Chemical exploitation of metal contaminated biomass produced in phytoextraction

This article describes some aspects of the chemical recovery of the metal contaminated biomass produced in phytoextraction technologies. Taking advantage of the adaptive capacity of certain plants to hyperaccumulate metallic cations in their aerial parts, phytoextraction could be a sustainable way to remediate trace metals pollution. A possible exploitation of the metal contaminated biomass produced in phytoextraction is the direct use of metallic cations derived from plants as Lewis acid catalysts for organic chemistry. These original polymetallic systems serve as heterogeneous catalysts in chemical transformations enabling the synthesis of molecules with high added value. Results for Friedel-Crafts acylations and alkylations are presented in this paper: the acetylation of anisole and benzylation reactions are considered in more detail. The use of mine tailings as catalytic supports is also investigated: it could represent a new integrated outlet for tailings and phytoextraction products. Each step of the process is designed to minimise environmental impacts in accord with the principles of Green Chemistry. The process seeks to be an incentive for the economic development of phytoextraction. As phytoremediation gains momentum, it could also prove a concrete solution to the criticality of non-renewable mineral materials with new sources of zinc, nickel and other metals.