1070-4272/05/7807-1064+2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 7, 2005, pp. 1064 !1066. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 7,
2005, pp. 1085!1087.
Original Russian Text Copyright + 2005 by Blinkova, Eliseev.
OF SYSTEMS AND PROCESSES
Dissolution of Calcium Carbonate in Aqueous Solutions
of Acetic Acid
E. V. Blinkova and E. I. Eliseev
Ural State Technical University, Yekaterinburg, Russia
Received July 14, 2004; in final form, February 2005
Abstract-A kinetic equation for the calcium carbonate dissolution, fitting the experimental data to within
8.1%, was obtained. The additional diffusion hindrance caused by the CO
evolution in the course of the dis-
solution was considered.
To extract zinc from slimes obtained in blast fur-
nace gas treatment, a process based on the acetate
leaching with acetic acid solutions was suggested .
The blast furnace slime contains about 6% calcium,
mainly in the form of carbonate , which is formed
by the reaction of CaO and CO
in the gas-conduit
channel of a blast furnace.
Since the slurry from the treatment of blast furnace
gases to remove dust contains calcium oxide and dis-
solved carbon dioxide, calcium carbonate is also
formed in the course of its transportation by the pipe
system. Calcium carbonate in the form of thin crystals
is deposited on the walls of the pipes and causes their
overgrowing. Therefore, the pipelines, which are rela-
tively long, get out of order from time to time. One
of the methods for overcoming this negative phe-
nomenon is the dissolution of salt crystals in a solu-
tion of acetic acid.
To choose proper conditions for this process, it is
necessary to study the calcium carbonate dissolution
in acetic acid solutions. This reaction was not com-
prehensively studied previously.
The acetate method of the calcium carbonate dis-
solution is described by the reaction
We used a 1 : 3 aqueous solution of analytically
pure acetic acid. The concentration of the CH
(HAc) solution was determined by potentiometric
titration with NaOH.
dissolution was studied by the rotating
disc method. The discs were made of white marble,
which, according to the data of the potentiometric
titration, contained 98.9% CaCO
. Samples in the
form of a cylinder (diameter 29 mm) were cut out
from a bulk mineral with a tubular cutter. The discs
were attached to an ebonite cartridge with a silicone
acryl sealant. Prior to each experiment, the disc was
trimmed with an emery paper (fineness 0.2) and flush-
mounted to the cartridge.
The dissolution conditions were varied in the fol-
lowing ranges: temperature, from 283 to 343 K,
COOH concentration in the initial solution, from
0.3 to 3.1 g dm
, and the disc rotation frequency,
from 3.6 to 18.5 Hz. The process was performed in
a beaker (inner diameter 14 cm).
The content of the dissolved substance was judged
from the content of Ca(II) in the solution. The solu-
tions were analyzed for the Ca(II) content by the
volumetric (complexometric) titration with Acid
Chrome Dark Blue indicator , using a plunger
microburet. The analytical error in determining the
Ca(II) concentration did not exceed 1.5%. The experi-
mental time was 3 h.
During the experiment, the rate of the CaCO
solution remained virtually constant and increased
with the CH
COOH concentration. The reaction order
with respect to HAc was 0.5.
The dissolution rate was a linear function of the
square root of the rotation frequency n in the fre-
quency range 3.6318.5 Hz (Fig. 1), which is one
of the essential evidences of a diffusion-controlled
One of the reasons why dissolution is diffusion-
controlled is formation of new (gas) phase . The
diffusion limitations due to CO
evolution should be