KINETIC STUDY OF LEAD (II) ADSORPTION IN SAWDUST OF CEDRA (CEDRELA ODORATA)

Abstract

Introduction:
Cedar sawdust is a good adsorbent for heavy metals and organic molecules. Lead is a metal widely used in mechanical industry, but it is highly polluting.
Objective:
To evaluate biosorption capacity, through a kinetic study of cedar sawdust, taking into account contact time between the biosorbent and Pb²⁺ model solutions.
Materials and Methods:
Cedar sawdust is used as an adsorbent material. The kinetic model governing the adsorption of Pb²⁺ ions in cedar sawdust is exposed at 298 and 333K. It is determined that the pseudo-first order model responds to kinetic requirements for both temperatures, allowing activation energy of the adsorptive and diffusive process to be obtained. Free energy, entropy and enthalpy variations are obtained within temperatures framework studied.
Results and Discussion:
The pseudoprimer model reproduces the adsorptive process for both temperatures with an activation energy of 5.07 kJ/mol that reflects a physical adsorption process. The
values of ΔHads = -19.40 kJ/mol and ΔSads = -0.04 kJ/(mol.K) reflects an exothermic process, where the process randomness is decreased. The diffusion coefficients correspond to values of 10^-9 m²/s order.
Conclusions:
Pb^{2 +} ions in aqueous solution adsorption obeys a pseudo-first order model. The process is spontaneous, exothermic and low random.