Chemical polishing waste phosphoric acid treatment method and fertilizer preparation method

Abstract

The invention provides a chemical polishing waste phosphoric acid treatment method. The method comprises the following steps: a neutralizer is added to mother liquor of urea phosphate crystals prepared from chemical polishing waste phosphoric acid, a stirring reaction is performed, a precipitate of metal ions is formed and filtered, and a filtrate is obtained; a precipitant is added to the filtrate, foreign ions are precipitated, filtering is performed again, and a purified solution is obtained; the purified solution is subjected to reduced-pressure evaporation until the mass ratio of urea to water is 0.75-1.4, then cooling crystallization, filtering separation, washing and drying are performed, and a monopotassium phosphate product is obtained; mother liquor obtained after cooling crystallization is evaporated and concentrated until phosphorus content of the mother liquor is 3.5%-5.0%, vacuum drying is performed, and nitrogen-phosphorus-potassium compound fertilizer is obtained. Nitrogen and phosphorus resources in the mother liquor of the urea phosphate crystals are recovered mainly in forms of monopotassium phosphate and the nitrogen-phosphorus-potassium compound fertilizer, production process is simple and low in cost, nitrogen-phosphorus resource using rate is high, and the economic value is high.

Description

technical field [0001] The present invention relates to the technical field intersecting environmental protection and phosphorus chemical production, mainly to the technical field of industrial waste liquid, in particular to a treatment method for preparing urea phosphate crystallization mother liquor from chemical polishing waste phosphoric acid, nitrogen-phosphorus-potassium compound fertilizer and phosphoric acid The preparation method of potassium dihydrogen. Background technique [0002] Chemical polishing waste phosphoric acid mainly comes from a large amount of waste liquid produced by polishing metal surfaces in electroplating industry, coating, anodic oxidation and various surface treatment processes. It contains high concentration of phosphoric acid, sulfuric acid, nitric acid, acetic acid and heavy metal ions, etc. Harmful chemical substances, highly corrosive, belonging to the HW34 category of the "National Hazardous Waste List". [0003] The general way to deal...

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Problems solved by technology

This method will produce a large amount of phosphorus-containing sludge, increase the cost of landfill, and even cause environmental pollution

[0004] At present, there are some relevant patents and literature reports on the comprehensive utilization of this kind of waste phosphoric acid. For example, patent CN101456547 B uses lime milk as a neutralizing agent, and realizes the purification of heavy metal ions and the production of fertilizer-grade calcium hydrogen phosphate by step-by-step precipitation method. preparation, but the market sales of calcium hydrogen phosphate is not good, and the added value of the product is low

Patent 201610795470.0 proposes a resource recycling method for aluminum polishing waste phosphoric acid solution, which adopts adding fluorine-containing solution and sodium salt to precipitate and remove aluminum in the form of cryolite, and then produces calcium hydrogen phosphate and ordinary calcium by calcium salt three-step precipitation method, sulfuric acid and Phosphoric acid is fully utilized, but the precipitation and separation are complicated and the added value of the product is low

[0005] In view of the fact that such waste liquid contains a large amount of phosphoric acid components, and phosphorus-containing products have high economic value, the inventor has developed a series of recycling processes, which include purifying and removing impurities of such waste acid and preparing products such as urea phosphate, Because this kind of waste acid often contains more impurities, and urea phosphate is easily soluble in water, although the process of preparing urea phosphate products has undergone relevant purification processes and multi-stage recovery, the recovery rate of phosphorus resources has reached about 90%, but there are still A small amount of high-concentration phosphorus and urea-containing mother liquor

At present, there are almost no relevant research reports on the comprehensive utilization of this kind of mother liquor. Generally, comprehensive treatment is used to meet the discharge standards.

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