Adsorption of Cu(II) ions onto crosslinked chitosan/Waste Active Sludge Char (WASC) beads: Kinetic, equilibrium, and thermodynamic study.

In this study, crosslinked chitosan/Waste Active Sludge Char (WASC) beads were developed as a novel composite adsorbent for the removal of Cu(II) ions from aqueous solution. The surface morphology and elemental composition of chitosan/WASC beads were characterized using Scanning Electron Microscopy (SEM). Adsorption isotherms of Cu(II) ions on adsorbents were correlated with the Langmuir and Freundlich models, and the data fitted better to the Freundlich isotherm model. The kinetic data were evaluated to calculate the theoretical metal uptake as a function of time. The highest correlation coefficient (R2) was calculated with the pseudo-second order kinetic model for the adsorption. The successive adsorption studies (0.25 g/L adsorbent dosage, contact time 180 min, pH 5) indicated that the WASC beads were able to remove 81.7% of Cu(II) from the aqueous solution contained 300 mg/L Cu(II) ions, and the adsorption capacity was obtained as 980.80 mg Cu(II)/g beads. This value is a great significant as it is much higher than any reported paper. The thermodynamic parameters like ∆G°(298K), ∆H°, and ∆S° changes for the adsorption of Cu(II) ions have been calculated as - 7.122 kJ·mol-1, 19.25 kJ·mol-1, and 88.49 J·mol-1·K-1, respectively.