Black shale ore of Big Karatau is a raw material source of rare and rare earth elements

Abstract

Abstract The ores of Big Karatau are a valuable, currently unused source of rare and rare earth elements (REEs). To develop an integrated technology for processing black shale ore, it was studied using chemical, X-ray phase, infrared, mineralogical, X-ray spectral, and electron microscopic analyses. Rare and particularly REEs in the ore are found in various minerals in the form of inclusions in the siliceous‑carbonaceous matrix. This explains the failures of the previously proposed processing methods, which either resulted in the incomplete extraction of the valuable components or were not profitable. For more complete extraction, novel ore processing approaches are required. A method for the early development of the original black shale ore using sintering with (NH4)2SO4 in the presence of concentrated H2SO4, followed by leaching of the cake with a diluted H2SO4 solution, is proposed. The optimal conditions for each stage are determined. The kinetic dependencies of the extraction of rare and REEs from sulfated cake under the most suitable conditions yielded maximum extractions of 98% for U, 92% for V, 89% for Mo, and 78% for the REEs. The rate constant and effective activation energy of V leaching, as the most representative of the rare and rare earth metals, were calculated. The process was limited by diffusion. After the leaching of the valuable components, the cake may be used in froth flotation enrichment to recover the carbonaceous material, and then it may be used as part of the charge to obtain ferrosilicon. The solution obtained from the leaching of the initial cake may be used to recover U, Mo, V, and the REEs using sorption.