טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentShocron Amit
SubjectThe Effect of Surface Transport On Water Desalination
By Capacitive Deionization
DepartmentDepartment of Mechanical Engineering
Supervisor Assistant Professor Matthew E. Suss
Full Thesis textFull thesis text - English Version


Abstract

Capacitive deionization (CDI) is a technology in which water is desalinated by ion

electrosorption into the electric double layers (EDLs) of charging porous electrodes.

In recent years significant advances have been made in modeling the charge and salt

dynamics in a CDI cell, but the possible effect of surface transport within diffuse

EDLs on these dynamics has not been investigated. We here present theory which

includes surface transport in describing the dynamics of a charging CDI cell. We

investigated the effect of surface transport using macroscopic 1D models and also

local 2D models to probe the effect of multi-scale pore structure. Through our

numerical solution to the presented models, the possible effect of surface transport on

the CDI process is elucidated. While at some model conditions surface transport

enhances the rate of CDI cell charging, counter-intuitively this additional transport

pathway is found to slow down cell charging at other model conditions.

In the second part of this thesis, we present the development of a 1D model simulating

the salt and charge dynamics in a flow-through electrode CDI cell, and show a

comparison to experimental results. A boundary condition analysis reveals that

appropriate simulation of the cell requires use of upstream and downstream reservoirs

in the model domain at conditions of low and moderate Peclet numbers. The

comparison to experimental equilibrium results agree at low voltage conditions, but

model to experiment results for salt storage diverge at cell voltages above 0.5 V.