Recovery and extraction of platinum from spent catalysts: A review

Abstract

According to the technological importance of platinum in the modern industries, demand for platinum has been increasing. On the other hand, the supply of platinum from mineral resources had environmental and economic challenges. Therefore, recovery of platinum from secondary sources such as spent catalysts is inevitable and important as a valuable solution for waste management and supply of required platinum. The general methods of extracting and separating platinum from spent catalysts include pyrometallurgy and hydrometallurgy. Choosing and optimizing the method of platinum recovery includes advantages such as: lower energy consumption, production of more platinum and less gas pollutants, less production of industrial waste, more safety and less investment. In this article, the hydrometallurgical method was chosen by examining various references, which includes pretreatment and leaching steps. Also, the effect of parameters such as: amount of crushing and temperature in the pre-treatment stage, type of solvents, temperature, solid-to-liquid ratio and time in the leaching stage has been investigated on the efficiency of platinum recycling. Consequently, crushing to 100 μm and calcination at about 500 °C or oven drying at about 100 °C are suggested for pretreatment. In the leaching step, the replacement of metal salts with acid, microwave heating speed and the use of bio/nano solutions help the environment. Washing efficiency increases with increasing temperature up to 100 °C, ratio of acidic agent to solid catalyst and washing time. Attention to economic and environmental issues is suggested for future works.