Research On Typical Antibiotics Treatment By Fenton-Like Process With Copper-Organic Complexation In Water

The typical Fenton oxidation method is one of the classic advanced oxidation technologies（AOPs）,Fe²⁺in aqueous solution activates H₂O₂ to produce hydroxyl radical（·OH）,·OH is highly oxidizable and can degrade organic pollutants in water non-selectively.Although typical Fenton process is convenient to operate and has simple reaction conditions,its effective p H range is narrow,H₂O₂ is prone to disproportionation,which is not convenient for transportation and storage,and leads to low utilization rate;Fe（OH）₃precipitation is easily generated when p H value is high,and the cycling rate between Fe³⁺and Fe²⁺is slow.These deficiencies affect the practical application of typical Fenton process.In order to solve the above problems,the homogeneous Fenton process has gradually become a research hotspot in related fields in recent years.In this paper,Fe²⁺is replaced with Cu²⁺,the degradation efficiency of the Fenton reaction was significantly improved by the addition of complexing agents（Hydroxylamine,tartaric acid,gallic acid）,which broadened the p H range of the process and effectively promoted the cycling between Cu²⁺/Cu⁺in solution.At the same time,calcium peroxide（Ca O₂）and persulfate（PDS）can be used as stable oxidants to effectively replace H₂O₂.Ca O₂ as a solid H₂O₂ source dissolved in water can slowly and stably release H₂O₂,and the addition of PDS can produce sulfate radicals(SO₄^·-),which have a higher redox potential than·OH and can improve the degradation efficiency of organic pollutants in water.Therefore,the homogeneous Fenton oxidation process has a better application prospect in actual wastewater treatment.In summary,the specific research content of this paper is as follows:（1）Using Ca O₂ instead of H₂O₂ as oxidant,hydroxylamine（HA）as complexing agent and Cu²⁺as catalyst to construct Cu²⁺/HA/Ca O₂ system to degrade the typical antibiotic—Dexamethasone（DXM）.The optimum experimental conditions of this reaction were determined by studying the influence of each reaction condition on the degradation performance of the reaction system.The results showed that the removal rate of DXM can reach 87.1%when the initial p H value was 5,the concentration of Cu²⁺,HA and Ca O₂ was0.1 mmol L^-1,1 mmol L^-1 and 1 mmol L^-1,respectively.The concentration determination of Cu and H₂O₂ showed that the addition of HA can promote the Cu²⁺/Cu⁺cycle efficiency and the decomposition of H₂O₂.Free radical quenching experiments and electron paramagnetic resonance（EPR）showed that·OH and singlet oxygen（¹O₂）were involved in the reaction,and the active species that played a major role in the reaction was·OH.The degradation intermediates of DXM were identified by high performance liquid chromatography-mass spectrometry（HPLC-MS）,and the possible degradation paths of DXM were speculated.Toxicity evaluation software（T.E.S.T）was used to evaluate the biological toxicity of DXM degradation byproducts.Finally,the effects of four common inorganic anions(Cl^-,HCO₃^-,NO₃^-and SO₄^2-)in natural water on the degradation performance of the system were investigated.（2）Using Ca O₂ as oxidant,tartaric acid（TA）as complexing agent and Cu²⁺as catalyst to construct Cu²⁺/TA/Ca O₂ system to degrade metronidazole（MTZ）.The reaction conditions of the system were optimized by exploring the effect of reaction parameters on the removal efficiency of MTZ.The results showed that MTZ in the system could achieve great removal rate under the condition of the initial p H value was 5,the concentration of Cu²⁺,TA and Ca O₂ was 0.1 mmol L^-1,2 mmol L^-1 and 2 mmol L^-1,respectively.The concentration determination of Cu and H₂O₂ showed that the addition of TA can promote the Cu²⁺/Cu⁺cycle efficiency and the decomposition of H₂O₂.Free radical quenching experiments and EPR showed that·OH,¹O₂ and superoxide radicals(O₂^·-)were involved in the reaction,and the active species that played a major role in the reaction was·OH.HPLC-MS was used to identify the degradation intermediates of MTZ,and the possible degradation path of MTZ was speculated.T.E.S.T was applied to evaluate the biotoxicity of MTZ degradation byproducts.（3）Using PDS as oxidant,gallic acid（GA）as complexing agent and Cu²⁺as catalyst to construct Cu²⁺/GA/PDS Fenton-like system to degrade sulfamethoxazole（SMX）.The optimum experimental conditions of this reaction were determined by studying the influence of each reaction condition on the degradation performance of the reaction system.The results showed that the removal rate of SMX can reach 84.8%when the initial p H value was 7,the concentration of Cu²⁺,GA and PDS was 0.2 mmol L^-1,0.1 mmol L^-1 and 1.5mmol L^-1,respectively.The role of GA in the system was investigated by measuring the concentration of GA and PDS.The UV-visible full spectrum（UV-Vis）and cyclic voltammetry（CV）indicated the formation of Cu-GA complex.Free radical quenching experiments and EPR demonstrated the existence of SO₄^·-,·OH,¹O₂ and O₂^·-in Cu²⁺/GA/PDS process.Coumarin fluorescence probe experiment showed that the addition of GA promoted the production of more·OH in the system.The degradation byproducts of SMX were detected by HPLC-MS,and four degradation paths of SMX were proposed.Finally,the continuous catalytic experiment of high concentration wastewater and the removal experiment of typical dye were carried out,which proved that the synergistic system has certain practical wastewater treatment potential.