Activation Of Peroxymonosulfate By Copper Oxide Composite Multi-walled Carbon Nanotubes For The Degradation Of Diclofenac

Advanced oxidation technology based on sulfate radical(SO₄^·-)has received more and more attention in recent years.SO₄^·-has a high REDOX potential（2.5～3.1 V）,which makes a strong ability to oxidize and remove organic pollutants.Group at its early research has shown that copper oxides reduced by citric acid can improve the ability of catalyzing PMS.Copper oxides have small specific surface area and narrow adsorption ability of organic pollutants.Copper oxides/PMS system can generate free radicals,which may not attack the organic matter before quenching.In order to solve these problems,a well-crystallized copper oxides（Cu_xO）were synthesized via a sol-gel method and further loaded on the commercial multi-walled carbon nanotubes to activate PMS for water decontamination.The degradation efficiency of DCF by the synergistic process of adsorption and catalysis on the surface of the catalyst was studied.The catalysts were synthesized by controlling the mass ratios of Cu²⁺/MWCNTs,and the catalyst（named Cu_xO@CNTs）with an optimal mass ratio of 1:8 was used for the studies.X-ray powder diffraction（XRD）,scanning electron microscope（SEM）,high-resolution transmission electron microscopy（HRTEM）,X-ray energy spectrum（EDS）,specific surface area and pore size analysis（BET）,X-ray photoelectron spectroscopy（XPS）and Raman spectroscopy（Roman）were carried out on the catalyst morphology structure,phase composition,element analysis and defect analysis.Various factors affecting the catalytic degradation of DCF by PMS,such as the amount of catalyst,the amount of PMS and the initial concentration of DCF,were studied.The results showed that when the initial concentration of DCF was 1 mg/L,the dosage of PMS was 12.5 mg/L,the dosage of catalyst was 25 mg/L,the initial p H was6.7,and the reaction temperature was 23℃,the removal rate of DCF could reach94.82%.In addition,the effects of water quality parameters,such as solution p H,reaction temperature,inorganic anions in water,basicity of bicarbonate and humic acid on DCF degradation were also studied.The experiment also explored the practicability of Cu_xO@CNTs,including its recyclability,safety and stability.It is worth noting that calcined Re-Cu_xO@CNTs can restore the initial adsorption and catalytic performance.The signals generated by reactive oxygen species（ROS）complex were captured by electron spin resonance（ESR）.Tests performed with various quenchers in the process further evaluated the role of the ROS for DCF degradation.It was proved that there were·OH,SO₄^·-,O₂^·and ¹O₂ in the system,and O₂^·and ¹O₂ played a leading role in catalytic process.Eight intermediates and some small molecular organic acids were detected by UHPLC-QTOF/MS.Combined with density functional theory,DCF degradation can be divided into two pathways:free radical oxidation degradation and non-free radical oxidation degradation.In a word,this topic has laid a theoretical foundation for the application of PMS/Cu_xO@CNTs in actual water treatment.