Platinum group metals recovery

Aqua Cat Process, Johnson Matthey UK Platinum group metal recovery, destroy organic contaminants, 3000 kg h- Commissioned 2002... 

Solvent extraction is proposed as a suitable method for PGMs (platinum group metals) recovery from low concentrated sources. Several extractants have been studied and proposed, e.g., hydroxyoximes, alkyl derivatives of 8-hydroxyquinoline, dialkyl sulphides, hydrophobic amines and quaternary ammonium salts, derivatives of pyridine and pyridinecarboxamides. However, the problems of a slow extraction rate or low metal separation remain to be solved. Looking for extractants permitting possibly fastest extraction of Pd, two phosphonium ionic liquids, i.e., [QP][C1] and [QP][Bis], have been used (Cieszynska et al., 2007 Cieszynska, 2010 Cieszynska Wisniewski, 2010, 2011). To overcome problems caused by the high viscosity of ILs, the mixtures with toluene have been used for extraction, similarly as for extraction of Zrf+. 

The application of these methods is described in some detail for recovery of base metals and platinum group metals in Sections 9.17.5-9.17.6 focusing mainly on solution-based hydrometal-lurgical operations, largely those involving solvent extraction, because the nature of the metal complexes formed is usually best understood in such systems. NB. Extraction of lanthanides and actinides is not included as this subject is treated separately in Chapters 3.2 and 3.3. 

Preparation of base metals by coupled reduction with platinum group metals. Very pure metals of the alkaline- earth, lanthanide and actinide series can be prepared from their oxides (or fluorides) through coupled reduction by pure hydrogen in presence of platinum group metals. According to a precursory paper on this subject (Berndt et al. 1974), the preparation scheme of Li, Ca, Sr, Ba, Am and Cf was described. As an example, Ca can be obtained by synthesis of a Pt compound, followed by its vacuum decomposition and recovery by distillation of the more volatile base metal ... 

The use of solvating extractants in the recovery of gold and platinum-group metals (PGM) was described in the previous section. These extractants have also found some specialized applications in the extractive metallurgy of base metals. For example, they have been used in the recovery of uranium, the separation of zirconium and hafnium, the separation of niobium and tantalum, the removal of iron from solutions of cobalt and nickel chlorides, and in the separation of the rare-earth metals from one another. 

Commercial apphcation of the ELM technology to the recovery of precious metals, such as the platinum group metals, has long been proposed in the literature [90]. Practical apphcations have, however, so tar been limited by the instabihty of the structurc(s) of the ELMs used. Several ways how to improve the stabihty have been suggested, for example, the use of bifunctional surfactants when one molecule acts as the emulsifier and extractant at the same time [91], and/or the apphcation of additives that alter the elasticity of the respective LM [92]. 

The ELM pertraction technology has good potential for more applications at industrial scale in the near future. The industries in question might include metal mining and refinery operations (precious metals and platinum group metals are good examples), tannery industry (recovery of hexavalent chromium), and processing of nuclear wastes (recovery of uranium, strontium, and other metals). 

Benson M, Bennett CR, Harry JE, Patel MK and Cross M (2000) The recovery mechanism of platinum group metals from catalytic converters in spent automotive exhaust systems. Resources, conservation and recycling 31 1-7. 

The difficulty from a practical perspective is that most of these catalysts will never perform sufficiently well at a commercial scale to be useful. Many catalysts developed in academia are also homogeneous catalysts and recovery is often not possible, but when it is possible, the recovery process can be problematic. From a sustainability perspective the use of the platinum group metals creates a number of challenges [65,66]. Most of these metals come from only two regions of the world Russia and South Africa. Russia has recently had pohtical and economic conflicts with Europe and the United States, while South Africa has a continued history of labor unrest related to the conditions under... 

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