Effectiveness of Phytoextraction of Cu, Zn, Ni, Sr and P from mining soils using three successive engineering cycles in bioreactors

Phytoextraction is a sustainable strategy for removing potentially valuable elements from contaminated substrates while contributing to site remediation. However, the effectiveness of repeated phytoextractive cycles remains poorly investigated. This study evaluated the phytoextraction performance of Helianthus annuus (HA) cultivated on mining soil from Complejo Minero Fabril Sierra Pintada (Argentina) containing elevated concentrations of Ni, Zn, Sr, P, and Cu over three successive three-month cultivation cycles in TRL-4 bioreactors (BRs). The scalability of the process was subsequently assessed through pro- jection to TRL 6 using a Vegetable Depuration Module (VDM). Elemental concentrations in soil and biomass were determined by X-ray fluorescence, while bioaccumulation coef- ficients, translocation factors, arbuscular mycorrhizal colonization and glomalin-related soil proteins (GRSP) were assessed to identify biological factors associated with phytoex- traction performance. Projected bioextractive potential at TRL 6 (VDM) during the first cycle reached 16.15 ± 2.40 g Cu, 20.81 ± 2.19 g Zn, 7.43 ± 1.15 g Ni, 11.39 ± 1.19 g Sr, and 126.87 ± 15.42 g P. Phytoextractive efficiency declined substantially after the first cultivation cycle, indicating that a single crop harvested at the flowering stage maximized element removal under the tested conditions. The accumulation of economically relevant elements in sunflower biomass could be integrated with downstream metal recovery processes, highlighting the potential of HA for phytomining applications.