444
J SCI IND RES VOL 66 JUNE 2007
Journal of Scientific & Industrial Research
Vol. 66, June 2007, pp. 444-449
Glaserite preparation by sodium sulphate and potassium chloride
V R K S Susarla*, K M Chudasama, V P Mohandas & P K Ghosh
Central Salt & Marine Chemicals Research Institute (CSMCRI), Bhavnagar 364 002
Received 31 May 2005; revised 29 January 2007; accepted 14 March 2007
Sodium sulphate reacts with potassium chloride to give glaserite, a double salt of sodium sulphate and potassium
sulphate. Sodium sulphate present in Sambhar brines and solid bittern crust of Sambhar Salts Ltd, Nawa has been converted
to glaserite at ambient temperature. Preparation and recovery of glaserite and potassium sulphate have been discussed using
Lowenherz’s projections based on the phase equilibrium data of J H Van’t Hoff at 25 and 50°C.
Keywords: Glaserite, Lowenherz, Solid bittern, Van’t Hoff
Introduction
In India, there are no traditional deposits of
potash except seawater concentrates and some potash
containing ores (polyhalites, potassium fluorosilicates,
gluconite etc), which are not being exploited
commercially due to economic reasons. The entire
requirement of potash in the country (3-3.5 million tons)
is met by imports from Chile, Israel, Germany, USA and
Canada. India is blessed with a long coastal line and
after recovering salt, concentrated seawater, called
bittern, is processed to get valuable salts of potash via
double salts of potash namely Kainite (KCl MgSO4
3H2O) and carnallite (KCl MgCl2 6H2O)1-10. CSMCRI,
Bhavnagar has developed and patented innovative
technologies for the recovery of potash from
bittern11-14. A double salt, glaserite (Na2SO4 3K2SO4)
(Fig. 1) containing Na2SO4 and K2SO4 (1: 3), is stable
between 4-55°C and is formed as
Na2SO4 + 2KCl
K2SO4 + 2NaCl
...(1)
In the manufacture of salt from the subsoil /
underground brines of Rajasthan, containing mainly
sodium salts of chloride, sulphate, carbonate and minor
amounts of bicarbonates, the bittern left after the
recovery of salt contains appreciable amounts of Na2SO4,
which on further evaporation, leaves a solid crust (dried
*Author for correspondence
Fax: 0278 – 2567562, 2566970;
E-mail: [email protected]
conc. brine) having considerable amounts of Na2SO4
along with NaCl and insoluble mud. Experiments have
been conducted with a view of utilizing these brines and
solid bitterns to obtain glaserite, which can be directly
used as a fertilizer. In present study, preparation of
glaserite from the brines and solid bittern of Sambhar
has been discussed at length with the help of
Lowenherz’s projection of phase equilibrium data.
Experimental Details
Brine samples from Nawa and solid bittern
samples of Sambhar (Rajasthan) have been chemically
characterized (Table 1).
Reaction of Brines containing Na2SO4 with KCl to get Glaserite
Two different brines (density, 24.6°Be’, 30.2°Be’;
Na2SO4, 5.49%, 7.82%) have been reacted with varying
amounts of KCl (2, 4, 8, 11.5, 18 and 20%) to optimize
Table 1 — Analysis of brine and solid bittern (Sambhar)
Constituents
Brineo
(24.6 Be’)
% (w/v)
Brineo
(30.2 Be’)
% (w/v)
Solid
bittern
% (w/w)
NaCl
26.31
26.31
11.02
Na2SO4
5.49
7.82
63.18
Na2CO3
0.13
0.53
-
Alkalinity
-
-
11.90
Insoluble
-
-
13.91
SUSARLA et al.: GLASERITE PREPARATION BY SODIUM SULPHATE AND POTASSIUM CHLORIDE
(a)
445
(b)
(c)
Fig. 1 — System 2NaCl + K2SO4
º Na SO
+ 2KCl by Lowenherz’s method in moles/1000 moles of
2
4
water at: A) 0°C; B) 25°C; and C) 50°C
the requirement of KCl for maximum yield of glaserite.
The resultant solution and solid phases in each case were
analyzed for compositions (Table 2). These solutions
were subjected to solar evaporation for fractional
crystallization of salts. The compositions of solutions
at varying concentrations obtained during solar
evaporation are represented on the Lowenherz’s phase
equilibrium diagram at 25°C and 50°C (Fig. 2).
Reaction of Na2SO4 Present in Solid Bittern with KCl to Get
Glaserite
Solid bittern (180 g) was dissolved in water
(500 ml) and the filtrate (Table 3) after removing
insoluble impurities was made to react with KCl (97 g)
to obtain glaserite. Fig. 3 shows compositions of
solutions by point y and formation of glaserite with
different amounts of solid bitterns, i e. different
concentrations of sodium sulphate present in the system
by points z and a. Points O1, O2, 1, 2, X1-X3, I, II, and
E1-E3 (Fig. 3 A and B) shows composition of liquid phase
during progressive solar evaporation of KCl treated
bittern solutions. Further, five different sets of
experiments (a-e) were carried out by evaporating
solutions with different concentrations of solid bittern
to optimize the parameters for glaserite formation
(Table 3). Solid phase in contact with the initial solutions
(a)
(b)
Fig. 2 — Composition of solutions obtained by reaction of KCl
with Sambhar brines in the system 2NaCl + K2SO4
Na2SO4
+ 2KCl by Lowenherz’s method in moles/1000 moles of water at:
A) 25°C; and B) 50°C
º
446
J SCI IND RES VOL 66 JUNE 2007
Table 2 — Composition of solutions
%
KCl
added
Constituents
2
NaCl
Na2 SO4
KCl
K2 SO4
NaCl
Na2 SO4
KCl
K2 SO4
NaCl
Na2 SO4
KCl
K2 SO4
NaCl
Na2 SO4
KCl
K2 SO4
NaCl
Na2 SO4
KCl
K2 SO4
NaCl
Na2 SO4
KCl
K2 SO4
NaCl
Na2 SO4
KCl
K2 SO4
NaCl
Na2 SO4
KCl
K2 SO4
NaCl
Na2 SO4
KCl
K2 SO4
NaCl
Na2 SO4
KCl
K2 SO4
NaCl
Na2 SO4
KCl
K2 SO4
NaCl
Na2 SO4
KCl
K2 SO4
NaCl
Na2 SO4
KCl
K2 SO4
2
2
4
4
8
8
8
11.5
11.5
18
18
20
Solution
g /100ml
Composition
Solution
g /100g
H2O
g /100g
Solid phase
18.749
9.542
11.875
—
26.890
13.910
9.800
—
30.398
1.706
3.240
—
24.000
10.664
5.160
—
24.710
9.459
2.780
—
17.900
7.123
9.150
—
22.120
9.850
6.080
—
18.000
—
6.854
5.904
28.820
1.937
0.630
14.950
23.287
6.325
6.825
9.010
22.215
2.764
14.429
1.834
27.030
6.033
5.031
—
32.000
4.386
0.195
20.802
14.782
7.523
9.360
—
21.220
10.590
7.730
—
23.810
1.336
2.540
—
18.850
8.376
4.050
—
20.270
7.761
2.281
—
13.980
5.638
7.150
—
17.43
7.750
4.790
—
13.824
—
5.241
4.534
22.620
1.520
0.495
11.740
18.320
4.980
5.370
7.090
17.342
11.264
2.158
1.431
20.990
4.685
3.907
—
25.437
3.486
0.155
16.535
20.042
10.199
12.691
—
35.100
17.520
12.790
—
32.930
1.848
3.510
—
28.390
12.623
6.100
—
29.090
11.140
3.270
—
24.660
9.945
12.620
—
24.889
11.070
6.840
—
18.094
—
6.859
5.934
35.550
2.388
0.780
18.450
28.520
3.920
8.360
11.040
25.575
16.612
3.182
2.116
29.809
6.653
5.548
—
46.771
6.411
0.285
30.405
H2O
moles /1000 moles
Na2Cl2
Na2 SO4
K2Cl2
K2 SO4
Na2Cl2
Na2 SO4
K2Cl2
K2 SO4
Na2Cl2
Na2 SO4
K2Cl2
K2 SO4
Na2Cl2
Na2 SO4
K2Cl2
K2 SO4
Na2Cl2
Na2 SO4
K2Cl2
K2 SO4
Na2Cl2
Na2 SO4
K2Cl2
K2 SO4
Na2Cl2
Na2 SO4
K2Cl2
K2 SO4
Na2Cl2
Na2 SO4
K2Cl2
K2 SO4
Na2Cl2
Na2 SO4
K2Cl2
K2 SO4
Na2Cl2
Na2 SO4
K2Cl2
K2 SO4
Na2Cl2
Na2 SO4
K2Cl2
K2 SO4
Na2Cl2
Na2 SO4
K2Cl2
K2 SO4
Na2Cl2
Na2 SO4
K2Cl2
K2 SO4
30.855
12.930
15.311
—
54.036
22.210
15.440
—
50.690
4.330
4.240
—
43.710
16.000
7.359
—
44.790
14.120
3.950
—
37.965
12.610
15.229
—
38.320
14.030
8.250
—
27.856
8.281
6.132
54.730
3.027
0.940
19.060
43.910
4.970
10.090
11.410
39.374
4.033
20.055
2.181
45.892
8.434
6.697
—
72.010
8.127
0.345
31.420
NaCl
NaCl + Na2SO4 & KCl.
NaCl + Na2SO4 & KCl
NaCl + Na2SO4
NaCl + Na2SO4 &
traces of KCl
NaCl + Na2SO4 &
traces of KCl
NaCl + Na2SO4 &
traces of KCl
NaCl + Na2SO4 & KCl
NaCl + Na2SO4 & KCl
NaCl + Na2SO4 + KCl
NaCl + Na2SO4 & KCl
NaCl + Na2SO4 & KCl
NaCl + Na2SO4 & KCl
Table 3 -
Reaction
components
Composition of solutions obtained by reaction of KCl with Na,SO, present in dissolved solid bittern
Point
Constituents
Solution
g/l OOml
Composition of the solution phase in
H,O
H,O
Solution
Moles/l 000 moles
g/l OOg
g/l OOg
NaCI
Na,SO,
KCI
K,SO,
17.53
4.68
0.29
5.97
14.63
3.91
0.24
4.98
19.18
5.12
0.31
6.53
Na,Cl,
Na,SO,
K,Cl,
K,SO,
NaCI
Na,SO,
KCI
K,SO,
6.64
5.82
19.09
5.29
4.65
15.25
7.08
6.22
20.38
Na,Cl,
Na,SO,
K,Cl,
K,SO,
10.90
6.42
24.46
Glaserite +
NaCI
NaCI
Na,SO,
KCI
K,SO,
23.07
5.01
8.00
18.14
3.93
6.29
25.32
5.49
8.76
Na,Cl, .
Na,SO,
K,Cl,
K,SO,
38.99
5.68
10.59
Glaserite +
NaCI
(a) First set of experiments
IOOg solid
NaCI
Na,SO,
bittern +
500ml H,O +
0,
KCI
105g KCI
K,SO,
2.22
12.60
9.70
1.85
10.53
8.10
2.55
14.52
11.17
Na,Cl,
Na,SO,
K,Cl,
K,SO,
3.93
18.41
13.49
NaCI
Na,SO,
KCI
K,SO,
7.51
9.12
4.00
9.21
6.37
7.75
3.39
7.82
8.54
10.38
4.55
10.47
Na,Cl,
Na,SO,
K,Cl,
K,SO,
1314
13.15
5.49
10.82
(b) Second set of experiments
250g solid
NaCI
bittern +
Na,SO,
1000mi 1-1,0 +
KCI
80g KCI
K,SO,
23.64
6.50
4.13
3.57
18.38
5.06
3.22
2.78
26.05
7.17
4.06
3.94
Na,Cl,
Na,SO,
K,Cl,
K,SO,
40.10
9.09
5.50
407
Evaporation of
above solutions
at room
temperature.
NaCI
Na,SO,
KCl
K,SO,
24.70
3.99
4.87
5.28
19.84
3.21
3.92
424
28.84
4.67
5.69
6.17
Na,Cl,
Na,SO,
K,Cl,
K,SO,
44.10
5.92
6.87
638
(c) Third set of experimcnts
100g solid
NaCI
bittern+240ml
X,
Na,SO,
II,O+45g KCI
KCI
K,SO,
15.79
10.70
106
12.54
8.49
8.42
17.78
12.06
11.95
Na,CI,
Na,SO,
K,Cl,
K,SO,
27.37
15.28
14.43
G1aserite+
NaCI
NaCI
Na,SO,
KCI
K,SO,
1.60
10.29
19.73
1.28
8.20
15.73
1.71
10.97
21.03
Na,Cl,
Na,SO,
K,Cl,
K,SO,
263
13.90
25.39
Glaserite+
NaCI
NaCI
Na,SO,
KCI
K,SO,
9.80
9.80
3.01
3.51
7.79
7.79
2.39
2.79
9.83
9.83
3.02
3.52
Na,Cl,
a,S04
K,Cl,
K,SO,
15.08
12.46
3.64
3.64
Glaserite+
a,S04+
NaCI
traccs
180g solid
bittern + 500ml
H,O + 97 g
KCI
216g solid
bittern + 500ml
1-1,0 + 150g
KCI
500g solid
bittern +
1135ml H,O +
350g KCI
500ml solution
from Point I
+ 500ml water
+ IOOgsolid
bittern + 51g
KCI
°
y
z
a
0,
2
On evaporation
of above
solution
X,
Continuation
of evaporation
X3
,
29.53
6.49
0.38
6.75
Solid
phase
Glaserite +
traces of
NaCI
NaCI+
KCI
NaCI+
K,SO,
NaCI
. +Na,SO, +
Glaserite
aCI+
K,SO, +
traccs of
KCI
...... Contd.
448
......Contd.
J SCI IND RES VOL 66 JUNE 2007
Table 3 — Composition of solutions obtained by reaction of KCl with Na2SO4 present in dissolved solid bittern (Contd.)
(d) Fourth set of experiments
Constituents
Reaction
Point
components
170g solid
bittern + 500
ml H2 O +
87.50 g KCl
Solution
g/100ml
Composition of the solution phase in
Solution
H2O
H2O
g/100g
g/100g
Moles/1000 moles
Solid phase
NaCl
Na2SO4
KCl
K2 SO4
16.26
0.89
0.07
12.95
13.58
0.74
0.06
10.82
18.16
0.99
0.08
14.46
Na2Cl2
Na2SO4
K2 Cl2
K2 SO4
27.95
1.26
0.09
14.95
NaCl
Na2SO4
KCl
K2 SO4
15.18
19.69
3.60
-
12.08
15.66
2.86
-
17.39
22.56
4.12
-
Na2Cl2
Na2SO4
K2 Cl2
K2 SO4
26.78
28.59
4.97
-
(e) Fifth set of experiments
NaCl
300g of solid
Na2SO4
bittern+1000ml
E1
KCl
H2O+200g KCl
K2 SO4
7.25
4.81
14.31
0.81
6.09
4.04
12.03
0.68
7.90
5.24
15.59
0.88
Na2Cl2
Na2SO4
K2 Cl2
K2 SO4
12.16
6.64
18.82
0.91
Glaserite+
traces of
NaCl
NaCl
Na2SO4
KCl
K2 SO4
11.52
14.60
3.73
9.44
11.96
3.05
12.49
15.83
4.04
Na2Cl2
Na2SO4
K2 Cl2
K2 SO4
19.23
10.62
4.17
K2SO4+
NaCl+
KCl
NaCl
Na2SO4
KCl
K2 SO4
25.83
2.89
8.40
-
21.14
2.37
6.87
-
30.35
3.41
9.87
-
Na2Cl2
Na2SO4
K2 Cl2
K2 SO4
46.73
4.32
11.92
-
KCl+
Na2 SO4
+ traces of
NaCl
Continuation
of evaporation
On evaporation
of the above
solution
Continuation
of evaporation
I
II
E2
E3
Glaserite +
traces of
NaCl
Glaserite+
NaCl traces
Fig. 3 — Composition of solutions obtained when solid bittern is treated with KCl in the system 2NaCl +
K2SO4
Na2SO4 + 2 KCl by Lowenherz’s method in moles/1000 moles of water at:
A) 25°C; and B) 50°C
º
immediately after the reaction in most of the cases is
mainly glaserite with little amounts of NaCl, but
evaporation at ambient temperature gave rise to glaserite
along with NaCl, KCl, K2SO4 or a mixture of two or
three salts.
Methods
In all the cases, sulphate was estimated as barium
sulphate by gravimetry, chloride by volumetric method
(Mohr’s method), KCl and NaCl by flame photometeric
method and alkalinity by titration with 0.1N HCl
solutions. KCl is of reagent grade (99.8% purity). The
error in results is about ± 0.1-0.2%.
Results and Discussion
Phase equilibrium diagram of reciprocal saltpair system (Eq. 1) at 0, 25 and 50°C (Fig. 1) indicates
that as the temperature increases, formation of double
present tn them with KCl to obtain glaserite
suggesting
a simple method for the preparation
glaserite (Fig. 4).
for
of
Conclusions
NaCl+K2SO.
Glaserite (NazSO • .3KzSO.)
Fillcred for rCaJvelYof polash in the form
of POlassiumSulphate and glaserite
Sodium sulphate present in brines and solid
bitterns can be processed to glaserite, a valuable fertilizer
product by its reaction with KCl under optimized
conditions. A simple method for recovery of glaserite
from solid bitterns
of Sambhar
lake (Rajasthan)
containing sodium sulphate has been worked out.
Acknowledgements
Authors thank Director, CSMCRI, Bhavnagar
for permitting to publish the results and Mis Sambhar
Salts Ltd, Sambhar for supplying brine and solid bittern
samples.
References
1
RecovelY of potash in the form of double
salt glaselile and polassiwll sulphates
2
3
sal t, glaserite, increases and the area occu pied by it in
the phase diagram is qui te large. In case of the solutions
obtained by treating the brines (24.6°and 30.2°Be') with
varying amounts of KCI at 25° (Fig. 2A) and 50°C
(Fig. 2B), even though, most of them fall in the glaserite
field, solid phases in contact with them did not show
appreciable
amounts of glaserite formation.
Further,
continued solar evaporation of these solutions, in most
of the cases, gave rise to the deposition of individual
salts (NaCl, NaZS04 and KCI) or their mixtures.
On the other hand, composition
of solutions
obtained at 25° (Fig. 3A) and 50°C (Fig. 3B) fall in
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of the sulphate ion 7 should be more than
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have been
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dissolving
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