A process for preparing sodium bicarbonate particles, comprising the steps of: (a) adding at least one alkali metal carbonate to an aqueous solution in order to form an aqueous composition; wherein the alkali metal carbonate comprises sodium carbonate and wherein the aqueous composition comprises at least one polycarboxylic acid and/or the salts thereof, in an amount of at least 200 ppm based on the weight of the aqueous composition; and (b) precipitating solid particles comprising sodium bicarbonate crystals and separating said sodium bicarbonate particles from the aqueous composition, in order to obtain sodium bicarbonate particles and an aqueous mother liquor.

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 soda ash and sodium bicarbonate production method is provided, in which solution mining, pretreatment, stripping, concentration, sodium carbonate decahydrate crystallization, separation, dissolution, sodium carbonate monohydrate crystallization, separation and drying are performed to obtain dense soda ash. A dissolved sodium carbonate decahydrate solution or a concentrated brine 3 is subjected to crystallization, separation and drying to produce sodium bicarbonate. A discharge liquid 1 generated in the sodium carbonate decahydrate crystallization and separation is subjected to causticization and evaporation to recycle sodium carbonate. Causticized sludge generated in causticization is calcined and then recycled for causticization. The process provided herein maximizes the resource utilization.

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.