This invention discloses a method for preparing 4N
ammonium permanganate from low-concentration
rhenium-containing waste acid, which is divided into a crude refining stage and a refining stage. The crude refining stage includes a
rhenium precipitation process, a leaching process, a
hydrolysis process, an acidification process, an extraction process, a back-extraction process, and a
crystallization process. The refining stage includes a crude
ammonium permanganate dissolution process, an
ion exchange process, an extraction process, a back-extraction process, a
crystallization process, and a
nitration-recrystallization process, ultimately obtaining
ammonium permanganate with a purity of 99.99%. In the crude refining stage, this invention first prepares 4N ammonium permanganate from low-concentration
rhenium-containing waste acid.
Rhenium is efficiently and selectively enriched in concentrated waste acid to obtain a 1% grade rhenium precipitate. Then, a weak oxidation leaching process is used to remove impurities from the precipitate, followed by
calcium hydroxide hydrolysis, acidification, high-efficiency extraction, back-extraction, and
crystallization to obtain a crude
ammonium perrhenate product with a grade of ≥99%. In the refining stage, the crude
ammonium perrhenate is dissolved a second time, and a resin
ion exchange, extraction, back-extraction, and crystallization process is used to obtain a refined
ammonium perrhenate with a grade of ≥99.9%. Finally, a
nitration-recrystallization process is used to remove impurities from the refined ammonium
perrhenate to achieve a 4N grade quality.