Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 5, pp. 801−804.
Pleiades Publishing, Ltd., 2009.
Original Russian Text
I.V. Goshu, Yu.V. Tsarev, V.V. Kostrov, 2009, published in Zhurnal Prikladnoi Khimii, 2009, Vol. 82, No. 5, pp. 749−752.
OF SYSTEMS AND PROCESSES
Kinetics of Chromium(VI) Adsorption
from Model Solutions on Iron Oxide
I. V. Goshu, Yu. V. Tsarev, and V. V. Kostrov
Ivanovo State University of Chemical Technology, Ivanovo, Russia
Received February 8, 2008
Abstract—Adsorption of Cr(VI) on Fe
from model solutions with various Cr(VI) concentrations was studied.
The adsorption capacity was determined, the constants of chromium(VI) adsorption on iron(III) oxide for the
pseudo-second-order model were calculated, and the diffusion coefﬁ cients for the process were evaluated.
Because of stringent requirements to the content of
Cr(VI) in industrial wastewaters , active efforts are
made to develop procedures for its removal. For example,
Chang Jun-ling et al.  examined how pH, Cr(VI)
concentration, sorption time, and dosage of activated
carbon affect the adsorption power toward Cr(VI). The
activated carbon tested in their study proved to be an
excellent sorbent which could be readily regenerated.
Channalov and Molebnov  examined the possibility
of purifying chromium-containing solutions using as
sorbents wastes from local industry (sawdust, lignin).
The treatment was performed in the static mode. To
increase the sorption capacity, the sawdust was modiﬁ ed
with alkalis or acids. It was found that modiﬁ cation
with 0.5% sulfuric acid or 0.5% sodium hydroxide was
the most efﬁ cient. The chromium concentration was
decreased in a six-step process to 0.1 mg l
. At pH 1–3,
the sorption capacity of VION anion-exchange ﬁ brous
materials studied by Zverev et al.  was higher than
that at higher pH values, which was attributed by the
authors to protonation of weakly basic groups of the
anion-exchange ﬁ bers.
In this study we examined the kinetics of Cr(VI)
adsorption on Fe
from model solutions with various
Experiments were performed with simulated waste-
water prepared by dissolving CrO
in water to obtain
chromic acid. The Cr(VI) concentration was 25–150 mg
. As adsorbent we used γ-Fe
with a bulk density
of 1.092 g cm
. Adsorption was performed under static
conditions with stirring for 60 min. The amount of Fe
(g) per 100 ml of H
solution was varied from 0.1
to 14. The size of Fe
granules was 1 mm. The content
of Cr(VI) and Cr(III) present in the simulated wastewater
simultaneously was determined photometrically .
All measurements were performed with a Spekol-211
spectrophotometer at λ = 320 nm, spectral band width
of 15 nm, ampliﬁ cation coefﬁ cient of 200, and cell
thickness of 10 mm. The solution temperature, 20°C,
was maintained with an accuracy of ±2°C using a UTU-4
thermostat. The pH of solutions was adjusted with HCl
(pH 2). The pH values of the simulated solutions were
measured with an I-130 pH meter using glass and silver
The adsorption kinetics was studied with the aim
to obtain a model of the solute adsorption. Obviously,
the adsorption depends on the time of contact of the
adsorbent with the solution. The kinetics of the Cr(VI)
adsorption on iron(III) oxide was analyzed using pseudo-
ﬁ rst- and pseudo-second-order equations [6, 7] and also
a kinetic model taking into account the diffusion inside
adsorbent grains [8, 9]. The pseudo-ﬁ rst-order equation
is as follows: