H-binding groups in lignite vs. soil humic acids: NICA-Donnan and spectroscopic parameters.
A comparative study has been carried out for two sets of humic acids isolated from lignites and soils. H-binding data were analyzed using the NICA-Donnan model, for three Greek lignite humic acids (HA) plus IHSS Leonardite reference HA, and five Greek soil HAs plus a commercial peat HA. (13)C-CP-MAS NMR and H-binding data provide quantitative estimates for functional groups, showing that lignite HAs of diverse origin have strikingly homogeneous properties, while the H-binding structural units of soil HAs are characterized by a large degree of variability. Consistent differences between soil HA vs. lignite HA are revealed at the level of functional groups' concentrations. In the pH range 4 to 10, soil HA showed a charge variation <3 [equiv kg(-1)] while lignite HAs showed a higher charge variation >3.5 [equiv kg(-1)].
Drosos
Marios
M
Laboratory of Physical Chemistry, Department of Environmental and Natural Resources Management, University of Ioannina, Seferi 2, 30100, Agrinio, Greece.
Jerzykiewicz
Maria
M
Deligiannakis
Yiannis
Y