Study On Degradation Of Tetracycline In Wastewater By Micro Nano Bubble Synergistic Advanced Oxidation Technology

In recent years,the residual antibiotics in the water environment have brought potential risks and impacts to the environment and human health.How to effectively remove antibiotics has become a topic of increasing concern Due to the problems of low treatment efficiency and long cycle in the current conventional treatment process,it is of great significance to develop an efficient and economical antibiotic treatment technology.Tetracycline antibiotics,as the second largest class of antibiotics in the world,are widely used.Micro nano bubbles（MBs）have developed rapidly in the field of environment because of their smaller size,slower rising speed,larger interface area,higher internal pressure and longer residence time.In this paper,tetracycline hydrochloride was selected as the target pollutant,and the degradation efficiency of simulated tetracycline hydrochloride wastewater by micro nano bubble/persulfate（PS）and micro nano bubble/vacuum ultraviolet（VUV）was proposed,and the degradation effect of MBs/PS/VUV system in the treatment of actual antibiotic wastewater was investigated.The main research contents are as follows:（1）The degradation effect of MBs/PS system on TC was systematically studied in this paper.Compared with MBs and PS alone,MBs/PS has a significant synergistic effect on the degradation of TC.When the initial concentration of TC was 20 mg·L^-1,the dosage of PS was 10 m M,the air intake of MBs was 30 ml·min^-1 and p H was 3,the removal rate of TC after 180 min was 82.23%.The degradation of TC in MBs/PS system conforms to the quasi first-order reaction kinetic model.Through the response surface analysis,the influence degree of influencing factors on the degradation of TC in MBs/PS system is as follows:initial concentration of TC>dosage of PS>intake of MBs,and the interaction between various factors is obvious.The optimal process conditions obtained by response surface method are as follows:the dosage of PS is 9.33 m M,the initial concentration is 10.0 mg·L^-1,and the air intake C is 30.77 ml·min^-1.Under these conditions,the maximum removal rate predicted by the model is 87.74%.The free radical quenching experiment and electron spin resonance experiment show that the free radicals produced in MBs/PS system are mainly·OH and SO₄^-·.The organic nitrogen on TC is transformed into NH₃-N and NO₃^--N.The possible degradation pathways of TC were proposed by LC-MS.（2）The degradation of TC by MBs/VUV system was systematically studied in this paper.The degradation effect of MBs/VUV was higher than that of MBs alone and VUV alone,and 81.25%of TC could be removed within 180 min.When the initial concentration of TC=20 mg·L^-1,the power of UV lamp=20 W,the air intake=30ml·min^-1 and p H=7,the removal rate of TC after 180 minutes of reaction can reach81.25%,and the removal of TC by MBs/VUV system conforms to the quasi first-order reaction kinetics.Natural water quality has a certain effect on the degradation of TC by MBs/VUV.The presence of NO₃^-,HCO₃^-and Ca²⁺can promote the degradation of TC,Cl^-,SO₄^2-and Mg²⁺can slightly inhibit the degradation of TC,and the presence of NOM can significantly inhibit the degradation of TC.The free radical quenching experiment and ESR capture experiment confirmed that the active free radicals in MBs/VUV system were·O₂^-and ~1O₂,and·O₂^-was dominant in the degradation process.The degradation mechanism of TC in the whole system was expounded.13 intermediates were determined by LC-MS,and the possible degradation pathways of TC were proposed.（3）The removal effects of MBs,MBs/PS,MBs/VUV and MBs/PS/VUV on COD in actual antibiotic wastewater were systematically investigated in this paper.In MBs/PS/VUV system,when the reaction time is 180 min,the dosage of PS is 5 g·L^-1,the power of vacuum UV lamp is 25 W and the air intake of MBS is 30 ml·min^-1,the COD removal rate can reach 33.47%,which is higher than that of other systems.The mechanism of removing COD from antibiotic wastewater by MBs/PS/VUV system is proposed,which provides a valuable reference for the treatment of actual antibiotic wastewater by MBs/PS/VUV system.