Nanocelluloses affixed nanoscale Zero-Valent Iron (nZVI) for nickel removal: Synthesis, characterization and mechanisms

Abstract

Application of nanoscale Zero-Valent Iron (nZVI) for heavy-metal enrichment and recovery have been hampered by aggregation induced by its high surface energy and intrinsic magnetic interactions. Herein, we present nanocelluloses (NC) affixed nZVI composite (NC-nZVI) with enhanced efficiency for Nickel(Ni) removal. The anchoring of nZVI at the functional sites of biomass derived NC was initiated by one-step liquid-phase reduction method, generating varied morphology and dispersion status of nZVI. Among developed composites, cellulose nanocrystals (CNC) modified nZVI (CNC-nZVI) showed most evenly distributed nZVI with uniform particle size. Characterizations with FTIR, XPS and XRD demonstrated that bindings between NC and nZVI were through hydrogen bonds, electrostatic attractions, coordination-covalent bonds and/or steric hindrance. For Ni2+ removal, 0.2 g/L CNC-nZVI achieved 98.5% removal rate at 100 mg/L initial Ni2+ concentration and pH = 5.0, significantly higher than bare nZVI (P < 0.05). The removal efficiency remained over 80% under wide pH range (3–5) and varied interference ions (NO3-, Cl- and Ca2+), indicating potential practical applicability. The observed "hollow-out" structure from scanning transmission electron microscopy after reactions with Ni2+ and Tafel extrapolation curves inferred that CNC activated diffusion path and accelerated electronic transfer from nZVI. The superior removal performance of NC-nZVI and abundance of raw materials offer promising prospects for environmental remediation and wastewater treatment.