The difference in absorbance between the two spectra in
Fig. 5 shows the extent to which sulphuric acid liberated
components from the original plant material. The broad absorption
at 3350e3500 cm1 which is the OeH stretching band
of the hydroxyl group associated with the breakage of
hydrogen bonds in cellulose. The many lignin bands show
that not all of the lignin was dissolved during the treatment.
The lignin left after pretreatment can be used for the production
of biodegradable plastics.