Metal–carboxylate interactions in metal–alginate complexes studied with FTIR spectroscopy Original Research Article

FTIR spectroscopy was used in order to obtain information about metal–carboxylate interactions in metal–alginate complexes of alginic acid and sodium alginate from the brown algae Laminaria digitata after crosslinking with Ca2+, Cu2+, Cd2+, Zn2+, Ni2+ and Pb2+. From the frequencies of the characteristic peaks for asymmetric COO stretching vibration (νasym(COO−) and symmetric COO stretching vibration (νsym(COO−)) a ‘pseudo bridged’ unidentate coordination with intermolecular hydrogen bonds is proposed for the metal–carboxylate complexes in polyguluronic regions while for the polymannuronic regions the bidentate bridging coordination was proposed. The PIB factor introduced previously as a relationship between metal sorption and frequencies of the asymmetric vibrations was found not to correlate with sorption capacity or any other physical property of the metal–alginate complexes studied.