron microscopy（SEM/TEM）,X-ray photoelectron spectroscopy（XPS）,UV-Vis diffuse reflectance spectroscopy（UV-Vis DRS）and photoluminescence spectroscopy（PL）.to determine their crystal shape,structure,chemical composition and light absorption range.（2）Photocatalytic degradation experiments were carried out on the solution ofloxacin using a photochemical reactor to investigate the effects of catalyst type,initial concentration of pollutants and catalyst addition on the degradation rate ofloxacin and to carry out the optimization of photocatalytic degradation conditions.It was found that the highest degradation efficiency of 34.24%was obtained at a concentration of 5 mg/L ofloxacin solution and a catalyst dose of 0.5 g/L of Zn-doped Ti O₂（molar ratio of Zn/Ti of 0.01:1.00）,and the optimum economic efficiency was achieved under this condition.（3）A custom-made venturi was used as a hydro cavitation generator for the degradation of ofloxacin solution to investigate the effect of inlet pressure and initial p H of the solution on the degradation rate ofloxacin and to carry out the optimization of the hydro cavitation degradation conditions.It was found that the highest degradation rate of 14.10%could be obtained at an inlet pressure of 3.0 bar and 19.24%at a neutral p H.（4）Combined hydro cavitation-photocatalytic technology was used for the treatment ofloxacin wastewater.The effect of the combined hydro cavitation-photocatalytic system on the degradation rate ofloxacin was investigated.The highest degradation efficiency of 72.24%was obtained when the inlet pressure was 3.0 bar,the p H was neutral,the Zn-doped Ti O₂（molar ratio of Zn/Ti was 0.01:1.00）catalyst was added,the ofloxacin solution concentration was 5 mg/L and the catalyst dose was 0.5g/L.The combined hydro cavitation-photocatalytic technology is consistent with the first order chemical kinetics.The hydro cavitation-photocatalytic degradation of ofloxacin was confirmed by the use of a capture agent,with·OH playing a major role.（5）To investigate the possible degradation mechanism of the hydro cavitation-photocatalytic degradation of ofloxacin.The degradation products in the hydro cavitation-photocatalytic degradation of ofloxacin were identified and their possible degradation pathways were analyzed by LC-MS technique.The results showed that seven degradation products were formed during the degradation of ofloxacin,and the possible degradation pathways ofloxacin under hydro cavitation-photocatalysis were suggested to be piperazine epoxidation,demethylation and decarboxylation.This study provides a very feasible method for the energy-efficient,high-efficiency and large-scale treatment of antibiotic wastewater,and provides a reliable theoretical basis and technical support for the future application of combined hydro-cavitation photocatalytic technology.