Xanthate-Modified Cellulose Nanofibrils for Efficient Heavy Metal Capture from Wastewater

Conventional adsorbents frequently exhibit limited selectivity and inadequate regenerability, particularly when addressing complex wastewater matrices containing coexisting metal ions. To tackle this issue, we present the development of xanthate-modified cellulose nanofibrils (XCNF), which incorporate surface-anchored xanthate groups that function as strong chelating sites. Comprehensive characterization through SEM, elemental analysis, ATR-FTIR, XRD, and XPS validates the successful covalent grafting, significantly enhancing both surface charge density and active site availability. XCNF with a degree of substitution (DS) of 0.16 achieves an impressive Cu(II) adsorption capacity of 738.47 ± 19.35 mg/g. The adsorption kinetics conform to a pseudo-second-order model, and the Freundlich isotherm suggests multilayer and heterogeneous adsorption. In selective adsorption experiments with multiple coexisting heavy metal ions, XCNF achieved removal efficiencies of 50-65% for each individual ion. By contrast, in the treatment of real high-concentration industrial wastewater under optimized conditions, the Cu(II) removal efficiency reached 99.53%. The material retains over 71% of its initial capacity after ten adsorption cycles and effectively reduces the Cu(II) concentration in high-concentration industrial wastewater. This study offers a selective, reusable, and efficient approach that addresses a critical gap in cellulose-based adsorbents for the remediation of complex wastewater.