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The Characterization of Water in Peat

Dep. of Physics, The O'Reilly Inst., Trinity College, Dublin 2, Ireland

M. Prasad

Bord na Móna Research Centre, Newbridge, County Kildare, Ireland

*Corresponding author (vmcbrrty{at}tcd.ie).

ABSTRACT

The functionality and ultimate use of peat are intimately bound up with the way in which absorbed water behaves in the host matrix. Control of the amount of absorbed water, the dynamics of water loss in drying, and the gain of water in rewatering are important determinants in its commercial exploitation. We examined the nature and behavior of water in a range of different Irish peat samples by exploiting the combined capabilities of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and proton nuclear magnetic resonance (NMR). Up to four different forms of water were detected in heavily hydrated peat: absorbed or tightly bound water, which is non-freezable and behaves like a glass at low temperatures; two forms of loosely bound water; and bulk water. Increasing temperature across the subambient regime revealed the sequential onset of mobility of the different forms of water. The transitions are well-defined in terms of both water concentration and the temperature at which motion sets in. Unlike hydrated polymers, NMR estimates of the maximum amounts of bound water at low temperatures depend on overall water content, reflecting the extent to which the peat matrix can restructure and swell when hydrated. The TGA, which maps out the loss of water under controlled conditions of temperature and atmosphere, offers additional evidence on the mechanism of dehydration, indicating that drying on a small scale under laboratory conditions is not grossly impeded by internal barriers. The gratifying consistency between the data from the three experimental techniques used, along with pertinent data in the literature, give additional insights into the role of water in peat.

Received for publication September 8, 1994.