Transition Metal Catalysts Activated Persulfate For Degrading Tetracycline

The impact of antibiotics in water on ecological environment and human health has attracted more and more attention.Advanced oxidation processes based on persulfate（PS-AOPs）are considered as promising antibiotic wastewater treatment methods due to the highly reactive oxygen species they produce that can oxidize and degrade organic pollutants.PS are thermodynamic oxidants,but their direct reaction with most pollutants is generally not feasible due to the low reaction rate.Therefore,proper activation of PS is required to generate highly reactive oxygen species.In PS-AOPs,the degradation efficiency of pollutants largely depends on the catalytic performance of the PS-activated catalyst.Therefore,finding high-efficiency and long-term stable catalysts is the key for PS-AOPs to remove pollutants.In this dissertation,starting from persulfate activation,a series of transition metal-based catalysts were prepared,and different advanced oxidation systems were constructed for catalytic degradation of tetracycline（TC）.The activation mechanism of persulfate,the mechanism of TC removal,and the long-term activity of the catalyst was deeply studied.The main contents are summarized as follows:（1）Due to the synergistic coupling of active sites,bimetallic composite catalysts exhibit higher persulfate activation performance and catalytic stability than monometallic oxides.Using carbon cloth（CC）as the carrier,a series of Cu and Co oxide supported catalysts were prepared:Cu O/CC,Co₃O₄/CC,Cu Co₂O/CC,and Cu₂Co O/CC.The performance of this series of catalysts for peroxymonosulfate（PMS）activated degradation of TC indicated that Cu-Co bimetallic oxides have higher catalytic activity and stability.Among them,the apparent rate constant of TC degradation by Cu₂Co O/CC reached 0.1693 min^–1,which was 3.5 and 7.8 times higher than that of single metal oxides Co₃O₄/CC and Cu O/CC,respectively.The effects of different experimental parameters on the catalytic degradation system of Cu₂Co O/CC activated PMS to degrade TC were explored.The study found that Cu₂Co O/CC has high catalytic performance under weakly acidic,neutral,and weakly alkaline conditions.Coexisting anions such as NO₃^–and SO₄^2–have little effect on the reaction system,while Cl^–and CO₃^2–have moderate inhibitory effects.The removal rate of TC still reached 90%after being recycled 5times,indicating that the Cu₂Co O/CC catalyst has good stability.Radical quenching experiments and electron spin resonance（ESR）analysis indicated that Cu₂Co O/PMS system participated in the catalytic degradation of TC through both radical pathways(SO₄^·–and·OH)and non-radical pathways（¹O₂）.In addition,the activation mechanism of PMS by Cu₂Co O/CC was further analyzed.（2）The combination of multiple technologies can make up for the deficiency of a single technology and generate a positive synergistic effect.Co Fe₂O₄/TNAs composite catalyst was prepared by in-situ growth on Ti meshes,and a photocatalysis coupled peroxydisulfate（PDS）oxidation system was constructed to enhance the treatment of TC wastewater.The matching band structure of Co Fe₂O₄ and TNAs promoted the effective separation of photogenerated electron-hole pairs,the addition of PDS further inhibited the recombination of photogenerated carriers,and PDS was activated by various pathways to generate SO₄^·-.In the photocatalysis coupled PDS oxidation system（Co Fe₂O₄/TNAs+PDS+light）,the apparent rate constant of TC degradation was 0.0933 min^–1,which was 7.1 and 6.4 times higher than that of the photocatalysis（Co Fe₂O₄/TNAs+light）and PDS oxidation（Co Fe₂O₄/TNAs+PDS）system,respectively.The Co Fe₂O₄/TNAs+PDS+light system has efficient catalytic performance in the p H range of 3–9 and has a strong anti-interference ability to the coexisting anions of NO₃^–,SO₄^2–and Cl^–.Free radical quenching experiments and ESR tests showed that h⁺,·OH and SO₄·-were the main active species for TC degradation,meanwhile O₂^·–and ¹O₂ also played an auxiliary role.In addition,the active components Fe（II）and Co（II）could be regenerated by the O₂^·–generated by the photocatalysis system,thus ensuring energetic activation towards PDS,resulting in the strong stability and long-term durability of the Co Fe₂O₄/TNAs composite catalyst.The removal rate of TC still reached 98%after being recycled 5 times.In continuous-flow experiments,when the flow rate was 2.5 m L/min,the removal rate of TC was still as high as 93%after continuous treatment for 12 h,and the removal flux was 0.74 g/（min m²）.In addition,the antibacterial activity of the degraded products of TC on Escherichia coli was significantly reduced.