Study On The Degradation Of Typical Macrolide Antibiotics By Sulfonated Carbon-based Solid Acids

Macrolide antibiotic production wastewater often has high concentration of antibiotic residues,which will inhibit the efficacy of subsequent biological treatment,and there is a risk of proliferation of drug-resistant bacteria.Therefore,it is necessary to carry out effective pretreatment of productive wastewater to ensure the efficiency and stable operation of subsequent biological treatment.Typical solid acid catalysts,represented by sulfonated carbon,could be used for catalytic hydrolysis to break the glycosidic bonds of macrolides and removed the pharmacodynamic active sugar groups.Due to the lack of systematic understanding of the characteristics of carbon materials,sulfonated carbonation characteristics and hydrolysis efficiency,solid acid materials capable of highly efficient catalytic hydrolysis pretreatment of macrolide antibiotics cannot be obtained.This study selected two typical macrolides antibiotics（tylosin and spiramycin）as the research object,using different ways to prepare sulfonated carbon-based solid acid.The hydrolysis effects on two kinds of antibiotics were studied,and the relationship among different structure,surface properties,and sulfonated properties of carbon materials and the catalyzed hydrolysis of antibiotic was also discussed.Biochar materials with different aromaticity and condensation degree were prepared at 300-650 ^oC and N₂ atmosphere.Solid acid loaded with-SO₃H was successfully prepared by sulfonation reaction,which was used for the catalytic hydrolysis of typical macrolide antibiotics spiramycin and tylosin under the assistance of microwave.The results showed that when the initial concentration of antibiotics was 40mg/L,the microwave power was 200 W,and the dosage of sulfonated carbon-based solid acid was 1.0g/L,the material CS300 could completely remove tylosin and spiramycin within 4 min and 6 min,and had the best catalytic effect.For these two antibiotics,the material CS300 was reused for 5 times,and the removal rate could still reach 100%within 10 min.The hydrolysis pathway of tylosin was analyzed.After complete hydrolysis,all three glycosidic bonds were broken.Raman spectroscopy,XPS,¹³C-NMR and topological analysis further revealed that lower pyrolysis temperature could lead to lower aromatic ring density,more sulfonation sites and higher total acid content,which led to higher catalytic hydrolysis efficiency.Surface structural characteristics of carbon materials were regulated by mechanochemical and chemical oxidation,three carbon materials with different physical and chemical properties including the improved Hummers method,nitric acid immersion,microwave nitric acid immersion and ball milling.The modified product was sulfonated.The sulfonation characteristics of the modified products and the catalytic hydrolysis efficiency of sulfonated carbon-based solid acid were investigated.It was found that the removal efficiency of the three kinds of solid acid materials modified by ball milling method could remove more than 80%of tylosin within 6 min,and the removal efficiency of the carbon materials modified by the improved Hummers method was the second.After ball-milling,the aromaticity of carbon materials decreased from 0.94,0.90 and 0.99 to 0.88,0.85 and 0.80,respectively.The specific surface area increased to 5～500 times before ball-milling,and the average particle size decreased by about 500μm.All of the above characteristics promoted the sulfonation reaction and resulted in higher total and sulfonic acid content,thus improving the hydrolysis efficiency of tylosin.In this study,it was shown that both of the two methods could effectively regulate the different surface structure characteristics of solid acid carbon-based precursors to obtain high acid content solid acids,thus promoting the catalytic hydrolysis efficiency of typical macrolide antibiotics.It provides a theoretical support for the development of catalytic hydrolysis pretreatment methods of macrolides antibiotic production wastewater,which will be helpful to promote the effective treatment of macrolide antibiotic production wastewater.