Applicability of Theoretical Adsorption Models for Studies on Adsorption Properties of Adsorbents(III)

Abstract

The aim of this study is to evaluate the applicability of adsorption models for understanding the thermodynamic properties of adsorption process. For this study, the adsorption isotherm data of NO3-N ion onto a commercial anion exchange resin obtained at various experimental conditions, i.e. different initial concentrations of adsorbate, different dosages of adsorbent, and different temperatures, were used in calculating the thermodynamic parameters and the adsorption energy of adsorption process. The Gibbs free energy change (ΔG o ) of adsorption process could be calculated using the Langmuir constant bM as well as the Sips constant, even though the results were significantly dependant on the experimental conditions. The thermodynamic parameters such as standard enthalpy change (ΔH o ), standard entropy change (ΔS o ) and ΔG o could be calculated by using the experimental data obtained at different temperatures, if the adsorption data well fitted to the Langmuir isotherm model and the plot of ln b versus 1/T gives a straight line. As an alternative, the empirical equilibrium constant(K) defined as qe / Ce could be used for evaluating the thermodynamic parameters instead of the Langmuir constant. The results from the applications of D-R model and Temkin model to evaluate the adsorption energy suggest that the D-R model is better than Temkin model for describing the experimental data, and the availability of Temkin model is highly limited by the experimental conditions. Although adsorption energies determined using D-R model show significantly different values depending on the experimental conditions, they were sufficient to show that the adsorption of NO3-N onto anion exchange resin is an endothermic process and an ion-exchange process.

Adsorption Characteristics of Cd, Cu, Pb and Zn from Aqueous Solutions onto Reed Biochar

“…2에서 log q에 대하여 log Ceq를 plot해서 얻은 (Na et al, 2011;Weber and Miller, 1989). Langmuir 등온흡착 식은 다음과 같이 표현된다 (Langmuir, 1918).…”

Adsorption characteristics of As(III) and Cr(VI) from aqueous solution by Sediment Amendment Composite

“…양 중금속에서 1/n 값은 1보다 작은 값을 형성하여 전체적으로 강한 흡착경향을 나타내었다. 또 한, 흡착강도 1/n 값이 1보다 적을 경우 일반적으로 Lanmuir 형의 흡착등온특성을 갖는 것으로 알려져 있다 (Na et al, 2011;Weber and Miller, 1989). Langmuir 모델의 적용에서는 최대흡착량(Q m )이 Cr(VI) (36.07 mg/g), As(III) (25.54 mg/g) 로 Cr(VI)이 높은 흡착량을 보였다( Fig.…”

Adsorption Characteristics of Heavy Metals using Sesame Waste Biochar

“…특히, (Freundlich, 1906). (Weber and Miller, 1989;Na et al, 2011). Langmuir 등온흡착식은 다음과 같이 표현된다 (Langmuir, 1918).…”