الفهرس 
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Abstract
Precious metals have long been used to jewelry and ornaments industry. Platinum-group metals (PGMs) are important precious metals in
many industrial fields. However, their natural resource deposits are
strictly limited. Accordingly, their recycling process from wastes and/or
secondary resources must be considered. Platinum group metals are
generally referred to the six precious metal elements (platinum,
palladium, rhodium, iridium, ruthenium, and osmium) [I]. These metals
have found new applications outside the jewelers and decorative
industries due to their excellent physical and chemical properties.
Besides, they are used extensively for electronic devices, catalysis in the
chemical and petroleum refining industries, glass industries and
pharmaceutical industries. The development and commercial application
of the catalytic control for automotive exhaust has increased worldwide
for decades, as a concern of environmental protection from major air
pollution [2-41. The catalyst manufacturing industry is the second largest
consumer of these precious metals after the jewelry industry [5]. In the
recycling of precious metals from such scraps, hydrometallurgical
techniques play a major role [6,7].
Platinum and rhodium are emitted from automobile catalytic
converters, which are used to reduce the emission of hydrocarbons,
carbon monoxide and nitrogen oxides. A clear link has been established
between the increasing use of automobile catalysts and increasing
environmental platinum group elements concentrations. The dust
originated from abrasion and deterioration of the bulk catalysts. Thus,
PGMs have been deposited along roadways, on vegetation and soil
surfaces adjacent to roadways, in streams, rivers and waterways either
directly or as runoff. Concerns have arisen that PGMs may haveز