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.

Process for producing sodium carbonate and sodium bicarbonate in a continuous mode out of trona comprising: c) feeding crushed trona, an extraction water and an additive in a first leaching tank containing a dissolution solution comprising sodium carbonate and sodium bicarbonate, wherein the additive is selected from the group consisting of: anionic hexametaphosphate, anionic polyphosphate, anionic polyphosphonate, soja lecithine, anionic polycarboxylate polymer, anionic polyacrylate polymer, anionic polyacrylate-polyacrylamide co-polymer, anionic hydrolyzed polymaleic polymers, anionic maleic-acrylic acids copolymers, anionic acrylic acid-phosphonic acid copolymers and combinations thereof; d) dissolving at least partially the crushed trona in the dissolution solution in order to produce a first suspension; e) removing continuously the first suspension from the first leaching tank and feeding it with an additive into a second leaching tank wherein the additive is selected from the same group of additives of step c); f) dissolving at least partially the remaining crushed trona from step d) in the second leaching tank in order to produce a second suspension; g) separating the second solid particles from the second solution to produce a production solution comprising sodium carbonate and to produce a production solid comprising the second solid particles comprising sodium bicarbonate.

Process for producing sodium carbonate and sodium bicarbonate in a continuous mode out of trona comprising: c) feeding crushed trona, an extraction water and an additive in a first leaching tank containing a dissolution solution comprising sodium carbonate and sodium bicarbonate, wherein the additive is selected from the group consisting of: anionic hexametaphosphate, anionic polyphosphate, anionic polyphosphonate, soja lecithine, anionic polycarboxylate polymer, anionic polyacrylate polymer, anionic polyacrylate-polyacrylamide co-polymer, anionic hydrolyzed polymaleic polymers, anionic maleic-acrylic acids copolymers, anionic acrylic acid-phosphonic acid copolymers and combinations thereof; d) dissolving at least partially the crushed trona in the dissolution solution in order to produce a first suspension; e) removing continuously the first suspension from the first leaching tank and feeding it with an additive into a second leaching tank wherein the additive is selected from the same group of additives of step c); f) dissolving at least partially the remaining crushed trona from step d) in the second leaching tank in order to produce a second suspension; g) separating the second solid particles from the second solution to produce a production solution comprising sodium carbonate and to produce a production solid comprising the second solid particles comprising sodium bicarbonate.

A movable device, e.g., a laboratory, for obtaining lithium salt from brine has a movable box, and a device for removing impurities from brine and a lithium precipitation device that are disposed in the movable box. The device for removing impurities from brine is connected to the lithium precipitation device. The device for removing impurities from brine comprises one or more of an adsorption-separation device, a membrane device, an electrodialysis device, a device for deeply removing impurities with resin, and an evaporation device. The laboratory is in a form of box modular assembly and may be placed on a truck and flexibly transported to a brine lake. In a case of a large-scale pilot test, an adsorption-membrane coupling technology to evaporation and lithium precipitation may be completely implemented, so that a simulation test of a whole lithium carbonate process may be carried out on site.

A movable device, e.g., a laboratory, for obtaining lithium salt from brine has a movable box, and a device for removing impurities from brine and a lithium precipitation device that are disposed in the movable box. The device for removing impurities from brine is connected to the lithium precipitation device. The device for removing impurities from brine comprises one or more of an adsorption-separation device, a membrane device, an electrodialysis device, a device for deeply removing impurities with resin, and an evaporation device. The laboratory is in a form of box modular assembly and may be placed on a truck and flexibly transported to a brine lake. In a case of a large-scale pilot test, an adsorption-membrane coupling technology to evaporation and lithium precipitation may be completely implemented, so that a simulation test of a whole lithium carbonate process may be carried out on site.