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 (0.2 M 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 R ² = 0.96–0.98. Similarly, it was observed that pseudo-second-order reaction model with lower χ ² (0.002703–0.009351) and sum of square errors (0.0001–0.0144) value together with higher R ² (0.98–0.99) ruled in all the possibilities of sorption of Zn(II) ion on activated carbon surface as chemisorption. Bangham’s model (R ² = 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 (D _f = 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.

Keywords:

• Biosorption
• Zn(II) ion
• Pseudo-second-order model
• Film diffusion
• Diffusivity coefficient

Notes

a1.42 mmol g⁻¹ of Zn(II) ion = 92.83 mg g⁻¹