Reverse electro-osmotic filtration exploiting nanofluidic transport through asymmetric membrane

A process for purifying an electrolyte solution, comprising the following steps:

• i) Contacting a first volume V1 of a first electrolyte solution comprising a solute and a solvent with a first porous electrode;
• ii) Contacting a second volume V2 of a second electrolyte solution comprising a solvent with a second porous electrode;
• iii) Applying an alternating electric field between the first and second electrodes resulting in solvent transfer and solute filtration through a membrane element, the variation of the volume V2 being defined with the following formula (formula I):
• V
• 2
• (
• n
• ⁢
• T
• )
• =
• μ
• EOeff
• ⁢
• Δ
• ⁢
• V
• eff
• ⁢
• π
• ⁢
• r
• 2
• ⁢
• nTL
• -
• 1
• wherein T is the period of the applied signal(s), n the number of completed cycles, μEOeff is the effective electro-osmotic mobility (m2·V−1·s−1), ΔVeff, is the local potential difference at the membrane (V), r is the average radius of the pore of the membrane (m);
• and L is the membrane thickness (m);
• iv) Evacuating bubbles generated during parasitic electrochemical reactions
• wherein,
• the first electrode and the second electrode are separated by an asymmetric membrane element comprising a first side and a second side;
• the second side of the asymmetric membrane element has an average pore size 1.1 to 10 000 times smaller than that of the first side;
• a separator is positioned between the electrode and the second side of the asymmetric membrane element;
• the asymmetry between the first and second sides of the membrane element is geometric, physico-chemical, environmental nature, or a combination thereof;
• and
• the first and second electrodes and being operatively coupled via two current collectors to a source of electrical power.