Acta Phys. -Chim. Sin. ›› 2012, Vol. 28 ›› Issue (07): 1615-1622.doi: 10.3866/PKU.WHXB201204282

• THERMODYNAMICS, KINETICS, AND STRUCTURAL CHEMISTRY • Previous Articles     Next Articles

Kinetics and Thermodynamics of Adsorption of Chlorophenols onto β-Cyclodextrin Modified Chitosan

ZHOU Liang-Chun1, MENG Xiang-Guang1, LI Jian-Mei1, HU Wei2, LIU Bo1, DU Juan1   

  1. 1College of Chemistry, Sichuan University, Chengdu 610064, P. R. China;
    2. School of Chemistry and Pharmaceutical Engineering, Sichuan University of Science & Engineering, Zigong 643000, Sichuan Province, P. R. China
  • Received:2012-03-05 Revised:2012-04-27 Published:2012-06-07
  • Contact: MENG Xiang-Guang E-mail:mengxgchem@163.com
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21073126) and Key Project of the Science and Technology Department of Zigong, Sichuan Province, China (10X01).

Abstract:

β-Cyclodextrin (β-CD) modified chitosan (CS), β-cyclodextrin-6-chitosan (CS-CD), was prepared and subsequently characterized by Fourier transform-infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) analysis. The CS-CD was used as an adsorbent for the adsorption of 2-chlorophenol (2-CP), 2,4-dichlorophenol (DCP), and 2,4,6-tuichlorophenol (TCP) from aqueous solutions. The Langmuir and Freundlich models were applied to describe the adsorption isotherms of the chlorophenols. The adsorption parameters have also been evaluated. The calculated maximum adsorption capacities for 2-CP, DCP, and TCP on CS-CD were 14.51, 50.68, and 74.29 mg·g-1, respectively, indicating that the introduction of the β-CD moiety greatly increased the adsorption efficiency. Kinetic studies showed that the adsorptions were fast, in that all of the adsorption equilibria were reached within one hour, and that the adsorption processes followed a pseudosecond- order kinetic model. The thermodynamic parameters ΔG0, ΔH0, and ΔS0 were also calculated. The negative ΔG0 values indicated that all of the adsorption processes were spontaneous. A possible adsorption mechanism has been provided and discussed. The effects of electrolytes and pH values on adsorption revealed that hydrogen bonding between the chlorophenols and CS-CD dominated the adsorption process, which was further confirmed by FT-IR analysis. The adsorbent could be regenerated by washing with ethanol. Following six cycles of usage and regeneration, the mass and adsorption efficiency of the CS-CD remained at 90% and 82%, respectively. CS, however, showed greater mass loss and efficiency reduction following regeneration.

Key words: Chitosan, β-Cyclodextrin, Adsorption, Chlorophenols, Thermodynamics, Kinetics

MSC2000: 

  • O647