| Antibiotics are often used in human daily life and animal husbandry because of their bactericidal and antibacterial properties.Due to this characteristic,the microorganisms in the natural environment have poor degradation effect on antibiotics.Potassium permanganate?PM?is a common green oxidant,which can directly oxidize organic pollutants through its powerful oxidizing ability and destroy the molecular structure of organic matter.However,there are also some limitations when PM is used alone.Bisulfite?BS?is a commonly used reducing agent and preservative in industry and food industry.It has reducing ability and can react with PM to form active Mn???.In this paper,the optimal conditions for degradation of Tetracycline?TC?and Ciprofloxacin?CIP?two antibiotics in PM/BS system were studied.The production of active substances and the degradation mechanism of TC and CIP were explored.The main research contents are as follows:?1?By studying the effects of PM/BS addition ratio,dosage and initial pH on the degradation of two antibiotics.Under the optimal degradation conditions of initial pH=3.00,The ratio of PM/BS was 1:2.5,and the dosage was 50,125?mol/L respectively,the degradation rate of 5 mg/L TC was 84.2%;the optimal degradation of CIP was initial pH=3.00,PM/BS dosage ratio was 1:5,and dosage was 100,500?mol/L respectively.the CIP degradation rate of 5 mg/L was 97.2%.The change of temperature has little effect on PM/BS degradation of two antibiotics;CIP can preferentially degrade by PM/BS system when TC and CIP coexist due to the small molecular weight of CIP and the unstable structure of piperazine,the degradation rate of TC in PM/BS system is between 61.0%and 75.7%,and the degradation rate of CIP is between 84.5%and 100%.,?2?It was verified by experiments that Mn???,·OH and SO4?·in PM/BS system all played a role in the degradation of TC and CIP.The results of alcohol quenching experiments show that Mn???plays a major role in the degradation of TC in PM/BS system with PM/BS=1:2.5,and as the ratio of PM/BS decreases to 1:10,the production of Mn???,·OH and SO4?·increased,but the degradation rate of TC was reduced due to the reduction of Mn???by excessive BS.With the decrease of PM/BS ratio to 1:10,the yield of Mn???,·OH and SO4?·increases,and the degradation rate of TC decreases due to excessive BS reduction of Mn???.In order to further verify the effects of Mn???,·OH and SO4?·degradation of TC,6 kinds of reducing agents were used in the experiment to activate PM to produce Mn???for degraded TC.It was found that S?IV?-based reducing agents(SO32?,S2O52?)were able to produce Mn???,·OH and SO4?·hence have a equal degradation rate compared to the PM/BS system.Mn2+produced only Mn???without free radical and degradation rate is slightly reduced,C2O42?,NO2?activated PM had the lowest degradation rate of TC,and AA complex with Mn???slows the disproportionation of Mn???and release Mn???reactive with TC,so the degradation rate is slow but has good degradation effect;BS is used to activate Mn?IV???-MnO2?also has a good degradation rate for TC,indicating that the system produces Mn???,·OH and SO4?·free radicals,which are beneficial to the degradation of TC.Adding a complexing agent to the PM/BS system,the Mn???activity is lost or reduced due to the chelate formation of the complexing agent with Mn???,and the degradation of TC is inhibited;the inorganic salt and the real water had little effect on PM/BS system.The results of GC-MS indicate that the degradation degree of CIP is higher than that of TC.The alkyl groups linked by the two antibiotics tertiary amines are broken during the degradation process,and the N atoms are also removed. |
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