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Hydrometallurgy
Published in C. K. Gupta, Extractive Metallurgy of Molybdenum, 2017
The sixth section has dealt with ion exchange, solvent extraction, and carbon adsorption processes. General principles, various types of reagents and equipment, and elements of operational aspects have been briefly touched upon for an introductory appraisal of the ion exchange process. While this process has been used to extract molybdenum from molybdate-bearing solutions, its major contribution has been in the metallurgy of rhenium. In the roasting operation of molybdenite, the sources of rhenium vary depending upon the treatment method followed for the roaster off-gas. Rhenium values are collected as dust when electrostatic separators are used and in acid solutions when wet-dust-collecting system are utilized. The rhenium-bearing solutions from these sources are processed by using quarternary ammonium chloride anion exchange resins which selectively extract rhenium. Apart from this, the ion exchange process has also been used to prepare ammonium perrhenate from potassium perrhenate, by using either anionic or cationic exchange resins. Ammonium perrhenate, it may be mentioned here, is the most popular rhenium intermediate that is used in the most common method (involving reduction with hydrogen) for the production of rhenium powder. The subject of solvent extraction has been covered in lines similar to the coverage of ion exchange. As a typical example of the application of solvent extraction, reference has been made to the processing of nitric acid leached solutions to separated molybdenum and rhenium compounds (Cymoly process). Carbon adsorption, either by itself or in combination with ion exchange/solvent extraction, has been used to process molybdenum-bearing solutions generated in widely varying situations. Some representative examples have been included in the text. Processing of spent acid, employing the carbon adsorption route, has been very successful in cutting down ammonia consumption for the recovery of molybdenum in comparison with processes that do not make use of carbon adsorption. Besides this, mention has been made of the applications of carbon adsorption in the lime roasting and hypochlorite leaching processes investigated for low-grade molybdenite concentrates. Carbon adsorption, combined with solvent extraction, has been used for processing hypochlorite-leached solutions to recover molybdenum and rhenium values. In conjunction with ion exchange, carbon adsorption has been used to process solutions obtained after the recovery of molybdenum as calcium molybdate in the process involving alkali leaching of low-grade molybdenite calcine. This solution, in fact, is an additional source of rhenium besides the other two mentioned. In this process, molybdenum and rhenium are extracted from the solution by a selective absorption of the molybdenum ions on an anion exchange resin, followed by the sorption of rhenium on activated carbon.
Investigation on ammonium perrhenate behaviour in nitrogen, argon and hydrogen atmosphere as a part of rhenium extraction process
Published in Mineral Processing and Extractive Metallurgy, 2018
Shaya Sharif Javaherian, Hossein Aghajani, Hamed Tavakoli
It is well known that ammonium perrhenate (APR) is the most important initial substance in the production of pure rhenium powder. There are several methods to produce rhenium from APR but generally, hydrogen reduction of APR through gas–solid reactions is a common method in preparation of rhenium powder commercially. Some properties of the rhenium powder produced by these methods such as morphology, size distribution, tap density and fluidity has been studied before (Bai et al.; Shen et al.; Schrebler and Cury 2001; Schrebler et al. 2001; Mnnheim and Garin 2003; Stefan and Helmut 2007; Naor et al. 2009).