The removal of Cr ions from industrial wastage by adsorption on rice hulls was investigated based on activated pure rice hulls dosage, stay time, metal concentration and solution temperature. The optimum values of activated pure rice hulls dosage and stay time were determined to be 0.5 gm/50 ml solution and 60 min, respectively, for the adsorption of Cr ions. The constant for the Freundlich, D-R and Langmuir isotherms were calculated at (293 – 323 K). The adsorption of Cr from industrial wastage was found to be exothermic. Thermodynamic parameters such as free energy (∆G°), enthalpy (∆H°) and entropy (∆S°) of adsorption was also calculated and interpreted from the slope and intercept of the plots of In KD vs I/T. The ∆G° value decreases with rise in temperature and the negative values of ∆H°indicate that the adsorption of Cr from industrial wastage was an exothermic process while positive values of change in entropy (∆S°) were also observed.
Key words: Adsorption, Cr metal, activated pure rice hulls.
C = concentration of adsorbate ions at equilibrium, ∆Go = Gibbs free energy of adsorption (KJ/mol), ∆Ho = enthalpy of adsorption (KJ/mol), K and n= Freundlich isotherm coefficient, K = equilibrium constant (L/mol), m = the amount of adsorbent (g), ∆S
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