Chelator-Assisted Phytoextraction and Bioenergy Potential of Brassica napus L. and Zea mays L. on Metal-Contaminated Soils

This study investigates the accumulation potential of Brassica napus L. and Zea mays L. cultivated on soils contaminated with Zn, Cd, Cu and Pb, using HEDTA—Hydroxyethyl Ethylenediamine Triacetic Acid—to enhance metal mobility. The research addresses a gap in the literature regarding the dual-purpose use of energy crops for assisted phytoextraction and bioenergy recovery. Two pot experiments were conducted on soils of different textures, with HEDTA applied at 2.5 and 5 mmol·kg−1. Metal concentrations in soil and plant tissues were measured, and indices such as the geoaccumulation index (Igeo), bioconcentration factors (BCF), translocation factor (TF), metal tolerance index (MTI), crop growth rate (CGR) and higher heating value (HHV) were calculated. Results showed that HEDTA significantly increased Cd and Zn mobility, leading to higher accumulation in rapeseed shoots. Maize demonstrated phytostabilization by retaining metals in roots. Rapeseed biomass exhibited a higher HHV (up to 20.6 MJ·kg−1) and greater carbon and hydrogen content, indicating suitability for thermochemical conversion. Maize, with lower ash content, showed potential for bioethanol production. The findings support the integration of chelate-assisted phytoextraction with energy recovery from biomass.