Process for the Purification of Brine.
Year: 1898

page_text: Process for the Purification of Brine.
I, GERHARD NICOLAAS VIS, of Schweitzerhalle, near Basel, in the Republic of
Switzerland, Doctor of Philosophy, do hereby declare the nature of this invention to
be as follows:-
The present invention relates to the extraction of chloride of sodium (common
salt) from brine, and consists in a process for purifying the said brine from its
sulphates (sulphate of sodium, sulphate of potassium, sulphate of magnesium,
sulphate of calcium and so forth.)
The difficulties met with in the extraction of salt from brine by simple evaporation,
and especially in a vacuum, are principally due to the presence of sulphate of calcium
(gypsum) in the brine.
Numerous apparatuses and processes have been described,
which have for their object to remedy these drawbacks.
The calcium sulphate contained in the brine may be rendered innocuous either by
precipitating the one component (calcium) by means of carbonate of sodium, or the
other component (sulphuric acid) by means of barium compounds.
In order entirely to obviate the drawbacks which are caused by the presence of
calcium sulphate or gypsum on evaporating brine, it has been proposed to precipitate
the chloride of sodium from the brine by adding thereto certain fluids in which
common salt is hardly or not at all soluble, for instance, by means of chloride of
calcium, as described in British Patent No. 3015 of 1884; or by means of alcohol.
On the other hand, attempts have been made to treat crude rock salt in the heated
state with fluids which hardly dissolve gypsum, as for instance chloride of calcium,-
see German Patent No. 42422-and afterwards to cool the solution of salt thus
obtained, and thereby to obtain pure chloride of sodium direct, completely avoiding
the evaporation process. In view, however, of the concentrated solution of chloride
of calcium necessary in both cases, whereby there is obtained a salt containing
chloride of calcium, and being in consequence hygroscopic, and, further, in view of
the complication and expense of the above stated processes, they have been hitherto
of little value in practice. It remains, however, extremely desirable to have as simple
a process as possible, for extracting salt from brine, which will enable salt to be
obtained of the requisite degree of purity.
From this point of view the progress which has been already proposed for purify-
ing brine by means of barium salts, such as chloride of barium (Ba C12) or carbonate
of barium (Ba CO³) according to the reactions :--

page_text: high price, prevented by the very large quantities which would be requisite in the
case of most brines, as may be seen from the following table:-
I have discovered that chloride of calcium added even in small quantity to brine will
not only convert the sulphates of sodium, potassium, magnesium, and other non-calcic
sulphates, into gypsum (sulphate of calcium) which falls to bottom, but that also
the greater part of the gypsum which is original to the brine, will also precipitate, so
that but a very small amount of said gypsum is left for the removal by means
.barium compounds. The precipitation is proportional to the quantity of chloride of
calcium added, as is shewn in the following table :-
Thus my discovery enables the purification of brine from the sulphates to be
carried out by means of a greatly reduced proportion of barium compounds. In
applying my discovery it is possible to remove the greater part of the sulphates from
the brine almost free of expense, because the waste liquors of the ammonia soda works
containing chloride of calcium are applicable for the purpose.
Whilst the previous application of chloride of calcium for direct production of
culinary salt have been devised either for the purpose of precipitating chloride
of sodium from the brine, or for the purpose of dissolving solid salt in hot chloride
of calcium solution and re-precipitation of sodium chloride by subsequent cooling, in

page_text: this process on the contrary the addition of chloride of calcium serves for the partial
removal of sulphates from the brine. The quantity of chloride of calcium to be used
is a very different one from the foregoing, corresponding to the entirely different
principle and object of the present process. For instance, it has proved economical
and practicable to treat the brine of Schweizerhalle near Basle in Switzerland with an
addition of chloride of calcium, amounting to from 7 to 8 kilos. per cubic metre of
brine. By means of this addition no sodium chloride is precipitated. On the other
hand, the sulphates contained are so far precipitated, that the purification for instance
with carbonate of barium or witherite becomes profitable.
Obviously the above stated quantity of chloride of calcium is not to be regarded as
an invariable proportion, because this, as already stated, is adapted to the brine of
Schweizerhalle. In the case of brines containing a larger proportion of sulphates,
such a larger quantity of chloride of calciun must be applied as is required by the
principle of this invention, i.e. such a quantity that in addition to the conversion of the
non-calcic sulphates into precipitated sulphate of calcium, also the greater part of.
the gypsum originally present in solution in the brine is caused to deposit.
After the addition of chloride of calcium the mixture is allowed to rest until the
reaction is completed. It is, however, advantageous to keep the solution in motion
either by heating, or by stirring, or by stirring and heating whereby the reaction is
furthered.
The influence of the stirring or heating may be seen from the following table :-
In each of the three following cases, to one cubic metre of brine from Schweizerhalle
there were added 10 kilos. of chloride of calcium. The brine which has stood 24 hours
at 18 degrees Centigrade required 3.78 kilos. witherite per cubic meter. After
heating for 24 hours to from 40 to 50 degrees Centigrade the other cubic metre
required 3.72 kilos. witherite. After stirring for 24 hours at 18 degrees Centigrade,
the third cubic metre required 3.01 kilos. witherite.
After about 24 hours the liquid is allowed to settle, the clear brine is drawn off
from the precipitate, and transferred to a second reservoir, and it is there treated with
a proportion of witherite corresponding to the remaining quantity of sulphate, the
mixture being constantly stirred. This operation can be effected in a cold or warın
solution. Even in this reaction the presence of chloride of calcium appears to be
advantageous. After the reaction is complete it is advisable to continue the agitation
for some time; the sulphate of barium separated out is then allowed to settle, and
the clear brine is separated from the deposit and evaporated until a sample of the
precipitated salt, dried on a centrifugal machine, shews a tolerable amount of chloride
of calcium present. On this the mother lye is drawn off from the precipitated salt.
Said mother lye, which contains a good deal of chloride of calcium, is reused in the
treatment of a fresh quantity of brine.
If brine be made use of which contains organic substances, it is possible by
fractionating the addition of chloride of calcium, to remove first such substances, in
order to obtain by the second addition a pure gypsum, which can be utilized in
commerce.
Other compounds of calcium are also applicable for the purpose of the present
invention. Thus, for instance, the calcium salts easily soluble in water, such as the
bromide or the nitrate of calcium, act in a like manner to the chloride of calcium.
Also the quantity of sulphates in the brine may be reduced by the use of calcium
hydroxide.
By means of the above and other calcium compounds, chloride of calcium may be
totally or partially replaced if desired.
If there are added to one litre of Schweizerhalle brine (the sulphate contents
whereof correspond to 0.9770 grainme sulphate of barium per 100 cubic centimetre).
either calcium bromide or calcium nitrate or calcium hydroxide, the sulphate con-
tents of the brine are reduced with precipitation of sulphate of calcium corresponding.
to the addition of the above mentioned calcium compounds. In this case also the
reaction is furthered by stirring or heating.

page_text: Addition of calcic bromide to 1 litre of
Schweizerhalle brine.
Quantity of sulphate of barium in
100 cubic centimetres after stirring for
20 hours or heating to about
95° Centigrade.
The application of calcium hydroxide is suitable in the case of brines which
possess a large percentage of sulphates. Thus, for instance, the sulphate contents
of the brine of Tomblaine (containing a quantity of sulphates corresponding to
2.4070 grammes of barium sulphate in 100 cubic centimetres) is reduced by the
addition of 20 grammes of hydroxide of calcium and the use of a stirring apparatus
for 20 hours to a proportion which corresponds to 1.6680 grammes of barium sul-
phate for 100 cubic centimetres. The same addition in the case of the Schweizerhalle
brine causes the sulphate contents under like conditions to sink to an amount which
corresponds to 0.9140 gramme of barium sulphate per 100 cubic centimetres. The
proportion of hydroxide of calcium which goes into solution, should be precipitated
by passing in carbonic acid gas.
I, GERHARD NICOLAAS VIS, of Schweitzerhalle, near Basel, Switzerland; Doctor of
Philosophy and Chemist, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
The present invention relates to the extraction of chloride of sodium (common salt)

page_text: from brine, and consists in a process for purifying the said brine from its sulphates
(sulphate of sodium, sulphate of potassium, sulphate of magnesium, sulphate of
calcium, etc.).
The difficulties met with in the extraction of salt from brine by simple evaporation,
and especially in a vacuum, are principally due to the presence of sulphate of calcium
(gypsum) in the brine. Numerous apparatuses and processes have been described,
which have for their object to remedy these drawbacks.
The calcium sulphate contained in the brine may be rendered innocuous either
by precipitating the one component (calcium) by means of carbonate of sodium, or
the other component (the sulphuric acid) by means of barium compounds.
In order entirely to obviate the drawbacks which are caused by the presence of
calcium sulphate or gypsum on evaporating brine, it has been proposed to precipitate
the chloride of sodium from the brine by adding thereto certain fluids in which
common salt is hardly or not all soluble, for instance, by means of a solution of
chloride of calcium, as described in British Patent No. 3015 of 1884; or by means
of alcohol. On the other hand, attempts have been made to treat crude rock salt
with hot fluids which hardly dissolve gypsum, as for instance chloride of calcium,-
see German Patent No. 42422-and afterwards to cool the solution of salt thus
obtained, and thereby to obtain pure chloride of sodium direct, completely avoiding
the evaporation process. In view, however, of the concentrated solution of chloride
of calcium necessary in both cases, whereby there is obtained a salt containing
chloride of calcium, and being in consequence hygroscopic, and, further, in view of the
complication and expense of the above stated processes, they have been hitherto of little
value in practice. It remains, however, extremely desirable to have as simple a
process as possible, for extracting salt from brine, which will enable salt to be obtained
of the requisite degree of purity.
From this point of view the progress which has been already proposed for purifying
brine by means of barium salts, such as chloride of barium (Ba Cl³) or carbonate of
barium (Ba CO³) according to the reactions :-
appears to be the most desirable.
But such application of barium compounds is, in consideration of their relatively
bigh price, prevented by the very large quantities which would be requisite in the
case of most brines, as may be seen from the following table :-
I have discovered that chloride of calcium added even in small quantity to brine
will not only convert the sulphates of sodium, potassium, magnesium, and other
non-calcic sulphates, that is to say, the basic component of which is some other. base
than calcium, into gypsum (sulphate of calcium) which falls to the bottom, but that
also the greater part of the gypsum which is native to the brine, will also precipitate,

page_text: so that but a very small amount of said gypsum is left for removal by means of
barium compounds. The precipitation is proportional to the quantity of chloride of
calcium added, as is shewn in the following table: -
Thus my discovery enables the purification of brine from the sulphates to be
carried out by means of a greatly reduced proportion of barium compounds. In
applying my discovery it is possible to remove the greater part of the sulphates from
the brine almost free of expense, because the waste liquors of the ammonia soda
works containing chloride of calcium are applicable for the purpose.
Whilst the previous applications of chloride of calcium for direct production of
culinary salt have been devised either for the purpose of precipitating chloride of
sodium from the brine, or for the purpose of dissolving solid salt in hot chloride
of calcium solution and re-precipitation of sodium chloride by subsequent cooling, in
the present process, on the contrary, the addition of chloride of calcium serves for
the partial removal of sulphates from the brine, and the quantity of chloride of
calcium to be used is a very different one from the foregoing, corresponding to the
entirely different principle and object of the present process. For instance, it has
proved economical and practicable to treat the brine of Schweizerhalle near Basel in
Switzerland with an addition of chloride of calcium amounting to from 7 to 8 kilos.
per cubic meter of brine. By means of this addition no sodium chloride is pre-
cipitated. On the other hand, the sulphuric acid of the sulphates contained is so far
removed from the brine that the purification for instance with carbonate of barium
or witherite becomes profitable.
Obviously the above stated quantity of chloride of calcium is not to be regarded
as an invariable proportion, because this, as already stated, is adapted to the brine of
Schweizerhalle. In the case of brines containing a larger proportion of sulphates,
such a larger quantity of chloride of calcium must be applied as is required by the
principle of this invention, i.e., such a quantity that in addition to the conversion of
the non-calcic sulphates into precipitated sulphate of calcium, also the greater part
of the gypsum originally present in solution in the brine is caused to deposit.
After the addition of chloride of calcium the mixture is allowed to rest until
the reaction is completed. It is, however, advantageous to keep the solution in
motion either by heating, or by stirring, or by stirring and heating, whereby the
reaction is furthered.
The influence of the stirring or heating may be seen from the following
examples
In each of the three following cases, to one cubic ineter of brine from
Schweizerhalle there were added 10 kilos. of chloride of calcium. The brine which

page_text: bad stood 24 hours at 18 degrees Centigrade required 3.78 kilos. witherite per cubic
meter. After heating for 24 hours to from 40 to 50 degrees Centigrade, the other
cubic meter required 3.72 kilos. witherite. After stirring for 24 hours at 18 degrees
Centigrade, the third cubic meter required 3.01 kilos. witherite.
After about 24 hours the liquid is allowed to settle, the clear brine is drawn off
from the precipitate, and transferred to a second reservoir, and it is there treated
with a proportion of witherite corresponding to the remaining quantity of sulphate,
the mixture being constantly stirred. This operation can be effected in a cold or
warm solution. Even in this reaction the presence of chloride of calcium appears to
be favourable. After the reaction is complete it is advisable to continue the
agitation for some time; the sulphate of barium separated out is then allowed to
settle, and the clear brine is separated from the deposit and evaporated until a
sample of the precipitated salt, dried on a centrifugal machine, shews a tolerable amount
of chloride of calcium present. On this the mother lye is drawn off from the
precipitated salt. Said mother lye, which contains a good deal of chloride of
calcium, is used again for the treatment of a fresh quantity of brine.
If brine be made use of which contains organic substances, it is possible by frac-
tionating the addition of chloride of calcium, to remove first such substances, in order
to obtain by the second addition a pure gypsum, which can be utilized in commerce.
Other compounds of calcium are also applicable for the purpose of the present
invention. Thus, for instance, the calcium salts easily soluble in water, such as the
bromide, or the nitrate of calcium, act in a like manner to the chloride of calcium.
Also the quantity of sulphates in the brine may be reduced by the use of calcium
hydroxide.
By means of the above and other calcium compounds chloride of calcium may be
totally or partially replaced if desired.
If there are added to one litre of Schweizerhalle brine (the sulphate contents whereof
correspond to 0.9770 gramme sulphate of barium per 100 cubic centimeter) either
calcium bromide or calcium nitrate or calcium hydroxide, the sulphate contents of the
brine are reduced with precipitation of sulphate of calcium corresponding to the
addition of the above mentioned calcium compounds. In this case also the reaction
is furthered by stirring or heating.

page_text: The application of calcium hydroxide is suitable in the case of brines which possess
a large percentage of sulphates. Thus, for instance, the sulphate contents of the
brine of toblaine (containing a quantity of sulphates corresponding to 2.4070 grammnes
of barium sulphate in 100 cubic centimeters) is reduced by the addition of 20 grammes
of hydroxide of calcium and the use of a stirring apparatus for 20 hours, to a pro-
portion which corresponds to 1.6680 grammes of barium sulphate for 100 cubic
centimeters. The same addition in the case of the Schweizerhalle brine causes the
sulphate contents under like conditions to sink to an amount which corresponds to
0.9140 gramme of barium sulphate for 100 cubic centimeters. The proportion of
hydroxide of calcium which goes into solution, should be precipitated by passing in
carbonic acid gas.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is: —
The process for purifying brine from sulphates which consists in adding to the
brine a water-soluble compound of calcium in such proportion that the non-calcic
sulphates are transformed into, and separated out as, calcium sulphate and part of the
calcium sulphate original to the brine is caused to precipitate, agitating or heating
the brine while under the action of said reagent, separating the liquor from the
deposit, and removing therefrom the remainder of dissolved calcium sulphate by
means of barium compounds, substantially as and for the purpose specified.
Dated the 3rd day of August 1899.
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester and Birmingham.