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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 |