1070-4272/03/7609-1489$25.00C2003 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 76, No. 9, 2003, pp. 1489!1493. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 9,
2003, pp. 1528!1532.
Original Russian Text Copyright C 2003 by Vashurina, Pogorelova, Kalinnikov.
AND INDUSTRIAL ORGANIC CHEMISTRY
Effect of Humic Acids on the State of Disperse, Acid,
and Vat Dyes in Aqueous Solutions
Yu. S. Vashurina, A. S. Pogorelova, and Yu. A. Kalinnikov
Institute of Chemistry of Solutions, Russian Academy of Sciences, Ivanovo, Russia
Received May 22, 2003
Abstract-Effect of humic acids (biopolymeric compounds of anionic type recovered from peat) on the state
of disperse, acid, and vat dyes in aqueous solutions was studied; vat dye was studied in the form of water-
soluble sodium salt of leuco acid.
The adsorption and diffusion processes occurring in
aqueous solutions of organic dyes  in the course of
textile dyeing can be controlled by addition of various
synthetic textile-processing chemicals, which are
environmentally hazardous and fairly expensive .
Hence, search for new readily available and environ-
mentally safe compounds to improve the dyeing proc-
ess is urgent.
As such compounds, we studied humic acids, bio-
polymeric compounds of irregular structure, which
contain various functional groups  and can react
with both hydrophilic [43 6] and hydrophobic 
organic compounds. Humic acids are human safe and
are already used as broad-spectrum medical products
[12, 13]. The effect exerted by a humic sample re-
covered from peat of deep degradation  on the
state of three organic dyes of different classes was
studied by spectroscopy.
In our work we used the following dyes: Disperse
Red 2S (1-hydroxy-4-amino anthraquinone), Acid
Green Anthraquinone N2S (sulfonated 1,4-dibutyl-
phenylaminoanthraquinone), and Vat Goldish-Yellow
KKh (brominated dibenzopyrenoquinone). The dyes
were preliminarily treated to spectral purity by known
procedures . The humic preparation was used
as an aqueous solution with pH 8.4; under these con-
ditions, humic acids behave as anionic polyelectrolytes
[18, 19], whose total charge is determined by com-
plete dissociation of carboxy groups and partial dis-
sociation of phenolic hydroxy groups. The content
of carboxy and hydroxy groups in peat humic acids is
2.5033.65 and 3.33 4.2 mg-equiv g
, respectively [3,
20322]. The measurements were carried out at 20oC.
Since humic acids can affect dyes in both truly dis-
solved (I) and associated (II) form, we studied the
disperse and acid dyes at two concentrations of humic
acid. At the first, relatively low concentration c
the dyes occur in solution in the monomeric form;
at this concentration, the Lambert3Bouguer3Beer law
is obeyed. At the second, relatively high concentration
, significant deviations from the above law are
observed, which suggests association of dyes. The vat
dye, which was dissolved using large amounts of elec-
(reducing agent) and NaOH], occurs
in the above solutions in the associated form.
The experimental dependences of the position of
the long-wave absorption maximum in the spectrum
of Disperse Red 2S on the concentration of humic
in solution for both forms I and II are shown
in Fig. 1a.
As seen, associates of 1-hydroxy-4-aminoanthra-
quinone, appearing in water in the absence of any
additives with increasing its concentration by a factor
of 35, slightly shift l
to longer waves by 132 nm.
This effect of the dye association is well known and is
predicted by physicomathematical simulation. It is
known that the main shift of the absorption peak
occurs upon formation of dimers, and it remains vir-
tually constant with subsequent coarsening of the
On adding humic acids into a disperse dye solu-
tion, the bathochromic shift of l
reaches 539 nm,
which suggests interaction between the dye and addi-
tive. Moreover, the difference in l
of the mono-
meric I and associated II forms of the disperse dye
in the presence of the biopolymeric compound shows
that both forms of the dye-nonelectrolyte can interact
with humic acids.