Description:

Shock electrodialysis (Shock ED) is an emerging electrokinetic process for water treatment, leveraging the formation of ion concentration polarization (ICP) zones and deionization shock waves in macroporous material near to an ion selective element (ion exchange membranes or electrodes)

Recent generations of this system shown in Fig. 1 involve a cross-flow architecture that enables continuous operation. The main component of the shock ED is a weakly charged macroporous material sandwiched between two identical cation exchange membranes (CEM). In this prototype, the macroporous material and both ion exchange membranes have negatively charged surfaces.

The process of SED requires formation of a sharp gradient—a shock wave—in the concentration of ions in the macroporous material, which is accomplished by applying an electric field. Like ED, when current is passed through the shock ED cell, the membranes block the transport of coions (i.e., anions) and cause ion concentration polarization, which leads to extreme concentration gradients in the macroporous material.  As the applied voltage is increased, ion concentration near this element approaches zero, and the system can reach the classical diffusion limited current. However, unlike ED, in shock ED the presence of a surface charge along the porous media’s internal surfaces can enable transport of ions faster than diffusion.

 

Objective:

Electrokinectic process for water treatment, especially selective removal of multivalent ions from electrolyte mixtures. As a result of this selectivity, shock ED can be used to capture target species of high value.

 

Type of water

Seawater.

Brackish water.

 

Applications:

Seawater desalination.

Brackish water desalination.

Water purification (removal traces of toxic heavy metal ions, especially lead).

 

Applications:

Seawater desalination.

Brackish water desalination.

Water purification (removal traces of toxic heavy metal ions, especially lead).

 

Applicability:

TRL 3-4

Technological readiness level (TRL), it is an indicator of maturity of a particular technology.  TRL is measured on a scale from 1 to 9, 1 being the lowest and 9 being the highest. A TRL of 9 reflects the implementation of an actual system in operational environment.

Reference:

J.C. Mankins, Technology Readiness Levels. White Paper, April, 1995 https://www.spacepropulsion.org/uploads/2/5/3/9/25392309/john_mankins_paper_of_4-6-95_trl.pdf

 

Research directions:

Theory behind shock ED.

Process optimization.

Pilot-scale systems.

 

Data sources:

1. Deng; W. Aouad, W.A. Braff; S. Water purification by shock electrodialysis: Deionization, filtration, separation, and disinfection. Desalination 357 (2015) 77–83

M.A. Alkhadra, T.Gao, K. M. Conforti, H. Tian, M. Z. Bazant. Small-scale desalination of seawater by shock electrodialysis. Desalination 476 (2020) 114219.

615. Tian; M. A. Alkhadra, M.Z. Bazant. Theory of shock electrodialysis I: Water dissociation and electrosmotic vortices. Journal of Colloid and Interface Science 589 (2021) 605–615.

H. Tian; M. A. Alkhadra, M.Z. Bazant. Theory of shock electrodialysis II: Mechanisms of selective ion removal. Journal of Colloid and Interface Science 589 (2021) 589 (2021) 616–621.