| The CO2 capture technology of membrane contactors has broad application prospects,combining the advantages of absorption and membrane separation.However,the phenomenon of hydrophobic membrane wetting is a major obstacle to its development.Membrane wetting means that the hydrophobic membrane pores are gradually filled with the solution,which causes the resistance to mass transfer to rise greatly,which seriously affects the absorption efficiency of the membrane contactor.Membrane wetting can be divided into forced wetting and spontaneous wetting.Forced wetting is due to the effect of the pressure difference between liquid and gas phases,while spontaneous wetting needs further exploration.This paper conducts research on the basis of the mechanism of adsorption and wetting,and revises and improves the mechanism of adsorption and wetting to make it possible to describe the process of spontaneous wetting more reasonably.Then based on the wetting mechanism,a correction coefficient is introduced into the membrane wetting equation and the core dynamic model is used to simulate the entire process of spontaneous wetting.Finally,a suitable method for retarding wetting is found according to the mechanism of adsorption and wetting,which provides a reference for improving the working efficiency of the membrane contactor.The main research contents and conclusions of this paper are as follows:(1)The solid-liquid adsorption constant of DEA molecules on the hydrophobic membrane wall of PVDF was calculated by the surface tension-contact angle and adhesion tension method combined adsorption equation,and then the molecular diffusion and adsorption processes in the membrane pores were analyzed to derive its Adsorption on the membrane wall is a controlled phase of spontaneous wetting.According to Darcy's diffusion theorem,a synergetic mode of liquid-vapor pressure difference and additional pressure during the wetting process is proposed.The liquid-vapor pressure difference can make the solution form a solid-liquid adsorption interface near the liquid level in the membrane pores.The layered three-phase contact line generates different additional pressures to push the solution to move in the membrane pores.Finally,the adsorption and wetting mechanism is modified according to the theory of the multilayered three-phase contact line.(2)The average contact angle between the DEA solution and the inner wall of the PVDF hydrophobic membrane pore was calculated by the average mass method of the invading solution in the hydrophobic membrane pore,and then the concentration at the meniscus at the front of the liquid surface in the membrane pore was obtained by the diffusion equation transformation..Based on the modified mechanism of adsorption and wetting,a correction coefficient term was introduced into the wetting equation of the hydrophobic membrane,and the modified wetting equation was combined with MATLAB simulation algorithm,and the PVDF hydrophobic membrane in DEA solution was established by calculating the membrane pores one by one.The spontaneous wetting dynamics model in can accurately predict the change of the wetting ratio over time,and associate the different stages of the wetting process in a complete model.(3)According to the modified mechanism of adsorption and wetting,a method of retarding membrane wetting was found,that is,the surface tension of the solution was increased by adding an inorganic salt/alkali to the DEA solution,and the anions and cations in the solution could Adsorption on the solid-liquid interface causes disturbances,which delays the occurrence of membrane wetting.Experiments have found that inorganic salts/bases that can produce more anions and cations at the same concentration and have a relative molecular mass similar to that of DEA molecules have a better retardation of wetting. |
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