CHAPTERshodhganga.inflibnet.ac.in/bitstream/10603/85388/8/08chapter 2.pdf · This Chapter is divided into thr3e different sections. rha section 2.1 deals with the cllemical ana-lysis

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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


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

,-- ~


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


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

---,--


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


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


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


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


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


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


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


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.


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


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


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


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


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


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.

I

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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CHAPTERshodhganga.inflibnet.ac.in/bitstream/10603/85388/8/08chapter 2.pdf · This Chapter is divided into thr3e different sections. rha section 2.1 deals with the cllemical ana-lysis