Process for Purifying Brine.
Year: 1891

page_text: COMEDIE DIDOLFICATION.
Process for Purifying Brine.
I, CALEB GROZIER COLLINS of Woodsburgh in the County of Kings and State
of New York United States of America Electrician, 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 :-
My invention relates to the purification of brine for the manufacture of common
salt, (chloride of sodium,) and for other purposes, and consists primarily in subjecting
the brine to a current of electricity having an electro-motive force not exceeding
24 volts in intensity, which, while it is sufficient to decompose most of the
impurities contained in the brine, is insufficient to decompose the chloride of
sodium, the decomposition of these impurities resulting in the formation of
insoluble precipitates, which may be removed by mechanical means, as more fully
set forth hereafter.
A secondary feature of my invention consists in first treating the brine with
electricity as above set forth and then effecting the prompt and positive removal of
the impurities thus rendered insoluble by filtration. Since however certain
substances when present in a brine, have a tendency after having been rendered
insoluble by decomposition as above set forth, to re-dissolve, before they can be
eliminated therefrom, my invention in this connection includes the filtration of the
brine while under the influence of an electrical current whereby the precipitated
impurities are prevented from re-dissolving, the current of electricity being of an
electro-motive force not exceeding 2 volts in intensity, so as to avoid the
decomposition of the chloride of sodium.
In the accompanying drawing I illustrate symbolically apparatus suitable for
carrying out my improved process of purifying brine, although I do not confine
myself to the use of any special construction or arrangement of parts, since it is
obvious that the apparatus may be varied or modified materially and still be
adapted to meet the practical and essential requirements of my invention.
The drawing shows a tank A, divided into two compartments B and C, by the
vertical partition a.
"
In the first compartment B, are arranged a series of anodes b, and cathodes 6',
connected with the respective poles of a battery D, or other suitable source of
electricity.
A supply pipe E, is arranged above the electrodes b, b', and is preferably formed
with a series of discharge openings e, arranged to distribute the supply of brine
uniformly to the tank; and any suitable number of these supply pipes may be
employed in effecting this result.
The bottom of the tank B, is provided with a discharge pipe F, through which
the solid precipitates may be carried off; and with a brine discharge pipe G,
arranged at a suitable level through which the brine may be withdrawn after being
subjected to the action of the electric current and allowed to settle.
Both discharge pipes F, and G, are provided with valves, and g, respectively.
There is an opening a¹, in the partition a, of the tank A, which opening
establishes communication between the two compartments B and C. In the
compartment C, above the opening a¹, is situated a horizontal partition or floor c,
formed with a series of perforations through which the brine is enabled to rise
upward into the filtering chamber C, provided with a suitable filtering medium c³,
preferably having imbedded in it a series of electrodes ², c, connected alternately
with the positive and negative poles of the battery D', or other suitable source of
electricity, in such manner that the current may be thrown on or off the filtering
material, at pleasure.
The filtering chamber C¹, is provided with an outlet or overflow pipe of, which is

page_text: above the filtering material but on a lower level than that of the supply pipe E, so
that the purified brine will flow off naturally by hydrostatic pressure.
It is well known that the character of the impurities found in salt vary in the
different sources of supply, the deposits of rock salt, the salt springs, and even the
natural sea waters differing in composition.
The most common impurities in the natural deposits of salt and the brine arising
therefrom are ferrous bicarbonate, calcium bi-carbonate, magnesium bi-carbonate,
calcium sulphate, calcium chloride, magnesium chloride, and earths and clays and
organic matter.
The sea waters contain chlorides of potassium, calcium, and magnesium, bromides
of sodium and magnesium, sulphates of lime and magnesium and carbonates of
magnesium and lime.
I have found by experimental research that in the presence of an electrical
current of less intensity than 2 volts, some of these may be decomposed, rendered
insoluble and precipitated therefrom, without danger of the decomposition and loss
of chloride of sodium.
Thus by passing a current of electricity, of proper intensity and duly regulated
to protect the chloride of sodium, through the brine prior to subjecting it to
evaporation for the purpose of effecting the concentration and crystallization of the
salt, the decomposition of the deleterious substances contained in the brine, either
in solution or suspension, and their separation therefrom may be readily and
economically effected.
For instance, calcium bi-carbonate in solution under the influence of an electrical
current of less than 2 volts will be decomposed, carbonic acid being liberated at
the anode and calcic hydrate at the cathode (according to reaction Ča.H₂ (CO₂),
CH,O, +2 CO2). The calcic hydrate thus liberated reacts on another
equivalent of calcic bi-carbonate to form neutral calcic carbonate which is insoluble
and is precipitated (CaH,O, + CaH, (CO₂), = 2 CaCO, + 2 H,O).
=
Again, sulphate of lime in solution under the influence of an electrical current
of less than 2 volts will be decomposed; sulphuric acid being liberated at the
anode and calcic hydrate at the cathode (CaSO, + 2 H₂O = H₂SO + CaH₂O,)
In the presence of bi-carbonate of lime in the brine, the calcic hydrate thus
liberated reacts on an equivalent of bi-carbonate of lime to form neutral calcic
carbonate which is insoluble and is precipitated.
In substantial like manner calcium chloride, magnesium bi-carbonate, magnesium
sulphate and magnesium chloride, will suffer decomposition and precipitation.
My process is especially applicable to the removal of the bases of the above and
kindred compounds. It is also applicable to the removal of ferrous bi-carbonate
by oxidization resulting from the decomposition of water.
In operation the brine is simply introduced into the tank B, by the supply pipe
or pipes E, being thereby subjected to the influence of the electrical currents
passing between the anodes b, and cathodes b', resulting in the partial decomposition
of the water and the decomposition of some of the impurities of the brine. The
insoluble precipitates thus formed may be allowed to settle to the bottom and be
eventually removed through the discharge pipe or pipes F, or by other means
while the purified brine may be conducted off by the discharge pipe G, or the
impurities may be positively separated and eliminated from the brine by causing
the latter to flow through a filtering material c', preparatory to its discharge for
evaporation and crystallization.
When the brine is of such a character that the impurities after decomposition in
the tank B, are liable to re-combine to form soluble compounds, when beyond the
influence of the electrical current, I connect the anodes and cathodes in the filtering
material o', alternately with the poles of battery D', or other source of electricity,
care being taken to duly regulate and maintain the current at an intensity
below 2 volts in which case these soluble compounds if so formed are again
decomposed into insoluble products and positively removed from the filtering
brine.

page_text: An electrical current of 2 volts in intensity is sufficient to decompose the impuri-
ties in brine as hereinbefore set forth for the reason that their chemical affinities,
expressed in electrical terms, are in each case less than the voltage described. With
sodium chloride, on the contrary the affinity between the sodium and the chlorine,
expressed in electrical terms, is greater than the aforesaid voltage, and the essential
feature of my invention consists in the discovery, by experimental investigation, of
this fact, and its practical utilization in the purification of brine.
The importance of removing all traces of iron from the brine is obvious in view
of its injurious effects on the color of the salt if allowed to remain. Hence the
decomposition of the iron compounds and their oxidization and consequent precipi-
tation under the influence of the electrical current simultaneous with the
decomposition of the other impurities is another important feature of my improved
process.
I am aware that in the American Patent to Webster, dated August 8th 1888,
No. 387,467, filtration is described as conducted under the influence of an electrical
current, but in that case the object is the oxidization of animal matter, and I do
not seek to cover herein the equivalent of the process therein set forth, neither do I
wish to cover broadly the idea of the filtration of a liquid solution while under the
influence of electricity, but
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
First. The process of purifying brine, substantially as herein set forth, consisting
in rendering the impurities insoluble by subjecting the brine to a current of
electricity having an electro-motive force not exceeding two and one-half volts.
sufficient to decompose the impurities in the brine, but below the intensity
necessary to decompose the sodium chloride in the brine whereby the impurities are
rendered insoluble through decomposition, while the sodium chloride is unaffected
by the electric current.
Secondly. The process of purifying brine as herein set forth, consisting in
rendering the impurities insoluble by subjecting the brine to a current of electricity
having an electro-motive force not exceeding two and one-half volts in intensity,
and then separating the brine from such precipitates by passing it through a
filtering medium substantially in the manner and for the purpose described.
Thirdly. The process of purifying brine as herein set forth, consisting in
rendering the impurities insoluble by subjecting the brine to a current of electricity
having an electro-motive force not exceeding two and one-half volts in intensity,
and then separating the brine from such precipitates by passing it through a
filtering medium which under the influence of an electrical current not exceeding
two and one-half volts in intensity to insure the re-precipitation and render such
impurities as tend to re-dissolve after passing beyond the influence of the first.
electrical current, substantially as described.
Fourthly. The process of purifying brine as herein set forth, consisting in
rendering impurities insoluble and simultaneously removing them from the brine by
passing the latter through a filtering medium in which it is subjected to a current
of electricity having an electro-motive force not exceeding two and one-half volts
in intensity, substantially in the manner and for the purpose described.
Dated this 31st day of August 1891.
FELL & WILDING,
1, Queen Victoria Street, London, E.C., Agents for the Applicant.