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Russian Journal of Applied Chemistry, Vol. 74, No. 1, 2001, pp. 82!85. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 1,
2001, pp. 79!82.
Original Russian Text Copyright + 2001 by Plokhov, Barinova, Mikhalenko.
OF CHEMISTRY AND TECHNOLOGY
Features of Cr(III) Cation-Exchange Recovery
from Wash Water of Standard Chrome Plating
S. V. Plokhov, N. A. Barinova, and M. G. Mikhalenko
Nizhni Novgorod State Technical University, Nizhni Novgorod, Russia
Received October 25, 1999; in final form April, 2000
Abstract-Features of treatment of the standard chrome plating wash water to remove Cr(III) with KU-1
cation exchanger in the H form were considered. The optimal conditions of Cr(III) recovery and ion exchanger
regeneration were determined.
In [1, 2], a two-stage scheme of recovery and utili-
zation of the main components of the standard chrome
plating wash water was proposed. The scheme is
based on the ion exchange followed by electrochemi-
cal treatment of chromium-containing eluates. The
model and real wash waters with variable content of
metal ions (g l
) were used: chromium(VI) (in the
form of CrO
) up to 2.0, copper(II) up to
0.01, nickel(II) up to 0.01, and iron(III) up to 0.015.
Along with chromium(VI) and the above foreign
metal ions, wash water of standard chrome plating
contains Cr(III). The chromium(VI) recovery from
wash water by ion exchange was studied in [3, 4].
In this work we studied the features of Cr(III)
ion-exchange recovery from wash water of standard
chrome plating and determined its optimal parameters.
To recover Cr(III), we used a KU-1 cation ex-
changer in the H form, which was loaded into a col-
umn of 160 mm height and 18 mm inner diameter.
The ratio of the cation exchanger bed height and col-
umn diameter was 9 : 1. The average diameter of ion
exchanger grain was 2.5 10
m. Ion exchange was
studied by both dynamic (with the concentration con-
trol at the ion-exchange column outlet) and static
methods. The chromium(III) content was determined
spectrophotometrically and by atomic absorption with
SF-26 and S-115 spectrophotometers, respectively.
The error of the above methods was 1.5!2.0%.
Ion exchange involves a series of successive stages
of mass transfer over the interface controlled by hy-
drodynamic regime of the movement of the liquid
phase . Therefore, the efficiency of ion exchange
should depend on the linear velocity of the flow of
chromium-containing wash water. This is confirmed
by ion-exchange output curves at various flow veloci-
ties (Fig. 1a) and ion-exchange characteristics (dy-
namic exchange capacity DEC and capacity up to
breakthrough CB). DEC is the maximal mass of chro-
mium(III) ions retained by 1 kg of swollen ion ex-
changer under the taken dynamic conditions of water
flow. CB is the maximal mass of Cr(III) ions retained
by 1 kg of ion exchanger up to appearance of Cr(III)
in the eluate. The velocity of wash water flow U
3.25 m h
corresponds to the absence of CB and in-
significant decrease in DEC. At this and higher flow
rate, CB cannot be determined quantitatively by the
above method of analysis. Hence, only linear flow
velocities lower than 3.25 m h
are of practical in-
terest. DEC and CB (Fig. 1b) are nonlinear functions
of U: CB has a maximum at the flow velocity of
2.0 m h
, and DEC decreases with increasing U. The
flow velocity of 2.0 m
is optimal, as it corresponds
to high DEC value and maximal CB (31.6 and 10.6 g
per kg of the resin, respectively).
The analysis of the ion-exchange kinetics with
equations of diffusion kinetics suggests existence of
the limiting stage of ion exchange. It is known  that
at the metal concentration from 0.003 to 0.1 M ion
exchange proceeds under conditions of mixed kinetics.
The contribution of the internal diffusion constituent
increases with increasing metal concentration. Since
for these conditions the theory is not developed com-
pletely, to determine the limiting stage we used equa-
tions of internal diffusion kinetics for the case of sim-
plest models (sphere, cylinder, plate) , which are as
3ln(1 3 F)=Bt 3 ln A, (1)
where A and B are coefficients depending on the