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Keywords:

  • TGA;
  • nonisothermal kinetic analysis;
  • master plots method;
  • CaC2O4 · H2O

Abstract

Thermal dehydration process of calcium oxalate monohydrate, CaC2O4 · H2O, was reinvestigated from a viewpoint of reaction kinetics. On the basis of data of thermogravimetry, kinetic analysis was performed under nonisothermal conditions using an integral composite procedure, which includes a integral isoconversional method and an integral master plots method. The results of the integral isoconversional method of TGA data at various heating rates suggested that dehydration of CaC2O4 · H2O followed a single step with an activation energy of 99.02 ± 2.61 kJ/mol, and from the master plots method, the reaction was described by an Rn model. Finally, it was estimated that the pre-exponential factor A = (2.82 ± 1.81) ×109 s−1, and the kinetic exponent n = 2.3 ± 0.2. The results of nonisothermal kinetic analysis of the thermal dehydration reactions of CaC2O4 · H2O suggested that the integral composite procedure be very successful in evaluating kinetic parameters and describing kinetic model of solid-state reactions. © 2006 American Institute of Chemical Engineers AIChE J, 2006