| Chemical industry is one of the most important industries for Chinese national economy.It can provide important basic materials and energy for the social and economic development as well as the national defense construction.Besides,it plays an important role in the aerospace,industrial production,life science and medicine,information industry and other fields.However,the production process of chemical industry is often accompanied by "three wastes pollution and energy waste",and some other problems,which restricts the green development of chemical industry.The process intensification technology will benefit a lot for "reducing three wastes,saving energy,and consumption decreasing".As a typical process intensification technology,Higee is helpful to realize this goal.The liquid is broken into fluid elements,such as liquid films,lines,and droplets by means of centrifugal force field generated in the Higee reactor,enhancing the interphase mass transfer and mixing process.Now,the Higee technology has been widely used in the rapid reaction process.To further expand the application of the Higee technology toward medium/slow rate reactions,such as oxidation,it is necessary to consider the coupling enhancement between physical transport and chemical reaction process.The intrinsic rate of oxidation can be modulated by plasma that has high chemical activity and the physical transport(transfer)process can be enhanced by Higee technology.Through the action of plasma and Higee technology,the oxidation reaction environment and the intrinsic oxidation reaction process can be coordinated and matched.In this paper,a novel plasma-assisted Higee reactor(The Higee is realized by a rotating disk reactor)has been developed.The oxidation rules of plasma-RDR are evaluated.The ozone mass transfer model of plasma-RDR is established to guide the structure optimization of the novel reactor.In addition,the oxidation capacity of the plasma-RDR is further improved with the presence of TiO2 catalyst and the oxidation degradation efficiency of metronidazole is enhanced.Finally,the application of disinfection is investigated.The main research conclusions are shown as follows:(1)A micron-scale liquid film is formed on the rotating low voltage plate based on the centrifugal force,which can improve the pulse discharge uniformity and the apparent oxidation reaction rate.Experimental results show that the oxidation efficiency increases with the increase of peak voltage,gas flow rate,and liquid flow rate and decreases with the increase of electrode gap,initial concentration,water conductivity,and pH value.According to the experimental results,the correlation of oxidation efficiency is established,and the error between the predicted value and the experimental value is within ± 10%.The mineralization capacity of plasma-RDR is further analyzed.When the oxidation efficiency of plasma-RDR is 83.6%,the mineralization efficiency is 23.7%.(2)Based on the characteristics of active substance in the coupled fields,the concentration of the target active substance-gas phase ozone is tracked.Experimental results show that the gas phase ozone concentration increases with the increase of rotational speed,peak voltage,and pulse frequency,decreases with the increase of electrode gap,and changes a little with the variations of the liquid flow rate and pH value.According to the above experimental results,a mass transfer model about "gas phase ozone-water" in the coupled field is established to predict the liquid phase ozone concentration.Experimental values match well with the predicted values by the mathematical model with a deviation in the range of±20%.Model results show that the liquid phase ozone concentration increases with the increase of rotational speed,changes a little with the liquid flow rate,and decreases with the increase of pH.Furthermore,the predicted model is used to guide the structure optimization of plasma-RDR.(3)According to the optimized plasma-RDR,the TiO2 photocatalyst is used to further improve the oxidation capacity to enhance the oxidation degradation of metronidazole.Experimental results show that(i)The oxidation degradation efficiency of metronidazole decreases with the increase of initial concentration and solution volume,and increases with the increase of pulse frequency;(ii)The energy efficiency increases with the increase of the initial concentration and pulse frequency,and decreases with the increase of solution volume.The synergistic catalytic effect is significant.The oxidation degradation efficiency of metronidazole increases by 12%and the concentration of the generated hydroxyl radical increases by 0.671 mg/L under the optimal TiO2 concentration.Besides,the analysis of SEM,TEM,HRTEM and other characterization methods shows that the TiO2 photocatalyst has good application performance.The synergistic effects between plasma-RDR and TiO2 photocatalyst are revealed according to the above experimental results.(4)Based on the improvement of discharge uniformity and the increment in the concentration of the active substance in the plasma-RDR,the application of disinfection is preliminarily investigated.Escherichia coli(E.coli)is considered as the indicative microorganism.The plasma-RDR is adopted to enhance the disinfection efficiency.Experimental results show that the disinfection efficiency increases with the increment of peak voltage and liquid flow rate,and decreases with the increment of initial concentration of E.coli,electrode gap,and water conductivity.Weibull distribution model reveales the significant synergistic effects of plasma and acid or alkali on the disinfection efficiency,and the critical pH values of cumulative lethal effect are 10.4 and 5.3 By means of SEM characterization analysis,the electroporation effect is the main disinfection process,at the same time which is accompanied by oxidation etching effect of active particles.Besides,compared with other reported plasma reactors and disinfection technologies,the plasma-RDR has higher disinfection efficiency with a lower energy consumption. |
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