Method for extracting potassium nitrate from circulating mother liquor for producing aluminum oxide through Bayer process

Abstract

The invention belongs to the field of inorganic chemistry and provides a method for extracting potassium nitrate from circulating mother liquor for producing aluminum oxide through a Bayer process. The method comprises the following steps: 1) dissolving sodium nitrate in the Bayer process circulating mother liquor; 2) carrying out three-stage cooling; 3) stirring the solution at a constant temperature for crystallization after the third stage of cooling, centrifugally separating the slurry after the crystallization, adding water to the separated-out potassium salt for re-dissolving, and then cooling to the range from 20 to 30 DEG C for primary recrystallization; and 4) centrifugally separating the slurry after the recrystallization to obtain refined potassium salt, adding demineralized water for re-dissolving, and then cooling for secondary recrystallization. The method provided by the invention is characterized in that the sodium nitrate is used for displacing the potassium nitrate in a strong basic sodium aluminate solution system according to the mechanism of utilizing the solubility difference of the nitrates, the solubility of salts is greatly reduced due to strong basicity, and therefore, a foundation is laid for the extraction of potassium ions at high efficiency. The method provided by the invention realizes value promotion by exchanging a cheap matter (sodium nitrate) for an expensive matter (potassium nitrate), and has very low influence on the Bayer process solution; potassium-sodium nitrate has no double salt; subsequent potassium salt purification is easy to implement.

Description

technical field [0001] The invention belongs to the field of inorganic chemistry, and in particular relates to a method for extracting alkali metal nitrates. Background technique [0002] Potassium nitrate KNO 3 , with a molecular weight of 101.11, is a colorless transparent orthorhombic or rhombic crystal white powder, easily soluble in water, insoluble in ethanol, and not easy to deliquesce in the air. Potassium nitrate is mainly used for fireworks, black gunpowder, matches, fuses, candle wicks, tobacco, color TV picture tubes, medicines, chemical reagents, catalysts, ceramic glazes, glass, fertilizers, and leaves of economic crops such as flowers, vegetables, and fruit trees. Spray fertilizer, etc. In addition, potassium nitrate is used as auxiliary material in metallurgical industry and food industry. More than 70% of the world's potassium nitrate is used in agricultural production, and it reaches about 90% in my country. [0003] There are few natural potassium nitr...

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Problems solved by technology

[0004] The by-product potash salt from the alumina process has industrial experience in some factories in the former Soviet Union and Russia that use nepheline sintering to produce alumina. The subsequent potassium extraction is to use the carbonized mother liquor after thorough carbonization to undergo deep evaporation and fractional crystallization. Process extraction, according to the solubility difference of different salts and alkalis, sequentially crystallize sodium carbonate (first stage), potassium sulfate, sodium carbonate (second stage), potassium carbonate sodium double salt, potassium chloride, and finally crystallize potassium carbonate, the process is very complicated

Because alumina is produced by the sintering method, the current alumina basically belongs to the Bayer process, and the mother liquors of the two systems are completely different, so the potassium extraction process in the former Soviet Union cannot meet the needs of the Bayer process.

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