Lemna minor as a phytoremediator of cobalt nanoparticles: Insights into toxicity and remediation

The extensive use of cobalt nanoparticles (CoNPs) in industrial and biomedical applications has raised environmental concerns, necessitating effective mitigation strategies. This study examines the phytotoxicity and phytoremediation potential of CoNPs using Lemna minor L., a recognized Co-hyperaccumulator. CoNPs exhibited significant sublethal toxicity at concentrations ≥1000 ​μg Co 2+ /L, leading to oxidative stress and impaired growth, photosynthesis, and respiration. Despite these challenges, L. minor effectively removed over 99 ​% of CoNPs from the medium, even at high concentrations (up to 20.000 ​μg Co 2+ /L), with gravimetric cobalt concentrations reaching 1771 ​μg Co 2+ /g dry weight in plant tissues. Physiological responses to CoNPs were similar to those induced by equivalent concentrations of CoCl 2 , suggesting that CoNPs dissolve into Co 2+ ions upon interaction with plants. However, ultrastructural analysis revealed distinct intracellular cobalt localization with CoNPs causing more severe chloroplast damage than ionic Co 2+ . These findings suggest two toxicity mechanisms: ionic effects from dissolved Co 2+ and direct physical damage from intact nanoparticles. The resilience and hyperaccumulation capacity of L. minor makes it a promising candidate for the phytoremediation of cobalt-contaminated waters. The study underscores the importance of further research to elucidate CoNP environmental behavior and optimize phytoremediation approaches. • Toxic effects of CoNP concentrations ≥1000 ​μg Co 2+ /L were observed in L. minor. • CoNP accumulation in chloroplasts impacts photosynthesis and plant growth. • Toxic concentrations of CoNP induce oxidative stress in plants. • L. minor removes over 99 ​% of CoNP, even at toxic levels. • L. minor shows promise for CoNP phytoremediation.