Microwave-based extractive metallurgy to obtain pure metals: A review

Abstract

Although metals are fundamental to the economy and human well-being, natural ore depletion is inevitable with the continuation of mining. Awareness of the importance of new developments in technologies to process natural ores and to recycle waste materials to obtain pure metals with high efficiency has been growing over time. The microwave-based furnace, which heats samples rapidly, uniformly and selectively, has recently been given more attention as an alternative to the conventional heating systems. However, the current progress of microwave technology for obtaining pure metals has not been fully monitored. This study reviews the extractive metallurgical approaches for obtaining pure metals by subjecting virgin materials and waste materials to the microwave heating method. In this paper, the principles of the microwave-based furnace to heat the samples are first summarized. Then, the studies of microwave-based pyrometallurgical and hydrometallurgical approaches to produce the virgin metals and to recycle metals are abridged. Finally, the limitations of current progress and the future prospects of microwave-based metallurgical technology are identified. A number of clear advantages of microwave irradiation emerged through the review process. The two most noteworthy advantages are that some materials difficult to reduce using conventional technology can be treated effectively using microwave irradiation, and microwave technology has the potential for a number of materials to facilitate a more rapid chemical reaction with fewer impurities considering the more than 50% of reduction in the apparent activation energy under microwave irradiation.

Keywords

• Microwave
• Virgin metals
• Recycled metals
• Distributed recycling system
• Extractive metallurgy
• Permittivity and magnetic permeability