Method of utilizing caprolactam waste alkalis to prepare sodium fluoride and white carbon black

Abstract

The invention discloses a method of utilizing caprolactam waste alkalis to prepare sodium fluoride and white carbon black. The method comprises following steps: (1) mixing waste alkalis with desalinated water, heating to dissolve waste alkalis, filtering the solution when the solution is still hot to remove insoluble impurities to obtain a filtrate (A), and cooling and re-crystallizing the filtrate (A) to obtain sodium carbonate decahydrate and a filtrate (B); (2) adding fluoro-silicic acid into the filtrate (B), after reactions, growing the grains, filtering to obtain sodium fluorosilicate crystals and a filtrate (C); (3) mixing sodium fluorosilicate obtained in the step (2) and sodium carbonate decahydrate obtained in the step (1), adding water, stirring to carry out reactions, finally adding a surfactant, and evenly mixing; and (4) settling the stock solution obtained in the step (3), removing the supernate, separating sodium fluoride and white carbon black, carrying out centrifugation, and drying to obtain sodium fluoride crystals and white carbon black. The caprolactam waste alkalis and the byproduct namely fluoro-silicic acid of the phosphate fertilizer industry are comprehensively utilized, the wastes are converted into valuable resources, and a high environment protection value and economic value are generated.

Description

technical field [0001] The invention relates to the recycling of spent caprolactam alkali and fluosilicic acid, in particular to a method for preparing sodium fluoride and white carbon black by utilizing spent caprolactam alkali and fluosilicic acid by-product of phosphorus chemical industry. Background technique [0002] At present, a large amount of waste caustic soda is produced in the production process of caprolactam in our country. The spent caustic soda contains a large amount of sodium sulfate impurities, which is poor in quality, low in purity, and difficult to separate. Therefore, enterprises generally sell it as a burden at a very low price, which is economical. Extremely low value. On the other hand, a large amount of fluosilicic acid is produced by-product in my country's phosphate fertilizer industry, most of which are recovered in the form of sodium fluosilicate, and sodium fluosilicate has narrow uses, low price, and low economic benefits, which seriously res...

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Problems solved by technology

[0002] At present, a large amount of waste caustic soda is produced in the production process of caprolactam in our country. The spent caustic soda contains a large amount of sodium sulfate impurities, which is poor in quality, low in purity, and difficult to separate. Therefore, enterprises generally sell it as a burden at a very low price, which is economical. extremely low value

On the other hand, a large amount of fluosilicic acid is produced by-product in my country's phosphate fertilizer industry, most of which are recovered in the form of sodium fluosilicate, and sodium fluosilicate has narrow uses, low price, and low economic benefits, which seriously restricts The enthusiasm of enterprises to recycle fluosilicic acid and the development of phosphate fertilizer industry have also caused the waste of fluorine resources in my country

[0003] CN104030317A discloses utilizing sodium carbonate and fluorosilicic acid to prepare sodium fluorosilicate, and then further prepares the technology of sodium fluoride and white carbon black, but wherein directly adopts sodium carbonate decahydrate raw material to produce, and cost is higher, and the obtained fluorine Sodium chloride and white carbon black are easy to form co-precipitation, and the separation effect is poor

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