Lynne Wong's PhD thesis

6.2 THE NUMBER OF ADSORBED MONOLAYERS N o , THE DENSITY OF
BOUND WATER AND THE PERCENTAGE OF BOUND OR NON-
FREEZABLE WATER
A number of parameters can be derived from the Caurie I sorption model proposed by
Caurie (1981). Although this model did not fit the experimental data best, it did give a
passable fit to the data up to activity values of about 0.6. Hence it was used to give an
indication of the magnitude of a number of properties of the sorbed water.
The number of adsorbed monolayers, N o , can be obtained from N o =
2
where sc is the
s c
slope of the Caurie I plot, and can be deduced to be N o =
2b
m o
(Rao et al., 2006).
m o
b
since the slope of the plot is
The density of the bound water is represented by the Caurie constant b as already
mentioned in Section 6.1.
The percentage of bound water or non-freezable water is given by the product of the
number of adsorbed monolayers N o and the monolayer moisture content m o , i.e. N o x m o .
The results of these calculations for the cane component parts of R 570 of two ages
(including reconstituted cane stalk, dry leaf and green leaf) at various temperatures are
shown in Table 6.2.
At 52 weeks, the number of monolayers N o and the percentage of bound water decreased
with increased temperature; samples at 36 weeks also showed this tendency but there were
discrepancies, while the density of bound water increases with temperature at both ages,
and did not differ much among the cane components. For cane components aged 52
weeks, the highest number of adsorbed monolayers was shown by dry leaf fibre at low
temperature and by rind fines at high temperature. The highest bound water was exhibited
by rind fibre and fines at low temperature and by rind fines at high temperature; this was
true for these components of both ages.
Over the temperature range studied, the number of monolayers varies from about 7 to 4.
This is similar to the number of hydration layers (5 or 6) estimated at the fibre saturation
point in wood (Berry and Roderick, 2005).
244