Authors:Sakine Yalçin, A. Ergün, Handan Erol, Suzan Yalçin, and B. Özsoy
Eren, M., Deniz, G., Gezen, S. S. and Türkmen, I. I. (2000): Effects of humates supplemented to the broiler feeds on fattening performance, serum mineral concentration and bone ash [in Turkish, with English abstract]. Vet. J. Ankara Univ. 47, 255
The complexation of the uranyl ion with humic acid is investigated. The humic acid ligand concentration is described as the
concentration of reactive humic acid molecules based on the number of humic acid molecules, taking protonation of functional
groups into account. Excess amounts of U(VI) are used and the concentration of the humic acid complex is determined by the
solubility enhancement over the solid phase. pH is varied between 7.5 to 7.9 in 0.1M NaClO4 under normal atmosphere and room temperature. The solubility of U(VI) in absence of humic acid is determined over amorphous
solid phase between pH 4.45 and 8.62. With humic acid, only a limited range of data can be used for the determination of the
complexation constant because of flocculation or sorption of the humic acid upon progressive complexation. Analysis of the
complex formation dependency with pH shows that the dominant uranyl species in the concerned pH range are UO2(OH)+ and (UO2)3(OH)5+. The complexation constant is evaluated for the humate interaction with the to UO2(OH)+ ion. The stability constant is found to be logβ = 6.94±0.3 l/mol. The humate complexation constant of the uranyl mono-hydroxo species thus is significantly higher than that
of the nonhydrolyzed uranyl ion (6.2 l/mol). Published data on the Cm3+, CmOH2+ and Cm(OH)2+ humate complexation are reevaluated by the present approach. The higher stability of the hydrolysis complex is also found
for Cm(III) humate complexation.
The influence of aqueous solution of sodium humate on the transport of241Am from the soil into solution and acceleration of movement through a soil layer has been studied. It was found that under static condition the presence of 150 mg sodium humate in 100 ml water accelerates the liberation of241Am from soil into the solution. The mobility of241Am through a column of soil increased significantly since the concentration of sodium humate in the entering solution exceeded 100 mg.1–1. Artificially contaminated podsol soil from Brno site and sodium humate isolated by alkaline extraction from sediments of North Bohemian (Duchcov) origin have been used for the investigation.
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.
Tracer110mAg has been used to investigate the speciation of silver in natural waters, which may contain chloride, sulphide or humate ions. Silver chloride or oxide is readily absorbed from waters by many materials, and some may be photochemically reduced to metallic silver. Absorbed silver, silver chloride and silver sulphide may be distinguished by their desorption behaviour. Humates form complexes with silver chloride, silver sulphide and the silver cation, which can be separated from smaller species by gel permeation chromatography.
Authors:K. Štamberg, P. Beneš, J. Mizera, J. Dolanský, D. Vopálka, and K. Chalupská
A general model, the so called Mean Molecular Weight Model (MMWM), of complexation of metal cations (Mez+) with macromolecular polyanions of humic acid (HAp-) is proposed. The model is based on the results of previous studies of the electrophoretic mobility of humate complexes and assumes that the complexation proceeds by consecutive neutralization of the dissociated carboxyl groups of the central polyanion HAp- with Mez+ cations. It reflects the macromolecular character of humic acid, applies molar concentrations of reacting components with equations for stability constants and incorporates also the mean charge of humic macromolecules. The model has been verified with experimental data obtained in the study of complexation of Eu(III) with Aldrich humic acid using ion exchange (Amberlite IR-120), over a broad range of [Eu] to [HA] ratio, at pH 4 and 7.
Tin(II) and tin(IV) are absorbed from aqueous solutions by Sephadex G-25 gel, from which they can be eluted by humates or
fulvates, with which they interact more strongly. Methyltin species are not absorbed by Sephadex G-25, and so can be separated
from inorganic tin. Both inorganic tin and methyltin species in natural waters at pH 7.4 can be quantitatively retained by
passing through small columns of Chelex-100 resin: the methyltin species can then be washed off the resin with 4M nitric acid.
Trimethyltin chloride113Sn in water scarcely interacts with fulvates, humates, kaolinite or montmorillonite but is absorbed bySphagnum peat. Dimethyltin dichloride-113Sn reacts significantly with all the above materials after 2 hours equilibration. Methyltin trichloride-113Sn interacts weakly in alkaline solutions.
Authors:Y. Takahashi, Y. Minai, Y. Meguro, S. Toyoda, and T. Tominaga
Binding constants of Eu(III)- and Am(III)-complexes with soil-derived humic acid were determined by solvent extraction at various pH and ionic strength. Based on the dependence of binding constants on pH and ionic strength, stabilities of the humate complexes in land water and seawater were estimated. Speciation calculation based on the binding constants indicated that Am(III) could combine with humic substances in natural water system.
Authors:Y. Takahashi, Y. Minai, T. Ozaki, S. Ambe, M. Iwamoto, H. Maeda, F. Ambe, and T. Tominaga
The multitracer technique was applied to elucidate of influence of humate formation on adsorption behavior of ultratrace elements. Dissolved fractions of Co, As, Rb, Sr, Y, Zr, Ba, Ce, Eu, Gd, Tb, Yb, Lu, Hf, Re and Pt in contact with kaolinite or silica gel were determined simultaneously either in the presence or absence of humic acid, which was partly adsorbed on the solid. Percentage of dissolved fraction of rare earth elements was identical to that of humic acid, indicating high stability of the rare earth-humate complex. Hydrolysis was the most important factor controlling the behavior of Zr and Hf. Both hydrolysis and humate complexation influenced the adsorption of Co, Sr, Ba and Pt, whereas neither affected the distribution of As, Rb and Re.
The preparation of technetium-99m-humic complex without presence of any metal reductant was studied. For the preparation of Tc-HA complex by ligand substitution hexakis(thiourea-S)technetium(III) complex was used as a precursor. Ligand exchanging reaction was studied with two different humate/thiourea concentration ratios. After mixing of [99mTc(tu)6]3+ complex with natrium humate under a nitrogen atmosphere a formation of technetium humate wasobserved. The determination of reaction products was performed by combination of gel and paper chromatography. Reaction yields are dependent on humate/thiourea concentration ratio and reaction time. Tc-HA complex was obtained with the highest yield of 62%. Reaction mixture also contains a technetium dioxide as a side product of exchanging reaction and other technetium species, which are also discussed. Oxidation state of technetium in prepared Tc-HA complex is apparently unchanged.