Worldwide Tailings Dumps: A potential untapped source of critical metals

By Ellsworth Dickson

While tailings dumps are an integral part of the mining and ore processing procedure, little thought has been given to the possibility that they may contain valuable concentrations of a mine’s non-targeted metals such as lithium, cobalt, various rare earth elements, tungsten, phosphate and other critical metals.

With society’s increasing demand for critical metals for electric vehicles, telecommunications, renewable energy, aerospace, medical, defense and other applications, a source of these metals from tailings dumps would lessen the need to develop more mines. This is particularly of interest when considering the continuous depletion of primary sources and supply risk due to geopolitical issues. For example, the production of rare earths, cobalt and lithium are concentrated mainly in China, the Democratic Republic of Congo and Australia. It is worth noting that for most critical minerals, there are no substitutes.

While there is no official list as to how many tailings dumps exist, it has been estimated there are about 3,500 dumps around the world.

A study reported in the Journal of Environmental Chemical Engineering observed the startling fact that the potentially recoverable amount of critical metals in abandoned mine tailings is often higher than the concentration in some primary ores. In addition, some heavy metals such as copper and zinc can also be recovered. Clearly, this is a topic worth following up.

It is the advancement of modern recovery techniques in froth flotation, solvent extraction, bioleaching, hydrometallurgical and bio-hydrometallurgical processes that make this concept possible, especially when considering that tailings have already been mined, crushed and concentrated – a huge de-risking economic benefit. With various metals removed, the reprocessed tailings are less harmful to the environment and can be used as backfills for open pit and underground mines, building materials and fertilizer.

There have already been a number of studies that have shown promising results in the recovery of various metals from tailings (Peelman, Tunsu, Sutterlin, Makinen, Chen). The Journal of Cleaner Production details an investigation by the ENVIREE European Project (2015-2018) that assessed the use of solvent extraction to recover rare earth elements from tailings from New Kankberg, Sweden, and Covas, Portugal.

As with any mineral project, there would be associated risks; however, there is obviously a great deal lower capital costs involved to reprocess tailings compared to mining, crushing and concentrating rock. It is an easy job to sample tailings dumps to obtain metal grades. Metallurgical studies would be needed to determine the best way to recover valuable metals from tailings.

The recovery of critical and other metals from tailings dumps is a new industry still in its infancy; however, the economic and environmental considerations are compelling. This is a topic worth considering for mine owners and those considering acquiring tailing dumps.