Abstract
A preliminary study on the hydrometallurgical recovery of rhenium from an engine-reverted superalloy, CMSX-4, was performed. The novelty of this work dealt with (i) the applicability of electro-generated Cl2 in rhenium leaching and (ii) the maneuvering of the organic extractants based on the metal speciation in leach liquor. In a two-step HCl leaching, more than 98% rhenium was selectively leached in the presence of dissolved chlorine (Cl2aq. and Cl3aq.–) in the second step, which was performed after a leaching of thermal-barrier and base-alloy elements in 4 mol L–1 HCl. The leaching kinetics of rhenium indicated a shift from surface diffusion to a chemically controlled reaction with a variance in temperature from 313 to 353 K. The first use of phosphinic acid in molybdenum separation from rhenium in the leach liquor yielded a high separation value (βMo/Re = 839) using 0.067 mol L–1 extractant; whereas the mixed-phosphine oxides showed a tremendous selectivity for separating rhenium from the base-metal im...
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