Production of sodium and aluminum chemicals and recovery of rare earth elements after leaching cryolite from Pitinga mine (Amazonas - Brazil) with sulfuric acid

This work examines the production of sodium and aluminum chemicals and the recovery of rare earth elements (REE) after leaching cryolite from the Pitinga Mine (Amazonas - Brazil) with sulfuric acid for production of hydrogen fluoride. The residue containing sodium, aluminum and REE sulfates and the non-reacted sample was leached with water and the insoluble matter was isolated. REE were extracted using PC 88A (10 vol% in n-hexane, 25 °C, A/O = 1 vol./vol., pH 2.5, two stages). The yield increased as the atomic number of the REE increased. Extracted REE were stripped by 3 mol L−1 HCl. Sodium and aluminum compounds were recovered by evaporation/crystallization and precipitation steps. The best strategy was to precipitate Al(OH)3 by addition of aqueous NaOH, followed by recovery of Na2SO4 via evaporation of the aqueous solution to dryness. Both compounds were recovered with high yield (>99 wt%) and purity (>99 wt%).