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Ultrasonic Degradation of Xanthan and Locust Bean Gums in Aqueous Solutions: Rheological and Kinetic Studies

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2014, Doctor of Philosophy, Case Western Reserve University, Chemical Engineering.
This work consists of experimental studies and analytical modeling of the ultrasonic degradation of polysaccharides in both the dissolved and suspended phases. In the experimental part of this work, natural xanthan gums, modified xanthan gums, locust bean gums, and waste coffee grounds have been sonicated in aqueous solutions for specific times and ultrasonic field and chemical conditions. Three models, including the Huggins and the Solomon-Ciuta equations, have been applied and compared for estimation of intrinsic viscosity of gum solutions, and the experimental results confirm the existence of a disorder-order conformational transition during the degradation process. Besides performing the sonication in deionized distilled water, two categories of salts with different behavior have been utilized, and their influences on molecular conformation, molecular interaction, and degradation efficiency have been carefully screened and studied by comparing a series of parameters, including the Huggins constant, the power-law exponent, the salt tolerance parameter, and the relative chain stiffness parameter. The results of the experiments confirm that the influence of salt species and concentration is more significant in the ultrasonic degradation of polyelectrolyte-type polysaccharides than that of non-polyelectrolyte type polysaccharides. The function of pyruvate groups located on xanthan gum side chains has also been studied by comparing the degradation results of a series of blends of natural xanthan gum with pyruvate-free xanthan gum. These results furthered the basic understanding of how pyruvate groups affect the stability of xanthan gum molecular backbones, while demonstrating the influence of the salt on molecular conformation and subsequently the resulting differences in degradation efficiency. Two kinetics models have been applied and compared to understand the degradation rate and the factors that impact degradation efficiency. Negative reaction orders with respect to concentration confirm that the ultrasonic degradation occurs mainly via a mechanical mechanism, in which the degradation rate increases with decreasing the polymer concentration. Reaction rate constants, the advantages and disadvantages caused by different factors, including salt species, salt concentration, polymer concentration, degradation temperature, functional groups, have been clearly quantified, and this enables the analysis and prediction of degradation efficiency.
Donald Feke (Advisor)
172 p.

Recommended Citations

Citations

  • Li, R. (2014). Ultrasonic Degradation of Xanthan and Locust Bean Gums in Aqueous Solutions: Rheological and Kinetic Studies [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1380200700

    APA Style (7th edition)

  • Li, Ruoshi. Ultrasonic Degradation of Xanthan and Locust Bean Gums in Aqueous Solutions: Rheological and Kinetic Studies. 2014. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1380200700.

    MLA Style (8th edition)

  • Li, Ruoshi. "Ultrasonic Degradation of Xanthan and Locust Bean Gums in Aqueous Solutions: Rheological and Kinetic Studies." Doctoral dissertation, Case Western Reserve University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1380200700

    Chicago Manual of Style (17th edition)