Application Research Of Removing Sulfamethazine By Electro-Fenton Based On Pyrite

Nowadays,antibiotics have been widely used in the whole world,but the environmental pollution caused by them is becoming more and more serious.The residual antibiotics in the water and soil environment have teratogenic and carcinogenic effects,and even lead to death.Therefore,more and more scholars begin to pay attention to develop new technologies that can effectively treat antibiotic wastewater,so as to reduce the harm to human beings,animals and the environment.In this study,the electrocatalytic degradation of antibiotic,sulfamethazine（SMZ）,was investigated by using graphite felt with copper modified（GF/Cu）as cathode,graphite plate as anode,synthetic pyrite（syn-FeS₂）and natural pyrite（com-FeS₂）as catalysts.The effects of operating conditions（such as,applied voltage,catalyst dosage,initial p H and GF/Cusize）and environmental factors(such as,antibiotics concentration,water temperature and common anions,such as,Cl^-,NO₃^-,CO₃^2-,HCO₃^-)on the degradation efficiency of SMZ were explored.The specific research contents are as follows:（1）The syn-FeS₂ synthesized by hydrothermal method and ball milled showed excellent surface catalytic activity,which led to an efficient degradation of SMZ in syn-FeS₂-GF/CuEF system.After 120 minutes of reaction,0.2 mmol/L SMZ can be completely degraded with the mineralization rate of 73.8%.The catalytic activity of used syn-FeS₂ can be completely restored after washed with ethanol and deionized water and dried.And,this system can work effectively in a wide range of salinity（[Na₂SO₄]=0.05～0.6 mol/L）.（2）The deposition of Cuimproved the ability of the graphite felt（GF）electrode to activate O₂ in situ to produce H₂O₂ and O₂-·,and promoted the decomposition of H₂O₂ to produce·OH.Also,the·OH and O₂^-·were detected in the syn-FeS₂-GF/CuEF system,which were mainly attributed to the catalytic effect of GF/Cuelectrode,Fe（Ⅱ）and sulfur vacancy on the surface of syn-FeS₂.Therefore,when the initial concentration of SMZ was0.2 mmol/L,it can be rapidly oxidized and completely degraded.（3）The results of single factor experiments and response surface method（RSM）experiments showed that the optimal experimental conditions of the system were as follows:[com-FeS₂]of 0.65 g/L,initial p H of 6.5,applied voltage of-0.83 V,and GF/Cuelectrode area of 8.98 cm²,that can almost completely degrade SMZ in 1.5 h.The higher water temperature（35℃）can promote the degradation process.The CO₃^2-and HCO₃^-reduced greatly the degradation rate of SMZ.While Cl^-accelerated the degradation.In addition to,the NO₃^-had almost no effect.（4）There were four kind of ROS for SMZ degradation in com-FeS₂-GF/CuEF system,and their contribution rate was·OH>¹O₂>O₂^-·>·OH_ads.It was speculated that there were four important processes in the degradation of SMZ by the HR-LC-MS test.They were the cleavage of the sulfonamide N-S bond,the opening of the benzene ring and the nitrogen-containing heterocyclic ring,the extrusion of SO₂and the direct oxidation of SMZ.Finally,the intermediates were transformed to CO₂,H₂O,NO₃^-,NH₄⁺,SO₄^2-（SO₂）and so on.