Applicability of thermal methods for characterization of peats and plants

Abstract

Differential thermogravimetric (DTG) and differential thermal analysis (DTA) curves were obtained for some peat materials and peat-forming plants. Four peats were selected on the basis of botanical composition and degree of decomposition. Granulometric fractions and holocellulose preparations from the peats were also analyzed. The DTG curves showed three main regions of weight loss: the first at 275°–325°C the second at 360°–460°C and the third at 500°–560°C. The first region with a peak at 300°C was by far the most important. It was associated with cellulosic materials which may reflect the degree of decomposition. The size of the 300°C peak could be used for measuring holocellulose in peats, and this might be a valid substitute for chemical means for that measurement, specially in more decomposed peats. The nature of the 300°C peak did not change significantly with changes in particle size, although the position of the 420°C peak was shisfted toward lower temperatures as particle size decreased. The original features of the peats were generally retained in the separates. Even though the predominance of residues from one species of plants in a particular peat did not greatly influence the shape of the DTG curves, some generalizations concerning the botanical sources of peats were obtained. In a comparison of DTG and DTA methods, the former appears to provide more useful information on the chemical make-up and on the degree of decomposition of peats.