Concentrated aqueous sodium hydroxide solution comprising: at least 25% by weight of NaOH, sodium chloride (NaCl) and/or sodium sulfate (Na.sub.2SO.sub.4), and one soluble impurity from a sodium carbonate or bicarbonate ore deposit, said soluble impurity being selected among: As, Ba, B, Ca, Co, K, Li, Mg, Mo, P, Pb, Se, Si, Sr, Te, Tl, Ti, V, W, and the soluble impurity being in specific concentrations ranges. And process for producing such concentrated aqueous sodium hydroxide solution by treating a purge stream comprising sodium carbonate or bicarbonate.

A method for treating a purge stream derived from a sodium carbonate, sesquicarbonate, wegsheiderite, or bicarbonate crystallizer, said purge stream comprising sodium carbonate and/or sodium bicarbonate and at least 1% by weight of sodium chloride and/or sodium sulfate, the method comprising: causticizing at least 50 mol. % of the sodium from sodium carbonate and/or sodium bicarbonate into a caustic solution and into a calcium carbonate mud with lime and water, separating the calcium carbonate mud from the caustic solution; concentrating the caustic solution by removing part of the water to obtain a concentrated caustic solution comprising at least 25% NaOH, and a crystallized solid comprising sodium carbonate and sodium chloride and/or sulfate, separating the crystallized solid from the concentrated caustic solution, said crystallized solid to be disposed of or to be further valorized, recycling part of the concentrated caustic solution to the sodium carbonate, sesquicarbonate, wegsheiderite, or bicarbonate crystallizer.

A method for treating a purge stream derived from a sodium carbonate, sesquicarbonate, wegsheiderite, or bicarbonate crystallizer, said purge stream comprising sodium carbonate and/or sodium bicarbonate and at least 1% by weight of sodium chloride and/or sodium sulfate, the method comprising: causticizing at least 50 mol. % of the sodium from sodium carbonate and/or sodium bicarbonate into a caustic solution and into a calcium carbonate mud with lime and water, separating the calcium carbonate mud from the caustic solution; concentrating the caustic solution by removing part of the water to obtain a concentrated caustic solution comprising at least 25% NaOH, and a crystallized solid comprising sodium carbonate and sodium chloride and/or sulfate, separating the crystallized solid from the concentrated caustic solution, said crystallized solid to be disposed of or to be further valorized, recycling part of the concentrated caustic solution to the sodium carbonate, sesquicarbonate, wegsheiderite, or bicarbonate crystallizer.

A process to produce battery grade lithium hydroxide monohydrate with low content of carbonate from an impure lithium feed by forming a concentrated lithium hydroxide solution that is saturated or nearly saturated with lithium hydroxide monohydrate, removing at least some lithium carbonate from the solution, crystallizing the lithium hydroxide monohydrate, and separating the crystallized lithium hydroxide monohydrate from the solution.

A process to produce battery grade lithium hydroxide monohydrate with low content of carbonate from an impure lithium feed by forming a concentrated lithium hydroxide solution that is saturated or nearly saturated with lithium hydroxide monohydrate, removing at least some lithium carbonate from the solution, crystallizing the lithium hydroxide monohydrate, and separating the crystallized lithium hydroxide monohydrate from the solution.

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.

The invention is related to a layered double hydroxide electride which can be produced without high-temperature treatment, and a production method of which cost can be reduced. The layered double hydroxide electride contains electrons between layers and has an electron density of 2.010.sup.18 cm.sup.3 or more. The method of producing the layered double hydroxide electride includes a step of mixing a starting layered double hydroxide with an electron exchanger for exchanging anions existing between layers of the starting layered double hydroxide for electrons to produce the layered double hydroxide electride.

The invention is related to a layered double hydroxide electride which can be produced without high-temperature treatment, and a production method of which cost can be reduced. The layered double hydroxide electride contains electrons between layers and has an electron density of 2.010.sup.18 cm.sup.3 or more. The method of producing the layered double hydroxide electride includes a step of mixing a starting layered double hydroxide with an electron exchanger for exchanging anions existing between layers of the starting layered double hydroxide for electrons to produce the layered double hydroxide electride.

A method for producing a concentrated aqueous sodium hydroxide solution from a purge stream deriving from a sodium carbonate, or sesqui-carbonate, or wegsheiderite crystallizer, or sodium bicarbonate crystallizer, said purge stream comprising sodium carbonate and/or bicarbonate, and at least 1% of sodium chloride or sodium sulfate and a soluble impurity from an ore deposit comprising at least one of the following elements: As, Ba, B, Ca, Co, K, Li, Mo, P, Pb, Se, Sn, Sr, Te, Tl, Ti, V, and W, to be purified, the method comprising: causticizing at least 50 mol. % of the sodium carbonate into a caustic solution and into a calcium carbonate mud with lime and water; separating the mud from the caustic solution; concentrating the caustic solution by removing part of the water to obtain a concentrated caustic solution comprising at least 25% NaOH, and a crystallized solid comprising sodium carbonate and sodium chloride and/or sulfate; and separating the crystallized solid from the concentrated caustic solution, said crystallized solid to be disposed of or to be further valorized.