Production of hydrogen and solid lithium hydroxide

Process for producing hydrogen and lithium hydroxide, comprising the following steps:

• a) providing a feed comprising at least water, Li ions and also impurities, the concentration of Li ions in the feed CF being at least 200 ppm by weight or between 500 ppm by weight and 140 000 ppm by weight, in each case based on the total weight of the feed;
• b) providing a poor working medium comprising water and lithium hydroxide dissolved therein, the concentration of lithium hydroxide in the poor working medium CM0, based on the total weight of the poor working medium, being at least 50 ppm by weight;
• c) providing at least one electrochemical cell, wherein the electrochemical cell has the following properties:
• i. the electrochemical cell includes a first compartment in which an anode is arranged;
• ii. the electrochemical cell includes a second compartment in which a cathode is arranged;
• iii. the electrochemical cell includes a membrane that separates the first membrane from the second membrane, the membrane having the area A;
• iv. the membrane comprises an inorganic material that possesses conductivity for Li ions and that is electrically insulating;
• d) providing at least one electrical voltage source that is connected to the anode via a first electrical lead and to the cathode via a second electrical lead;
• e) charging of the first compartment with the feed;
• f) charging of the second compartment with the poor working medium;
• g) charging of the electrochemical cell with an electrical voltage U drawn from the electrical voltage source such that an electrical current/flows between the anode and cathode, the ratio Q of the current strength of the electrical current/and the area A of the membrane being between 100 A/m2 and 500 A/m2 or between 150 A/m2 and 350 A/m2;
• h) withdrawing from the first compartment of wastewater comprising at least water, Li salts dissolved therein, oxygen and also impurities, the concentration of Li ions in the wastewater CW, based on the total weight of the wastewater, being lower than the concentration of Li ions in the feed CF based on the total weight of the feed;
• i) withdrawing from the second compartment of a rich working medium comprising water, hydrogen and lithium hydroxide, wherein the concentration of lithium hydroxide in the rich working medium CM1 based on the total weight of the rich working medium is greater than the concentration of lithium hydroxide in the poor working medium CM0 based on the total weight of the poor working medium, and wherein the concentration of lithium hydroxide in the rich working medium CM1 based on the total weight of the rich working medium is greater than the solubility of lithium hydroxide in water at a temperature TM1, where the temperature TM1 refers to the temperature of the rich working medium at the time of its withdrawal from the second compartment.