Nano-Fe₃O₄ Activated Persulfate To Remove Sulfamethoxazole And Norfloxacin

For many years,my country has always been the world’s largest producer and consumer of antibiotics.While antibiotics have brought huge benefits to human society,they have also shown a kind of "water-solubility,stability,and low volatility characteristics in the environment." The state of "persistent" existence.Long-term continuous input has led to the emergence of resistant strains and resistant genes,causing serious harm to human health and the ecological environment.Therefore,it is necessary to remove antibiotics from water bodies.Among them,sulfonamides and quinolone antibiotics have attracted much attention due to their frequent detection in a variety of environmental media.Fe₃O₄ material,as a heterogeneous catalyst,is widely used to remove antibiotics in the advanced oxidation of persulfate due to its catalytic properties,non-toxicity and easy magnetic separation.In this paper,Fe₃O₄ activated persulfate（PS）was used to degrade sulfamethoxazole（SMX）and norfloxacin（NOR）.The effects of PS concentration,Fe₃O₄ dosage,initial pH,temperature,anion and natural organic matter on the degradation reaction were investigated.The reaction conditions were optimized,the reaction free radicals were identified,and the possible degradation pathways and intermediate products of SMX and NOR in the system were inferred.The following conclusions were obtained from the experiment:（1）The optimal reaction parameters for degradation of sulfamethoxazole（SMX）with Fe304 activated persulfate（PS）are:temperature 30℃,PS concentration 0.5mM,Fe₃O₄ dosage 1.2 g/L,pH=7 After 180 minutes of reaction,SMX has achieved 93.3%removal;after response surface optimization,the experimental parameters are set as follows:PS concentration 0.51 mmol/L,Fe₃O₄ dosage 1.39 mg/L,initial pH value of 5.56,the reaction obtains the final SMX The degradation rate is close to the theoretical prediction value of 99.94%;the degradation process follows the pseudo-first-order kinetic model;the increase in pH is not conducive to the removal of SMX;Cl-,CO32-and HA have different degrees of inhibition on the removal of SMX;NO3-shows Slight promotion effect;free radical quenching and EPR experiments prove that ·OH and SO4-participate in the reaction,and So4-plays a leading role in the degradation process;7 kinds of SMX degradation intermediates have been detected by the high-resolution liquid-mass system product.Based on the intermediate products detected during the reaction,three possible degradation pathways were proposed:partial oxidation of aniline,nitration,hydroxylation of oxazole ring,and S-N cleavage of sulfonamide.（2）The optimal reaction parameters for degrading norfloxacin（NOR）with Fe₃O₄ activated persulfate（PS）are:temperature 30℃,PS concentration is 0.8mM,Fe₃O₄ dosage is 1.2 g/L,pH=7 After a reaction time of 150 min,NOR achieved 94.8%removal;after response surface optimization,the experimental parameters were set as follows:PS concentration 0.87 mmol/L,Fe₃O₄ dosage 1.7 mg/L,initial pH value 5.08,NOR It can be completely degraded;the degradation process follows the pseudo-first-order kinetic model;acidic conditions are conducive to the removal of NOR;Cl-,CO32-,NO3-and HA all have different degrees of inhibition on the removal of NOR,and the order of inhibition is CO32->Cl->NO3-;free radical recognition experiments prove that ·OH and SO4-· are involved in the reaction,and SO4-· plays a leading role in the degradation process;the high-resolution liquid-mass system detected 8 NOR degradation intermediates.Based on the intermediate products detected during the reaction,four possible degradation pathways were proposed:dehydroxylation,defluorination,conversion of the piperazinyl ring,and decarboxylation.