SYNTHESIS OF IRON NANOPARTICLES MEDIATED BY CELLULOSE NANOCRYSTALS

Abstract

Colloidally-stable zero valent iron nanoparticles (nZVI) were synthesized through a classical redox reaction of iron sulfate with minor modifications using cellulose nanocrystals (CNCs) as stabilizers. We obtained spherical nZVI particles with high surface roughness and a mean size of 130nm. Particles remain colloidally stable after more than two months. Cellulose nanocrystals play a dual role in nZVI stability: a foreign surface to encourage stable nucleation over fast aggregation and a stabilizer to prevent iron nanoparticles aggregating into fractal colloids. Our results highlight the impact of the presence of CNCs on the rates and mechanisms of nucleation, growth, aggregation, and aging of nZVI particles, indicating promise in controlling size and morphology of similarly redox-generated nanoparticles. Cellulose nanocrystal-stabilized nZVI nanoparticles demonstrate properties well-suited for enhanced soil and groundwater remediation. //Nanocomposites composed of carboxylated cellulose nanocrystals and iron (Fe-oxCNC) were prepared through a classical redox reaction of iron sulfate using TEMPO-oxidized cellulose nanocrystals (oxCNCs) as a template and stabilizer. Morphological control over Fe-oxCNC nanoparticles was realized by varying the amount of oxCNC added to the redox process. As the molar ratio between oxCNC and Fe was increased from 1 to 8, the morphology of Fe-oxCNC nanoparticles evolved from rounded iron aggregates supported by cellulose nanocrystals to thin film iron-coatings on cellulose nanocrystals. Transmission electron microscopy (TEM), Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), and chemical analyses (EDX, EELS) revealed that oxCNCs were coated by iron. Small changes to the density and type of functional groups on the CNC surface have large impacts on the morphology and the oxidation state of adsorbed iron nanoparticles.