Removal of Fluorine during the Extraction of Phosphoric Acid
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Academic Journal Incorporations
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Task The article The defluorization and desulfurization of EPA in the process of its extraction by the introduction of sodium sulfate in an improved filtration mode in the presence of a chemical reagent sodium naphthenate, which has flocculation and biological active properties, which makes it possible to reduce fluorine emissions during the evaporation (concentration) of EPA, and to obtain defluorinated fertilizers have been studied.
Methods. One of the valuable results of these studies is that the introduction of a small amount of alkali metal petroleum (or oil refinery waste) into the extractor can improve the structure of calcium sulfate crystals (especially when desulfurizing the extraction pulp by introducing an additional amount of phosphate), leading to improved filtration of the extraction pulp in 1, 5 - 1.7 times and, accordingly, increase the productivity of the extraction shop.
Results In order to reduce the rate of the precipitant and increase the effect of defluorization at the same time, as well as improve the crystallization (i.e., the filterability of the pulp) of calcium sulfate (by reducing the silicofluoride ions in the solution) and the precipitation of silicofluorides on the "pad" of phosphogypsum during the decomposition of Karatauphosphorites, the extractor was introduced sodium naphthenate (first used for this purpose), which can affect crystallization as surface active agents. To improve the process of defluorination of EPA and crystallization of calcium sulfate, 10% sodium sulfate was replaced with sodium naphthenate (40% aqueous solution). Sodium naphthenate when interacting with hydrofluorosilicic acid forms large crystals of sodium silicofluoride and naphthenic acid. Therefore, the aim of these studies was to defluorinate EPA with a simultaneous improvement in the filterability of the extraction pulp.
Conclusion. The process of defluorination with simultaneous desulfurization using sodium sulfate and with partial replacement of it with sodium naphthenate during the extraction of phosphoric acid from phosphates has been studied and obtaining defluorinated fertilizers.
Keywords
Phosphorite, Karatau, sodium naphthenate, sodium silicofluoride, naphthenic acid, phosphogypsum, fluorine