Electrodeionization and electrodialysis systems which eliminate or substantially prevent the feed water from entering the concentrating compartments, for improving the recovery of product water as well as improving the current efficiency. Electro-osmotically generated flows of water entering from the diluting compartments of the stack constitutes the majority of concentrate feed, leading to the production of high purity, desalinated waters in the diluting compartments and highly concentrate solutions in the concentrate compartments.

A hybrid electro-pressure driven method for the recovery, purification, and concentration of lithium salts is described. A fractionating electrodialysis stack equipped with selective ion exchange membranes is s used to separate a lithium containing brine into a monovalent enriched fraction and a divalent enriched fraction. The monovalent enriched fraction is further processed to remove remaining impurities by use of pressure driven nanofiltration. An optional concentrating electrodialysis device may further concentrate the monovalent enriched fraction in lithium content. The method may be combined with a subsequent solvent extraction and electrolysis step to produce lithium hydroxide, a Li+ selective sorbent step for producing purified lithium chloride, or a Li+ selective sorbent and precipitative step to produce lithium carbonate.

A stack of ion exchange membranes suitable for water purification comprising a plurality of anion exchange membranes (AEMs) and a plurality of cation exchange membranes (CEMs), wherein the colour properties of the AEMs are visibly different to the colour properties of the CEMs. The invention also provides a process for making membrane stacks in which the likelihood of there being two consecutive membranes of like charge is reduced. Furthermore, it is easy to identify whether there are two consecutive membranes of like charge present in the stacks.

A method for desalination is provided. An electric potential difference is applied across a saline solution, where a salinity of the saline solution is in a range of 2.5 to 7.8 parts per thousand. The saline solution is separated, using electrodialysis, into a concentrated saline solution and a first diluate. The concentrated saline solution is transferred to a reverse osmosis chamber. The concentrated saline solution is pumped through a partially permeable membrane, thereby removing salt ions from the concentrated saline solution, and creating a second diluate and a brine solution. A pressure of the solution is then increased, using a pressure exchanger, by transferring water pressure from the brine solution to the concentrated saline solution. The first diluate and the second diluate are combined, where a first recovery ratio of the first diluate is greater than a second recovery ratio of the second diluate.

An ion-exchange apparatus has a raw-water tank 1, a treatment tank 2, an ion exchanger 3 and a voltage applying device E. The raw-water tank 1 contains a to be treated liquid that has impurity ions. The treatment tank 2 contains a treatment material with exchange ions exchangeable with the impurity ions. The ion exchanger 3 enables the passage of the impurity ions from the raw-water tank 1 to the treatment tank 2 and the passage of the exchange ions from the treatment tank 2 to the raw-water tank 1. The voltage-applying device E applies a voltage to the ion exchanger 3.

Ion exchange membranes obtainable by curing a composition comprising: (a) a monomer comprising an aromatic group and at least one polymerisable ethylenically unsaturated group; (b) a photoinitiator which has an absorption maximum at a wavelength longer than 380 nm when measured in one or more of the following solvents at a temperature of 23° C.: water, ethanol and toluene; and (c) at least one co-initiator.

Provided are electrodialysis systems for removing ions from heavy ends. The electrodialysis systems include an electrodialysis device comprising a brine inlet stream, a heavy ends inlet stream, a brine outlet stream, and a product outlet stream, wherein the brine outlet stream comprises more acetic acid than the brine inlet stream, and the product outlet stream comprises no more than 10% the amount of ions relative to an amount of ions in the heavy ends inlet stream.

A dryer system includes an electrodialytic regenerator that comprises a first channel that dilutes a first stream of liquid desiccant and a second channel that concentrates a second stream of the liquid desiccant. An air-liquid interface is in fluid communication with the second stream of the liquid desiccant and an input air stream and exposes the second stream of the liquid desiccant to the input air stream. The absorption of the water from the input air stream creates a dehumidified air stream. The system includes a heat transfer element in thermal communication with the air-liquid interface. The heat transfer element carries latent heat generated from the absorption of the water from the input air stream. The system includes a drying chamber coupled to receive the dehumidified air stream and the heat.

A method is disclosed for concentrating and purifying an eluate brine and producing a purified lithium compound. An extraction eluate, rich in lithium, is directed to a nanofiltration unit or a softening process that removes sulfate and/or calcium and magnesium. Permeate from the nanofiltration unit or the effluent from the softening process is directed through an electrodialysis unit. As the lithium-rich solution moves through the electrodialysis unit, lithium, sodium and chloride ions pass from the solution through a cation-transfer membrane and an anion-transfer membrane to concentrate compartments. A dilute stream is directed through the concentrate compartments and collects the lithium, sodium and chloride ions. The electrodialysis unit also produces a product stream which contains non-ionized impurities, such as silica and/or boron. Concentrate from the electrodialysis unit is subject to a precipitation process that produces a lithium compound that is subsequently subjected to a purification process.

Disclosed are electrochemical systems that include an electrodialyzer and a vapor-fed CO.sub.2 reduction (CO.sub.2R) cell to capture and convert CO.sub.2 from ocean water. The electrodialyzer includes a stack of bipolar membrane electrodialysis (BPMED) cells between end electrodes. The electrodialzyer incorporates monovalent cation exchange membranes (M-CEMs) that prevent the transfer of multivalent cations between adjacent cell compartments, allowing continuous recirculation of electrolytes and solutions, and thus providing a safer and more scaling-free electrodialysis system. In some embodiments, the electrodialyzer may be configured to replace the water-splitting reaction at end electrodes with one-electron, reversible redox couples in solution at the electrodes. As a result, in the entire electrodialyzer stack, there is no bond-making, bond-breaking reactions and there is no gas generation, which significantly simplifies the cell design and improves operational safety. The systems provide a unique technological pathway for CO.sub.2 capture and conversion from ocean water with only electrochemical processes.