oa South African Journal of Chemical Engineering - Thermodynamic characterization of adsorption of lead(II) ions on activated carbon developed from tamarind wood from aqueous solution
Batch kinetic studies were conducted for the adsorption of Pb(II) on activated carbon developed from tamarind wood (ATW). The adsorption studies were conducted for the adsorbent dose of 2 g/l and initial Pb(II) concentration of 10 mg/l and in the temperature range of 10 to 50 °C. With the increase in temperature from 10 to 50 °C, the lead uptake was observed to increase from 78.3 to 95.4 %. The equilibrium time was found to be 60 min. The adsorption was very fast from the beginning up to 30 min and then for next 30 min, uptake increased gradually from 78.3 to 99.15- %. This paper attempts to develop simple and easily understandable thermodynamic parameters related to the adsorption process at equilibrium. The Gibbs free energy (∆G°) at 10, 20, 30, 40 and 50 °C for the adsorption process of Pb(II) were obtained as -2.98, -3.86, -6.93, -9.05 and -12.34 kJ/mole respectively. The negative value of ∆G° confirms the feasibility of the adsorption process and spontaneous nature of adsorption. The values of ∆H° and ∆S° for Pb(II) were obtained as 36.85 kJ/mol and 140.92 J/mol respectively. The positive value of ∆H° indicates endothermic nature of adsorption, while positive ∆S° value confirms the increased randomness at the solid-liquid interface during adsorption. The activation energy for the sorption of Pb(II) was found as 32.47 kJ/mol, indicating chemisorptions.
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