Physical and chemical researches of nickel-cobalt concentrates made from wastes of heat-resistant nickel alloys

Abstract

The wastes of rhenium-containing heat-resistant nickel alloys (HRNA) contain 50-75% of Ni, 3-15% of Co. While electrochemical processing of the wastes of the HRNA up to 80-90% of Re, Ni and Co passes into the solutions, and a small part of them remains in the anode slurry. The remaining part of the metals from the slurry is chemically dissolved into the solution. After electrochemical treatment of wastes and chemical dissolution of slurry the solutions are combined and Re is extracted from them. The Ni – Co concentrate was precipitated (until a pH of 8–9 was established, at a temperature of 40 °C, by intensive stirring for 1 h) from the raffinate (g/dm3: 14.26 Ni; 2.48 Co) after the extraction of Re by NaOH (500 g/dm3) solution. Physical and chemical studies of the concentrate using X-ray fluorescent, X-ray phase, thermo gravimetric and X-ray methods showed that it contains the following phases, wt. %: 62.6 Na2SO4; 37.4 Ni2 (NO3)2 (OH)2 • 2H2O and Co (OH)2. Washing the concentrate from sodium by water at L:S = 10: 1 ratio allowed reducing its mass (~ 2.4 times), reducing the content of sodium, increasing the content of Ni (from 15.68 to 37.55 %) and Co (from 1.89 to 4.48%). When the concentrate is annealed in the temperature range of 300-400 °C, the processes of dehydration of the hydroxides of Ni and Co and their transition to the oxide forms occur. The resulting concentrate can be sent for further processing in order to extract non-ferrous metals from it or used to produce some ferroalloys.