Research On The Degradation Of Organic Pollutants By Biochar Activated Peroxymonosulfate

As one of typical sulfa antibiotic,sulfamethoxazole（SMX）is widely used in animal husbandry and human medicine.SMX has led to the drug resistance of pathogenic microorganisms and the ecological pollution of the water environment on account of its extensive use worldwide.In this study,biochar was used to activate peroxymonosulfate（PMS）to degrade sulfamethoxazole in water on a laboratory scale;used nanocellulose and thiourea as raw materials to successfully synthesize nitrogen-sulfur co-doped biochar（N,S-BC）with a hierarchical pore structure through a one-step pyrolysis method.Nitrogen-sulfur co-doped biocarbon prepared at high temperature has excellent catalytic activation ability and can effectively activate permonosulfate to degrade sulfaethoxazole in water.The kinetics and mechanism of degradation of sulfamethoxazole in N,S-BC/PMS system were studied.Under the same conditions,the removal efficiency of SMX by this oxidation system is the most common metal oxide（such as Fe₃O₄,Fe₂O₃,Mn O₂）2.3-3.1 times.The main conclusions are as follows:A series of characterization methods were used to characterize N,S-BC to analyze its structure and chemical properties.The results showed that:N,S-BC is a tiny block structure with a particle size of several micrometers to tens of micrometers,nitrogen and sulfur.The elements have been successfully doped into N,S-BC;the prepared N,S-BC belongs to graphite-based materials because of its certain degree of graphitization;the specific surface area of N,S-BC is 128.53 m²/g;The main pore size distribution of N,S-BC is in the range of 2-10 nm,which belongs to the mesoporous structure;ID/IG is 1.45,which indicates that the carbon catalyst has a certain degree of defects.In this paper,the effects of different activator dosage,PMS concentration,initial p H value of solution and different water substrates on the degradation of sulfamethoxazole were investigated.It was found that the degradation of sulfamethoxazole could maintain excellent catalytic capacity under a wide p H range and different water substrates.As the dosage of N,S-BC was 0.2 g/L,the concentration of PMS was 0.8 m M,and the initial p H of the SMX without adjustment,the degradation rate of SMX in N,S-BC/PMS system was 91.32%.The amount of carbon catalyst added to the N,S-BC/PMS system degraded SMX ability in line with Langmuir-Hinshelwood（L-H）kinetic model;the amount of PMS added and the p H value of the N,S-BC/PMS system degraded SMX ability in line with the second level Kinetic equations.Obtained by Reactive oxygen species（ROS）quenching experiment and EPR test,the mechanism of N,S-BC/PMS process is inferred:free radicals and singlet oxygen play an important role in the degradation of SMX.Surprisingly,the^·OH and SO₄^·-produced in the system react with SMX in a combined state on the surface of the carbon catalyst instead of being dispersed in the aqueous solution.This provides new insights for the application of carbon catalysts in actual water pollution control.Surprisingly,a new catalytic mechanism was discovered in the N,S-BC/PMS system,that is,surface-bound free radicals and singlet oxygen together play a major role.After repeated use,the PMS activation performance of N,S-BC catalyst to degrade the SMX in the water decreased significantly.N,S-BC catalyst has great potential to remove SMX.This special form of free radicals can resist the influence of background substances and p H changes in the water,and can maintain a good SMX degradation effect under different water quality and p H.