Utilization of distiller waste and residual mother liquor
to prepare precipitated calcium carbonate
Canzhu Gao
*
, Yuan Dong, Hongjuan Zhang, Jiaming Zhang
School of Environment Science and Engineering, Shandong University, 27 Shanda Nanlu, 250100 Jinan, Shandong Province, PR China
Received 12 January 2005; accepted 17 June 2006
Available online 9 November 2006
Abstract
The purpose of this research is to examine the utilization of basic waste of soda ash industry: distiller waste. The aim of the process described
is to obtain spherical ultrafine calcium carbonate by means of calcium ions contained in distiller waste liquid. Another raw material is residual
mother liquor, a filtration liquid which is created after the process of carbonization and filtration in the Solvay towers. The process of calcium
carbonate precipitation is based on calcium ions contained in distiller waste liquid and carbonate ions contained in residual mother liquor.
ðNH
4
Þ
2
CO
3
þ CaCl
2
/ CaCO
3
Y þ 2NH
4
Cl
Results of research have shown that the production of spherical ultrafine calcium carbonate based on soda ash waste materials is possible. The
new products achieve the standards necessary for filler of rubber, paint and pigment industries. The additional advantage of the described method
is not only obtaining spherical ultrafine calcium carbonate precipitation, but also reducing waste dangerous for the natural environment: distiller
waste and caustic sludges. Soda ash factories may also benefit from the introduction of the technology (sale of spherical ultrafine calcium car-
bonate, release from environment pollution fees).
Ó 2006 Published by Elsevier Ltd.
Keywords: Soda ash industry; Waste utilization; Distiller waste; Residual mother liquor; Precipitated calcium carbonate; Clean technology
1. Introduction
The standard ammonia-soda process (the Solvay method) is
shown in Fig. 1, which is based on the chemistry reaction
given below [1,2]:
NaCl NH
3
H
2
O CO
2
NH
4
Cl NaHCO
3
NaHCO
3
Na
2
CO
3
H
2
O CO
2
CaCO
3
CaO CO
2
CaO H
2
O Ca(OH)
2
2NH
4
Cl Ca(OH)
2
2NH
3
CaCl
2
2H
2
O
The first step in the standard ammonia-soda process is the
preparation of purified brine. Sodium chloride solution is
obtained by solution mining of salt deposits, which gives
a raw, near-saturated brine. On site, brine has to be purified
to remove calcium and magnesium ions by treatment with
a milk of lime and soda ash solution. The reaction leads to
a purified brine and suspension, which mainly contains
CaCO
3
and Mg(OH)
2
. Then, purified brine is divided and di-
rected into the soda process.
A disadvantage in the process is the production of distiller
waste and caustic sludges (the circles indicating in Fig. 1).
In the Solvay process, the ammonia brine is carbonated in
steel towers (Solvay towers). The process of carbonation leads
to bicarbonate (NaHCO
3
) sediment and residual mother liquor
of unprocessed NaCl (the efficiency of carbonation is only
about 70%), NH
4
Cl and (NH
4
)
2
CO
3
. After filtration, the fil-
tration liquid (residual mother liquor) is distilled with the ad-
dition of lime obtained in the process of limestone burning in
* Corresponding author. Tel./fax: þ86 53188365296.
E-mail address: gaocz@sdu.edu.cn (C. Gao).
0959-6526/$ - see front matter Ó 2006 Published by Elsevier Ltd.
doi:10.1016/j.jclepro.2006.06.024
Journal of Cleaner Production 15 (2007) 1419e1425
www.elsevier.com/locate/jclepro