Study On Water Treatment Based On Advanced Oxidation Technology Of Persulfate

With the improvement of industrial production technology and the rapid development of society,the pollution of water resources is becoming more and more serious.While conventional wastewater treatment processes are difficult to remove these pollutants with complex compositions effectively,chemical advanced oxidation has been widely studied by domestic and foreign scholars for its advantages of easy operation,fast degradation rate and small secondary pollution,etc.Advanced oxidation technology using peroxymonosulfate is an important way for large-scale wastewater treatment and water resources problems.The advanced oxidation technology based on peroxymonosulfate（PMS）has attracted a lot of attention from water treatment researchers because of its advantages such as fast reaction rate and wide p H adaptation range.The generated reactive species have a strong oxidation capacity and exhibit excellent anti-pollutant and bacterial properties in terms of free and non-free radicals.Therefore,this thesis focuses on transition metal catalysts to ensure their stable and efficient activation of persulfate while providing an in-depth investigation of their activation mechanisms.The main findings of this paper are as follows:Based on the stability and scalability problems of the current persulfate system,carbon nanotube-coated cobalt（Co-NC）membranes were prepared by Chemical vapor deposition（CVD）to further construct a PMS catalytic system for flow reactors.The bactericidal efficiency against Escherichia coli（E.coli）was 99.99%,and it also showed 100%inactivation activity for Staphylococcus aureus,respectively,maintaining a superior stability of 96.29%after 40 repeated cycles.In addition,it reaches an average degradation efficiency of 92.5%at 362 L m^-2 h^-1.723 L m^-2 h^-1,1448 L m^-2 h^-1 for organic pollutants（Rh B）tested at high fluxes.The effect of different experimental conditions（including concentration,p H,flow rate,presence of inorganic anions and humic acid concentration）on the bactericidal activity of E.coli was also tested.The installation of the Co-NC/PMS system was extended to Autumn Creek water.The inactivation efficiency also reached 99.99%in a real wastewater treatment for 12 consecutive hours.Mechanistic experiments showed that most of the Co elements of the Co-NC membrane were in the form of Co metal nanoparticles,which were oxidized to form high-valent Co metal(Co ^IV=O)as the primary active species.SO₄^?-and ¹O₂ as secondary species.During water flow,the Co-NC membrane is used as a catalytic platform for the reaction between the PMS and the bacteria,and the active species will first attack the cell wall/membrane and cause lipid peroxidation,leading to the breakage of the cell membrane.The intracellular defense system is then disrupted,followed by leaching of large amounts of potassium ions,which further leads to cell lysis.Cellular respiration is also interrupted and energy supply is gradually lost,which in turn affects cell viability,leading to loss of key cellular functions（nucleic acids）and eventually complete cellular inactivation.To address the cost and efficiency problems of the current persulfate system,high-entropy alloy oxides（HEOs）were synthesized by co-precipitation thermal method,and HEOs were applied to activate the persulfate system with excellent degradation effect.The experiments showed that the degradation of ATZ,BPA,RHB,TC and other organic pollutants achieved more than 96%removal rate within 5 min.HEOs could also achieve almost 100%inactivation performance in terms of bacteria.Subsequently,environmental resistance tests were conducted to show that HEOs/PMS showed potential for practical water purification applications.The HEOs-fiber spheres/PMS reactor was designed and tested for continuous water purification at a hydraulic retention time of about 1 s and a flow rate of 362 L m^-2 h^-1.The HEOs-fiber spheres/PMS system in flow operation mode showed stable treatment performance with TC removal rates of 92.7%during continuous operation.Electrochemical experiments show that PMS form transition state PMS*on the surface of HEOs.In addition,the DFT results proved that（Zn Co）on the surface of HEOs（010）had strong adsorption energy with PMS,and the differential charge proved that HEOs had strong interaction ability with PMS.Molecular mechanisms of enhanced HEOs/PMS activity and regulatory pathways through Co-Mn superexchange interactions and synergistic interactions.Smaller electrochemical impedance ground facilitates charge transport.Active species tested were Co^IV/Mn^V as the main active species generated in the HEOs/PMS system.HEOs also exhibited 90.21%non-free selectivity in activating PMS.