Study On The Method Of Promoting The Degradation Of Tetracycline In Fenton System

Tetracycline（TC）is widely used in both human and aquaculture because of its good bactericidal effect and broad antibacterial spectrum.However,a large number of unmetabolized TC will enter the water body along with excreta,causing strong harm to the environment and human body.The existing methods to treat tetracycline wastewater mainly include adsorption,membrane treatment and biological treatment,etc.,but these methods have some shortcomings such as slow degradation rate,low treatment efficiency and easy to cause secondary pollution.Therefore,it is urgent to find an economical and efficient tetracycline wastewater treatment technology without secondary pollution.Fenton technology is widely used in the field of environmental governance because of its advantages such as fast reaction rate,energy saving,environmental protection and easy reaction control.In this paper,Fenton system was used to study the degradation of TC.Using TC concentration and COD value as judgment indexes,the ability of H₂O₂,·O₂^-,HO₂·and·OH four active substances in the system to break the bond of TC molecules and remove COD was studied under two judgment indexes,and then the role of each active substance was clarified.The promoting effect of four reducing agents,ascorbic acid（C₆H₈O₆）,hydroxylamine hydrochloride（HONH₂·HCl）,sodium sulfite（Na₂SO₃）and hydroquinone（C₆H₆O₂）on Fenton system was investigated.A suitable additive HONH₂·HCl is optimized,and the optimal reaction conditions of Fenton/HONH₂·HCl improved system are obtained through experiments.Finally,the degradation effect of TC was further improved by adding HONH₂·HCl in several times and simultaneously adding HONH₂·HCl and H₂O₂ in several times successively.The effects of various active substances in Fenton system were investigated under the two judgment indexes of TC concentration and COD value.In the process of breaking the bond of TC molecules into small molecular organic compounds,the contribution rate of·OH and HO₂·is 57.47%and 41.82%,respectively.It can be seen that·OH and HO₂·can effectively break the bond of TC molecules.The ultimate goal of water treatment is to make the pollutants finally degraded and mineralized into inorganic substances.When the small molecular organic matter after the bond breaking is further degraded and mineralized,the contribution rate of·OH is as high as 80.13%,and the contribution rate of HO₂·is only 19.87%.It can be seen that·OH plays a greater role in the complete degradation and mineralization of TC.Therefore,it was finally determined that the key active substance that played a major degradation role in the system was·OH.In order to promote the formation of·OH in the system,the promoting effects of C₆H₈O₆,HONH₂·HCl,Na₂SO₃ and C₆H₆O₂ in Fenton system were studied,and HONH₂·HCl was selected as a suitable additive.Single-factor analysis of Fenton/HONH₂·HCl improved system is carried out.When the reaction temperature is 40℃,the initial TC concentration is 50 mg·L^-1,and the concentration ratio of H₂O₂ to Fe²⁺is 10:1,when the concentration of H₂O₂ was 3.0mmol·L^-1,the concentration of Fe²⁺was 0.3 mmol·L^-1,the concentration ratio of HONH₂·HCl to Fe²⁺was 0.5:1,the initial p H value was 2.0,and the addition time of HONH₂·HCl was 4 min,the TC removal rate of the improved system reached 70.6%.To further improve the treatment effect of TC wastewater,it is proposed to add HONH₂·HCl in several times and simultaneously add HONH₂·HCl and H₂O₂ in several times successively to promote the degradation of TC.When the total amount of HONH₂·HCl was the same,the degradation effect of TC was better than that of single addition no matter how many times the system was added.Add HONH₂·HCl and H₂O₂ in batchs at the same time can greatly improve the oxidation capacity of the system for TC,and the TC removal rate is increased by nearly 21%compared with the single addition of HONH₂·HCl.