Study On The Degradation Of Tetracycline By Persulfate Activated By Nitrogen-doped And Boron-nitrogen Co-doped Carbon Material

Based on the traditional hydroxyl radical advanced oxidation technology,persulfate advanced oxidation technology can produce sulfate radical with stronger oxidation capacity than hydroxyl radical,which has become a research hotspot in recent years,and has been widely used in the removal of various refractory pollutants in wastewater.It is difficult for persulfates to directly degrade pollutants by themselves.Carbon-based catalysts have great potential in activating persulfates to degrade tetracycline hydrochloride due to their advantages of environmental friendliness,rich structure,large specific surface area and excellent conductivity.Although the preparation of pure carbon materials is simple,there are shortcomings of insufficient active sites and low catalytic activity.Non-metallic doping is considered to be a better modification method at present.In this study,nitrogen-doped biocarbon and boronnitrogen co-doped biocarbon were used as catalysts to activate persulfate(PMS)to degrade typical antibiotic of tetracycline hydrochloride(TC)in water,respectively.The main research contents and conclusions are as follows:(1)Nitrogen-doped carbon material N/LC was prepared using bioresources lignin,melamine and urea for activating PMS to degrade TC.When N/LC catalyst dosage was 0.3 g/L and PMS dosage was 0.5 m M,the removal rate of TC of 20 mg/L concentration reached 90.4%and mineralization rate was 27.3% within 60 min.The catalyst had good stability and reusable performance.The effects of common anions and pH in water on TC degradation by this catalytic system were evaluated,indicating that the N/LC-PMS system had good adaptability to different environmental water bodies and had a promising application prospect.The free radical quenching experiment and EPR test showed that the N/LC-PMS system degrades pollutants mainly through electron transfer and singlet oxygen.Raman spectroscopy and XPS analysis showed that defect structure,pyridine nitrogen and carbonyl C=O play important roles as active sites in catalytic degradation.Eighteen intermediates were detected by analytical liquid mass spectrometry and four possible degradation paths of tetracycline hydrochloride were proposed.(2)Using glucose as carbon source,boron and nitrogen co-doped catalyst BNC was prepared by low melting point eutectic method,and was used to activate PMS to degrade TC.The results showed that BNC-10 had excellent adsorption properties,and the adsorption capacity of tetracycline hydrochloride reached 121.81 mg/g.When the dosage of BNC-10 catalyst was only 0.1 g/L,the TC removal rate reached 90.3% and the mineralization rate was34.3% within 60 min,which had higher activity than N/LC catalyst.BNC-10/PMS system could effectively degrade TC at the initial pH of 3.01-11.00,and could rapidly degrade 90% TC at pH of 11 within 5 minutes.The common anions in water did not affect the catalytic degradation performance of TC,especially chloride ions could promote TC degradation.Through free radical quenching experiment,EPR test and XPS analysis,the active substances of TC oxidation in BNC-10/PMS system and the important active sites in catalyst were discussed.Three possible degradation paths of tetracycline hydrochloride were proposed after 15 intermediates were detected by liquid mass spectrometry.