Electrodialysis stack

An electrodialysis stack comprising:

• a first electrode and a second electrode spaced apart from the first electrode;
• a plurality of electrodialysis cell pairs (cp) arranged in a stack and positioned between the first and second electrodes to provide an electrically conductive fluid connection therebetween, each of the electrodialysis cell pairs including, in sequence, a first ion-exchange membrane, a first spacer, a second ion-exchange membrane, and a second spacer, wherein each of the first and second ion-exchange membranes and each of the first and second spacers have a plurality of apertures;
• and
• a distribution manifold including a plurality of manifold ducts, wherein each of the manifold ducts is formed by aligned ones of the plurality of apertures in each of the first and second ion-exchange membranes and each of the first and second spacers, wherein at least one of the plurality of manifold ducts is a concentrated stream inlet and at least one of the plurality of manifold ducts is a concentrated stream outlet,
• wherein at least one of the first and second electrodes is a recessed electrode having a recessed edge that is spaced apart from the distribution manifold,
• wherein each of the spacers comprises a plurality of electrically resistant structures that extend from the distribution manifold, past the recessed edge, and overlap with the recessed electrode for an overlap distance that is about equal to:
• (0.062 cm−1)*(exp(−60/total cp)*(area in cm2 of the manifold ducts of the concentrated stream at the recessed edge),
• wherein each of the plurality of electrically resistant structures of the first spacer contact the first and second ion-exchange membranes and each of the plurality of electrically resistant structures of the second spacer contact the second ion-exchange membrane and the first spacer of an adjacent one of the electrodialysis cell pairs.