Application Of "pressure-concentration" Double-driven Diffusion Dialysis For The Treatment Of Acid/Alkali Wastewater And Mathematical Modeling Of Its Mass Transfer Process

The acidic wastewater comes from metallurgy,metal processing,petrochemical engineering,chemical fiber,electroplating and other industries,while the alkaline wastewater comes from papermaking,leather making,oil refining and other industries.Discharging the wastewater into water and soil directly without any treatment can not only waste a lot of available resources,but also destroy the ecological stability and physicochemical properties of the soil,and affect the normal growth of crops.Hence,the wastewater should be handled with.Diffusion dialysis is a membrane separation process driven by the concentration difference.And it is widely used in industrial wastewater treatments because of its simple operation,environmentally friendliness and low-cost.With the deep application,the shortcomings of diffusion dialysis gradually appear,such as small treatment capacity and serious water osmosis phenomenon.Aiming at the shortcomings of diffusion dialysis,this dissertation presents a“pressure-concentration”double-driven diffusion dialysis process,which adds the pressure difference as an auxiliary mass transfer driving force on the basis of main mass transfer driving force-original concentration difference.Also,it can achieve the diffusion dialysis mass transfer under the synergy of pressure difference field and concentration difference field,which can suppress water osmosis and increases the treatment capacity simultaneously.The dissertation is divided into four chapters and the content of each chapter is as follows:The first chapter describes the diffusion dialysis and its development process,it introduces the principle membranes,membrane modules,theoretical model and application status of diffusion dialysis.In addition,the research content of this dissertation is brought out.The second chapter studies on the recovery of H₂SO₄ from the simulated steel acid wastewater（H₂SO₄/FeSO₄ mixed solution）through the"pressure-concentration"double-driven diffusion dialysis process.Effects of pressure difference intensity,the initial H₂SO₄ concentration and the initial FeSO₄ concentration in the feed are mainly investigated.The results show that as the pressure difference intensity increases,the_,increases,water osmosis has been effectively suppressed,the acid-salt separation factor decreased and stabilized at～65;as the initial H₂SO₄ concentration in the feed decreases,and the acid-salt separation factor increases.In addition,based on the non-equilibrium thermodynamics,a mass transfer mathematical model is established for the"pressure-concentration"double-driven diffusion dialysis process.The results show that the experimental values are in good agreement with the calculated values.The third chapter studies on the recovery of NaOH from the simulated tungsten ore wastewater（Na OH/Na₂WO₄ mixed solution）through the"pressure-concentration"double-driven diffusion dialysis process.Effects of pressure difference intensity,the initial NaOH concentration and the initial Na₂WO₄ concentration in the feed are mainly investigated.The results show that as the pressure difference intensity increases,the OH^-dialysis coefficientU_OH-and the WO₄^2-dialysis coefficient suppressed;the alkali-salt separation factor decreases with the increment of pressure difference intensity.As the initial NaOH concentration in the feed increases, between 20 and 25.As the initial Na₂WO₄ concentration in the feed increases,U_OH- from 24.9 to 16.2.The fourth chapter summarizes the experimental results of this dissertation,and prospects the future of"pressure-concentration"double-driven diffusion dialysis according to the conclusion.In conclusion,a new type of diffusion dialysis process is proposed for the recovery of acids and alkalis in this dissertation,and obtained satisfactory experimental results in laboratory research.