School of Physical Sciences

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Browsing School of Physical Sciences by Subject "Adsorption"

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    Adsorptive removal of methylene blue from aqueous solution using agricultural waste: Equilibrium, kinetic and thermodynamic studies
    (U. P., 2015) Enenebeaku, K. Conrad; Okorocha, J. Nnaemeka; Akalezi, O. Chris
    The potential of raw corn cobs (RCC) powder, for the removal of methylene blue (MB) dye from aqueous solution was investigated. The adsorbent was characterized by FTIR and SEM analysis. Batch adsorption studies were conducted and various parameters such as contact time, adsorbent dosage, initial dye concentration, pH and temperature were studied to observe their effects in the dye adsorption process. The optimum conditions for the adsorption of MB onto the adsorbent (RCC) was found to be: contact time (30mins), pH (10.0) and temperature (343K) for an initial MB dye concentration of 100mg/l and adsorbent dose 1.0g. The experimental equilibrium adsorption data fitted best and well to the Freundlich and Halsey isotherm models. The maximum adsorption capacity was found to be 18.28mg/g. The kinetic data conformed to the pseudo-second-order kinetic model, suggesting that the rate limiting step may be chemisorptions. Adsorption mechanism was investigated with intra-particle diffusion model and it indicated that intra-particle diffusion was not the rate determining step. Thermodynamic quantities such as Gibbs free energy (∆G0), enthalpy (∆H0) andentropy (∆S0) were evaluated. The negative values of ∆G0 and the positive value of ∆H0 obtained indicated the spontaneous and endothermic nature of the adsorption process while the positive ∆S0 value obtained indicated increased randomness during the adsorption process.
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    Effect of adenine, guanine and hypoxanthine on the corrosion of mild steel in H3PO4
    (U. P., 2015) Chahul, H. F.; Akalezi, C. O.; Ayuba, A. M.
    The corrosion inhibition potentials of adenine (AD), guanine (GU) and hypoxanthine (HYP) on the corrosion of mild steel in 0.1 M H3PO4 was investigated at 303 and 333 K using weight loss and potentiodynamic polarization techniques. The results obtained, indicated that AD, GU and HYP inhibited the corrosion of mild steel in phosphoric acid. Results obtained from potentiodynamic polarization studies showed that AD, GU and HYP acted as mixed corrosion inhibitors by retarding both the anodic and cathodic half reactions of the corrosion process. Iodide ions, I- increased inhibition efficiencies of the purines. Adsorption of AD, GU and HYP on the mild steel surface was spontaneous and aligned with Langmuir isotherm model.