Study On Degradation Of Ofloxacin By Thermally Activated Persulfate System

The environmental pollution caused by the widespread use of quinolone antibiotics has become one of the major environmental problems in China and even in the world.Ofloxacin?OFX,Ofloxacin?is widely used in the clinical treatment of human and animal bacterial infections because of its higher drug tolerance,longer half-life,higher bioavailability and lower incidence of adverse reactionsin.However,the ofloxacin metabolites discharged from the body still have certain activity and can further form the matrix in the environment,thus causing water pollution.Therefore,the efficient degradation of ofloxacin is of great significance.In this paper,OFX degradation by thermal activated persulfate was studied.?1?The effects of reaction temperature,initial pH of the system,sodium persulfate?PS?dosage,OFX dosage and common ions in water?bicarbonate?HCO₃^-??chloride?Cl^-??humic acid?HA??on degradation of OFX by thermal activated PS were studied and the residual rate of PS in the reaction process was also analyzed.The optimal reaction conditions:reaction temperature was 60?,[PS]₀=4 mM,pH=4.7,[OFX]₀=0.03 mM,the degradation efficiency of OFX was 99.19%at 180 min.The degradation of OFX by thermal activated PS was fitted well with pseudo-first-order reaction kinetics?R²>0.98?,and the apparent reaction rate constant was 2.74×10^-2 min^-1.The results also showed that the apparent reaction rate constant increased significantly with the increase of temperature,OFX degradation is also fitted well with the Arrhenius equation under the influences of temperature,the calculated apparent activation energy calculated is 105.58 kJ·mol^-1 by the fitting equation.The removal rate of OFX will be decreased to varying degrees with the increase of the dosage of coexisting anions and organic acids.In addition,the residual rate of PS decreased with the increase of temperature,OFX dosage and PS dosage,the extremely acidic or alkaline environments caused the ineffective degradation of PS.?2?Response surface method?RSM?was used to optimize the OFX degradation conditions.The results of the quadratic regression equation model are as follows:the determination coefficient R²=0.9998,the correction determination coefficient R²_adj=0.9996,and the coefficient of variation CV=0.71%<10%.These data indicate that the model fits well.In the thermal activated PS degradation OFX reaction system,the order of influence of various factors on the degradation efficiency of OFX is:reaction time>initial dosage of OFX>initial dosage of PS>initial pH.The optimal degradation conditions obtained by the simulation:0.02 mM OFX,4.62 mM PS,pH=4.18,and the reaction time is 41.7 min,the predicted degradation efficiency of OFX is 95%,and the actual result obtained by parallel experiments is 93.78%.It shows that the actual and predicted values of OFX degradation efficiency have good consistency.?3?The mechanism of thermal activated PS degradation OFX and the kinetics of OFX degradation when quencher was added at different pH conditions were studied.EPR spectrometry experiments have proved that sulfate radicals and hydroxyl radicals are the main free radicals;the contribution of sulfate radicals and hydroxyl radicals to OFX degradation is 65.73%and 33.10%,respectively;the rate of change in the apparent reaction rate of the two quenching systems under different pH conditions showed no significant difference in the whole pH range.The mineralization of OFX reached 97.86%,The maximum accumulation of NH₄⁺and NO₃^-generated during the mineralization process were 0.962 mg·L^-1 and 0.268 mg·L^-1,respectively,which accounted for 76.35%and 21.27%of their equivalent values,which was consistent with the theoretical value.