Application Of Ac Impedance Technology In Research Of Spontaneous Wetting Of Hydrophobic Microporous Membrane

In the process of capturing CO2 by the membrane contactor absorption method,the pores of the hydrophobic microporous membrane will be wetted by the liquid-phase absorbent,which cause a substantial increase in the resistance of the membrane phase mass transfer and a decrease in absorption efficiency.The membranes properties changed due to spontaneous wetting,and spontaneous wetting accounted for a higher proportion of total wetting,so that the phenomenon of spontaneous wetting was emphasized.The research on its mechanism has achieved certain results.In order to further describe the spontaneous wetting of hydrophobic microporous membranes in gas absorbents,this paper proposes a method for monitoring spontaneous wetting based on AC impedance,and based on previous studies on the kinetics of spontaneous wetting,simulate the impedance change throughout the wetting process;the relationship between the wetting percentage and the impedance value is quantified using the impedance model of the membranes.The paper mainly includes the following contents:1.Design appropriate experimental devices and operations for different kinds of hydrophobic microporous membranes impedance experiments then fit the experimental data by the equivalent circuit.The results show that when the wetting phenomenon occurs,the membrane resistance was reduced while the membrane capacitance increased slightly.It means that after the infiltration occurs,the membrane pore properties and the membrane conduction mechanism have changed.2.Based on the static impedance spectroscopy measurement,a continuous impedance test method for monitoring spontaneous wetting progress is designed.The results show that the impedance test method with a fixed AC frequency can be used to monitor the change of the same electrochemical properties in the wetting process continuously and continuously.The results are consistent with the spontaneous wetting mechanism.3.Based on the establishment of the equivalent circuit of the solution and the membrane,obtaining impedance fitting result.The results show that the theoretical calculation value is consistent with the experimental fit value.That is,the AC impedance test results and equivalent circuits can correctly reflect the electrochemical properties of the membrane,and this method can be used to quantitatively calculate the membrane spontaneous wetting degree.4.Establish an electrochemical model of membrane spontaneous wetting,reveal the conductivity mechanism of the wetted membrane,and combine it with the kinetics of spontaneous wetting to simulate the change of impedance value during the entire wetting process;The calculation method introduces the relationship between the impedance value and the wetting percentage,which achieves the purpose of using the AC impedance method to reveal the wetting law and improve the dynamic model of spontaneous wetting.