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 2.0×10.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 2.0×10.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 sesquicarbonate, 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.

A method for producing a concentrated aqueous sodium hydroxide solution from a purge stream deriving from a sodium carbonate, or sesquicarbonate, 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.

Method of concentrating aqueous alkali and apparatus suitable for this purpose. A very energy-saving method of concentrating aqueous alkali originating, for example, from a chloralkali electrolysis plant and an apparatus suitable for this purpose are described. The method/the apparatus utilizes heat of reaction from the formation of 1,2-dichloroethane and includes multistage concentration of the aqueous alkali, where at least part of the heat required for concentrating the aqueous alkali originates from the plant for preparing 1,2-dichloroethane and at least a further part of the heat required for concentrating the aqueous alkali originates from at least one of the higher stages of the plant for concentrating the aqueous alkali and is used for partial heating of the first stage. The apparatus can be used for retrofitting existing integrated plants made up of a DCE plant and chloralkali electrolysis or in the erection of new plants.

Method of concentrating aqueous alkali and apparatus suitable for this purpose. A very energy-saving method of concentrating aqueous alkali originating, for example, from a chloralkali electrolysis plant and an apparatus suitable for this purpose are described. The method/the apparatus utilizes heat of reaction from the formation of 1,2-dichloroethane and includes multistage concentration of the aqueous alkali, where at least part of the heat required for concentrating the aqueous alkali originates from the plant for preparing 1,2-dichloroethane and at least a further part of the heat required for concentrating the aqueous alkali originates from at least one of the higher stages of the plant for concentrating the aqueous alkali and is used for partial heating of the first stage. The apparatus can be used for retrofitting existing integrated plants made up of a DCE plant and chloralkali electrolysis or in the erection of new plants.

A method for producing a concentrated aqueous sodium hydroxide solution from a purge stream deriving from a sodium carbonate, or sesquicarbonate, 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.

A method for producing a concentrated aqueous sodium hydroxide solution from a purge stream deriving from a sodium carbonate, or sesquicarbonate, 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.

A method of concentrating and/or producing lithium hydroxide in an evaporator entails feeding a stream comprising lithium, hydroxide and carbonate to the evaporator. In the evaporator, the feed is concentrated to form lithium hydroxide and lithium carbonate crystals. Further, the method entails reducing the tendency of lithium carbonate to scale the evaporator by increasing the concentration of lithium carbonate crystals in the evaporator by: (1) clarifying at least a portion of the concentrate in the evaporator to form a clarified solution; and (2) discharging the clarified solution as a clarified solution stream from the evaporator.

A method of concentrating and/or producing lithium hydroxide in an evaporator entails feeding a stream comprising lithium, hydroxide and carbonate to the evaporator. In the evaporator, the feed is concentrated to form lithium hydroxide and lithium carbonate crystals. Further, the method entails reducing the tendency of lithium carbonate to scale the evaporator by increasing the concentration of lithium carbonate crystals in the evaporator by: (1) clarifying at least a portion of the concentrate in the evaporator to form a clarified solution; and (2) discharging the clarified solution as a clarified solution stream from the evaporator.