The evaluation of the thermodynamic stability of the dimethylsulfoxide inserted in the structures of the kaolins of the northeast area of Brazil.

by da Silva, Marcus Venicio

Abstract (Summary)
The present work presents the development of a synthesis methodology and characterization of kaolins modified chemically, leaving of natural kaolins of thenortheast area of Brazil. The kaolins were modified through procedures of removal organic matter, obtaining in a sodic way, obtaining of form amoniacal, obtaining in theacid way and collation with dimethylsulfoxide. For characterization of the kaolins obtained after all the modification, techniques of X?Ray diffraction (DRX), chemical analysis (atomic absorption), thermogravimetry (TG), differential scanning calorimetry (DSC) and infrared absorption spectroscopy (FT-IR). The results obtained through the chemical analysis and of X?Ray diffraction confirmed that the composition of the kaolins was basically kaolinite and some sludges, such as, present Mica as claymineral joined in the gray kaolin. Through the obtained results of capacity of change cationic (CTC), it was possible to evaluate and to adapt the methodologies for theobtaining of better results. The evaluation of the thermodynamic stability of the dimethylsulfoxide inserted in the structures of the kaolins it was accomplishedthrough thermogravimetry, tends as base the method of Ozawa, where starting from the curves TG in the reasons of heating 2, 5, 7 and 10oC.min-1, it was obtained thegraph of the heating reason by the reciprocal of the temperature, later he/she took place lineal regression, soon after it was obtained the coefficient angular(B), thatwhen substituted in the expression: ? E = -18,2045.B, it is obtained the activation energy, being this a fundamental thermodynamic parameter in the evaluation of thestability. The dimethilsulfoxide inserted in the structure of the white kaolin it demonstrated more expressive values of activation energy (Ea) in relation to theinserted in the gray kaolin, denoting like this a larger thermodynamic stability, being able to in that way a better departure material to be considered in the obtaining ofadsorventes of larger efficiency.
This document abstract is also available in Portuguese.
Bibliographical Information:

Advisor:Lindomar Roberto Damasceno da Silva; Antoninho Valentini; Oyrton Azevedo de Castro Junior

School:Universidade Federal do Ceará

School Location:Brazil

Source Type:Master's Thesis

Keywords:quimica caulins intercalado dimetilsulfóxido estabilidade termodinâmica kaolins intercalated dimethylsulfoxide stability thermodynamics


Date of Publication:03/02/2007

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