Theoretical and Practical Foundations of the Selective Separation of Phosphate Ions from Phosphate Ores with a High Content of Iron Impurities with the Recirculation Method

Calculations and experimental analysis of phosphate ores contaminated with Fe(III) compounds showed that advanced processing of these ores in a scheme with recycling of Fe(III) compounds is possible. The selective precipitation of PO43- ions from a nitric acid extract with Fe(III) ions in the form of a FePO4 precipitate, the subsequent alkaline extraction of PO43- ions from FePO4, and the dissolution of the formed Fe(OH)(3) precipitate in HNO3 make it possible to obtain soluble phosphates and to recycle Fe(III) ions for the precipitation of PO43- from the nitric acid extract. The residual P(V) content in the Fe(OH)(3) precipitate under the conditions of the recycling of Fe(III) ions is 0.80 wt %, which corresponds to a degree of PO4 extraction from FePO4 of 97.1%. The results of the theoretical calculations agree with the obtained experimental data. The proposed original solutions make it possible to process more phosphate ore contaminated with Fe(III) compounds with smaller amounts of Fe(III) compounds, including those contained in the ore.