Long-root Eichhornia crassipes waste plants dual-purpose resource utilization: green preparation of magnetic carbon quantum dots for heavy metal deep removal

Abstract Long-root Eichhornia crassipes, an aquatic plant with extensive root systems, has demonstrated potential in remediating eutrophicated water bodies. However, improper disposal of large quantities of discarded plants post-remediation can easily cause secondary pollution. In this study, rapidly recoverable magnetic carbon quantum dots (MCQDs) were greenly synthesized via hydrothermal treatment of long-root Eichhornia crassipes and subsequent coupling with Fe3O4 nanoparticles. Adsorption experiments demonstrated that MCQDs displayed a commendable adsorption capacity for various heavy metals in municipal wastewater under the synergistic effect of CODs and Fe3O4. Mechanistic analyses revealed that the adsorption involved chemical binding with oxygen-containing functional groups and amino groups on the surface of MCOQs. The saturated MCQDs were efficiently recovered within 5 min using an applied magnetic field, offering a practical solution for nanoparticle recovery. This study provides valuable insights into the green resource utilization of Long-root Eichhornia crassipes based on CQD technology. Graphical abstract