Study On The Degradation Of Ciprofloxacin By Peroxymonosuifate Activated By Biochar Prepared By Heavy Metal Super-enriched Plant

The abuse of antibiotics has led to the discharge of wastewater containing antibiotics into the environment,which has caused new problem of environmental pollution.The presence of antibiotics in the environment will have certain effects on aquatic and terrestrial ecosystems.Due to the complex structure of antibiotics and their antibacterial properties,it is difficult for conventional biological treatment methods to achieve complete degradation of antibiotics.The advanced oxidation technology has the characteristics of strong oxidizing property and non-selectivity,which can realize the efficient degradation of antibiotics.In this paper,a heavy-metal super-enriched plant,Sedum southeast,was used as a raw material to prepare a biochar with high catalytic activity for the activation of peroxymonosulfate to degrade ciprofloxacin.First,BET,XRD,Raman,XPS,FTIR and other characterization methods were used to analyze the morphology,composition,structure,and surface chemical characteristics of the prepared catalytic materials.The adsorption properties of the prepared different biochar were compared.Southeastern Jingtian biochar MBKx(x represents pyrolysis temperature)were utilized to activate different oxidants(hydrogen peroxide,peroxydisulfate,peroxymonosulfate)for degradation of ciprofloxacin.The effects of different factors on the catalytic degradation of ciprofloxacin by MBK700/PMS system were studied.Chemical stability of biochar MBK700,cyclic stability and metal ion dissolution of MBKx were studied.Finally,the mechanism of MBK700/PMS catalytic degradation of ciprofloxacin was investigated.The mechanism that MBK700/PMS catalyzed PMS to degrade ciprofloxacin was investigated.The results of characterization indicated the specific surface area of the Southeastern Sedum biochar MBK700 prepared under the same conditions was significantly larger than the biochar prepared from other biomass(peanut shell,wheat straw,activated sludge).As for the biocharl MBKx,the specific surface area gradually increased and the average particle size gradually decreased with the increase of pyrolysis temperature.The specific surface areas of MBK700 and MBK800 were 973.8 and 1090.7 m2/g,respectively.As for the biocharl MBKx,the specific surface area gradually increased and the average particle size gradually decreased with the increase of pyrolysis temperature.The specific surface areas of MBK700 and MBK800 were 973.8 and 1090.7 m2/g,respectively.Cu,Zn,and N elements were found in biochar MBKx,and their presence can improve the catalytic performance of carbon materials.Adsorption experiments indicated that the adsorption performance of biochar MBK700 was significantly better than other biochar,and the adsorption performance of MBK800 and MBK700 were significantly better than that of the biochar prepared at other temperatures.MBKx can efficiently activate peroxymonosulfate to degrade ciprofloxacin,the activation of peroxydisulfate was weaker,and it was almost impossible to activate hydrogen peroxide,and the removal rate of ciprofloxacin by MBK700/PMS system was the highest.In the MBK700/PMS system(ciprofloxacin concentration 80 mg/L,initial pH 7.0,PMS concentration 5.0 mM,catalyst loading 0.1 g/L),ciprofloxacin could be decomposed about 85%within 1 h.After 4 runs,the removal rate of ciprofloxacin was reduced because the surface active sites were occupied,catalysts treated with organic reagents could achieve effective regeneration of catalyst.The leaching concentration of copper and zinc iron was below the country standard,and XPS results show that the carbon material MBK700 was slightly oxidized after repeated use.The factors influencing ciprofloxacin degradation were studied,and the results were as follows:① Temperature showed a certain positive effect on degradation of ciprofloxacin by MBK700/PMS system,the higher the temperature,the higher the removal rate;humic acid hardly affected ciprofloxacin removal.② Chloride and dihydrogen phosphate ion hardly affected the removal of ciprofloxacin by MBK700/PMS system,while bicarbonate had a greater effect on it and exhibited that low concentration inhibited removal of ciprofloxacin and high concentration promoted removal of ciprofloxacin.The mechanism that MBK700/PMS system catalyzed PMS to degrade ciprofloxacin was as follows:Quenching experiments and EPR experiments confirmed the simultaneous existence of hydroxyl radicals,sulfate radicals,and singlet oxygen in the reaction system,they do not play a leading role in the degradation of ciprofloxacin,D2O experiments and different substrate degradation experiments had further confirmed that singlet oxygen did not play a leading role in the degradation of ciprofloxacin.Electrochemical experiments confirmed the existence of electron transfer during the degradation of ciprofloxacin,therefore,the degradation of ciprofloxacin was likely to be dominated by the electron transfer mechanism,and free radicals and singlet oxygen play only part of the role.