Remediation of phenanthrene-contaminated soil by iron oxide/carboxylate-rich porous carbon composites from vinegar residue

Abstract

Conversion of solid wastes into useful remediation materials is an encouraging strategy in resource recovery. Iron oxide/carboxylate-rich porous carbon composites (IOCRPC) can be synthesized by using vinegar residue (VR) and ferrous sulfate heptahydrate (FeSO4∙7 H2O) recovered from a waste acid of a titanium dioxide factory. Characterization of FeSO4-impregnated VR exhibited a high proportion of ferricarboxylate complexes [i.e. FeII(R-COO)n2-n]. Pyrolysis temperature was the most important reaction parameter to define IOCRPC phase composition. Thermal decomposition of FeII(R-COO)n2-n produced Fe3O4 nanoparticles partly at a relatively lower pyrolysis temperature (350 ºC), while successful carbonization of VR formed the porous structures of carbon. Both Fe3O4 and ferricarboxylate complexes were the components of IOCRPC responsible for its excellent visible light absorption ability. Under visible light, phenanthrene in contaminated soil was efficiently degraded (90.1%) by IOCRPC at circumneutral pH. Phytotoxicity bioassays demonstrated significant removal of toxicity after treatment with IOCRPC, highlighting its application potential in revegetation strategies.