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'rH~ S'W0LS ON IONIC "LJILIB'U" FOR n:pi{O\f"I~ .id D{ ,i.];,LIrI 0" ,:i"Lf [<,HOH mI ..... ;~j) 3Rn~i~
49
In our country, a regular large scale proQuction
of salt from sub soil brines is carried out in two states
viz. lZujarat andfamil i.adu. .Ju" to difference in the
~lemical composition of sub suil orines to tnat of sea
brine, the -l,uality of salt ootained from these brines is
inferior to that obtained from sea brine. '£0 modify the
existing method of production or to develop a new method,
it was first of all necessary to obtain data on variations
in th8 chemical composition of sub soil brines from diffe
rent locations in both the states. It was also necessary
to obtain data on composition, volume reductionl1u~ntities
obtain0.d of lifferent fractions during pro~ressive solar
evaporation of brines from different locations in these
states.
In view of this, about 35 sub soil brine samples
were collected from uifferent bore wells of Ahara~loda
»uua ",rea (.L..ittle Harm of .\outcn) of lZujarat .>tate.
uimilarly 20 suo soil orine samples were collected from
l.lJ:laruch area of lZujarat state. Jl.oout 50 sub soil brine
samples were collected fromruticorin area of ramil l'adu
state. Number of brine samples in different areas was
fixed by the number of salt manufacturing units in the
particular area.
r This Chapter is divided into thr3e different
sections. rha section 2.1 deals with the cllemical ana-
lysis of tne sub soil brine samples and the discussion
based on their results.l'he section 2.2 comprises of
the stu:lies on progressive solar evaporation of these
brines. fhe section 2.3 reports tile results on the
effect of increase in sulphate ion conc~ntration in the
brine on cry8tallization of calcium sulphate for improv
ing the ~uality of salt from sub soil brines.
The ions required to be determined were sodium,
potassium, magnesium, calcium/chloride and sulphate; as
the inVestigation is basically related to marine salts.
The procedures adopted were the same as described in the
literature. Chloride ions ~,ere determined by Mohr's
classifal volumetric method using standard silver nitrate
solution and potassium chromate as an indicator135•
Calcium and magnesium ions were estimated complexomctri
cally by ethylcndiamine tetra acetic acid (...:.JJfJ>.) using
~rio-ctlrome rllack-r and ~Qtton and rl~aders indicators136 •
.:io.:dum and potassium ions 137 in the orine samples were
directly determined by simple flame pnotometric method
using the standard solLltion of sodium and potassium ions
. with internal calibration. .:icllphate ions were analysed
by gravimetric method as barium sulphate ~ecipitation
method135• The pH and specific gravity values were also
50
I ,
65S00
(letermined by tile known metnou.. rIlrougllout t;he course
of chis investiJation, the chemical analysis of solid
samples as well as liqUid samples have been carried out
on wet basic and represented as grams per 100 gms of
substances or grams per 100 ml liquid samples respec
tively. dhere it is necessary for sake of comparison,
the values of wet analysis are conv~rted to dry basis
by calculation.
2.1 The ch,rnical analysis of sub soil brine samples of different areas:
"s mentioned in tne foregoing para, first of
51
all the pli and specific gravity values of the brine samples
were (letermined at rOOm temperature. rhereafter the che
mical an",lysis of tll,; brine samples were carried out. rhe
ionic analysis as well as tne ,:>rooable cnemical compositions
of eaCh orine sample of LUlaraiSlloda-!\.uda, ilharuch andruti
corin areas are given density wise in the tables 6, 7 and 8.
~'or c.:omparison, the compositions of sea brine samples at
different densities are also given in table 9.
'RESUT,TS -------
The analytical results of th~ sub soil brine
samples collected from Kharaghoda-Kuda area are compiled
and presented in the table 6. It is ''lvident from the
Table - 6:
Sr. Consti-No. tuents
% w/v
1 Sp. Gr.
2 aBe'
3 pH
1 Ca
2 S04 3 Mg
4 Cl
1 caS04 2 NaCl
3 MgS04 4 MgC12 5 KCl
6 CaC12 .
--,--
Analysis of sub soil brine samples collected from Kharaghoda-Kuda area (Little Rann of Kutch, Gujarat)
BRINE SAMPLE NUMBERS
1 2 3 4 5 6 7 8
1.126 1.137 1.137 1.137 1.139 1.140 1.140 1.142
16.3 17.5 17.5 17.5 17.7 17.8 17.8 18.0
7.2 7.2 7.3 7.4 7.4 . 7.3 7.3 7.2
IONIC COMPOSITIONS
0.11 0.20 0.15 0.23 0.26 0.28 0.15 0.24
0.76 0.48 0.48 0.43 0.39 0.36 0.88 0.40
0.90 0.75 0.68 0.77 0.81 0.77 0.75 0.77
11.80 12.70 12.45 13.20 13.40 13.20 14.10 13.33
THE PROBABLE CHEMICAL COMPOSITIONS
0.36 0.67 0.63 0.62 0.55 0.51 0.49 0.57
15.80 17.20 17.40 . 17.40 17.80 17.80 20.20 17.85
0.65 0.08 0.03 0.67
3.00 2.93 2.70 3.03 3.20 3.00 2.40 3.00
0.35 0.31 0.33 0.34 0.38 0.36 0.38 0.33
0.14 0.27 0.35 0.20
9 10
1.142 1.142
18.0 18.0
7.3 8.3
0.10 0.18
0.34 0.51 • 0.96 0.83
13.30 13.20
0.33 0.62
19.20 17.93
0.10 0.10
3.52 3.10
0.37 0.38
11
1.142
18.0
7.4
0.25
0.41
0.82
13.55
0.58
18.10
3.20
0.32
0.22
12
1.142
18.0
7.2
0.18
0.57
0.86
12.40
0.61
16.55
0.20
3.20
0.33
f
c.., N
Table - 6: (Contd ...... )
Sr. Consti- BRINE SAMPLE NUMBERS No. tuents 13 14 15 16 17 18 19 20
% w/v
1 Sp. Gr. 1.142 1.143 1.144 1.145 1.145 1.146 1.149 1.149
2 aBe' 18.0 18.1 18.3 18.4 18.4 18.6 18.8 18.8
3 pH 7.2 7.2 7.3 7.3 7.3 7.2 7.3 7.4
IONIC COMPOSITIONS
1 Ca 0.20 0.23 0.24 0.20 0.25 0.11 0.14 0.26
2 S04 0.49 0.45 0.38 0.48 0.40 0.70 0.55 0.35
3 Mg 0.70 0.73 0.81 0.77 0.84 0.87 0.92 0.90
4 Cl 12.70 13.23 13.55 13.40 14.00 13.70 14.03 14.20
THE PROBABLE CHEMICAL COMPOSITIONS
1 CaS04 0.68 0.64 0.53 0.68 0.56 0.37 0.48 0.50
2 NaCl 17.44 18.30 17.90 18.10 18.80 18.90 19.00 .18.75
3 MgS04 .. 0.53 0.26
4 MgC12 2.75 2.90 3.20 3.10 3.30 2.90 3.35 3.50
5 KCl 0.32 0.30 0.33 0.38 0.32 0.39 0.39 0.34
6 CaC12 0.12 0.24 0.24 0.31
21 22
1.149 1.149
18.8 18.8
7.4 7.1
0.25 0.25
0.3'9 0.40
0.88 0.78
14.40 13.90
0.55 0.57
19.00 19.10
3.44 3.10
0.37 0.34
0.24 0.22
23
1.152
19.1
7.2
0.15
0.59
0.91
13.80
0.52
18.70.
0.30
3.33
0.39
24
1.152
19.1
7.7
0.14
0.60
1. 50
13.60
0.50
15.70
0.29
5.50
0.34
CJ1 W
L
Table - 6:
Sr. Can"! i .. No. tuents
% w/v
1 Sp. Gr.
2 °Be'
3 pH
1 Ca
2 S04 3 Mg
4 Cl
1 CaS04 2 NaCl
3 MgS04 4 MgCl2 5 KCl
6 CaCl2
(Contd ....... )
25 26
1.154 1.154
19.4 19.4
7.4 7.9
0.21 0.11
0.82 0.67
0.91 1.02
13.50 13.20
0.70 0.37
18.30 17.40
0.40 0.50
3.25 3.60
0.34 0.33
,-- ~
BRINE SAMPLE NUMBERS
27 28 29 30 31 32 33 34 35
1.154 1.155 1.155 1.155 1.155 1.155 1.155 1.157 1.157
19.4 19.5 19.5 19.5 19.5 19.5 19.5 19.7 19.7
7.6 7.7 7.6 7.2 7.6 7.3 7.4 7.2 7.2
IONIC COMPOSITIONS·
0.12 0.11 0.17 0.11 0.21 0.25 0.11 0.21 0.26
0.78 0.61 0.57 0.70 0.40 0.38 n.71 0.42 0.38
1.10 1.05 0.99 0.97 0.91 0.88 1.03 0.92 0.94
13.41 13.80 14.20 14.03 13.70 13.63 13.85 13.70 14.20
THE PROBABLE CHEMICAL COMPOSITIONS
0.40 0.37 0.58 0.37 0.57 0.54 0.37 0.60 0.51
17.52 18.10 18.80 ·19.00 18.00 18.10 18.25 17.90 18.92
0.63 0.44 0.21 0.56 0.55
3.70 3.72 3.72 3.40 3.60 3.45 3.92 3.60 3.70
0.38 ·0.42 0.40 0.41 0.38 0.38 0.43 0.33 0.32
0.12 0.23 0.08 0.29
C .. " ......
Table - 7: Analysis of sub soil brine samples collected from Bharuch area (Gujarat)
Sr. Consti-BRINE SAMPLE NUMBERS
No. tuents 1 2 3 4 5 6 7 8 % w/v
1 Sp. Gr. 1.040 1.044 1.044 1.048 1.049 1.050 1.050 1.055
2 aBe' 5.3 6.0 6.0 6.Z 6.3 6.9 6.9 7.6
3 pH 7.4 7.6 7.3 7.3 7.Z 7.2 7.4 7.2
IONIC CmlPOSITIONS
1 Ca 0.07 0.10 0.09 0.09 0.09 0.08 0.11 0.12
2 S04 0.38 0.40 0.42 0.44 0.44 0.49 0.55 8.46
3 Mg 0.21 0.Z3 0.35 0.21 0.24 0.24 0.26 0.38
4 Cl 3.00 3.42 3.45 3.50 3.60 4.00 4.10 4.30
THE PROBABLE CHE~IICAL COMPOSITIONS
1 CaS04 0.24 0.34 0.30 0.29 0.31 0.29 0.36 0.40
2 KaCl 4.10 4.75 4.38 5.00 5.10 5.55 5.70 6.10
3 ~lgS04 0.28 0.20 0.27 0.Z8 0.30 0.34 0.37 0.25
4 MgC12 0.66 0.77 1.17 0.60 0.70 0.67 0.74 1.00
5 KCl 0.08 0.12 0.11 0.15 0.13 0.14 0.14 0.13
6 CaCI Z
9
1.056
7.8
7.6
0.14
0.46
0.30
4.55
0.46
6.25
0.20
1.00
0.13
10
1.056
7.8
7.2
0.11
0.55
0.36
4.55
0.37
6.15
0.36
1.20
0.15
..
c..n CJl
Table - 7: (Contd ....... )
Sr. Consti-No. tuents 11 % w/v
1 Sp. Gr. 1.058
2. aBe' 8.0
3 pH 7.2
1 Ca 0.10
2 S04 0.50
3 Mg 0.30
4 Cl 4.50
1 caS04 0.32
2 NaCl 6.10
3 MgS04 0.31
4 MgCl2 0.94
5 KCl 0.16
6 CaCl 2
---,--
BRINE SAMPLE NUMBERS
12 13 14 15 16 17
1.060 1.060 1.062 1.065 1.067 1.069
8.3 8.3 8.5 9.1 9.2 9.4
7.1 7.2 7.5 7.2 7.5 7.6
IONIC COMPOSITIONS
0.11 0.10 0.13 0.13 0.12 0.17
0.52 0.60 0.53 0.78 0.66 0.48
0.32 0.30 0.32 0.39 0.42 0.34
4.85 4.15 5.00 5.32 5.34 5.70
THE PROBABLE CHEMICAL COMPOSITIONS
0.39 0.34 . 0.43 0.46 0.40 0.59
6.75 6.00 7.00 7.40 7.22 7.73
0.36 0.45 0.30 0.57 0.48 0.08
1.00 0.83 1.00 1.05 1.25 1.25
0.16 0.18 0.16 0.19 0.19 0.20
18 19
1.070 1.074
9.5 10.0
7.4 7.2
0.12 0.12
C.79 0.66
0.41 0.37
5.53 6.00
0.40 0.40
7.18 8.55
0.73 0.48
0.75 1.10
0.21 0.24
20
1.074
10.0
7.2
0.13
0.68
0.42
6.10
0.46
8.40
0.44
1.30
0.20
f
Ul 0')
Table - 8: Analysis of sub soil brine samples collected from Tuticorin Area (Tamil Nadu)
Sr. Consti~ BRINE SAMPLE NUMBERS No. tuents 1 2 3 4 5 6 7 8 9 % w/v
1 Sp. Gr. 1.037 1.037 1.040 1.040 1.046 1.050 1.052 1.055 1.056
2 aBe' 5·.2 5.2 5.5 5.5 6.3 7.0 7.2 7.5 7.7
3 pH 8.0 7.5 7.6 8.1 7.9 7.3 7.9 7.6 7.9
IONIC COMPOSITIONS
1 Ca 0.19 0.13 0.13 0.10 0.06 0.10 0.18 0.08 0.14 •
2 S04 0.58 0.47 0.44 0.48 0.47 0.53 0.52 0.66 0.74
3 Mg 0.34 0.26 0.31 0.46 0.27 0.28 0.41 0.33 0.53
4 Cl 2.90 2.95 2.80 3.10 3.45 3.20 4.10 4.20 4.25
THE PROBABLE CHE~lICAL COMPOSITIONS
1 CaS04 0.64 0.44 0.43· 0.36 0.19 0.34 0.61 0.28 0.49
2 NaCl 3.30 3.80 3.30 3.30 4.70 4.80 4.95 5.80 4.95
3 MgS04 0.17 0.20 0.18 0.28 0.42 0.36 0.18 0.58 0.50
4 MgC12 1.20 0.83 1.10 1. 60 0.71 0.88 1.45 0.84 1. 70
5 KCl 0.09 0.10 0.09 0.10 0.13 0.13 0.12 0.14 0.16
6. caC12
10
1.060
8.2
7.9
0.17
0.53
0.63
4.50
0.58
4.80
0.16
2.30
0.16
,.
UI -J
Table - 8: (Contd ...... j
Sr. Consti-No. tuents 11
% w/v
1 Sp. Gr. 1.060
2 aBe' 8.2
3 pH 7.7
1 Ca 0.19
2 S04 0.54
3 Mg 0.61
4 Cl 4.45
1 caS04 0.64
2 NaCl 4.58
3 MgS04 0.11
4 MgC12 2.32
5 KCl 0.10 6 CaCl?
-- - ----- -
BRINE SAMPLE NUMBERS 12 13 14 15 16 17
1.060 1.061 1.061 1.065 1.066 1.068
8.2 8.3 8.3 8.8 9.0 9.2
7.3 7.5 7.7 7.7 7.8 7.6
IONIC COMPOSITIONS
0.23 0.12 0.19 0.19 0.26 0.19
0.47 0.52 0.56 0.66 0.60 0.66
0.54 0.33 0.61 0.74 0.65 1.10
4.55 4.80 4.80 5.20 5.31 5.50
THE PROBABLE CHEMICAL COMPOSITIONS
0.78 0.42 0.64 0.64 0.88 0.64
4.95 5.10 4.95 5.40 5.70 4.1
0.10 0.28 0.14 0.26 0.26
2.05 1.20 2.35 2.70 2.50 4.1
0.10 . 0.17 0.13 0.13 0.10 0.16
18 19 -
1.068 1.070
9.2 9.5
7.4 7.9
0.12 0.10 ·0.78 0.71
0.44 0.41
5.25 5.70
0.41 0.34
7.00 7.62
0.62 0.60
1.20 1.40
0.19 0.13
---,---------------------
20
1.070
9.5
7.4
0.13
0.77
0.35
5.38
0.45
7.30
0.55
1.10
0.18
UI 00
----r
Table - 8: (Contd ........ )
Sr. Consti- BRINE SAMPLE NUMBERS No. tuents . 21 22 23 24 25 26 27 % w/v
1 Sp. Gr. 1.070 1.074 1.074 1.075 1.076 1.076 1.077
2 0B I e . 9.5 10.0 10.0 10.1 10:3 10.3 10.4
3 pH 7.9 7.9 7.3 7.6 7.6 7.3 7.5
IONIC COMPOSITIONS
1 Ca 0.22 0.08 0.31 0.26 0.24 0.14 0.09
2 S04 0.63 0.66 0.58 0.72 0.70 0.82 0.67
3 Mg 0.76 0.51 0.90 0.75 0.84 0.50 0.37
4 Cl 5.50 5.80 6.20 6.00 6.10 5.70 5.30
THE PROBABLE CHEMICAL COMPOSITIONS
1 CaS04 0.75 0.30 1.07 0.87 0.82 0.48 0.31 2 . NaCl 5.70 7.60 5.80 6.50 6.50 7.30 7.50
3 MgS04 0.30 0.59 T 0.14 0.16 0.59 0.57
4 MgClz 2.75 1.50 3.50 2.74 3.10 1.50 1.00
5 KCl 0.15 0.17 ·0.10 0.14 0.18 0.20 0.22
6 CaCl2
28 29
1.080 1.080
10.7 10.7
7.6 7.2
0.08 0.15
·0.96 0.67
0.68 0.74
6.05 6.10
0.27 0.52
7.70 7.00
0.97 0.41
1.88 2.50
0.30 0.22
30
1.082
11.0
7.2
0.22
0.70
0.85
6.70
0.75
7.40
0.23
3.05
0.31
,.
c.., :.c
Table - 8: (Conld ....... )
Sr. Consti- BRINE SAMPLE NUMBERS No. tuents 31 32 33 34 35 36 37 % w/v
1 Sp. Gr. 1.082 1.082 1.083 1.084 1.086 1.087 1.087
2 °Be' 11.0 11.0 11.1 11. 2 11.5 11.6 11.6
3 pH 7.5 7.5 7.7 7.8 7.4 7.9 7.8
IONIC COMPOSITIONS
1 Ca 0.18 0.11 0.24 0.10 0.16 0.15 0.10
2 S04 0.85 0.90 0.53 0.95 0.83 0.99 2.11
3 Mg 1.14 0.56 1.10 0.62 1. 80 0.57 0.65
4 C1 6.93 6.35 6.90 6.61 7.00 7.30 6.60
THE PROBABLE CHEMICAL COMPOSITIONS
1 CaS04 0.60 0.37 0.82 0.34 0.55 0.51 0.33
Z NaCl 5.69 8.30 6.10 7.15 3.50 9.80 9.90
3 MgS04 0.54 0.80 T 0.90 0.54 0.80 2.36
4 MgCIZ 4.00 1. 58 4.30 1.72 6.70 1.60 0.70
5 KCl 0.18 0.25 0.18 0.29 0.18 0.28 0.32
6 CaC12
38 39
1.087 1.090
11. 6 12.0
7.7 7.9
• 0.11 0.23
0.80 0.90
0.63 0.91
7.10 7.10
0.37 0.79
9.40 8.10
0.68 0.45
1.92 3.20
0.28 0.21
40
1.090
12.0
7.5
0.18
0.77
1.10
7.33
0.60
7.20
0.44
4.00
0.19
en o
Table - 8: (Cantd .•..... )
Sr. Cansti- BRINE SAMPLE NUMBERS Ka. tuents 41 42 43 44 45 46 47 % w/v
1 Sp. Gr. 1.090 1.095 1.102 1.110 1.118 1.148 1.131
2 aBe' 12.0 12.6 13.4 14.3 15.3 18.7 16.8
3 pH 7.2 7.7 7.8 7.4 7.5 7.1 7.6
IOKIC COMPOSITIONS
1 Ca 0.15 0.25 0.10 0.18 0.07 0.17 0.08
2 S04_ 1.05 0.70 0.86 0.80 1.11 0.90 1.04
3 Mg 0.49 1.22 0.74 1.41 0.93 1.97 1.08
4 Cl 7.50 7.70 8.32 8.90 9.92 13.15 10.95
THE PROBABLE CHEMICAL COMPOSITIONS
1 CaS04 0.50 0.83 0.35 0.61 0.24 0.58 0.27
2 NaCl 7.20 12 . .40 8.20 13.03 12.75 13.70 11. 70
3 MgS04 0.80 0.14 0.77 0.46 1.18 0.62 1.07
4 MgG12 1.60 4.60 2.30 5.30 2.30 7.30 3.36
5 KGl 0.26 0.20 0.30 0.20 0.32 0.25 0.27
6 GaG12
48 49
1.135 1.138
17.5 17.6
7.3 7.4
0.17 0.08
·1.10 1.22
0.87 1.03
9.50 11.47
0.58 0.28
15.20 15.00
0.88 1.29
2.70 3.03
0.30 0.39
50
1.160
20.0
7.4
0.13
1.10
1.82
13.80
0.44
1.00
6.30
0.48
r
en .....
----,--
Table - 9: Analysis of sea brines at different density
Sr. No.
1
2
1
2
3
4
1
2
3
4
5
6
Constitllents % wjv
Sp. Gr.
°Be'
Ca
S04
Mg
Cl
CaS04
NaCl
MgS04 MgC12 KCl
CaC12
1 2
1.020 1.040
2.8 5.6
0.03 0.07
0.22 0.44
0.11 0.21
1.58 3.12
0.12 0.23
2.22 4.40
0.17 0.35
0.28 0.54
0.60 0.12
BRINE SAMPLE NUMBERS
3 4 5 6 7
1.050 1.070 1.080 1.090 1.110
6.9 9.5 10.7 12.0 14.4
IONIC COMPOSITION
0.08 0.12 0.13 0.15 0.13
0.55 0.77 0.90 1.00 1.13
0.26 0.37 0.42 0.48 0.59
3.91 5.50 6.32 7.11 8.93
THE PROBABLE CHEMICAL COMPOSITIONS
0.28 0.39 0.45 0.51 0.44
5.50 7.75 8.90 10.00 12.60
0.44 0.62 0.72 0.81 1.03
0.67 0.94 1.07 1.21 1.51
0.15 0.21 0.24 0.27 0.34
8 9 10 11
1.120 1.130 1.150 1.160
15.5 16.7 18.9 20.0
0.12 0.11 0.09 0.09
1.20 • 1.26 1.40 1.46
0.66 0.71 0.84 0.90
9.84 10.75 12.60 13.50
0.40 0.38 0.32 0.29
13.90 15.20 17.90 19.10
1.14 1.24 1.46 1. 60
1.70 1.81 2.12 2.27
0.38 0.41 0.48 0.52 t----.. '_'_ J
I . :.:. . .. ' . ~,' &~ k ~
. \. '" :I ;';A ;'.' 1 . -t:. ,;, .. C1:I ..,[ . N, ~~ ''"'' ........
results that the density of brine obtained
higher. The density of brine varies from
63
is significantly
160ae l to
20.00ae l • The pH values are found to be between 7.1 and
7.9. It is also concluded trom the results that the calcium
content ot the brines are comparatively higher to the extent
of two times than those of sea brines of e~uivalent density.
On the other hand, sulphate content is Significantly lower
which ultimately results in more of calcium sulphate and
magnesium chloride and also less or almost total absence ot
magnesium sulphate content in the respective brines. About
lt5'.O percent brine samples are tOWld to be contaminated with
calcium chloride where magnesium sulphate is totally absent.
The brine samples with no magnesium sulphate have compara
tively lower potassium chloride concentration. However, the
remaining brine samples have more or less same potassium
Chloride content as reported for the sea brines of similar
density.
The analytical results reported (table 7) for the
sub soil brines collected from Bharuch area (Gujarat state)
clearly indicate that the density values for the brines are
found between 5'.)0 and 10.0°.8e l only. The pH values are
obtained to be between 7.2 and 7.6. The results further show
that calcium content of the brine samples is comparatively
higher, but magnesium and sulphate content are more or less
'.
the same as compared to sea brines of the equivalent
density. Higher calcium content of the samples results
in the brines having lower concentration of magnesium
sulphate and more of magnesium chloride than those reported
for the sea brines of similar density. The brine samples
which contain higher magnesium chloride have comparatively
lower concentration of potassium chloride than the sea
brines; whereas rest of the samples have more or less same
potassium chloride concentration as those of sea brines.
The analytical results of the sUb soil brine
samples collected from Tuticorin area (Tamil Nadu) are
j presented density wise in the table 8. It can be
. seen from the results that the values ot density of brine
samples vary from 5.20Be l to 20.0%e l ; whereas pH values
remain between 7.2 to 7.9 at room temperature. It can
also be visualized from the results that most ot the brine
samples contain more or less same concentration of calcium,
magnesium and sulphate ions as those reported for the sea
brine samples of equivalent density. However, few samples
contain higher calcium sulpbate and comparatively low
magnesium sulphate and sodium chloride concentration with
respect to sea brines of same density. In this case,
potassium chloride concentration is found to be 2/3rd ot
the sea brine concentration. The remaining brine samples have more or less same potassium chloride concentration
as reported tor the sea brines.
J
65
To account for the commonly observed deficit in
magnesium sulphate concentration in sub soil brin9s; it is
a hypothesis that in past, sea water during evaporation might
have reacted slowly with CaC03 present as lime stone beneath
the deposits138• The brine might have been trapped under
the soil due to geograpbic activities. The reaction can be
symbollzed as
The dolomite (CaMg(C03)2) would be deposited near
the base of salt sequence.
We can also derive a hypothesis that the calcium
sulphate precipitation by the reaction ot magnesium sulphate
with lime stone at an elevated temperature might have reacted wi!:h "e/
L to form syngenite, a double sulphate ot calcium and potassium,
according to tollowing equation
2KCl + 2CaSOq. H2 0 ----+ ~S,\.CaS.,\. :H20 + CaC~
The presence of small amount of calcium chloride
in Some ot the brine samples is explained .~ the above reac
tion. 'rhe hypothesis thus clearly explains lower potassium
chloride concentration in the brines in which calcium chloride
has been found to be present.
66
The average sulphate content increases in going
from Kharaghoda to Bharuch to Tuticorin area brine samples.
Thus the Tuticorin bittern is nearly similar to sea bittern
in composition, while the bittern from Bharuch area vary
little from sea bittern composition as far as magnesium
sulphate content is concerned. The bittern from Kharaghoda
area containing very low sulphate can prove a promising
potash recovery source because this type of bittern can
directly yield carnallite type of mixed salt.
2.2 '!he progressive solar evaporation of sub soil brines of different areas
In view of obtaining the experimental data on the
composition of sub soil brines of different areas, as men
tioned earlier, at different stages and also to study the
course of fractional crystallisation of various salts viz.
calcium sulphate, sodium chloride etc. by stage wise evapo
ration, progressive solar evaporation experiments for these
brines were performed on the bench scale by collecting
typical brine samples from respective places.
For this, 2,.0 litre brine was collected from
Kharaghoda-Kuda area (Little Rarm of Kutch) and Bharuch area
of Gujarat state respectively. Similarly 2,.0 litre sub soil
67
brine was collected from Tuticorin area ot Tamil Nadu state.
Prior to evaporation, the density and pH values along with
the chemical analysis were determined. The brine was taken
in a 30.0 litre capacity plastic tray for evaporation in all
the cases. :rhe density of the brines was determined every
day in the morning with a beaume hydrometer as well as by
the specific gravity values. The brines were analysed at
the stage wise rise in density during the course of progres
sive evaporation to determine the saturation stages ot calcium
sulphate and sodium chloride respectively. The difterent salt
fractions were collected, at the brine density stages as shown
in tables 10 to 12. The evaporation was continued till the
density ot brines reached 290 - 29.,ase'. After separation ot
salt tractions, the analysis ot the liquors as well as SOlids
were carried out. All the relevant analytical data ot the
sub soil brines ot particular area are shown in tables 10 to 12.
For comparison, the compositions of corresponding
salt fractions a nd brines obtained during solar evaporation
of sea brine are also given in table 13.
In addition to this, in another set of experiments
only two fractions (1) gypsum and (2) salt at 2~.,ase' and
29.5'%e' were collected during solar evaporation of the sub
soil brines and sea brine of the same composition as reported for earlier experiment. The analytical results tor the salt
fractions of the particular areas are given in table 1~.
Table - 10: Experimental data on progressive solar evaporation of Kharaghoda sub soil brine.
a) Analysis of brine samples at different densities.
Descriptions
Density
Volume
Constituents percent w/v
CaSo4 NaCl
MgS04 MgC1
2 KCl
Brine I
19.60 Be'
25.00 litre
0.5537
17.00
0.16
4.40
0.40
Brine II
22.20 Be'
22.36 litre
0.62
19.10
0.20
4.95
0.44
Brine III
24.40 Be'
18.61 litre
0.40
22.30
0.22
5.94
0.53
Brine IV
25.30 Be'
11.11 litre
0.34
22.50
0.40
9.60
0.88
Brive V
26.10 Be'
6.42 litre
0.255
16.70
0.55
15.50
1.53
Brine VI
26.80 Be'
4.72 litre
0.19
12.80
0.70
18.80
2.00
b) Analysis of salt fractions collected between different densities of brine
Brine VII
29.30Be'
2.92 litre
0.034
6.80
0.91
28.50
2.80
Descriptions Salt Fraction-I Salt Fraction-II Salt Fraction-III Salt Fraction-IV Salt Fraction-V
Density 19.60 -24.40 Be' 24.40 -25.30 Be' 25.30 -26.10 Be' 26.10 -26.80 Be' 26.80 -29.30 Be'
Quantity 0.165 kg 1.800 kg 1. 445 kg 0.445 kg 0.500 kg
Constituents percent w Iv
CaS04 40.10 2.00 1. 76 1.55 1.50
NaCl 53.30 94.50 94.20 93.30 92.80
MgS04 Traces 0.10 0.10 0.30 0.22
MgCl2 0.80 1.80 2.44 5.10 5.40
Percentage CaS04 separation 47.80 26.00 18.35 5.00 5.42 in the fraction
en 00
Table - 11: Experimental data on progressive solar evaporation of Bharuch sub soil brine
a) Analysis of brine samples at different densities
Descri p tions
Density
Volume
Constituents per wlv
Caso4 NaCl
MgS04 MgCl2 KCl
Brine-I
7.50 Be'
25.00 litre
0.34
6.30
0.32
0.935
0.13
Brine-II
10.30 Be'
19.10 litre
0.45
8.25
0.41
1.27
0.185
Brine-III
14.1oBe'
12.90 litre
0.63
12.25
0.64
1.81
0.260
Brine-IV
25.8oBe'
5.575 litre
0.285
24.7
1.42
4.07
0.62
Brine-V
26.6oBe'
2.60 litre
0.13
18.8
3.0
8.8
1.25
b) Analysis of salt fractions· collected between different densities of brine
Descriptions Salt Fraction-I Salt Fraction-II Salt Fraction-III
Density 14.1o-25.8oBe' 25.8o-26.6oBe' 26.6o-29.7oBe'
Quantity 0.165 kg 1. 020 kg 0.430 kg
Constituents percent w Iv CaS04 38.80 0.80 0.55
NaCl 58.20 91.20 93.60
MgS04 0.30 0.28 0.60
MgCl2 0.82 1.50
Percentage CaSo4 separation 75.30 9.70 3.00 in the fraction
Brine-VI
29.7oBe'
1.25 litre
0.08
8.1
5.2
18.45
2.52
en ~
Table - 12: Experimental data on progressive solar evaporation of Tuticorin (Tamil Nadu) sub soil brine.
a) Analysis of brine samples at different densities
Descriptions Brine I Brine II
Density 10.30 Be' 14.00 Be'
Volume 25.00 litre 17.05 litre . Constituents percent w /v
CaS04 0.345 0.505
NaCl 8.30 12.10
MgS04 0.72 1.07
MgC12 1.32 1.95
KCl 0.145 0.23
Brine III
24.10 Be'
8.25 litre
0.22
23.5
2.1
4.0
0.49
Brine IV
26.30 Be'
7.15 litre
0.11
19.5
2.5
4.8
0.575
Brine V
29.50 Be'
2.15 litre
0.044
18.1
6.8
14.5
2.1
b) Analysis of salt fractions collected between different densities of brine
Descriptions Salt Fraction-I Salt Fraction-II Salt Fraction-III
Density 14.00 -24.10 Be' 24.10 -26.30 Be' 26.3° -29. 30 Be'
Quantity 0.210 kg 0.575 kg 1. 070 kg
Constituents percent w/v
CaSo4 32.0 1.5 0.64
NaCl 58.6 94.0 94.3
MgS04 0.20 0.30 1.98
MgC12 0.50 0.50 1.90
Percentage Caso4 separation 77.90 10.00 8.10 in the fraction
-....J <::)
Table - 13: Experimental data on progressive solar evaporation of sea brine
a) Analysis of brine samples at different densities
Descriptions Brine-I Brine-II Brine-III Brine-IV Brine-V Brine-VI Brine-VII
Density 5. 50 Be' 9.50 Be' 14. 50 Be , 22.30 Be' 24.1 °Be' 26.00 Be' 27.20 Be'
Volume 25.00 litre 13.85 litre 8.25 litre 4.65 litre 4.20 litre 3.20 litre 1.80 litre
Consti tuents per w /v
caS04 0.25 0.42 0.47 0.274 0.164 0.105 0.065
NaCl 4.4 7.B5 13.05 22.41 24.74 25.B7 22.47
MgS04 0.34 0.60 1.00 1. 74 1.92 2.50 4.13
MgC12 0.53 0.95 1.5B 2.62 2.90 3.85 6.40
KCl 0.1 0.187 0.30 0.55 0.625 0.75 1.40
b) Analysis of salt fractions collected between different densities of brine
Descriptions Salt Fraction-l Salt Fraction-II Salt Fraction-III
Density 5.5° -24.1 °Be' 24.10 -27.20 Be' 27.20 -29.50 Be'
Quantity 0.125 kg 0.650 kg 0.260 kg
Constituents percent w/v
CaSo4 44.10 0.89 0.58
NaCl 46.40 97.20 97.30
MgS04 2.40 0.6B 0.B2
MgC12 4.00 0.66 0.80
Percentage CaS04 separation B6.40 9.30 2.40 in the fraction
Brine-VIII
29.50 Be'
0.90 litre
0.011
16.0
7.0
11.32
2.5
'.l ......
Table - 1it-: The cmemical analysis of salt fractions crystallized out from different sub soil brines and. trom sea brine.
(on dry basis)
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-Constituents
percent wlw
Sub soil salt -------------------Kharaghoda
Bharuch Tutl-corin
Sea salt
-------------------------.------------------------------caS<\. 1.4-8 1.10 1.2, 0.90
NaCl 93.80 97.00 96.25' 98.00
Mg3,\ 0.20 0.,0 0.89 0.60
MgC~ it-.15' 1.28 ~ .it-5' 0.4-8
-.-.-.-.-.-.~.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-. -.-
72
73
1. The results of r~araghoda~Kuda area sub soil brine:
It can b') visualized from the data presented in
table 10 that magnesium sulphate content of this brine is
comparatively low, whereas calcium sulphate and magnesium
chloride concentration is significantly higner as compared
to sea brine of the same denSity. In the case of potassium
chloride, it is tne same as tll(;lt of sea brine. rhe calcium
sLll.pdate se;Jaration, till tae d.ensity of orine reacned
2~.~o~el is only ~d.O percent. For sea brine it is found
to oe 84-.0 percent. J)uring tlW separation of calcium sulphate
rich fraction, sodium chloride separation is found to be 1.5
percent only. During further evaporation of this brine four
salt fractions were collected at the density ranges of 24.4 -
2~.30Bel, 25.3 - 26.10se l , 26.1 - 26.80se l and 26.8 - 29.3OUe ' •
During the separation of these fractions, calcium sulprlate
separation with the salt fractions is 26.10 percent, 18.4 per~
cent, 5.0 percent and 5.4 percent of the total calcium sul
~hate present in the brine. The results further showed that
the impurity of calcium sulphate with each fraction is 2.00
percent, 1.76 perccnt, 1.55 p-drccnt and 1.50 percent respec
tively. For sea brine salt frdctions, the impurity is 0.89
percent and. 0.58 percent maximum only. It is also concluded
that about 92 percent of total salt present in tne initial
brine is separated during the four salt fraction till the
brine density reached 29.30Be'. For sea brine, the salt
separation upto this density is found to be 85.0 percent
only. The bittern contains only ~.7 percent of the total
sodium chloride content, compared to sea bittern which
contains 13.0 percent maximum.
2. The results of Bharuch area sub soil brine.
7~
It can be seen from the analysis presented in
table 11 that the brine is having more or less same calcium
sulphate content as that of sea brine of similar density.
In the case of magnesium sulphate content, it is slightly
less and magnesium chloride content is more compared to sea
brine analysis.
The results further aistinctly indicated that the
calcium sulphate crystallization during progressive evapora
tion of 7.50Be' brine upto 25.80Be' is about 75.0 percent of
the total calcium sulphate content. During this, only 6.2
percent sodium chloride is lost with the calcium sulphate as
an adhering impurity. In the case of sea brine evaporation
about 85.0 percent calcium sulphate is crystallized at the
density 2~.196e' of the sea brine. At the same time, only
6.0 percent sodium chloride crystallizes out with calcium
sulphate at 2~.196e' density of the brine.
By further evaporation of the 25.896e' brine two
fractions of common salt between the density ranges of
25.896e l - 26.696e' and 26.696e' - 29.796e l were co~ected.
75
.l)uring the separation of first and second fractions, the
calcium sulpnate crystallization with the sut is 9.7 and
3.0 percent of the total caS~ content of the sub so11 brine.
The results also show that the impurity of calcium sulphate
in the first fraction ot salt is more (0.80 percent) as
compared to second traction of sut; ..,hich is 0077 per~ent
only. The results on further evaporation of 2~.19Be' sea . brine clearly show that the crystallization of calcium
sulphate along ..,ith the two salt fractions between the
density range ot 2~.19Bel - 27.29Be' and 27.29Be ' - 29.50£e'
is about 9.3 percent and 2.5 percent respectively. The
results also indicate that the impurity of calcium sulphate
with the two salt fractions is 0.89 percent and O.,S per
cent only. Furthermore it is also visualized that in the
case or sub soil brine, the bittern lett after separation
of salt, contains only 6., percent of totu sodium chloride
content; ..,hereas for the sea bittern, it is about 13.0 per
cent ot the totu sodium chloride content.
3. The results ot Tuticorin area sub soil brine:
The chemical composition ot the brine is similar
to the composition of sea brine with regard to potassium
chloride and sodium chloride content (table 12). The brine
contains slightly higher magnesium Chloride and less magnesium
sulphate than sea brine. The results further showed that
during the evaporation of brine upto the density of 2~.19Be',
76
calcium sulphate separation is about 78.0 percent alongwith
6.0 percent of sodium chloride separation. During further
evaporation at 2~.198el brine, two salt fractions were
collected between the density ranges of 2~.198e' - 26.098e l
and 26.00 - 2.9SoBe l • During this, the calcium sulphate
crystallization with the fractions is 10.0 percent and 8.1
percent of the total content. The impurity of calcium
sulphate contamination with the two salt fractions was found
to be 1.50 percent and 0.6~ percent respectively. During
the separation of these two salt fractions, only 75.0 per
cent of the total sodium chloride content is crystallized
out. It is also visualized that about 18.0 percent of total
sodium chloride is retained with the bittern left after
removal of two salt fractions. The composition of the bittern
is same as that obtained from sea bittern except its magnesium
chloride content, which is slightly higher. This may be owing
to higher magnesium chloride content in the initial brine
compo~ition.
The impurity of calcium sulphate alongwith the salt
by evaporation of the sub soil brines from 2~.598e' to 29.598e'
is found to be 1.~ percent, 1.10 percent and 1.25 percent
for the brines of Kharaghoda, .oharuch and Tuticorin areas
respective~. In the Case of salt obtained from sea brine,
the impurity is found to be 0.90 percent only (table 1~).
77
The percent calcium sulphate separation before and
after crystallization of common salt depends on equilibria
existing between the ions present in the systems. There are
two different effects which are opposing each other resulting
from the concentration of different species of ions. The
first one known as salt effect helps in increasing the solu
bility of an electrolyte such as calcium sulphate while the
effect of common ion counteracts and reduces its solubility.
Beth these effects are explained in relation to the results
obtained in our experiments.
When an electrolyte such as calcium sulphate is
dissolved in a solution containing a second electrolyte e.g.
sodium chloride, the solvent for caa~ is not pure water but
is a solution of NaCl. The effect of inter-iOnic attraction
is much greater in solutions of salts than in pure water.
For this reason, these ions combine less rapidly to form
molecules, which means that solutions are better ionizing
media than is pure water. This action is called the salt
effect 139. The increase in solubility of caS~ with the rise
in NaCl and MgC~ concentration during progressive solar
evaporation of sea and sub soil brines is easily explained
considering this "salt effect".
Sea and sub soil brines are very
; ----...... . '. · ... 1..; .• ~"".:.._,_ • 'W" __ "0 .. :'. I . ~ ......... 0 . .. '" ~ " ,.
',:", "" 7~'" r "II .. ~. '1«(' i .
. 7". ~'-".~~" ... , ....... '~---'.". ~ } complex systems ~.
and the equilibria is established progressively for different
icnic species during evaporation. As total iOnic concentra
tion goes on increasing in the brines due to evaporation,
the sulphate ion will exert a common ion effect on the caS<\. equilibrium.
Calcium sulphate ionizes according to the equations
caS<\.
Applying the principle of Le Chatelier, we
readily see that the effect of adding either calcium or
sulphate ions to a solution of calcium sulphate is to shift
the point of equilibrium so as to decrease the amount of
calcium sulphate that is ionized or in other words to increase
the amount of unionized caS<\. in the equillbrium mixture.
By applying the law of Chemical Equillbrium, we
have calculated the extent to which this system is effected
by the increase in concentration of total sulphate ions.
We have also calculated the solubility product constants for
calcium sulphate (Ksp caS<\.) in each case of brines; just
before it reached saturation with regard to sodium chloride
and the concentration of calcium ions at which the caS<\. would have crystallized out; . if there were no effect due
to presence of other ions in the brines. Simultaneously
we have given the percentage of caS<\. crystalllzed out trom
the total which was initially present (table 15).
79
Table - 1;1 Solubility product constants and the effect of total sulphate ion concentration in different brines near saturation of sodium chloride
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-Brine samples Solubi- Concen- Concen- Percent-
l1ty tration tration age product ot ot calcium constants calcium calcium sulphate
ions ions separation
Ksp Cca1 MIL Cca2 MIL
--------------------------------------------------------------. 1. .:>ea Brine 1 .4-; x1 04- 0.0121 0.84-x103 85.0
2. :)ub soll brines
(a) Tuticorin ..It 2.62x10 0.0162 -3 1.37x10 78.0
(0) Bharuch ..It 4-.39x10 0.0210 3.1;x103 75.0
(c) Kharaghoda a.65xit 0.0294- 18.1x103 4-8.0
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
80
It can be seen that in sea brine, the total sulphate
ion concentration is maximum amongst all the four brine samples.
This has resulted in obtaining the lowest calCium ion concen
tration (cc~) in the brine. This indicated that maximum
percentage of calcium sulphate should have crystallized out
in reaching to this stage. Percentage calcium sulphate sepa
ration of 85.0 percent concurs with this the ora tical deductions.
Going from Tuticorin to Kharaghoda in case of sub sol1 brines
the total sulphate ion concentration reduces, in turn, increas
ing the calcium ion concentration (Cc~) in the brines. A.
regular reduction in calcium sulphate separation is observed
as the concentration of calcium ion increases in the brines.
CONCLUSIONS ---_._------
The studies on the progressive evaporation of these
brines led me to the understanding of equilibria existing
between the different ioniC species in different brine samples.
vle may generalise from the comparative studies of the brine
samples from Kharaghoda, Bharuch and Tuticorin that due to
common ion effect, if a brine contains low concentration of
sulphate ions, the salt will be more impure with respect to
calcium sulphate. On the basis of the results of comparative
studies it was possible to plan further experiments to improve
the quality of salt from Kharaghoda area.
81
2.3 dtudies on the effect of increasing sulphate ions in the brines on caS'\. separation in salt
The concentration of magnesium sulphate in the sub
soil brine collected from Kharaghoda area is roughly 1/3rd
times to that of sea brine at similar density. The discus
sion based on the results obtained for the experiments have
clearly reveaJ.ed that this factor is very important in sepa
ration of more calcium sulphate Prior to crystallization
of common salt and subsequently obtaining good quality of
salt.
In this context, the further experim~ntal studies
were planned to investigate the effect of addition of sulphate
ion in form of either inorganic salts such as magnesium sul
phate, sodium sulphate or sea bittern of higher density
(32.0OSe l ). Sea bittern contains sufficient concentration
of magnesium sulphate. The experimental details are described
as follows.
Three different experiments were conducted by taking
5.0 litre of 2~.1OSel sub soil brine in three different plastic
evaporating trays. The brine was analysed for its totaJ.
sulphate ion content. Thereafter, the calculated quantity of
magnesium sulphate, sodium sulphate and sea bittern was added
in the brine, separately in the three trays; so as to obtain
82
approximately 1.7 g sulphate ions per 100 ml of the brine
in each case a concentration similar to that which exists in
sea brine at same density.
After treatment of all the three brine samples as
mentioned above the trays were kept for evaporation. The
first fraction i.e. gypsum was remove~ at 2~.?50ee', 2~.90sel
and 25.10ee ' brine iensity from magnesium sulphate, sodium 'I
sulphate and bittern added trays respectively. After removal
of gypsum fractions, evaporation of brine samples was con
tinued till the density of 29.20se l - 29 .eOse l , in all the
cases. The common salt fractions, crystallized out between
these density ranges (2~.750Bel - 29.eOse l ) were collected.
At the same time 5.0 litre of 2~.60sel sea brine and un
treated 2~.10sel sub soil brine were also kept for evapora
tion to compare the calcium sulphate impurity separation in
salt fractions with those obtained by addition of chemicals
and sea bittern experiments. A.11 the experimental data and
analysis of different salt fractions are incorporated in
table 16. The composition of salt fractions are calculated
on dry basis.
To study the effect of variation in the total
sulphate ion concentration of the brine on the lual1ty of
salt with regard to calcium sulphate impurity; a second set
of experim~nts were carried out. The sulphate ion concen-
tration was increased by addition of Hg3~.7H20 crystals.
The results are given in table 17 and Fig. 9 respectively.
Tab~e - 161 Effect or suJ.phate ions addit:>.on on crystalllzaticn of' caS'\. impurity ,.,ith sut fractions from sub soll brine
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
Ddscriptions
Constituents percent wlw
Chem1c~ composition of' s~t fractions (on dry basis) --------------------------------------------------------------------------S~t separated S~t separated S~t separated S~t separated S~t separated from sub soll from sub soll from sub soll from sub soil. from sea brine lJrine + brine .. brine .. brine between MSSO"'. 7H20 N~Go... (Anhy) sp-a bittern (bl.ank) 24-.6~e' _ between between between between 29.~~e'
2~+.9~e' - 24-.7~e' - 25'.·1~e' - 24-.7~e' -29.2~e' 29.1~e' 29.7~e' 29.3Use'
----------------------------------------------------------------------------------------Ca.S~ OSS 0.60 0.7~ 1';0 0.S1
NaCJ. 9S.01 9S.36 97 .It-~ 93.80 98.10
l-l:g ~~ O';~ 0.1fl+ 0050 0.22 0';8
MgC~ O.S' 0.60 1.30 4-." 0.60
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
f
00 w
Table - 171
,.
Effect of increasing the total sulphate ion conoentration on quality of salt in relation to oaloium sulphate impurity
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-Sr. Total sulphate ion Calcium sulphate Ho. ooncentration oontent in salt
g/1oo ml brine g/100 g salt --------------------------------.--------------------------
1. 1.31t .... 1.50
2. 1.91 0.50
3. 2.20 0.1t<>
It. 2.68 0.26 .-] . 2.85 0.20
.... Blank Kharaghoda Brine
84
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
3'0r-~--------------____________________________ --,
w Z 0:: III
Z
2'5
1 . 5 z u z o u Z o
-J o (f)
...J 1'0 ~ o f-
10 20 30 40 50 60 70 80 90 PERCENTAGE. CaS04 CRYSTALLIZATION (BEFORE SALT SEPN.)
FIG.9. EFFECT OF INCREASE IN SULPHATE ION CONCENTRATION ON THE CALCIUM SULPHATE CRYSTALLIZATION FROM THE BRINE
r
85
RGSULTS &: ulliClliSION
It was observed that after addition of magnesium
suJ.phate and sodium suJ.phate in the sub soil brine, immediate
preCipitation of calcium suJ.phate was observed; whereas in
case of sea bittern addition, no precipitates were seen in
the brine. It was also Visualized that by addition of mag
nesium sulphate and sodium suJ.phate, about ,0.0 - ".0 per
cent of the total calcium sulphate content of the 2~.1Dsel
sub soil brine couJ.d be reduced till the density of brine
reached 2~.7,Dse' and 2~.9Dsel. In the case of sea bittern
addition, about ,8.0 percent reduction in calcium sulphate
of total content of the brine at 2,.1Dse ' was obtained.
The salt fractions crystallized from the untreated
(blank) sub soil brine contained higher percentage of calcium
suJ.phate impurity which is found to be 1"0 percent. The
salt fractions crystallized from the brine treated with both
the Chemicals and sea bittern contained almost same calcium
sulphate content as compared to that crystallized from the
sea brine. The impurity of calcium sulphate contaminated
with the salt fractions separated from sea brine is found to
be 0.81 percent. The salt fractions of the brine treated with
sodium sulphate and magnesium sulphate were contaminated with
0.60 percent and 0.,8 percent calcium sulphate impurity. The
brine treated with sea bittern yielded salt fraction contain
ing D.?' percent calcium sulphate only.
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86
It can be seen from the table 17 that as total
sulphate ion concentration increased, the calcium sulphate
content in the salt fractions between the two fixed brine
density (i.e. 2, - 29.,Ose'> followed a gradual decrease
in its concentration. Separation of calcium sulphate from
the brine prior to salt crystallization is also, in turn,
related to the total sulphate ion concentration in the brine.
The curve for the percentage calcium sulphate separation
against the total sulphate ion concentration of brine is
shown in Fig. 9.
thus it can De concluded that the ~ystall1zation
of calcium sulphate from the brine is directly proportional
to the total sulphate ion concentration; on account of common
ion effect. It is possible to arrive at the quality of salt
with regard to calcium sulphate impurity to be obtained from
a brine sample by the knowledge of total sulphate content.
From the experimental study, it was possible to
evolve a method by which salt from the sub soil brine can be
improved in quality to that obtained from sea brine. In
Kharaghoda area it has been observed that in the viCinity
of low sulphate containing brine wells, some wells are found
which contained high sulphate brines, bittern of such brines
can easily be mixed with the low sulphate containing brine to
improve the quality of salt. In Bharuch and Tuticorin areas,
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87
the salt works should be modified to pro~uce salt partly
from sub soil brine and partly from sea brine, the sea bittern
should be utilized for mixing with sub soil brine to improve
the sub soil brine salt. By following the above suggestions,
the agarias can improve their quality of salt which can be
easily marketed.
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