Sorption of Zn(II) ion onto the surface of activated carbon derived from eucalyptus bark saw dust from industrial wastewater: isotherm, kinetics, mechanistic modeling, and thermodynamics

Abstract

The activated carbon was derived from base (0.2M NaOH)-mediated activation of biomass followed by thermal treatment at 1,123 K. The utmost metal ion uptake capacity and sorption percentage of activated carbon derived from eucalyptus biomass were 1.42 mmol g-1 and 93.42%, respectively. Freundlich isotherm model proved to be superior with higher linear correlation coefficient R2 = 0.96–0.98. Similarly, it was observed that pseudo-second-order reaction model with lower χ2 (0.002703–0.009351) and sum of square errors (0.0001–0.0144) value together with higher R2 (0.98–0.99) ruled in all the possibilities of sorption of Zn(II) ion on activated carbon surface as chemisorption. Bangham’s model (R2 = 0.93–0.95) applicability in the present investigation demarcated the fact that the main rate-controlling step in the sorption of Zn(II) ions on activated carbon surface was film diffusion rather than intraparticle diffusion. The results of diffusivity coefficients (Df = 7.16 × 10-6 cm2 s-1) reproduced the analogous viewpoint that film diffusion is quite a dominant step in the biosorption of Zn(II). ΔG, ΔH, and ΔS values obtained through the thermodynamic study of Zn(II) biosorption system were—9798 kJ mol-1, -34.74 kJ mol-1, and -107.63 kJ mol-1 K-1, respectively.