Method for preparing calcium phosphite from industrial sodium hypophosphite waste residues

Abstract

The invention relates to a method for preparing calcium phosphite from industrial sodium hypophosphite waste residues. According to the technical scheme, the method comprises the following steps: firstly, reacting the sodium hypophosphite waste residues, water and sodium carbonate, and separating to prepare a filter cake I and filter liquor I; secondly, reacting the filter cake I with hydrochloric acid, and separating to prepare filter liquor II; thirdly, enabling the filter liquor I to pass through an active carbon adsorption system, adding the filter liquor I and the filter liquor II into a continuous reaction crystallizer, ageing, separating and drying to obtain calcium phosphite crystals with the purity of more than 99.0% and crystal mother liquor II; and finally, evaporating and crystallizing the crystal mother liquor II to obtain crude sodium chloride salt and crystal mother liquor III, and returning the crystal mother liquor III to the reaction crystallizer for circulation. According to the method, a continuous reaction crystallization process is adopted, calcium phosphite is prepared from the industrial byproducts-sodium hypophosphite waste residues used as raw materials, the sodium hypophosphite waste residues are recycled during solid waste treatment, and waste liquid is not generated in a production process; moreover, the method has the advantages that the process is simple, the operating condition is mild, the energy consumption is low, the product quality is stable, the industrialization is facilitated, and the like.

Description

technical field [0001] The invention belongs to the technical field of preparation of fine chemicals, and in particular relates to a method for preparing calcium phosphite from industrial waste residue of sodium hypophosphite. Background technique [0002] Sodium hypophosphite is one of the main raw materials of the electroless plating industry. At present, the one-step process with yellow phosphorus, quicklime and caustic soda (or soda ash) as the main raw materials is mainly used for industrial production at home and abroad. However, this process will produce a large amount of industrial waste residue, commonly known as sodium hypophosphite waste residue, which is mainly composed of calcium phosphite (about 40~50wt%), calcium carbonate (about 10~30wt%), calcium hydroxide (15~30wt%), al 2 o 3 (about 1~1.5wt%), SiO 2 (about 1~3wt%), other 0~7wt%. [0003] At present, the treatment methods of sodium hypophosphite industrial waste mainly include: (1) landfill; (2) converti...

AI Technical Summary

Problems solved by technology

Among them, method (1) fails to effectively utilize a large amount of calcium phosphite in the waste residue, which wastes resources and pollutes the environment; method (2) is essentially a low-end industrial route, with high energy consumption and high pollution, and low added value of products; method (3 ) and (4) the process is complex, the production cost is high, and the amount of waste liquid produced is large

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