Numerical Simulation Of Electrokinetic Desalination Of Prarllel Microchannels Based On Permselective Membranes

Rapid growth of population and living standards,along with the expansion of agricultural and industrial activities in the world,the shortage of fresh water resources worldwide is severe.Meanwhile,the treatment of industrial high salinity waste water is also urgent.Among all methods,reverse osmosis method and electrodialysis method are the most widely used and developed.The electrodialysis technology is limited by concentration polarization effect,which hinders its further development in industry.A large-scale desalination system is proposed,which is composed of an ion-selective membrane with many micropores,and the system can be set as the combination of Reverse osmosis method and Electrodialysis method.A two-dimensional simulation model is used to study the desalination performance of such system based on three governing equations under corresponding boundary conditions,namely Poisson-Nernst-Planck controlling ion transport and electric field,and Navier-Stokes governing incompressible fluid.The salt removal ratio and the average velocity of fluid represent desalination performance.Pressure driven flow and electroosmotic flow of the second kind are the main driven force and the major factors influencing desalination performance.Meanwhile,the influence of number of parallel micropores on desalination performance is also demonstrated.The model predicts that salt removal ratio is over 98%for seawater salinity(realizing drinkable water)is achievable,reproducing earlier experimental results.A stronger cross membrane voltage strengthens electroosmotic flow of the second kind(EOF2)and increases both salt removal ratio and flow velocity.Increasing pressure will promote the fluid flow but decrease salt removal ratio and EOF2 significantly when the ion depletion zone is destroyed.Volumetric energy consumption and energy per ion removal(EPIR)were characterized in detail at various electric field and pressure conditions.The energy consumption as low as 12.82 k Wh/m~3 was realized to convert sea water(salinity?500m M)to the desalinated water(salinity?10 m M)at a flow speed of 0.56 mm/s.The overall cost of water for such a process was estimated to be 2.08$/m~3,which is competitive for portable(small-scale)desalination applications.Meanwhile,the feasibility of the system is also analyzed in detail.The unique meatures of the system compared with other desalination methods.The desalination system performed in this article figures out the limitation of microchannel in water scarcity problems.As a novel desalination method,our system will provide an effective way to relieve the water scarcity stress and can also be used in treatment of waste water widely in the future.