Processing of Plants to Products: Gold, REEs and Other Elements

Nickel recovery by agromining has been widely studied because of the abundance of species that hyperaccumulate this element. But at the same time, in the context of the circular economy, there is growing interest in recovery of other elements for both economic and environmental reasons. Firstly, the recovery of gold from mine tailings appears increasingly promising, as does that of rare earth elements, which are strategic for numerous advanced technologies. In both cases, the economic value is a driver but also a need to remediate mine tailing by nature-based solutions. Secondly, despite being less valuable, the recovery of Cd and Zn has been much studied, because these two elements are contaminants of many industrial or agricultural soils and many plants are capable of accumulating them. It is therefore essential to find solutions for disposal of the biomass contaminated with metals and preferably by profiting from it. For this set of elements, processes based on thermal or chemical methods have been proposed on a small scale and some are on the verge of being scaled up. Other elements, such as metals of the platinoid family, Mn or molecules of pharmaceutical interest, have been the subject of pioneering work that remains to be developed. At the present time, it can be considered that in this area there is still a world to explore.