Development of a novel hydrometallurgical process for zinc recovery from hyperaccumulator plants

Soil pollution has become a serious concern due to human activities, with limited techniques available for remediating large volumes of metal-contaminated soil. Phytoextraction using hyperaccumulator plants offers a promising approach, as it enables the removal of metals directly from soils. However, the resulting metal-rich biomass must be treated to detoxify residues and recover valuable metals within a circular economy framework. The aim of this work was to propose a complete process for recovering zinc (Zn) from two hyperaccumulator species, Noccaea caerulescens (Ganges and Vosges populations) and Sedum plumbizincicola , cultivated from Zn-contaminated agricultural or industrial soils. The harvested biomass, containing up to 9 g Zn/(kg dry biomass ), but also other metals (namely aluminium (Al)), was subjected to combustion at 620 °C to produce Zn-rich ash. Sequential treatments—water washing, alkaline leaching with sodium hydroxide, and nitric acid acidification—were then applied. This process yielded a Zn-enriched solid product containing 8 wt% Zn, from a plant containing 0.9 wt%, with an overall recovery efficiency exceeding 84 %. Characterization of the recovered material indicated the presence of a zinc aluminosilicate phase, along with residual sodium nitrate. Although further purification would be necessary to obtain higher Zn purity, the approach demonstrates that it is possible to convert contaminated biomass into a valuable Zn-based product while strongly depleting other undesirable elements such as cadmium. Overall, this work illustrates the potential of integrating phytoextraction with hydrometallurgical recovery processes to develop sustainable agromining strategies for metal-contaminated soils. • An innovative method for both soil remediation and zinc recycling. • Hyperaccumulator plants cultivated in contaminated sites in France. • Hyperaccumulator plants achieving significant zinc accumulation. • A hydrometallurgical process with acceptable zinc content and recovery yield. • New opportunities to produce a Zn Al product such as oxide or alloy.