Study On Hydrodynamic Cavitation Degradation Of Alkaline Dyes And Heat Generation By Double Parallel Orifice Plates

Basic organic dyes are the most commonly used industrial dyes,which are often used in printing and dyeing wool,silk and leather,and are also commonly used disinfection preservatives in medicine.In recent years,with the continuous development of dye industry,the discharge of alkaline dye organic wastewater is also increasing.Therefore,it is necessary to find an efficient and low-energy organic wastewater treatment method.Usually,basic organic dyes are difficult to be degraded because of their complex structure and stable properties,which undoubtedly brings great difficulties to the use of traditional water treatment methods.Therefore,it is of great significance to find new and effective methods and technologies for treating dye wastewater.As an advanced oxidation processes with simple equipment and no secondary pollution,hydrodynamic cavitation（HC）has been widely concerned by researchers.In addition,it is also found that during the degradation and mineralization of organic pollutants by HC,there is a phenomenon that the temperature of the solution rises rapidly.Therefore,this kind of HC technology,which can produce clean energy and reduce disposable energy consumption,has become the focus of social research.Based on the degradation and heat generation advantages of HC technology,the geometric parameters of orifice plate and the operating conditions of degradation experiment were investigated,the device parameters in HC system were optimized,the combination method of HC and other advanced oxidation technologies was explored,and the heat generation efficiency of HC technology and the energy consumption of HC device are analyzed.It is of great significance and value to develop large-scale high-efficiency and energy-saving wastewater treatment technology and process.In the first part,the degradation effect and heat generation efficiency of alkaline organic dye by single orifice plate hydrodynamic cavitation（HC）technology were studied.HC technology is not only a promising waste water treatment technology but also an efficient heat generation technology,which can degrade and mineralize organic matter non-selectively and release a large amount of heat.In this study,by comparing the temperature changes with or without HC effect,the various ways of heat generation in the process of HC degradation of organic pollutants are clarified.By using different kinds of organic dyes（Auramine O,Indigo Carmine and Alphazarine A）for degradation and heat generation experiments,it is proved that HC technology has high mineralization ratio and strong heat generation ability for most dyes.The effects of different geometrical parameters（orifice angles（α=0°and±45°）and orifice numbers（n=3-9））and different experimental parameters（inlet pressures（2.0-4.0 bar）,solution temperatures（30-60°?）and initial concentrations（5.0-15 mg/L））on the AO degradation and heat generation in orifice plate HC system were investigated.These parameters were optimized to obtain the optimal conditions to enhance the HC effect.Total organic carbon（TOC）analysis was performed to determine the mineralization degree of AO solution treated under optimal conditions.The intermediates in the AO degradation process were detected by liquid chromatography-mass spectrometry（LC-MS）.In addition,in order to deeply study the degradation and heat generation of AO organic dye by HC system,the produced free radicals were identified by adding some reagents to capture corresponding active substances.The final results show that under the experimental conditions of 6-hole orifice plate,4.0 bar inlet pressure,5.0 L total solution volume and 10 mg/L initial concentration,81.39%degradation ratio of AO and 1082.52 k J heat can be obtained during 90 min continuous cycle,and the thermal efficiency can reach 40.09%.This work provides a new effective strategy for large-scale degradation of organic dyes and resource utilization of heat sources by enhanced orifice plate HC.In the second part,the degradation effect and heat generation efficiency of alkaline organic dye（Basic Violet 1）by hydrodynamic cavitation（HC）technology with double parallel orifice plates were studied.On the basis of good degradation effect and high heat generation efficiency brought by single orifice plate HC technology,double parallel orifice plate HC technology can further increase the working efficiency of orifice plate HC system,which further verifies the practicability and economy of HC technology in large-scale treatment of organic wastewater.In this study,through studying the degradation and heat generation of Auramine O by a single orifice plate HC device on the main line,the orifice plate with the best number of effective holes was optimized and selected.Then,based on the number of holes in the main line single orifice plate,the influence of the hole number of orifice plates on degradation and heat generation in the double parallel orifice plate HC system was studied in detail.Furthermore,the effects of different experimental parameters（inlet pressure,initial concentration and treated water volume）on the degradation and heat generation of Basic Violet 1 in the double parallel orifice plate HC system were studied in detail,and the effects of the parallel orifice plate HC system on the degradation of Basic Violet 1were studied on the basis of controlling the experimental temperature.Then,the effects of different molar ratios of hydrogen peroxide on the degradation and heat generation of Basic Violet 1 in double parallel orifice plate HC system were studied.In addition,the trapping experiment of free radicals（·OH and·O₂^-）was also carried out.Finally,the degradation pathway and possible degradation mechanism of Basic Violet 1（BV-1）were proposed by analyzing the data of UV-vis spectrum,LC-MS and Total Organic Carbon（TOC）.The final results showed that under the conditions of 4+4 parallel orifice plates,3.0 bar inlet pressure,5.0 L total solution volume and 10 mg/L initial concentration,the degradation ratio of BV-1 dye was 75.98%,and 785.40 k J heat was generated at the cost of 48.50 USD/m~3,reaching 29.09%heat production efficiency.Under the condition of BV-1:H₂O₂=1:30,the degradation rate of BV-1 dye was 95.38%and the heat was 909.72 k J,the thermal efficiency was 33.69%.This work provides a new effective strategy for enhancing large-scale degradation of organic dyes by orifice plate HC and utilizing heat sources as resources.It is hoped that the treatment method of printing and dyeing wastewater can lay a foundation for environmental protection and further development of energy production.