Study On Immersion Negative Pressure Orifice Plate Assisted Orifice Plate(INPOP-AOP) HC System For Auramine O Degradation And Heat Generation

Cationic dyes,also known as basic dyes,are a type of textile dye.Cationic dyes have advantages such as high strength,bright color,and good light fastness,and are therefore widely used in many fields,such as textiles,leather,wood,paper,metals,and coatings.The widespread use of cationic dyes provides people with a variety of color choices and practicality,enriching their lives and work.However,with the continuous development of the dye industry,a large amount of dye wastewater containing cationic dyes has been generated,leading to increasingly serious environmental problems.The molecular structure of cationic dyes is complex and their chemical properties are relatively stable,so traditional water treatment methods are not effective in treating printing and dyeing wastewater containing cationic dyes.Therefore,finding an efficient method to treat cationic dye wastewater is urgently needed.Hydrodynamic cavitation（HC）,as a new advanced oxidation technology,has advantages such as good treatment effect,fast processing speed,simple equipment,and convenient operation,and has attracted more and more researchers’attention.In addition,when using HC technology to treat dye wastewater,a large amount of heat is generated,which rapidly increases the temperature of the water and provides additional energy.Based on these characteristics,the application of HC technology in the treatment of dye wastewater will become a research hotspot in today’s society.Traditional hydrodynamic cavitation devices use water pumps as the power source,utilizing the positive pressure hydrodynamic cavitation effect generated by the water pump lift to degrade organic pollutants and generate heat.Previously,most researchers have also studied and optimized hydrodynamic cavitation based on the hydrodynamic cavitation effect generated by the positive pressure of the water pump,but the improvement of the organic pollutant degradation effect was not very satisfactory.In this study,in order to develop the potential of water pumps used in hydrodynamic cavitation technology,a novel immersion negative pressure orifice plate assisted orifice plate（INPOP-AOP）HC system was established.The INPOP-AOP HC system combines negative pressure hydrodynamic cavitation and positive pressure hydrodynamic cavitation,which exhibits a stronger hydrodynamic cavitation effect than traditional hydrodynamic cavitation systems,greatly enhancing the degradation effect of organic pollutants and the heat generation efficiency of the system.After establishing the INPOP-AOP HC system,this paper compared the degradation effect of simulating pollutant AO by the INPOP-AOP HC system and the single positive-pressure hydrodynamic cavitation system.The experiment investigated the effects of factors such as inlet pressure,number of positive-pressure orifices,initial concentration and temperature of AO solution,volume of AO solution,and amount of oxidant（H₂O₂）on AO degradation and system heat generation.The active substances generated in the INPOP-AOP HC system were explored by adding free radical scavengers.The mineralization degree of AO was determined by TOC analysis.Based on the LC-MS test results,possible degradation pathways and mechanisms of AO were proposed.Finally,the cost of hydrodynamic cavitation degradation of AO solution was estimated.The main research results are as follows:（1）The optimum operating conditions for the INPOP-AOP HC system were obtained through experiments,which are 4 bar inlet pressure,a negative pressure plate with 29 holes,a positive pressure plate with 3 holes,a 20 mg/L solution of Auramine O,and a total solution volume of 10 L.During the 90-minute experiment,the degradation ratio of Auramine O using the INPOP-AOP HC system was 48.87%,which is significantly higher than the degradation rate of 32.15%using the traditional positive pressure hydrodynamic cavitation system under the same conditions.In addition,the INPOP-AOP HC system showed excellent heat generation capacity,producing 1399.30 k J of heat with an efficiency of 51.83%under the aforementioned conditions.（2）Free radical capture experiments were conducted to investigate the effects of superoxide radicals（·O₂^-）and hydroxyl radicals（·OH）on the degradation of Auramine O in the INPOP-AOP HC system.The hydrodynamic cavitation effect in the INPOP-AOP HC system produces a large amount of highly oxidative free radicals that react with Auramine O molecules and decompose them.BQ was used as a·O₂^-capture agent,and IPA was used as a·OH scavenger.The degradation ratio of Auramine O decreased from 30.01%to 13.38%after the addition of BQ and from 30.01%to 27.33%after the addition of IPA.Therefore,both·O₂^-and·OH play a role in the degradation of Auramine O in the INPOP-AOP HC system,with·OH being the primary contributor and·O₂^-playing a secondary role.The addition of BQ and IPA did not significantly affect the solution temperature,indicating that the HC effect is the main contributor to the temperature increase.（3）LC-MS testing of the Auramine O solution was conducted to analyze the intermediates generated during the HC degradation process of Auramine O molecules,and possible hydrodynamic cavitation degradation pathways and mechanisms of Auramine O were proposed.It was found that after 90 minutes of circulation degradation,the absorption peaks at 430 nm and 370 nm in the Auramine O solution were significantly weakened.In addition,the TOC data showed that the mineralization ratio of the Auramine O solution after 90 minutes was 32.06%.This indicates that the INPOP-AOP HC system can effectively degrade the Auramine O solution.（4）To further demonstrate the feasibility of combining negative pressure hydrodynamic cavitation effect and positive pressure hydrodynamic cavitation effect,the theoretical cavitation number of the water pump negative pressure hydrodynamic cavitation effect was calculated at 20℃,40℃,and 60℃.It was found that the outlet pressure range of the negative pressure plate that produces effective hydrodynamic cavitation effect at all three temperatures is within the vacuum range that the water pump can produce.Furthermore,the experimental data of the INPOP-AOP HC system were compared with data from other researchers,and both theoretical and practical studies demonstrated the feasibility of the INPOP-AOP HC system.