Abstract: A sheet having anion exchange functionality and a sheet having cation exchange functionality are juxtaposed and joined by current bonding into a unitary bipolar membrane. This may be done without added reactants or bonding agents by placing the two-layer assembly between opposed electrodes in a fluid cell, preferably at pressure, and applying power across the cell to split water in a junction region of the membrane assembly. Preferably the anion exchange sheet is treated with an iron salt solution so as to incorporate or immobilize the metal in the polymer during the current bonding process, and enhance operating characteristics of the bipolar junction. Membrane peel strength is comparable to or greater than that of an underlying sheet of ion exchange material, but the bonding is fully reversible, e.g., by soaking in a concentrated solution. Preferably both sheets include an aromatic backbone or cross-linker component.

Abstract: A fluid from a fermentation process or the like is passed or circulated through chambers of a bipolar membrane electrodialysis unit to separate an ionizable organic acid stream and at least one co-ion or residual stream. The organic acid stream is preferably concentrated (e.g., by recirculation, dewatering or both), and a product is recovered from the concentrated stream, for example by crystallization, and other outputs from the electrodialysis unit may be integrated with overall treatment and applied elsewhere in the treatment system. Depleted feed may be returned upstream to enhance yield, condition the medium or form a by-product. Treatment systems of the invention may replace a cation exchange bed and/or various filter arrangements, and recirculation of the feed and product flows through the unit enhance recovery, separation and quality of the target species.