Biosorption of lead by spent coffee ground: Kinetic and isotherm studies

The use of spent coffee ground (SCG) for the removal of Pb (II) from aqueous solution has been investigated as a potential low-cost treatment method for heavy metal adsorption. Batch experiments were performed to obtain kinetics and adsorption isotherm. The heavy metal adsorption capacities of SCG were studied as a function of adsorbate concentration (5, 120 and 207 mg/L) and stirring speed (200, 300 and 400 min-1). Equilibrium isotherms for the adsorption of Pb (II) were analyzed by the Langmuir and Freundlich isotherm models. The Langmuir isotherm model was found to represent better the experimental data (%25e= 4.00). The maximum removal of Pb (II) is found to be 40 mg/g at pH 4.5 and initial Pb (II) concentration of 207 mg/L. The effect of stirring speed was found to a significant factor for the external mass transfer resistance at 200 min-1 and the external mass transfer coefficients were estimated by the Mathews and Weber model. The Pseudo First Order model and Crank model were used to fit the kinetic data, the results suggest that intraparticle diffusion could be the rate controlling step with an intraparticular diffusion coefficient 1.46 × 10-11 m2/s. The results indicate that the SCG could be considered as a low cost potential adsorbent for Pb (II) removal from aqueous solutions. © 2011 AIChE. All rights reserved.

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