Oxidative leaching of rhenium from grinding waste of rhenium-containing superalloys

Abstract

The study investigated the feasibility of oxidative leaching rhenium in the presence of hydrochloric acid from machining waste (grinding waste) derived from products made of ZhS-32VI, a nickel-based heat-resistant alloy containing rhenium. This was achieved through agitation leaching process. The grinding waste fraction size of –0.071 mm, which accounted for the highest yield (49.2 wt.%), was utilized in the experiments. The rhenium leaching process was conducted in two variations: in the first option, grinding waste was mixed with a hydrochloric acid solution at ~100 °C, followed by the addition of hydrogen peroxide to the leaching solution after it had cooled; in the second option, leaching was performed using a hydrochloric acid solution with the gradual addition of hydrogen peroxide solution. The highest degree of rhenium leaching (91.0 %) was achieved in the first option. In this case, the initial concentration of hydrochloric acid was 8 M, and the molar ratio of the added reagents was ν(HCl): ν(H2O2) = 2.7 : 1.0. The kinetics of nickel leaching using a 6 M hydrochloric acid solution at 70 °C, with a solid-to-liquid phase ratio of 1 g : 50 ml, was also examined. The analysis of the kinetic data, processed using the “contracting sphere,” Ginstling–Brounshtein, and Kazeev–Erofeev models, indicates that the nickel leaching process occurs within the kinetic region. Additionally, the kinetics of rhenium leaching from the solid residue obtained after the hydrochloric acid leaching of nickel from grinding waste was investigated. Employing the same kinetic models to analyze the data, it was determined that the limiting stage of this process involves the diffusion of hydrogen peroxide within the rhenium-containing solid residue.