Study On The Performance And Mechanism Of Antibiotic Degradation In Water By Modified Porous Carbon Coupled With Peroxydisulfate

Antibiotics are widely used in medicine,aquaculture,and livestock farming.However,the antibiotics ingested by humans or animals are not fully absorbed,and most of them are excreted in their origin form in urine and feces.Due to the recalcitrance and persistence of antibiotics,the antibiotics discharged into the aquatic environment will exist stably for a long time.With the continuous application and discharge of antibiotics,the concentration of antibiotics continues to rise,which brings the risk of inducing resistance or even resistance genes in aqu atic organisms while disrupting the ecological balance of the aquatic environment.More importantly,antibiotics are bioaccumulative,which can spread through the food chain and eventually enter the human body,threatening human health and safety.Therefor e,it is imperative to explore a green,economical,and efficient antibiotic wastewater treatment technology.Heterogeneous persulfate（PS）activation holds the advantages of easy operation,economic efficiency,and wide applicability,which makes it an ideal antibiotic wastewater treatment technology.The key to this technology is the PS activator.Porous carbon（PC）is a quite promising material for PS activation because of its wide source,low cost,high specific surface area,good electrical conductivity,stable physicochemical properties,well-developed and easily adjustable pore structure.Nevertheless,pristine PC often exhibits limited PS catalytic activity due to its inherent chemical inertness.Based on this,this paper modified PC by metal loading,defect engineering,and heteroatom doping to further improve its PS activation ability,and focused on the performance and mechanism of these modified PC materials degrad ing ciprofloxacin（CIP）in water,which not only provided design ideas for the performance improvement of PC,but also provided theoretical guidance and technical support for the remediation of antibiotic sewage.The specific research contents and conclusions of this paper are as follows:（1）Firstly,a copper metal-organic framework（Cu-MOF）derived porous carbon（1 Cu-BTC-800）was synthesized by one-step pyrolysis using Cu-MOF as a self-template.The material characterization results showed that 1 Cu-BTC-800 was a PC composite containing metallic Cu and Cu_xO（x=1,2）.1 Cu-BTC-800 exhibited good peroxydisulfate（PDS）activation performance,achieving 84.22%CIP（10 mg/L）removal at a degradation rate of 0.0065 L·mg^-1·min^-1under the condition of unadjusted pH（pH=5.3）and room temperature（T=25℃）.Furthermore,1 Cu-BTC-800/PDS system had satisfactory CIP removal effect in the pH range of 3～9,demonstrating its wide pH applicability.Active species quenching experiments and electron spin resonance（ESR）results indicated that this activation system was a hybrid system containing sulfate radical（SO₄˙ˉ）,hydroxyl radical（˙OH）,superoxide radical（O₂˙ˉ）,and singlet oxygen（¹O₂）.Cu 2p high-resolution photoelectron spectra and Auger electron spectra analysis of 1 Cu-BTC-800 before and after the reaction,as well as theoretical calculation results collectively showed that surface Cu₂O was the main active site.It tended to preferentially adsorb PDS and transfer electrons to PDS,thereby inducing PDS activation for CIP degradation.In the third run,1 Cu-BTC-800/PDS system still removed about 76%CIP,showing good reusability.In addition,this activation system was less affected by common environmental substrates,which manifested its good potential for practical application.（2）To further improve the PDS activation performance of Cu-MOF derived carbon material,Zn²⁺was employed as the second metal node and constructed directly into Cu-MOF,thus forming a Cu,Zn bimetallic organic framework（Cu,Zn-MOF）.Subsequently,Cu,Zn-MOF was further pyrolyzed at high temperature to prepare Cu,Zn-MOF derived porous carbon（Cu,Zn-BTC-800）.Compared with Cu-BTC-800,Cu,Zn-BTC-800 had higher CIP（10 mg/L）removal rate and faster CIP degradation rate,and its excellent catalytic activity originated from Cu₂O and defective sites caused by Zn removal.Among the catalysts with different Cu/Zn molar ratios,Cu,Zn 2:1-BTC-800 had the highest CIP removal rate（93.63%）and the fastest CIP degradation rate(0.0156 L·mg^-1·min^-1).Moreover,Cu,Zn 2:1-BTC-800/PDS system had a wide pH applicability,which could achieve good CIP removal in the pH range of 3～9.Active species quenching experiments and ESR results indicated that this activation system contained SO₄˙ˉ,˙OH,O₂˙ˉ,and ¹O₂.In addition,although the reusability of Cu,Zn2:1-BTC-800 needed to be improved,this activation system was less affected by the common interfering substances in the aqueous environment,showing a certain potential for practical application.（3）To solve the metal ion leaching problem in the above two systems,a green and efficient metal-free heterogeneous PDS activator,namely sulfur-doped ordered mesoporous carbon（S-OMC）,was synthesized by pyrolysis method.Since O-containing and S-containing functional groups would undergo thermal decomposition at different calcination temperatures and lose O and S in the form of gas release,resulting in the generation of defects,a pyrolysis temperature gradient（400～1000℃）was set to regulate the defect level of S-OMC.In all S-OMC/PDS activation systems,¹O₂ was the dominant active species,and a high linear correlation（R²=0.9091）was found between the defect level of S-OMC and its corresponding ¹O₂ production yield,thus establishing a structure-activity relationship between defects and ¹O₂ production.Besides,the effects of pH,catalyst dosage,and PDS dosage on S-OMC-1000/PDS system were investigated.Under the condition of no pH adjustment（pH=5.3）and slight catalyst dosing（50 mg/L）,this activation system could remove 85.84%CIP（20 mg/L）with a degradation rate of 0.0039 L·mg^-1·min^-1.In the effect survey of common environmental substrates,it was found that S-OMC-1000/PDS system could exhibit a relatively stable CIP removal effect in the presence of Clˉ,H₂PO₄ˉ,SO₄²ˉ,or NO₃ˉ,while HCO₃ˉand humic acid（HA）even promoted CIP degradation,indicating its good potential for practical application.Furthermore,although the reusability of S-OMC-1000 was poor,secondary calcination treatment was proved to be a feasible method to restore its catalytic performance.