| Diclofenac?DCF?,as a typical pharmaceuticals and personal care products?PPCPs?,is frequently detected in different environment?such as surface water,groundwater,sediment,etc.?.Various advanced oxidation processes?AOPs?can be used to treat low-dose DCF in water,but they also have their own disadvantages.For example,the persulfate has limited direct oxidation ability,and activation technologies such as catalytic materials might be employed to enhance the oxidation ability of persulfate.Although ultrasound enhanced ozonation?UEO?has improved oxidation performance,high energy consumption of UEO limits the practical application.Therefore,taking DCF as the target pollutant,this article creates the high-performance persulfate activation system and ultrasonic enhanced ozone oxidation?UEO?system,explores the synergistic mechanism of persulfate system and ozone system,and clarifies the internal relationship between enhancing mechanism and applicational conditions.In order to improve the oxidation efficiency of peroxymonosulfate?PMS?,WS2,as a typical 2D layered transition metal dichalcogenides?TMDs?,was employed to activate PMS.The WS2 nanosheets were prepared by ultrasonic peeling method and characterized by various characterization methods.The oxidation efficiency and influencing factors of the system were studied.the reactive oxygen species in the system were verified by quenching experiments and EPR.The decomposition route of DCF was calculated by DFT.The results show that in the WS2/PMS system,WS2 could effectively activate PMS to decompose DCF,and the reaction rate constant increases more than three times.The decomposition efficiency of the system was positively correlated with the dosage of WS2 and the initial concentration of PMS,and negatively correlated with the initial concentration of DCF.The decomposition efficiency was consistent in the p H range from 5.0 to 9.0.DCF was decomposed by not only direct oxidation of PMS,but also singlet oxygen?1O2?and superoxide radical(O2·-),which were produced by the system.DCF can be decomposed by four potential routes:C-N bond breaking,dichlorination coupling,hydroxyl addition and decarboxylation.To further improve the oxidation efficiency of PMS,Mo S2 was prepared by hydrothermal method for activation of PMS.The experiment was carried out in the same way as the WS2/PMS system.The results show that in the Mo S2/PMS system,the oxidation efficiency was further enhanced,the decomposition rate of DCF is 5 times higher than PMS alone,and the total organic carbon?TOC?removal rate reached 75.6%within three hours.The decomposition efficiency of the system was positively correlated with the dosage of Mo S2 and the initial concentration of PMS,and negatively correlated with the initial concentration of DCF.The decomposition efficiency was consistent in the p H range from 5.0 to 9.0.Different from the WS2/PMS system,the reactive oxygen species generated by the Mo S2/PMS system was only O2·-.The potential decomposition path of DCF was similar to WS2/PMS system.In order to improve the oxidation efficiency of the ozonation,the ultrasound?US?was employed to form the UEO system.The kinetic experiments were used to compare the decomposition and mineralization efficiency of DCF by O3 systems and UEO systems.The essence of TOC removal and enhancing mechanism of UEO were analyzed,and the decomposition path of DCF was simulated.Using self-sequential concept to create the self-sequential UEO system.The energy efficiency of UEO by different processes were characterized by mineralization energy efficiency?MEE?.The results show that,DCF was completely decomposed within 8 minutes in both ozone and UEO systems.And UEO systems had higher mineralization rate.The 200 k Hz UEO systems had the best enhancement efficiency,which completely mineralized DCF within 120 min.The total amount of·OH produced by 200 k Hz UEO systems was 3.8 times higher than O3 systems plus US systems.The·OH,which produced by the UEO system through ozone decomposition,H2O sonolysis,and ozone sonolysis,can effectively decompose intermediate products such as oxalic acids and oxamic acid.It was found that 60 min ozonation following by 60 min UEO,having best mineralization energy efficiency?MEE?(113 mg?k Wh?-1)at the base of complete mineralization,could reduce one-third of the total energy consumption comparing with single UEO.p H could be selected as the best judgment index of self-sequential UEO for indicating the time point of ultrasound irradiation.Through the engineering magnification analysis,the engineering feasibility of two typical advanced oxidation technologies were further analyzed.It could be found that the Mo S2/PMS system need more technical improvement for the DCF decomposition.The"pretreatment-PMS mixing-catalytic fluidized-ion precipitation-sand filter"process was proposed.The process was economically feasible and its investment was estimated to be between 760 and 1,060 yuan per ton water.UEO process has technical feasibility.The sequencing batch UEO process in intermittent operation was proposed.The investment was between 2000 and 2260 yuan per ton water.For the optimization between investment and efficiency,the air source ozone and shorter ultrasound irradiation time could be considered. |
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