Authors:A. Rotaru, Irina Nicolaescu, P. Rotaru, and C. Neaga
Over the ages, the deposits of dead vegetation buried by rock and mudflows, compacted and compressed out all of the moisture;
it slowly carbonized and became coal.
Humic acids are natural organic acids — brown coloured biological macromolecules, formed in coal by biochemical changes (decomposition,
pyrolysis) of lignocellulosic matter.
From lignite coal bed, the humates were extracted in alkaline medium and isolated from the residual fraction. Humic acids
were obtained by treating humantes’ solutions with HCl.
Thermal analysis (TG, DTG, DTA and DSC) was used in order to establish the decomposition and thermal effects of lignite, humates,
humic acids and residual matter extracted from Rovinari mines in Romania. A non-isothermal linear temperature regime was imposed
to reveal all decomposition steps.
Authors:D Montecchio, O Francioso, P Carletti, D Pizzeghello, S Chersich, F Previtali, and S Nardi
acids (HAs) extracted from soils developed under two Norwegian spruce (Picea
abies, (L.) Karst) subalpine forests of northern Italy were characterized
using chemical, thermal (TG-DTA) and spectroscopic (DRIFT) analyses. The samples
were taken from five sites which differed in orientation (northern and southern
exposure) and vegetal cover at different old age: grassland, regeneration,
immature and mature stands. In general, the thermal patterns of HAs were similar
(three exothermic reactions appeared around at 300, 400 and 500C) in
both sites in grasslands and regeneration while a considerable modification
appeared in HA from stands of different age at northern and southern exposure
site. DRIFT spectroscopy confirmed the differences observed through TG-DTA
analysis. In particular the main structural changes were ascribed to modification
of carbonyl group and of CH stretching in aliphatic components in each HAs
from different sites.
Fluoride (F–) binding to humic acid has been measured as a function of pH (5–6.6). The pH dependent binding is attributed to the anion being trapped within the large structure (territorial bound) but is not bound to a particular functional group (site bound). Studying fluoride binding provides insight to cation, anion and neutral species interactions with humic acid.
Authors:István Hullár, András Valentin Vucskits, Erzsébet Berta, Emese Andrásofszky, András Bersényi, and József Szabó
, L. E. , Nelson , D. W. and West , D. X. ( 1981 ): The mechanism of copper (II) binding by humicacid: an electron spin resonance study of a copper (II)-humicacid complex and some adducts with nitrogen donors . Soil Sci. Soc. Am. J. 45 , 745
Authors:József Szabó, András Valentin Vucskits, Erzsébet Berta, Emese Andrásofszky, András Bersényi, and István Hullár
. X. ( 1981 ): The mechanism of copper (II) binding by humicacid: an electron spin resonance study of a copper (II)-humicacid complex and some adducts with nitrogen donors . Soil Sci. Soc. Am. J. 45 , 745 – 749
The stability constants of the complex of Pu/III/ with a humic acid at pH 2.9 and 5.0 were measured using solvent-extraction technique. The organic extractant was dinonyl naphthalene sulphonic acid in sodium form /NaD/ in benzene while the humate aqueous phase had a constant ionic strength of 0.5M /NaClO4/. The total carboxylate capacity of the humic acid was determined by direct potentiometric titration to be 6.201 Meq g–1. The apparent pKa increased as the degree of ionization // increased. The 1g
1 values of the complex of Pu/III/ with humic acid have been determined to be 2.8 and 3.11 at pH 2.9 and 5.0, respectively.
Authors:A. Paulenová, P. Rajec, M. Žemberyová, G. Sasköiová, and V. Višacký
The binding of strontium by humic acid was studied in systems designed to model soil leaching conditions. Ultrafiltration experiments were conducted for a wide range of CaCl and NaCl concentrations and for the pH range 4 to 7. It was found that the recovery of humic acid slowly decreased with increasing pH. This occurred because at neutral and basic solutions the increasing degree of ionization of the carboxylate groups leads to the full repulsion state of the humic acid and to increasing of the strontium binding (strontium recovery 60% at pH 7) with this natural polyelectrolyte. The strontium complexation in the presence of calcium was studied in different series of metal concentrations at pH 5 and the ionic strength 0.1M NaCl. The results were explained on the base of the metal ion charge neutralization model of humic complexation (CNM). Loading capacity (cca 40%) and complexation constants and Sr (3.51±0.27) and Ca (3.10±0.29) with Aldrich humic acid were found.
Authors:N. Kamei-Ishikawa, K. Tagami, and S. Uchida
This study investigated selenium sorption kinetics on humic acid (HA) as a function of initial Se concentration (10–300 μg·1−1) and solid/liquid ratio (0.01–0.1). From the result, it was clear that the Se sorption kinetics on HA could be expressed
by a pseudo-second order equation. This was possible because the sorption mechanism on HA is a multiple sorption process including
specific and non specific mechanisms. Additionally, the 3-D empirical equation for the amount of sorbed Se could be determined
as a function of the initial Se concentration and solid/liquid ratio.