The present invention relates to a method for preparing lithium hydroxide, comprising subjecting an aqueous composition (A), comprising lithium sulfate and sodium sulfate, to bipolar membrane electrodialysis; said step of bipolar membrane electrodialysis comprises processing in an electrodialyser comprising at least one electrodialysis cell (200) comprising a first compartment (220), supplied with water and delimited between a first bipolar membrane (250) and an anionic central membrane (230), and a second compartment (210), supplied with said aqueous composition (A) and delimited between said anionic central membrane (230) and a second bipolar membrane (240), then recovering, from said at least one electrodialysis cell (200), an aqueous composition (B) comprising lithium hydroxide and sodium sulfate, and subjecting it to a crystallisation step in order to prepare a salt.

The present invention relates to a method for preparing lithium hydroxide, comprising subjecting an aqueous composition (A), comprising lithium sulfate and sodium sulfate, to bipolar membrane electrodialysis; said step of bipolar membrane electrodialysis comprises processing in an electrodialyser comprising at least one electrodialysis cell (200) comprising a first compartment (220), supplied with water and delimited between a first bipolar membrane (250) and an anionic central membrane (230), and a second compartment (210), supplied with said aqueous composition (A) and delimited between said anionic central membrane (230) and a second bipolar membrane (240), then recovering, from said at least one electrodialysis cell (200), an aqueous composition (B) comprising lithium hydroxide and sodium sulfate, and subjecting it to a crystallisation step in order to prepare a salt.

A system for controlling an electrochemical production process includes a variable controllable power circuit and an electrolytic cell. The cell includes two electrodes and operates in different states dependent on the potential difference across the electrodes. The system includes a power circuit controller that causes the power circuit to apply a given potential difference across the electrodes to initiate operation of the cell in the one of multiple possible states associated with the given potential difference. The possible states include a production state associated with a first non-zero potential difference in which a product of interest is produced, and an idle state associated with a second non-zero potential difference in which the product of interest is not produced. A monitoring and control subsystem maintains a predefined set of production process conditions, including a predefined operating temperature range, while the cell operates in both the production state and the idle state.

A system for controlling an electrochemical production process includes a variable controllable power circuit and an electrolytic cell. The cell includes two electrodes and operates in different states dependent on the potential difference across the electrodes. The system includes a power circuit controller that causes the power circuit to apply a given potential difference across the electrodes to initiate operation of the cell in the one of multiple possible states associated with the given potential difference. The possible states include a production state associated with a first non-zero potential difference in which a product of interest is produced, and an idle state associated with a second non-zero potential difference in which the product of interest is not produced. A monitoring and control subsystem maintains a predefined set of production process conditions, including a predefined operating temperature range, while the cell operates in both the production state and the idle state.

The present disclosure provides a resource utilization method of crude sodium sulfate. The method comprises the following step: reducing the crude sodium sulfate to form a sodium sulfide solution; making the sodium sulfide solution perform a first reaction with chlorine to obtain sulfur and a sodium chloride solution; and electrolyzing the sodium chloride solution to obtain a sodium hydroxide solution and chlorine, and supplying the generated chlorine to the sodium sulfide solution to perform the first reaction. In the above resource utilization method of crude sodium sulfate, the sodium hydroxide is generated by combining relatively simple and mature process steps, and the crude sodium sulfate containing sodium chloride and sodium sulfate can be effectively converted to the sodium hydroxide in large market demand, so that complete recycling of sodium element and sulfur element is realized, which not only can fully utilize the resources and protect the environment, but also can create great economic benefits and environmental benefits, thus having a great significance to realize the green development of relevant industries.

The present disclosure provides a resource utilization method of crude sodium sulfate. The method comprises the following step: reducing the crude sodium sulfate to form a sodium sulfide solution; making the sodium sulfide solution perform a first reaction with chlorine to obtain sulfur and a sodium chloride solution; and electrolyzing the sodium chloride solution to obtain a sodium hydroxide solution and chlorine, and supplying the generated chlorine to the sodium sulfide solution to perform the first reaction. In the above resource utilization method of crude sodium sulfate, the sodium hydroxide is generated by combining relatively simple and mature process steps, and the crude sodium sulfate containing sodium chloride and sodium sulfate can be effectively converted to the sodium hydroxide in large market demand, so that complete recycling of sodium element and sulfur element is realized, which not only can fully utilize the resources and protect the environment, but also can create great economic benefits and environmental benefits, thus having a great significance to realize the green development of relevant industries.

The present disclosure relates to a method for treating an electromembrane process aqueous composition comprising sodium and/or potassium sulfate, said process comprising removing water from said electromembrane process aqueous composition under conditions suitable for substantially selectively precipitating sodium and/or potassium sulfate monohydrate.

The present disclosure relates to a method for treating an electromembrane process aqueous composition comprising sodium and/or potassium sulfate, said process comprising removing water from said electromembrane process aqueous composition under conditions suitable for substantially selectively precipitating sodium and/or potassium sulfate monohydrate.

A cell for enhancing a lithium (Li) concentration in a stream includes a housing; a dense lithium selective membrane located in the housing and dividing the housing into a first compartment and a second compartment; a cathode electrode located in the first compartment; an anode electrode located in the second compartment; a first piping circuit fluidly connected to the second compartment and configured to supply a feed stream to the second compartment; a second piping circuit fluidly connected to the first compartment and configured to circulate an enrichment stream through the first compartment; and a power source configured to apply a voltage between the cathode electrode and the anode electrode to initiate an oxidative electrochemical reaction on the anode electrode and a reductive electrochemical reaction on the cathode electrode. The dense lithium selective membrane has a thickness less than 400 m.

Apparatus for producing alkali hydroxide and method for operating apparatus for producing alkali hydroxide are provided. A cooling chamber through which a coolant can pass is constructed by placing a separation wall in a cathode chamber on a side opposite to an ion-exchange membrane, and a flow rate adjuster, such as manual valves, which can adjust the supply flow rate of the coolant is placed in each unit cell. The electrolytic temperature of each unit cell is regulated at an optimum operating temperature depending on the current density by adjusting the flow rate of the coolant without individually adjusting the flow rate of salt water supplied to the unit cell or the concentration of the salt water.