Thiourea for mining | Leaching palladium with thiourea

Palladium is a platinum series element in Group VIII of the fifth period, with the element symbol Pd. Elemental palladium is a silver-white metal, soft, with good ductility and plasticity, and can be forged, rolled and drawn. Now, let’s explore how to use thiourea to leach palladium.

1. Dissolution Behavior of Precious Metals with Trihalide Ionic Liquids:

Researchers have investigated the dissolution behavior of precious metals, including palladium, using trihalide ionic liquids. These ionic liquids, such as [P 66614 ] [Cl 3], [P 66614 ] [Br 3], [P 66614 ] [IBr 2], and [P 66614 ] [I 3], were studied for their ability to selectively leach palladium from spent automotive catalysts. The highest dissolution rates were observed for the trichloride ionic liquid [P 66614 ] [Cl 3]. The stability of the trichloride anion at elevated temperatures was also investigated, emphasizing the need to store these reactive compounds in sealed and cool environments. The optimal leaching conditions were then applied to recover palladium from ceramic monolith powder obtained from end-of-life automotive catalysts.

2. Thiourea Leaching of Palladium:

Palladium can be dissolved in thiourea solutions in the presence of an oxidant, such as ferric ion. The dissolution process is believed to be chemical-reaction controlled, with an apparent activation energy of approximately 25.3 kJ/mol. Factors such as temperature, stirring speed, and the concentrations of thiourea, acid, and ferric ion influence the leaching behavior of palladium in thiourea solutions.

3. Selective Leaching of Palladium:

When using thiourea for leaching, it’s essential to consider the selectivity. In some cases, unwanted metals may also be codissolved. For example, substantial amounts of platinum and traces of rhodium were leached alongside palladium in certain experiments.

4. Mechanism of Thiourea Leaching:

Thiourea belongs to a class of compounds with the general structure (R’R₂S)(R₃R₄N)C=S. It is a planar organic sulphide. The mechanism of thiourea leaching of precious metals involves various process parameters, including temperature and thiourea concentration. Understanding these factors is crucial for efficient leaching processes.

In summary, both trihalide ionic liquids and thiourea can be effective for leaching palladium, but careful control of conditions and selectivity is essential. If you have any specific questions or need further details, feel free to ask!

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