FT-IR spectra showed similar absorbance area for the two
BRs (Fig. 1). Both spectra indicated a broad absorption
band at 3200–3500 cm−1 attributed to the O–H stretch
vibration of carboxylic and alcoholic groups. The high
absorption in the range of 1400–1700 cm−1 is usually
associated with C=O in carbonyl groups and C=C in aromatic
structures. The absorption peak at 1000–1100 cm−1
represents C–O stretching vibrations of C–O–C groups
from polysaccharides. These spectra showed that the BR
contains a great deal of carboxyl (–COOH), hydroxyl
(–OH), carbonyl (–C=O) and aromatic structures and also
corroborated the description of BR given by Rijkenberg
and Depree (2010). These structures can donate lone pairs of electrons. Thus these species are expected to play an
important role in trace metal complexation (Kaschl et al.,
2002). However, they also differed in the intensity of some
peaks, such as a sharp absorption of 1385 cm−1 in CBR that
might occur with –NO2 or terminal carboxylate –COO−
groups; in PBR, a high absorption was observed at 2920
cm−1 related to saturated aliphatic C–H stretching. These
differences in groups observed in the FT-IR spectra could
lead to dissimilar complexation behavior with Cu and Zn.