Dynamic studies and pseudo-second order modeling of copper(II) biosorption onto pine cone powder

The chemical interaction between biosorbent functional groups and metal ion species in solution can slightly be altered by chemical treatment of biosorbent surface. The biosorbent kinetics and mechanism for copper(II) biosorption onto pine cone powder and 0.15 mol dm− 3 NaOH treated pine cone powder were determined during batch kinetics with the variation in biosorption temperature and initial copper(II) concentration. Results from this study revealed that surface diffusion of copper(II) is not rate-controlling as observed by the failure of both the pseudo-first and modified pseudo-first order model to discribe the kinetic data. The pseudo-second order model gave a better description of the kinetic data and was able to correlate the model constants with process variables for both samples. Activation energies and thermodynamic parameters of activation obtained from the pseudo-second order model all indicate that the mechanism for copper(II) biosorption on both samples differ. The diffusion partten is complex for the biosorption process, involving pore and film diffusion in the rate determining step and did not follow the same pattern for both samples. Pseudo-isotherms were generated to confirm the fit of the experimental data to the predictions of the pseudo-second order model. It was observed that the generated isotherm data fitted better to the Pseudo-Langmuir-1 isotherm indicating that biosorption was indeed a monolayer coverage of the biosorbent surface confirming the applicability of this model. Effect of initial solution pH and desorption studies confirm the predominance of a slightly different mechanism using both samples.