Study on Adsorption Equilibrium, Kinetic and Thermodynamic Parameters of Murexide by Activated Carbon

입상 활성탄에 의한 Murexide의 흡착 평형, 동력학 및 열역학 파라미터에 관한 연구

Abstract

The equilibrium, kinetic and thermodynamic parameters of adsorption of murexide by granular activated carbon were investigated. The experiment was carried out by batch experiment with the variables of the amount of the adsorbent, the initial concentration of the dye, the contact time and the temperature. The isothermal adsorption equilibrium was best applied to the Freundlich equation in the range of 293 ~ 313 K. From the separation factor (${\beta}$) of Freundlich equation, it was found that adsorption of murexide by granular activated carbon could be the appropriate treatment method. The adsorption energy (E) obtained from the Dubinin- Radushkevich equation shows that the adsorption process is a physical adsorption process. From the kinetic analysis of the adsorption process, pseudo second order model is more consistent than pseudo first order model. It was found that the adsorption process proceeded to a spontaneous process and an endothermic process through Gibbs free energy change ($-0.1096{\sim}-10.5348kJ\;mol^{-1}$) and enthalpy change ($+151.29kJ\;mol^{-1}$). In addition, since the Gibbs free energy change decreased with increasing temperature, adsorption reaction of murexide by granular activated carbon increased spontaneously with increasing temperature. The entropy change ($147.62J\;mol^{-1}\;K^{-1}$) represented the increasing of randomness at the solid-solution interface during the adsorption reaction of murexide by activated carbon.

입상 활성탄에 의한 murexide 흡착의 평형, 동역학 및 열역학 파라미터들에 대해 조사하였다. 실험은 흡착제의 양, 염료의 초기농도, 접촉시간과 온도를 변수로 하여 회분식 실험으로 진행하였다. 등온흡착평형관계는 293 ~ 313 K의 범위에서 Freundlich 식에 가장 잘 적용되었으며, Langmuir 식의 분리계수 $R_L$과 Freundlich 식의 분리계수 ${\beta}$로부터 입상 활성탄에 의한 murexide의 흡착조작이 적절한 처리방법이 될 수 있다는 것을 알았다. 또한 Dubinin- Radushkevich 식에서 얻은 흡착에너지(E)로부터 물리흡착공정임을 알 수 있었다. 흡착공정에 대한 동역학적 해석을 통해 반응속도식의 적용 결과는 유사이차반응식이 유사일차반응식보다 일치도가 높은 것으로 나타났다. Gibbs 자유에너지 변화($-0.1096{\sim}-10.5348kJ\;mol^{-1}$), 엔탈피변화($+151.29kJ\;mol^{-1}$)을 통해 흡착공정이 자발적 공정 및 흡열과정으로 진행되었음을 알 수 있었다. 또한 Gibbs 자유에너지 변화는 온도가 올라갈수록 감소하였기 때문에 입상 활성탄에 의한 murexide의 흡착반응은 온도가 올라갈수록 자발성이 높아졌다. 엔트로피 변화 ($512.4J\;mol^{-1}\;K^{-1}$)는 활성탄에 의한 murexide의 흡착반응이 일어나는 동안 고-액 계면에서 무질서도가 증가함을 나타냈다.

Figure 1. Langmuir Isotherms for murexide adsorption on activated carbon at different temperatures.

Figure 2. Freundlich Isotherms for murexide adsorption on activated carbon at different temperatures.

Figure 3. Dubinin-Raudshkevich Isotherms for murexide adsorption on activated carbon at different temperatures.

Figure 4. Pseudo first order kinetics plots for murexide adsorption on activated carbon at different initial concentrations and 293 K.

Figure 5. Pseudo second order kinetics plots for murexide adsorption on activated carbon at different initial concentrations and 293 K.

Figure 6. Pseudo first order kinetics plots for murexide adsorption on activated carbon at different initial temperatures and C_o = 100 mg L^-1.

Figure 6. Pseudo second order kinetics plots for murexide adsorption on activated carbon at different initial temperatures and C_o = 100 mg L^-1.

Table 1. Physical properties of granular activated carbon

Table 2. Identification of murexide

Table 3. Langmuir, Freundlich, and Dubinin-Radushkevich isotherm constants for adsorption of murexide on activated Carbon

Table 4. Kinetic parameters for murexide adsorption on activated carbon at different initial concentration and 293 K

Table 5. Kinetic parameters for murexide adsorption on activated carbon at different temperature and C_o = 100 mg L^-1

Table 6. Thermodynamic parameters for murexide adsorption on activated carbon