| With the widely used of antibiotics in the industry of livestock,the content of antibiotics remaining in livestock wastewater has increased significantly,resulting in increasing the harm to human health and ecological environment.Antibiotic wastewater is a new type of pollutant in recent years,which has the characteristics of complex components and difficult to remove.Therefore,it is urgent to seek a high-efficiency and low-cost treatment technology to treat antibiotic wastewater.Fenton technology has been extensively studied in antibiotics removal from wastewater because of its simple operation,high degradation performance and environmental friendliness.Based on traditional Fenton oxidation technology,heterogeneous Fenton technology was developed,which can solve the disadvantages of homogeneous Fenton,such as narrow range of pH,low utilization rate of H2O2,and secondary pollution caused by large amounts of iron sludge.In addition,the heterogeneous Fenton catalyst has good application prospects with low cost and excellent reusability.In this paper,sulfamethoxazole（SMX）was selected as the target pollutant,and a new type of catalyst was developed to remove sulfamethoxazole in water.In this paper,schwertmannite was loaded on biochar（Sch@BC）by a biosynthesized method.Through the optimization experiment of the addition amount of biochar,the result shows that when the ratio of biochar to Schwertmannite was about 2:1,the composite catalyst has the best performance in degrading SMX.X-ray diffraction analysis（XRD）and Electron microscope scanning（SEM）analysis results show that:schwertmannite was successfully loaded on the surface of biochar,avoiding the agglomeration phenomenon of Electron microscope scanning（SEM）and X-ray diffraction analysis（XRD）analysis results show that schwertmannite was successfully loaded on the surface of biochar,avoiding the agglomeration phenomenon of schwertmannite during crystal growth.The measurement of specific surface area shows that the specific surface area of the composite catalyst can reach 79.5 m2·g-1.At the same time,the XPS characterization results show that the biochar and the Sch in the composite catalyst are bonded by C-O-Fe bonds.Through adsorption experiments,the adsorption properties of-sulfamethoxazole on biochar,Sch and Sch@BC were explored.The adsorption kinetics and isothermal adsorption results show that:biochar has the strongest adsorption capacity for SMX,and its adsorption capacity for SMX can reach 2.22 mg/g;Sch has the weakest adsorption capacity,only 0.09mg/g.The adsorption capacity for SMX on Sch@BC can reach 0.71 mg/g.Through the optimization experiment of the addition amount of biochar,it was found that when the ratio of biochar to Sch was about 2:1,the composite catalyst has the best performance for the degradation of SMX.The effects of initial pH,initial H2O2 concentration and catalyst dosage on the degradation of sulfamethoxazole were investigated using a single factor analysis method.At the same time,the effect of water quality factors（Cl-,NO3-,SO42-,COD and H2PO4-）on the degradation of sulfamethoxazole was also explored.These results indicate:Under optimal conditions（initial pH=3.0,H2O2 concentration=2.0 mM,Sch@BC dosage=1.0 mg/L）,SMX was completely degraded within 60 min and the TOC removal rate can reach 46%.At the same time,the study found that the present of Cl-,NO3-,SO42-in the water body has little effect on the removal of SMX.However,the existence of COD and H2PO4-in the water body has a certain inhibitory effect on the removal of SMX.The mechanism of degradation SMX in Sch@BC/H2O2 system was investigatived.The result shows that the hydroxyl radicals on the surface of the catalyst was play a dominant role on the degradation of SMX.At the same time,biochar can promote Fe（Ⅲ）/Fe（Ⅱ）cycle on the catalyst surface.The results of reusability and stability experimentation showed that the removal rate of SMX could still be kept above 96%after four consecutive reactions.Meanwhile,XRD results showed that the mineral phase of the Sch@BC did not change significantly before and after the reaction.Through liquid quality analysis（LC-MS）,six degradation intermediate products were identified,and three possible SMX degradation pathways were proposed. |
