| In recent years,the raging epidemic diseases,large-scale animal husbandry and medical industries highly developed directly or indirectly leaded to the large-scale use of antibiotics,resulting in a large amount of antibiotic wastewater that needs to be treated urgently.Among them,tetracycline and fluoroquinolone antibiotics were typical pollutants in aquatic environment.According to reports,the presence of antibiotics could be detected in various water bodies and even soil.At the same time,researchers had also turned their attention to the important threat that antibiotics may produce,that was,the production of antibiotic resistance genes and the immune diseases that they cause.How to remove antibiotics from the environment efficiently and at low cost has become a research hotspot.Nowadays,various methods had been developed to remove antibiotics from the environment,such as adsorption,Fenton oxidation,photocatalytic oxidation,biodegradation,and advanced persulfate-based oxidation.In order to protect the earth’s environment and promote sustainable development,garbage classification and resource utilization have become the trend of the times.Due to the rise of the stall economy and the e-commerce industry,the explosion of aquatic products products had spawned,resulting in a large amount of kitchen waste.The resource utilization of kitchen waste need to find new directions and ways.Based on this,this study used the chitin-based biomass material in aquatic products——crab shells as raw materials,and prepared it into biochar to remove antibiotics in the water environment.In this study,two kinds of crab shell-based biochar——crab shell biochar（CS）and acidified crab shell biochar（CS-H）,were synthesized and the removal effect of adsorption and degration of activating potassium hydrogen persulfate（PMS）typical antibiotic TC were studied.Through the analysis and discussion of the experimental results and the characterization results,a suitable explanation was put forward for the mechanism of its adsorption and advanced oxidation degradation.The main work done was as follows:（1）CS was obtained by pyrolyzing crab shells at a high temperature of 800℃,and the CS-H was activated by a variety of chemical reagents.The samples were characterized by X-ray powder diffraction,X-ray electron spectroscopy,Fourier transform infrared spectroscopy,N2absorption and desorption curve,electron spin resonance spectroscopy,and photocurrent.In addition,the effects of various factors such as p H,time,temperature,ions and other conditions on the adsorption and activation of PMS to degrade TC were also explored,and the adsorption mechanism and degradation mechanism were explored.（2）The adsorption experiment showed that CS could quickly and efficiently remove TC and reach adsorption equilibrium within 4 minutes;TC reached a high adsorption capacity of 934.5794 mg/g on CS-H at 19 hours.Both the adsorption of CS and CS-H fit the second-order kinetic model,which mainly removed tetracycline through chemical adsorption.On the isothermal model,CS and CS-H conformed to the Langmuir model and the Freundilich model,respectively.The adsorption mechanism of CS-H to TC includes physical adsorption of pore filling,chemical adsorption including hydrophobic interaction,π-πconjugate interaction,hydrogen bonding and electrostatic interaction.The main active site may be the graphite phase carbon in biochar,Benzene ring and oxygen-containing functional groups.CS could adsorb TC solution ultra-fast（4min to reach equilibrium）,mainly because Ca O met the water body and reacted rapidly to form Ca（OH）2,which had flocculation adsorption and surface adsorption with TC.The reason for the increase in the adsorption capacity of CS-H may be due to the formation of a large number of micropores and mesopores after the removal of Ca.（3）The activated PMS experiment showed that CS could significantly improve the degradation efficiency of PMS to TC（over 75%）,and the removal efficiency basically reached 86.99%within 20 minutes.The presence of Ca promoted the degradation of TC.The degradation mechanism was coordinated through the free radical pathway and the non-radical pathway.Among them,the non-radical pathway（surface oxygen vacancies）was dominant.CS had high conductivity and responded to photocurrent,which could lead to electron transfer.The active groups·O2-,·OH,·SO4-and 1O2also made a certain contribution to the process of degrading TC,and·O2-played a leading role.In summary,this research provided a new way for the resource utilization of kichen waste,and proposed the mechanism of free radicals and non-radicals to degrade pollutants.And surface oxygen holes in non-radical pathways could promote electron transfer. |
