Towards sustainable remediation: Understanding and boosting phytoremediation of soils contaminated with lithium ion battery material

Inadequate waste management and insufficient environmental standards in lithium ion battery production and recycling pose a substantial risk of environmental pollution. Phytoremediation offers a cost-effective and less-invasive strategy for removing metals from contaminated soils. We evaluated the phytoremediation potential for battery-contaminated soils and enhancement strategies using chelating agents and high-biomass-producing plants. Therefore, metal uptake in Alyssum murale and Brassica juncea was investigated in pot studies with soil amendments of shredded battery material ("black mass") and cathode material (NMC). Alyssum murale effectively accumulated cobalt (832 mg kg^-1) and lithium (1044 mg kg^-1). Although chelating agents increased metal leachability from the material, only nickel uptake was clearly enhanced by EDTA and EDDS soil amendments. Fast-growing Brassica juncea tolerated high levels of transition metals, while achieving lithium accumulation up to 6082 mg kg^-1 and bioaccumulation factors >25 for low-level contaminations. Up to 18.6 % of lithium were removed in a single treatment, corresponding to potential areal yields of 16.4 kg ha^-1. However, phytoremediation applications were limited to moderate contamination levels due to phytotoxicity of the battery materials. Overall, Alyssum murale showed strong potential for lithium and cobalt remediation, whereas nickel required mobilization. Brassica juncea proved effectiveness for the extraction of lithium.