Disclosed herein is a method for recovering water from a salt solution. The method can include mixing the salt solution with a salting out solution that includes at least one enolizable ketone and at least one alcohol. The salting out solution can absorb the water from the salt solution and the water can be released using a regenerant solution. A base solution can also be added to fully regenerate the salting out solution so that it can be reused.

Disclosed herein is a method for recovering water from a salt solution. The method can include mixing the salt solution with a salting out solution that includes at least one enolizable ketone and at least one alcohol. The salting out solution can absorb the water from the salt solution and the water can be released using a regenerant solution. A base solution can also be added to fully regenerate the salting out solution so that it can be reused.

The invention relates to an integrated process for conditioning process water (1) from the production (I) of polycarbonate, which process water contains at least catalyst residues and/or organic impurities and sodium chloride, and subsequently utilizing the process water (1) in a subsequent sodium chloride electrolysis (V).

The present disclosure provides a method for preparing an alkali and co-producing gypsum, and belongs to the technical field of chemical production. The method comprises the steps of placing a cation exchange membrane into an electrolytic cell, adding a solution of sodium salt of a weak acid and a compound MH to an anode region as an anode electrocatalyst, adding sodium carbonate or sodium hydroxide to a cathode region, adding a compound M as a cathode electrocatalyst, and applying a DC power supply between a cathode electrode and an anode electrode. The electrolysis oxidizes the MH into the M and releases H.sup.+, Na.sup.+ in the anolyte penetrates through the cation exchange membrane to reach a cathode region to be combined with OH.sup. in the catholyte to generate NaOH, or further absorbs CO.sub.2 and converts into Na.sub.2CO.sub.3; the anolyte containing a large amount of H.sup.+ is generated by the electrolysis for dissolution reaction with limestone, and the H.sup.+ is consumed to generate Ca.sup.2+, and SO.sub.4.sup.2 and Ca.sup.2+ are combined to generate high-purity CaSO.sub.4 precipitate. According to the present disclosure, a compound capable of generating PCET reaction is used as an electrocatalyst, while M is its oxidation state and MH is its reduction state, and mirabilite and limestone are used as raw materials to realize the preparation of soda ash, caustic soda and gypsum.

A method for preparing an Fe/Ni-free alkali metal hydroxide solution may include electrodepositing Ni ions of an alkali metal hydroxide electrolyte on surfaces of an Au anode and an Au cathode by placing the Au anode and the Au cathode within the Fe-free alkali metal hydroxide electrolyte and applying a voltage in a range of 1.75 to 2.25 between the Au anode and the Au cathode for a period in a range of 8 to 12 hours.

A method of producing lithium hydroxide using a variety of aqueous solutions as a source liquid. The method includes: providing a lithium ion extraction liquid, including a first mixing of an aqueous solution containing lithium and at least one kind of an element other than lithium and a base in a reaction tank, with a pH regulated to 6 or more and 10 or less, a second mixing of the aqueous solution and the base, with a pH regulated to 12 or more, and removal of a hydroxide of the element other than lithium formed through the first and second mixing; recovering only lithium ion from the lithium ion extraction liquid to a recovery liquid with an electrochemical device including a Li-selectively permeable membrane; and performing the regulation of pH by returning the lithium ion extraction liquid after recovering lithium ion with the electrochemical device to the reaction tank.

A method of producing lithium hydroxide using a variety of aqueous solutions as a source liquid. The method includes: providing a lithium ion extraction liquid, including a first mixing of an aqueous solution containing lithium and at least one kind of an element other than lithium and a base in a reaction tank, with a pH regulated to 6 or more and 10 or less, a second mixing of the aqueous solution and the base, with a pH regulated to 12 or more, and removal of a hydroxide of the element other than lithium formed through the first and second mixing; recovering only lithium ion from the lithium ion extraction liquid to a recovery liquid with an electrochemical device including a Li-selectively permeable membrane; and performing the regulation of pH by returning the lithium ion extraction liquid after recovering lithium ion with the electrochemical device to the reaction tank.

In a method of recovering a lithium precursor, a first electrode including an active material, and a second electrode are prepared. The first electrode and the second electrode are immersed in a first reaction solution in a first reaction vessel and a second reaction solution in a second reaction vessel, respectively. A voltage or a current is applied to the first electrode and the second electrode to recover a lithium precursor from the active material.

A method for concentrating an aqueous caustic alkali produced by a membrane cell process by using a single or multiple effect evaporator system in which the vapor flows in a counter direction to the aqueous caustic alkali flow and the heat recovered from the catholyte circulation line is used as part of the concentration process. In one embodiment, a catholyte heat recovery heat exchanger and flash evaporation chamber are located after the last effect of a multiple effect evaporator system. In another embodiment, the catholyte heat recovery heat exchanger and flash evaporation chamber are located prior to the single or multiple effect evaporator system. In yet another embodiment, the catholyte heat recovery process is used in conjunction with additional heat exchanger processes to further concentrate the final product as desired.

A method for concentrating an aqueous caustic alkali produced by a membrane cell process by using a single or multiple effect evaporator system in which the vapor flows in a counter direction to the aqueous caustic alkali flow and the heat recovered from the catholyte circulation line is used as part of the concentration process. In one embodiment, a catholyte heat recovery heat exchanger and flash evaporation chamber are located after the last effect of a multiple effect evaporator system. In another embodiment, the catholyte heat recovery heat exchanger and flash evaporation chamber are located prior to the single or multiple effect evaporator system. In yet another embodiment, the catholyte heat recovery process is used in conjunction with additional heat exchanger processes to further concentrate the final product as desired.