Spectroscopic study (DRIFT, SERS and H-1 NMR) of peat, leonardite and lignite humic substances

Diffuse reflectance infrared Fourier transform, surface-enhanced Raman and proton nuclear magnetic resonance spectroscopies were applied to investigat e the structure of humic acids (HA) extracted from peat (P-HA), leonardite (Le-HA) and lignite (Li-HA) samples. The combined use of these techniques h as shown a specific pattern of functional groups for each sample. P-HA was characterised by a greater content of oxygenate (COOH, C-OH in carbohydrate s and phenols) and aliphatic groups. Le-HA and Li-HA showed a lower content of sugar-like components and polyethers. On the other hand, the aromatic s tructures were ubiquitous in all samples, although the different compositio n in Le-HA and Li-HA could be employed to identify and distinguish the HA i n these two kinds of humic materials. (C) 2001 Elsevier Science B.V. All ri ghts reserved.