D. I. Mendeleev Russian University of Chemical Technology, Moscow, Russia

M. A. Solodovnikov, Postgraduate of the Department of Technology of Rare Elements and Nanomaterials on Their Base, e-mail: solodovnikovmaksim1@gmail.com
I. D. Troshkina, Professor of the Department of Technology of Rare Elements and Nanomaterials on Their Base, Doctor of Technical Sciences, Professor, e-mail: troshkina.i.d@muctr.ru

The rhenium mineral resource base available in Russia is insufficient to meet the demand for this strategically important metal, so secondary raw materials are becoming almost the only source that largely covers the demand for it. The waste generated during the manufacture of products from rhenium-containing superalloys can be lumpy and powdery. During their hydrometallurgical processing, after the dissolution operation with the transfer of rhenium, nickel and cobalt to the liquid phase, a solid semiproduct containing tungsten remains. Every year in Russia, about 30 t of secondary raw materials are accumulated during the processing of parts made of rhenium-containing special alloys. An average content of tungsten in them is 7–9 %. So up to 2.7 t of metal can be produced. The article studies the possibility of hydrometallurgical processing of tungsten-containing cake formed as a result of waste processing of rheniumcontaining nickel-based superalloys. Its tungsten content is 13% (mass.). In addition to tungsten, the semiproduct contains other metals such as tantalum, aluminum, cobalt, chromium, zirconium, and molybdenum. The proposed processing method includes sintering with an alkaline reagent, subsequent aqueous leaching of the sinter, precipitation and drying of the commercial product – tungstic acid. The results of experiments demonstrate that sintering should be carried out with a two-fold excess of sodium carbonate relative to the semiproduct at a temperature of 900 °C or with a three-fold excess of sodium hydroxide at a temperature of 550 °C. Kinetic curves of aqueous leaching of tungsten from sintered semiproducts with sodium hydroxide and carbonate have been obtained. To determine the limiting stage, they were processed using kinetic and diffusion models. Since the obtained dependences satisfy Yander, Gistling–Brownstein, and Prout–Tompkins equations, it can be concluded that the process is limited by external diffusion. An increase in its speed is achieved by increasing the intensity of mixing. When using mineral acids (HCl, HNO₃, H₂SO₄) as precipitators, the maximum degree of precipitation of tungstic acid from the leaching solution was achieved with a twofold excess of hydrochloric acid. Depending on the chosen alkaline reagent for sintering, the content of tungsten in acid was 73.3–73.5 % when it was extracted through sintering with sodium hydroxide over 99 %, which meets the requirements of GOST 2197–78.

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