Thermodynamic Properties of Chromium Adsorption by Sediments of River Watari, Kano State
The adsorption of Chromium from aqueous solution using river Watari sediment as an adsorbent was modeled. The influence of initial pH, solution temperature, adsorbent and adsorbate concentrations on the adsorption efficiency was investigated using batch equilibrium assays. From the results obtained for the adsorption envelop experiments, a good adsorption potential was recorded at initial pH of 2 and a temperature of 25oC. The experimental data obtained was subjected to different adsorption isotherm models including; Linear, Langmuir, Freundlich and Temkin to establish the mechanism of chromium adsorption onto the sediment. Amongst the four models tested, Langmuir gave the best fit with regression values ranging from 0.6494 to 0.7459 for 25oC, 30oC, 40oC and 50oC respectively which suggests a homogeneous surface for the sediment. The isosteric heat (ΔHr) of adsorption and enthalpy change (ΔH) did not change with temperature also indicating a homogeneous sediment surface. Based on the values of entropies, activation energies and Gibb’s free energies obtained, the adsorption was found to be spontaneous at all temperatures.
Keywords: Adsorption, Chromium ion, Equilibrium isotherms, and Sediment.