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Ammonium removal from aqueous solutions by clinoptilolite: determination of isotherm and thermodynamic parameters and comparison of kinetics by the double exponential model and conventional kinetic models.

Tosun I - Int J Environ Res Public Health (2012)

Bottom Line: D-R and R-P isotherms were the models that best fitted to experimental data over the other two- and three-parameter models applied.Kinetic parameters were determined by analyzing the nth-order kinetic model, the modified second-order model and the double exponential model, and each model resulted in a coefficient of determination (R(2)) of above 0.989 with an average relative error lower than 5%.Changes in standard free energy (∆G°), enthalpy (∆H°) and entropy (∆S°) of ammonium-clinoptilolite system were estimated by using the thermodynamic equilibrium coefficients.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Engineering, Süleyman Demirel University, Isparta 32260, Turkey. ismailtosun@sdu.edu.tr

ABSTRACT
The adsorption isotherm, the adsorption kinetics, and the thermodynamic parameters of ammonium removal from aqueous solution by using clinoptilolite in aqueous solution was investigated in this study. Experimental data obtained from batch equilibrium tests have been analyzed by four two-parameter (Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich (D-R)) and four three-parameter (Redlich-Peterson (R-P), Sips, Toth and Khan) isotherm models. D-R and R-P isotherms were the models that best fitted to experimental data over the other two- and three-parameter models applied. The adsorption energy (E) from the D-R isotherm was found to be approximately 7 kJ/mol for the ammonium-clinoptilolite system, thereby indicating that ammonium is adsorbed on clinoptilolite by physisorption. Kinetic parameters were determined by analyzing the nth-order kinetic model, the modified second-order model and the double exponential model, and each model resulted in a coefficient of determination (R(2)) of above 0.989 with an average relative error lower than 5%. A Double Exponential Model (DEM) showed that the adsorption process develops in two stages as rapid and slow phase. Changes in standard free energy (∆G°), enthalpy (∆H°) and entropy (∆S°) of ammonium-clinoptilolite system were estimated by using the thermodynamic equilibrium coefficients.

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Comparison of adsorption kinetic models at 10 °C.
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ijerph-09-00970-f002: Comparison of adsorption kinetic models at 10 °C.

Mentions: Adsorption kinetics are required for selecting optimum operational conditions of water and wastewater treatment facilities for full-scale processes. The results obtained from the experiments at 10 °C were examined to describe the reaction kinetics according to the nth-order kinetics, and the modified second-order and double exponential models. Figure 2 illustrates the kinetic models fitted to experimental data obtained at 10 °C. The determined kinetic parameters are shown in Table 3.


Ammonium removal from aqueous solutions by clinoptilolite: determination of isotherm and thermodynamic parameters and comparison of kinetics by the double exponential model and conventional kinetic models.

Tosun I - Int J Environ Res Public Health (2012)

Comparison of adsorption kinetic models at 10 °C.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3367291&req=5

ijerph-09-00970-f002: Comparison of adsorption kinetic models at 10 °C.
Mentions: Adsorption kinetics are required for selecting optimum operational conditions of water and wastewater treatment facilities for full-scale processes. The results obtained from the experiments at 10 °C were examined to describe the reaction kinetics according to the nth-order kinetics, and the modified second-order and double exponential models. Figure 2 illustrates the kinetic models fitted to experimental data obtained at 10 °C. The determined kinetic parameters are shown in Table 3.

Bottom Line: D-R and R-P isotherms were the models that best fitted to experimental data over the other two- and three-parameter models applied.Kinetic parameters were determined by analyzing the nth-order kinetic model, the modified second-order model and the double exponential model, and each model resulted in a coefficient of determination (R(2)) of above 0.989 with an average relative error lower than 5%.Changes in standard free energy (∆G°), enthalpy (∆H°) and entropy (∆S°) of ammonium-clinoptilolite system were estimated by using the thermodynamic equilibrium coefficients.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Engineering, Süleyman Demirel University, Isparta 32260, Turkey. ismailtosun@sdu.edu.tr

ABSTRACT
The adsorption isotherm, the adsorption kinetics, and the thermodynamic parameters of ammonium removal from aqueous solution by using clinoptilolite in aqueous solution was investigated in this study. Experimental data obtained from batch equilibrium tests have been analyzed by four two-parameter (Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich (D-R)) and four three-parameter (Redlich-Peterson (R-P), Sips, Toth and Khan) isotherm models. D-R and R-P isotherms were the models that best fitted to experimental data over the other two- and three-parameter models applied. The adsorption energy (E) from the D-R isotherm was found to be approximately 7 kJ/mol for the ammonium-clinoptilolite system, thereby indicating that ammonium is adsorbed on clinoptilolite by physisorption. Kinetic parameters were determined by analyzing the nth-order kinetic model, the modified second-order model and the double exponential model, and each model resulted in a coefficient of determination (R(2)) of above 0.989 with an average relative error lower than 5%. A Double Exponential Model (DEM) showed that the adsorption process develops in two stages as rapid and slow phase. Changes in standard free energy (∆G°), enthalpy (∆H°) and entropy (∆S°) of ammonium-clinoptilolite system were estimated by using the thermodynamic equilibrium coefficients.

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