Adsorption of Cu(II) and Pb(II) onto a grafted silica: isotherms and kinetic models.


The isotherms and kinetics of adsorption of lead(II) and copper(II) onto a grafted silica are studied at 20 degrees C. A commercial silica is grafted with an ethylediamine derivative, N-[3-(trimethoxysilyl)propyl]-ethylenediamine. From the Langmuir isotherms, maximum adsorption capacities of the grafted silica towards Pb(II) and Cu(II) are determined (0.184 mmol Pb(II)g-1 and 0.261 mmol Cu(II)g-1) and compared to those of non-modified silica (respectively, 0.019 and 0.036 mmol g-1). Four kinetic models, i.e., pseudo-first order, pseudo-second order, Langmuir and double-exponential are applied to fit the experimental kinetic data. The kinetic parameters are determined which allow to calculate the theoretical metal uptake as a function of time. The results are discussed and indicate the best fit is obtained with the double-exponential model. A discussion on the adsorption mechanism with respect to the double-exponential model leads to two possible interpretations: the metal uptake may follow a diffusion-controlled mechanism or a two-site adsorption process.


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@article{Chiron2003AdsorptionOC, title={Adsorption of Cu(II) and Pb(II) onto a grafted silica: isotherms and kinetic models.}, author={Nathalie Chiron and Richard Guilet and Eric Deydier}, journal={Water research}, year={2003}, volume={37 13}, pages={3079-86} }