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    Excess Molar Volume and Isentropic Compressibility for

    Binary or Ternary Ionic Liquid Systems

    Submitted in fulfillment of the requirements of the Degree of Doctor of Technology:

    Chemistry, in the Faculty of Applied Sciences at the

    Durban University of Technology

    Indra Bahadur

    M Sc : Chemistry

    July 2008

    Supervisor: Prof N. Deenadayalu

  • i   

    PREFACE

    The work described in this thesis was performed by the author under the supervision of

    Professor N. Deenadayalu at Durban University of Technology, Durban, South Africa, from

    2008-2010. The study presents original work by the author and has not been submitted in any

    form to another tertiary institution or university. Where use is made of the work of others, it

    has been clearly stated in the text.

    Signed: Date:

    Indra Bahadur

    Signed:

    Prof. N. Deenadayalu (Supervisor) Date:

  • ii   

    ACKNOWLEDGMENTS

    I would like to express my sincere gratitude to God, who always gives me strength and

    knowledge.

    I would like to express my sincere gratitude to the National Research Foundation (South

    Africa) for funding of the project.

    I would like to express my sincere gratitude to Durban University of Technology, Durban,

    South Africa, for part of my financial support and for giving me the opportunity to undertake

    my research at the institution.

    I deem it a great pleasure to express my deep sense of gratitude and indebtedness to my

    venerable supervisor Prof. N. DEENADAYALU, Associate Professor, Department of

    Chemistry, Durban University of Technology, Durban, South Africa, for introducing me to

    the World of Chemical Thermodynamics, inspiring guidance, valuable suggestions, and

    constant encouragement throughout the period of this research work.

    My sincere thanks to the Head of Department of Chemistry, Durban University of

    Technology, Durban, South Africa, for providing the facilities to carry out the present work.

    I express my profound respect and deep sense of gratitude to Prof. T. Hoffman, Warsaw

    University of Technology, Faculty of Chemistry, Division of Physical Chemistry, Warszawa,

    Poland, Prof. N. K. Kausik, Department of Chemistry, University of Delhi, India, Prof M.

    Kidwayi, Department of Chemistry, University of Delhi, India, Prof. S. M. S. Chuahan,

    Department of Chemistry, University of Delhi, India, Dr. P. Venkatesu, Assistant Professor,

    Department of Chemistry, University of Delhi, India, Dr. Sailendra Kumar Singh, Assistant

    Professor, Department of Chemistry, University of Delhi, India, Dr. N. Agasthi, Assistant

  • iii   

    Professor, Department of Chemistry, University of Delhi, India, Dr. Sunil Uppadhya, Dr.

    Sanjeev Shrama, for their valuable suggestions and the generous help in various ways

    throughout the course.

    I owe many thanks to my friends Dr. Ajit Kumar Kanwal, Dr. P. Pitchaito, Mr. Akhilesh

    Kumar Azad, Mr. S. R. Ramphal, Mr. Nitin Kumar, Ms. Sangmitra Singh, Mr. Arun

    Kumar, Mrs. Saroj Bala Kanwal, Ms. T. Singh, and Ms. Zikhona Tywabi, Ms. Krishna

    Purohit, Mr. Tarun Purohit, all who wished me success.

    Finally, my indebtedness extends to my parents, brother, sister and family members. Special

    thanks to my grandfather Mr. Mithai Lal, grandmother Mrs. Bhukhala Devi, my father Mr.

    Mangla Prasad, my mother Mrs. Rani Devi, my brother Mr. Sandeep Kumar, my sister

    Ms. Kumud Ben Joshi my family members Mr. Soti Ram, Mr. Lalji Ram, Mr. Rajendra

    Prasad, Mr. Jugjeevan Ram, Mr. Jagdish Prasad, Mr. Shyam Bihari Madhukar, Mr.

    Jitendra Kumar, Mr. Surendra Kumar, Mrs. Lachi Devi, Mrs. Sita Devi, Ms.

    Sangeeta Singh, Mrs. And Mr. Ram Singh, for their constant encouragement and patient

    endurance which made this venture possible.

    Indra Bahadur

  • iv   

    ABSTRACT

    The thermodynamic properties of mixtures involving ionic liquids (ILs) with alcohols or alkyl

    acetate or nitromethane at different temperatures were determined. The ILs used were methyl

    trioctylammonium bis(trifluoromethylsulfonyl)imide ([MOA]+[Tf2N]-) and 1-butyl-3-

    methylimidazolium methyl sulphate [BMIM]+[MeSO4]-.

    The ternary excess molar volumes ( E ) for the mixtures {methyl trioctylammonium bis

    (trifluoromethylsulfonyl)imide + methanol or ethanol + methyl acetate or ethyl acetate}and (1-

    butyl-3-methylimidazolium methylsulfate + methanol or ethanol or 1-propanol + nitromethane)

    were calculated from experimental density values, at T = (298.15, 303.15 and 313.15) K and

    T = 298.15, respectively. The Cibulka equation was used to correlate the ternary excess molar

    volume data using binary data from literature. The E values for both IL ternary systems were

    negative at each temperature. The negative contribution of E values are due to the packing

    effect and/or strong intermolecular interactions (ion-dipole) between the different molecules.

    The density and speed of sound of the binary solutions ([MOA]+[Tf2N]- + methyl acetate or

    ethyl acetate or methanol or ethanol), (methanol + methyl acetate or ethyl acetate) and

    (ethanol + methyl acetate or ethyl acetate) were also measured at T = ( 298.15, 303.15,

    308.15 and 313.15) K and at atmospheric pressure. The apparent molar volume, Vφ , and the

    apparent molar isentropic compressibility, κφ , were evaluated from the experimental density

    and speed of sound data. A Redlich-Mayer type equation was fitted to the apparent molar

    volume and apparent molar isentropic compressibility data. The results are discussed in terms

    of solute-solute, solute- solvent and solvent-solvent interactions. The apparent molar volume

    and apparent molar isentropic compressibility at infinite dilution, φ and κφ , respectively of

    the binary solutions have been calculated at each temperature. The φ values for the binary

  • v   

    systems ([MOA]+[Tf2N]- + methyl acetate or ethyl acetate or methanol or ethanol) and

    (methanol + methyl acetate or ethyl acetate) and (ethanol + methyl acetate or ethyl acetate)

    are positive and increase with an increase in temperature. For the (methanol + methyl acetate

    or ethyl acetate) systems φ values indicate that the (ion-solvent) interactions are weaker.

    The κφ is both positive and negative. Positive κφ , for ([MOA] + [Tf2N]- + ethyl acetate or

    ethanol), (methanol + ethyl acetate) and (ethanol + methyl acetate or ethyl acetate) can be

    attributed to the predominance of solvent intrinsic compressibility effect over the effect of

    penetration of ions of IL or methanol or ethanol. The positive κφ values can be interpreted in

    terms of increase in the compressibility of the solution compared to the pure solvent methyl

    acetate or ethyl acetate or ethanol. The κφ values increase with an increase in temperature.

    Negative κφ , for ([MOA] + [Tf2N]- + methyl acetate or methanol), and (methanol + methyl

    acetate) can be attributed to the predominance of penetration effect of solvent molecules into

    the intra-ionic free space of IL or methanol molecules over the effect of their solvent

    intrinsic compressibility. Negative κφ indicate that the solvent surrounding the IL or

    methanol would present greater resistance to compression than the bulk solvent. The κφ

    values decrease with an increase in the temperature. The infinite dilution apparent molar

    expansibility,  φ , values for the binary systems (IL + methyl acetate or ethyl acetate or

    methanol or ethanol) and (methanol + methyl acetate or ethyl acetate) and (ethanol + methyl

    acetate or ethyl acetate) are positive and decrease with an increase in temperature due to the

    solution volume increasing less rapidly than the pure solvent. For (IL + methyl acetate or

    ethyl acetate or methanol or ethanol) systems φ indicates that the interaction between (IL +

    methyl acetate) is stronger than that of the (IL + ethanol) or (IL + methanol) or (IL + ethyl

    acetate) solution. For the (methanol + methyl acetate or ethyl acetate) systems φ  values

  • vi   

    indicate that the interactions are stronger than (ethanol + methyl acetate or ethyl acetate)

    systems.

  • vii   

    CONTENTS Pages

    Preface i

    Acknowledgments ii-iii

    Abstract iv-vi

    List of Tables