An Investifation On Performance Of Capacitive Deionization Based On Polyelectrolyte Brushes Grafted Nanoporous Electrode

At present,there is a shortage of water resources in the world.Capacitive deionization(CDI)is a new type of seawater desalination technology that applies electric potential to nanoporous electrodes and uses static electricity to adsorb ions in the electrolyte(such as seawater)into the pores of the porous electrode to achieve electrolyte desalination.Compared with other desalination technologies,CDI technology has the advantages of green,pollutionfree and long service life,and has received widespread attention.In order to improve the performance of capacitive deionization technology,an effective method is to modify the electrode material,including grafting polyelectrolyte brushes onto the electrode surface.Grafting the polyelectrolyte brush on the electrode surface can improve the selective permeability of the electrode to the ions in the electrolyte,and has low thickness,low resistance,and is not easy to scale and block,and can effectively improve the capacitive deionization performance of the system.However,the effect of grafting polyelectrolyte brush on the electrode surface on the deionization performance of the system capacitance is still unclear.Therefore,this paper uses molecular dynamics simulation,finite element simulation,and molar purification rate model to study the effect of grafted polyelectrolyte brush on the double electric The layer interface,nanopores and capacitive deionization performance of the device embodied,explore the influence of grafted polyelectrolyte brush on the capacitive deionization performance of the system from different angles.The main research contents are as follows:Molecular dynamics simulation is used to analyze the influence of polyelectrolyte brush grafted on flat electrode on the capacitance characteristics of the electric double layer.Studies have shown that increasing the grafting density of the polyelectrolyte brush and the charging ratio of the polyelectrolyte brush will thicken the double layer,reduce the capacitance,and reduce the deionization performance of the capacitor.Increase the grafting density of the polyelectrolyte brush to keep the ions away from the electrode surface;increase the charging ratio of the polyelectrolyte brush,so that the counter ions gather at the charged part of the polyelectrolyte brush,and also keep the ions away from the electrode surface.COMSOL finite element simulation is used to analyze the influence of polyelectrolyte brush graft density on the charging characteristics of nanopores during the charging process of nanopores.Studies have shown that a small increase in the graft density leads to a decrease in the electric field force experienced by the ions,which reduces the flow rate and weakens the charging current;a large increase in the graft density leads to an increase in the electric field force experienced by the ions,which increases the flow rate in the opposite direction and enhances the charging current.Increase the grafting density,the characteristic constant of charging time is basically unchanged,and the capacitance increases,resulting in a decrease in resistance.In addition,the influence of the volume ratio and softness of the polyelectrolyte brush in the nanopores on the charging characteristics of the nanopores is analyzed.The molar purification rate model is used to analyze the effect of polyelectrolyte brush graft density on the deionization performance of the system capacitor under macro conditions.Studies have shown that increasing the grafting density of the polyelectrolytic brush can increase the system capacitance and reduce the resistance,resulting in an increase in desalination and effluent quality,and a reduction in energy consumption.In addition,the influence of electric potential,flow rate and flow channel volume on the deionization performance of the capacitance of the system is also analyzed.