Adsorption of Gold onto γ–aminopropyltriethoxysilane Grafted Coconut Pith

This study was carried out to investigate adsorption kinetic and adsorption thermodynamics of Au(III) ions onto γ–aminopropyltriethoxysilane grafted coconut pith. The results from equilibrium adsorption were fitted in various adsorption isotherm models such as Langmuir, Freundlich, Temkin and Dubinin-Radushkevich and the best fit for the experimental data was Langmuir isotherm. The maximum adsorption capacity for virgin coconut pith (VCP) and the grafted coconut pith (GCP) were 256.41 and 285.59 mg/g, respectively. The kinetic data was verified using pseudo-first-order, pseudo-second-order, elovich equation and intraparticle diffusion model. The correlation results suggested that the pseudo-second-order model fits the experimental data well. A thermodynamic study revealed the endothermic nature of reaction due to positive enthalpy (∆Ho) values and negative values of Gibbs free energy (∆Go) describes the spontaneity of adsorption process. The regenerability of VCP and GCP adsorbents were investigated with NaOH (1.0 M).

Muhammad Usman, Javaid Akhtar and Javed Iqbal