Degradation Of Sulfamethoxazole And Tetracycline By Persulfate Activated By Electric Field And Its Mechanism

The ecological and environmental problems caused by PPCPs(pharmaceutical and personal care products)have attracted attention at home and abroad.Sulfamethoxazole and tetracycline are the most abundant antibiotics in Liaohe River Basin.Sulfamethoxazole(SMX)is used in the treatment of respiratory tract,urinary tract infection,otitis media and other diseases,but the residual SMX in surface water and groundwater has certain harm to the microbial community and animal development.Tetracycline is the most representative antibiotic in livestock and poultry breeding and aquaculture.High concentration tetracycline has bactericidal effect.The residual tetracycline in water will bring adverse effects and lead to the production of a variety of drug-resistant bacteria.Persulfate(PMS)is one of the strongest oxidants in aqueous solution,which has stable properties.It is necessary to oxidize and degrade pollutants by sulfate radical generated by light,heat,transition metal(Fe,etc.)and other activation methods.Electrocoagulation is an efficient water treatment method,which has good adaptability for all kinds of organic wastewater,and low cost is also the advantage of electrocoagulation.In this paper,sulfamethoxazole and tetracycline were degraded by sulfate radical and hydroxyl radical with high redox potential generated by activated persulfate in the process of electrocoagulation.At the same time,the hydroxyl polymer of iron produced flocculation precipitation,which could degrade macromolecular antibiotics.In this paper,the simulated wastewater of sulfamethoxazole and tetracycline was used to investigate the removal efficiency of the two antibiotics by optimizing the plate conditions,initial PMS concentration,initial antibiotic concentration and initial pH value.The optimum conditions for sulfamethoxazole degradation were as follows:iron graphite plate combination,initial PMS concentration of 500 mmol,current intensity of 500 mA and pH value of 5.Under these conditions,94%of sulfamethoxazole can be degraded in 4 h.The optimum conditions for tetracycline degradation were as follows:iron graphite electrode combination,initial PMS concentration of 500 mmol,current intensity of 500 mA and pH value of 7.Under these conditions,tetracycline can be completely degraded within 4 h.The degradation of the two antibiotics followed pseudo first order kinetics.The results showed that the combination of persulfate and electrocoagulation had better degradation effect on the two antibiotics than oxidation or electrocoagulation alone.In this paper,the degradation mechanism of two typical antibiotics was studied by scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FT-IR)and electromagnetic spin resonance(EPR).It was proved that sulfate radical and hydroxyl radical were produced in the system,and the flocculation precipitation was mainly mononuclear and polynuclear hydroxides of iron.