Structural features of lignohumic acids

0444680 - BC 2016 RIV NL eng J - Journal Article
Novák, František - Šestauberová, Martina - Hrabal, R.
Structural features of lignohumic acids.
Journal of Molecular Structure. Roč. 1093, August (2015), s. 179-185. ISSN 0022-2860. E-ISSN 1872-8014
Institutional support: RVO:60077344
Keywords : C-13 NMR * FTIR * humic acids * lignohumate * lignosulfonate * structure
Subject RIV: DF - Soil Science
Impact factor: 1.780, year: 2015

The composition and structure of humic acids isolated from lignohumate, which is produced by hydrolytic-oxidative conversion of technical lignosulfonates, were characterized by chemical and spectral methods (UV/VIS, FTIR, and C-13 NMR spectroscopy). As comparative samples, humic acids (HA) were isolated also from lignite and organic horizon of mountain spruce forest soil. When compared with other HA studied, the lignohumate humic acids (LHHA) contained relatively few carboxyl groups, whose role is partly fulfilled by sulfonic acid groups. Distinctive C-13 NMR signal of methoxyl group carbons, typical for lignin and related humic substances, was found at the shift of 55.9 ppm. Other alkoxy carbons, were present in limited quantity, like the aliphatic carbons. Due to the low content of these carbon types, the LHHA has high aromaticity of 60.6%. Comparison with the natural HA has shown that lignohumate obtained by thermal processing of technical lignosulfonate can be regarded as an industrially produced analog of natural humic substances. Based on the chemical and spectral data evaluation, structural features of lignohumate humic acids were clarified and their hypothetical chemical structure proposed, which described typical "average" properties of the isolated fraction.
Permanent Link: http://hdl.handle.net/11104/0249912