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

Abstract

Introduction:
In the last years a great quantity of materials of low cost and with potential to be used in the biosorption of heavy metals have been studied; these include residues, mainly agricultural and forestry. Nickel is used in the manufacture of steel and some alloys. Its consumption causes different health problems.
Objective:
To determine the kinetic model and diffusivity corresponding to adsorption in the heterogeneous system of aqueous mass solution of Ni ²⁺ ions and cedar sawdust.
Materials and methods:
Cedar sawdust is used as adsorbent material. The kinetic model that governs the adsorption of Ni²+ ions in cedar sawdust at temperatures of 25, 35 and 45 ^oC is exposed. The order of the adsorption model, the activation energy and the isostatic heat is determined from the kinetic point of view. The equilibrium constants, the free energy, the enthalpy and adsorption entropy and the diffusion coefficients.
Results and Discussion:
The pseudo-first order model reflects the adsorptive process with activation energy of 38.4 kJ/mol that endorses a physical process. The values of ΔHads = -36.6 kJ/mol and ΔSads = -0.14 kJ/(mol.K) reflects an exothermic process. The diffusion coefficients range from the order of 10^-16 to 10^-17 m²/s.
Conclusions:
The adsorption of Ni²⁺ ions in aqueous solution, follows a pseudo-second order model. The diffusion coefficients at the three temperatures range from the order of 10^-16 to 10^-17 m²/s.