Study On The Removal Of Sulfonamide Antibiotics From Water By Fe-N Co-modified Biocha

Sulfonamide antibiotics are a kind of broad-spectrum antibacterial drugs synthesized by man.Because of their chemical stability,they can exist in the water environment for a long time and pose a severe threat to human,animal,and plant health,so the research on the removal of sulfonamides from water is of great significance.Biochar materials prepared from biomass charring have shown great potential for pollutant control in the water.Still,the specific surface area of common biochar is not developed enough and the distribution of surface functional groups is not reasonable,so it is necessary to enhance the performance of biochar by a modification to enable better adsorption and catalytic behavior of pollutants.This thesis selected Sulfamethoxazole（SMX）and Sulfathiazole（ST）as the target pollutants,and magnetic biochars Fe-N-BC and MN-X were prepared by chemical cheat method for the adsorption and catalytic degradation of sulfonamide antibiotics,respectively.The influence law of Fe-N modification on the properties of biochar was investigated,the mechanism of biochar material performance enhancement was revealed,the adsorption and catalytic mechanism of sulfonamide antibiotic pollutants by modified biochar was analyzed,and the possible influencing factors in the practical application of modified biochar were initially clarified,which provided the fundamental and technical support for the application of biochar-based water treatment technology.In this thesis,four biochars were prepared by individual and co-modification of palm fiber biochar with 7H₂O·FeSO₄and urea,and their surface physicochemical properties were characterized and compared.During the adsorption of SMX by Fe-N-BC,the adsorption rate of Fe-N-BC on SMX in water showed a fast and then slow trend,and the first 2 h belonged to the fast adsorption stage and gradually reached the adsorption equilibrium at 4 h.Theremoval rate of SMX reached about96%.The Kinetic fitting results showed that adsorption kinetics was more in line with the proposed secondary kinetic model,the adsorption isotherm was more in line with the Freundlich isotherm model,and the saturation capacity of Fe-N-BC for SMX was42.9 mg/g.Among several environmental ions,Ca²⁺had an obvious competitive adsorption effect on adsorption;when the p H was in the range of 3.0～10.0,the stronger the acidity,the higher the adsorption capacity,and the optimal p H for adsorption was around 3.0;the characterization results of XPS,XRD,FTIR,and Raman spectra indicate that the iron oxides are successfully loaded on Fe-N-BC;the adsorption process involves pore filling,surface complexation,hydrogen bonding,Lewis acid-base interactions,andπ-πEDA interaction effects.The shape and trend of the hysteresis line judged that Fe-N-BC is superparamagnetic and can be easily separated from the solution under the action of a suitable applied magnetic field;the regeneration study of magnetic activated carbon showed that the drenching of Fe-N-BC with a mixture of methanol and ammonia can achieve a stable desorption effect,and the adsorption capacity of the adsorbent was reduced after four times of recovery and regeneration,but still kept 93.4%of the adsorption capacity,which has a high recycling value.The MN-X biochar was synthesized by co-pyrolysis of nitrogen-rich Spirulina with FeCl₃,which enhanced the ratio of biochar mesopores,increased the content of carbonyl oxygen functional groups,and improved the performance of the resulting biochar-activated persulfate,and the biochar-persulfate system was applied to the treatment of sulfathiazole（ST）in wastewater.In the PDS/MN-X system,the PDS concentration increased in a certain range（0.5 m M-2 m M）,and the degradation rate of ST then first increased and then decreased due to the quenching effect of PDS itself;when the p H value increased from 2 to 10,the removal rate of ST reduced due to the change of the present form of sulfonamide in water,and the PDS/MN-2 system gradually lost the oxidation effect on ST;the CO₃^2-also reduced the degradation effect of the PDS/MN-2 system on ST to some extent.The pore capacity,zeta potential,and defect degree of biochar all have a high positive correlation with peroxynitrite adsorption.The free radical quenching（methanol,p-benzoquinone and histidine）,free radical capture,and electrochemical characterization confirmed that the free radical pathway with SO₄^·-and^·OH as the main active particles supplemented by the non-free radical pathway with electron transport was the main pathways for the degradation of ST in PDS/MN-2 system.