Sterilization Characteristics Of Activated Carbon Modified By Nanometer Metal Oxide And Study On The Performance And Mechanism Of Strengthening Sterilization Of Heterogeneous Fenton System

The pollutionof pathogenic microorganisms inwater may cause humanto be infected with cholera,dysentery,gastroenteritis and other diseases,which seriously threatens public health and humanlife.However,the traditional disinfectiontechnologies such as chlorine,ozone and ultraviolet still have problems such as disinfectionby-products,low energy efficiency and high cost.Therefore,the development of greenand efficient water disinfectiontechnology is animportant topic to ensure water safety.Nano silver oxide（nAg₂O）and nano copper oxide（nCuO）are widely used for bacterial inactivation,but they still have the defects of easy aggregation,low activity and difficult recovery inwater disinfection.Therefore,inthis study,nAg₂O/AC and nCuO/AC composites were synthesized by loading nAg₂O and nCuO onactivated carbon（AC）with large specific surface area and rich functional groups by chemical precipitationmethod,and their sterilizationcharacteristics were investigated with Escherichia coli as the target pollutant.Onthis basis,nAg₂O/AC-H₂O₂ and nCuO/AC-H₂O₂ heterogeneous Fentonsystems were constructed to explore their performance and mechanism of enhanced sterilization.The analysis of nAg₂O/AC and nCuO/AC by a series of means such as XRD,SEM-EDS,FTIR,BET and XPS showed that the average size of nAg₂O particles at 50～200 nm and nCuO particles at 100～200 nm were evenly distributed onthe AC surface,and some functional groups of AC were enhanced,weakened and shifted,indicating that a strong reactionoccurred betweenoxides and AC.The element compositionshows that Ag（I）/Ag and Cu（II）/Cu（I）both exist onthe AC surface,and their proportions change after the reaction,indicating that the two composites have undergone redox reactionduring sterilizationprocess.Therefore,insterilizationexperiment,nAg₂O/AC and nCuO/AC achieved complete inactivationof 6.0 log of bacteria after 180 and 240 minof reactionrespectively,which is much higher than0.8 log of nAg₂O and 1.1 log of nCuO.Inthe active oxygenquenching experiment,it was found that ROS,represented by O₂^·-,played a major role inthe inactivationof bacteria,while the enhanced reactivity of nAg₂O and nCuO combined with AC was the reasonwhy ROS was generated by activating dissolved oxygen.Inaddition,the damage caused by contact betweenmaterials and bacteria also has inactivationeffect.Inrepeated cycles and regenerationexperiments,both composites showed high sterilizationeffect of more than5.4 log,and maintained good stability inpH5～8,which laid a foundationfor their subsequent research.The heterogeneous Fentonsystems of nAg₂O/AC-H₂O₂ and nCuO/AC-H₂O₂ wereconstructed to enhance inactivationof bacteria.The results showed that under the optimal conditions of the dosage of nAg₂O/AC and nCuO/AC was 1 g/L,the dosage of H₂O₂ was 4 and3.2 m M,and the initial pH was 7,the complete inactivationof 6.0 log of bacteria by nAg₂O/AC-H₂O₂ and nCuO/AC-H₂O₂ systems took only 15 and 30 minutes,respectively,which was much higher than1.4 log of nAg₂O-H₂O₂ system and 1.2 log of nCuO-H₂O₂ system.The activationefficiency of H₂O₂ inthe two systems was 73.6%and 53.4%,respectively,reflecting the good activationability of the composites to H₂O₂.The coexisting anions and cations such as K⁺,Na⁺and NO₃^-have no obvious influence onsterilizationprocess of the two systems,Ca²⁺,Mg²⁺and HCO₃^-plasma have a certaininhibitiononsterilizationprocess,while Cl^-and SO₄^2-have a more obvious inhibitiononthe nAg₂O/AC-H₂O₂ system.Inaddition,natural organic matter has a great influence onsterilizationprocess of the two systems.The mechanism of sterilizationactionrevealed that nAg₂O/AC-H₂O₂ and nCuO/AC-H₂O₂ systems both conform to quasi first order kinetic model,the reactionrate constants are 0.256 and 0.126 min^-1,respectively,and the apparent activationenergies are 15.2 and 16.9 k J·mol^-1,respectively,which are beyond the activationenergy range of diffusionreaction,indicating that the two reactionrates are mainly controlled by the chemical reactionrate oncatalyst surface.Electronspinresonance（ESR）detectionand free radical quenching experiments confirmed that·OH played a major role inthe reactionsystem.FTIR and XPS analysis further revealed that the redox reactionbetweenAC surface functional groups and nAg₂O and nCuO promoted Ag（I）/Ag and Cu（II）/Cu（I）cycles,which was the key to activate H₂O₂ to generate·OH inthe system.Inaddition,cycles and regenerationexperiments were carried out onthe nAg₂O/AC-H₂O₂ and nCuO/AC-H₂O₂systems.The results showed that after 4 and 5 cycles respectively,sterilizationefficiency of the two systems still reached 4.9 and 5.4 log,and the two composite materials prepared after acid washing could still achieve sterilizationeffect of more than5.7 log,indicating that the two systems had good sterilizationstability and regeneration,which was significant for their applicationinactual water disinfectionprocess.