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Kinetic and thermodynamic models for the removal of aminophenol (dye) from aqueous solutions using groundnut (Arachis hypogea) shells as the biomass

Augustine K. Asiagwu, Hilary I. Owamah and Victor O. Illoh

The sorption of amino-phenol (dye) from aqueous solution using groundnut (Arachis hypogea) shells via kinetic and thermodynamic approaches has been investigated. From the various experimental parameters analyzed, the amount of dye adsorbed increased from 0.202mg/g-0.218mg/g as the adsorbent dosage was increased from 2-6g.In a similar manner, the amount of dye adsorbed was increased from 0.l9lmg/g-0.2l0mg/g with increases in contact time from 20- 100mins. Also, when the operating temperature was increased from 30°C to 70°C,the the amount of dye adsorbed increased from 0.207mg/g-0.2l0mg/g. The adsorption capacity increased from 0.186mg/g to 1.028mg/g with an increase in concentration of dye from l0mg/g-50mg/g. While examining the bio-sorption efficiency, Langmuir and Freundlich models were used. The coefficient of determination (R2) for both isotherms were 0.996 and 0.994 respectively. Pseudo-first order kinetics and Pseudo-second order kinetics were used to analyze the experimental data in which the rate constants k1 and k2 were observed to be 0.053 and 1.465 respectively. Thermodynamic parameters like free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) of the system were also determined and it was found that the adsorption process was endothermic in nature, non- spontaneous and a reversible isothermal process.