NITRIC-SULFURIC ACID DECOMPOSITION OF LOW-GRADE KARATAU PHOSPHORITES

Abstract

The presented article contains the results of studying a decomposition process of a low-grade phosphorite of the Zhanatas deposit of the Karatau Basin with a sulphuric and nitric acid mixture with a partial precipitation of calcium as phosphogypsum and the subsequent ammoniation of a pulp for the purpose of production of a nitrogen-phosphoric mineral fertilizer. Properties of phosphorite of the Zhanatas deposit were described. To determine an optimum regime of the phosphorite decomposition process the dependences of P₂O₅ extraction degree in the nitric acid extract on the concentration of applied nitric acid, temperature and duration of the process were studied. Initial phosphorite and the obtained products were analysed be means of physical and chemical analysis techniques. The offered way of nitric-sulphuric-acid processing of the off-grade phosphorite of the Zhanatas deposit of the Karatau Basin allows us to considerably increase a P₂O₅ content in the extract and to produce a nitrogen and phosphorus containing fertilizer as a result of its subsequent ammoniation.