| Recently,with the widespread use of antibiotics in the fields of medicine,livestock and poultry farming,agriculture and forestry,the content of residual antibiotic in the water environment has been increasing,which causes microbes to produce resistance and anti-drug genes.it will transfer among bacteria and even to human,causing potential threats to human health.Therefore,How to remove antibiotics from water environment in a green,efficient and rapid way is of great significance.In this study,calcium peroxide?CP?and peracetic acid?PAA?were used as oxidants,and metal ions and carbonaceous materials were used as activators respectively.The degradation effect of antibiotics under different systems and different reaction conditions were studied,and the degradation mechanism of antibiotics was analyzed and speculated by high performance liquid chromatography mass spectrometry instrument?HPLC-MS/MS?and Electron paramagnetic resonance?EPR?.Furthermore,the removal effect of antibiotics in actual wastewater was examined.Firstly,The physical and chemical properties of the prepared nitrogen-doped graphene?N-rGO?and CP were and characterized and analyzed:?1?SEM images reveal that Compared with GO,N-rGO has more wrinkles on the surface and more cracks on the edges;Raman spectroscopy results show that the degree of disorder and the intensity of defects on the surface of N-rGO were significantly improved;The results of XRD and FT-IR indicate the successful removal of oxygen-containing functional groups on the surface of N-rGO.With the doping of nitrogen,the amino functional groups are generated on the surface of N-rGO,which improves the activation properties of the graphene material.?2?The physical and chemical properties of commercial CaO2?CP1?and prepared CaO2?CP2?were analyzed,1the results show that CP2 has a finer particle size and relatively less agglomeration,and the specific surface area is significantly improved compared with CP1,and then further analysis by XRD shows that the main component of CP2 is CaO2.However,certain amounts of Ca?OH?2 and CaCO3 were identified in the synthesized products,along with small quantities of inorganic CaH2.Secondly,the process of degrading antibiotics by metal ion/peroxide system was studied.The degradation efficiency of cephalexin?CFX?by CP/Fe3+system alone is low,while the addition of chelating agents(nitrogen triacetate?NTA?,oxalic acid?OA?,ascorbic acid?AA?can effectively improve the degradation of CFX in the reaction system,among which AA has the best promoting effect;and the addition of AA could also effectively improve the degradation rate of CFX in HP/Fe3+system,but inhibited the PAA/Fe3+system.The results indicated that CFX was completely degraded after 20 min when 0.60 mmol·L-1 of Fe3+,0.15 mmol·L-1 of CFX,0.15mmol·L-1 of AA,and 0.144 g·L-1 of CP were present at pH=3.00.The degradation rate of CFX is positively correlated with the dosage of the drug in a certain range,and negatively correlated with pH.It can effectively degrade CFX under neutral alkaline conditions.The investigation of anions effects showed that sulfate ion(SO42-),chloride ion?Cl-?,humic acid?HA?had a minor impact on the degradation,however,HCO3-significantly inhibited CFX degradation.Both of hydroxyl radicals?HO·?and superoxide radicals?O2-·?were responsible for CFX degradationwhile HO·plays a major role in the degradation of CFX.The reaction site of HO·with CFX is on the S of the lactam ring,and produces two kinds of sulfoxide products.The CP/AA/Fe3+system has good removal effects for the other common types of antibiotics,but the removal effects of which are different.When dealing with the swine wastewater with complex components,an increase in reagent doses are required for effective antibiotics removal.Finally,the process of degrading antibiotics by carbonaceous materials/peroxide system was studied.It was found that the degradation rate of sulfamethoxazole?SMX?under N-rGO/CP and N-rGO/HP system was much lower than that of N-rGO/PAA system.When 1 mmol·L-1 of PAA,0.50 g·L-1 of N-rGO were present at a pH of 3.00 the degradation rate of SMX reached 96%in 60min,and the degradation rate of CFX is positively correlated with the dosage of the drug in a certain range,and negatively correlated with pH.The results show that Cl-and HA have little effect on the removal of SMX under this system,but the addition of HCO3-has a significant inhibitory effect on the degradation of SMX.The results of free radical experiments show that the free radicals that degrade SMX in the N-rGO/PAA system are carbon center radicals?CH3COO·and CH3COOO·?.The removal effect of different kinds of antibiotics in N-rGO/PAA system is different,but the overall removal effect is better;the degradation rate of SMX in actual water body:pure water>Sewage water?river water.In summary,CP/AA/Fe3+system and N-rGO/PAA system can effectively remove antibiotics in water.CP/AA/Fe3+system solves the demanding problems of traditional Fenton system,and N-rGO/PAA system avoids secondary contamination and potential toxicity.This study provides theoretical basis and technical support for the environmental remediation of water bodies contaminated by antibiotics,and has guiding significance for the development of antibiotic anti-control technology. |
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