Tungsten and cobalt can be recovered from cemented tungsten carbide-Co (WC-Co) scraps using a novel process based on roasting of the scraps with NaCO and water leaching of the calcine containing NaWO. The process was evaluated at different conditions testing several parameters, including NaCO/WC molar ratio 1:1-2:1, roasting temperature in the range 400-900°C, roasting time at 1-3 , leaching temperature at ambient - 90°C and leaching time 1-3 . Thermodynamic modeling of the roasting and leaching stages using HSC and Stabcal software allowed an understanding of the speciation of the products at different conditions. Subsequent experiments to determine an optimized conditions of both roasting and water leaching were conducted aiming to yield recoveries of both W and Co in solution over 95%. Roasting of the scraps with NaCO at 800°C in 3 using NaCO/WC molar ratio of 1:1 will produce a NaWO which can be easily water leached. Over 95% W was recovered after water leaching the calcines at 60°C in 3 . Over 94% Co was recovered as soluble CoSO using 1 M HSO with 1.5 M HSO added as a reductant. The double step of CoCO precipitation using 1.5 M NaCO and conversion to Co(OH) using 8 M NaOH allows a high purity product (>99.5% purity) to be produced with most of the major impurities as Cr and Fe remaining in the residual NaCO and NaOH liquors. The levels of these major impurities are 0.05% Cr and 0.3% Fe in the final Co hydroxide product.s: This is a new process to treat W-Co wastes and recover W and Co. To the best of our knowledge, no study was done before in this area.
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http://dx.doi.org/10.1080/10962247.2021.1876780 | DOI Listing |
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