14 Claims, 6 Drawing Figures
3,873,437 3/1975 Pulver 204/254
3,884,792 5/1975 McGilvery 204/268
3,910,827 10/1975 Raetzsch et a1. 204/98
Primary Examiner-F.C. Edmundson
Attorney, Agent, or FYrm-William G. Addison
An improved hybrid bipolar electrode particularly useful
in an alkali chloride electrolysis application, having
an anodic member and cathodic member connected in
spaced apart relationship by a fastener assembly, a seal
being formed between portions of the anodic member
and the cathodic member to substantially seal electrolyte
from the space between the anodic member and the
cathodic member. In one aspect, a barrier member is
interposed between the anodic member and the cathodic
member to inhibit the contact of migrating
atomic hydrogen with the anodic member. In one other
aspect of the present invention, a portion of the fastener
assembly is constructed of an electricaIly conductive
material and electrical continuity is established between
the anodic member and the cathodic member via the
fastener assembly, the barrier member serving to effectuate
a more even distribution of current flow between
the cathodic member and the anodic member in yet
another aspect of the present invention.
United States Patent (19]
Poush et al.
[54] HYBRID BIPOLAR ELECfRODE
[75] Inventors: Kenneth A. Poush, Lake Jackson,
Tex.; James E. Reynolds, Golden,
Colo.
[73] Assignee: Kerr-McGee Chemical Corporation,
Oklahoma City, Okla.
[21] AppI. No.: 545,016
[22] Filed: Jan. 29, 1975
[51] Int. Cl,2 e25B 9/00; C25B 11/00;
C25B 13/00; C25B 1/34
[52] U.S. Cl 204/268; 204/254;
204/286
[58] Field of Search 204/286, 268, 254, 255,
204/256
[56] References Cited
U.S. PATENT DOCUMENTS
806,413 12/1905 Kother 204/268
3,242,065 3/1966 Nora et a1. 204/255
3,312,614 4/1967 Schick 204/255
3,389,071 6/1968 Meyers 204/268
3,402,117 9/1968 Evans 204/286
3,752,757 8/1973 Stephenson et a1. 204/256
3,759,813 9/1973 Raetzsch et a1. 204/256
3,813,326 5/1974 Gunby 204/268
3,824,173 7/1974 Bouy et aI 204/284
3,859,197 1/1975 Bouy et aI 204/284
[57]
[11]
[45]
ABSTRACf
4,085,027
Apr. 18, 1978
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SUMMARY OF THE INVENTION
The present invention contemplates an improved
bipolar electrode and methods for constructing same
and electrolytic cells containing the same. The bipolar
electrode includes an anodic member and a cathodic
member secured in a spaced apart relationship via at
least one fastener assembly. The anodic member and the
cathodic member are electrically connected for conducting
current therebetween, and the space between
the anodic member and the cathodic member is sealed
to substantially inhibit the flow of electrolyte into such
space during the operation of the hybrid bipolar electrode
in an electrolytic cell. In one form, the bipolar
electrode of the present invention includes a barrier
member interposed in the space between the anodic
member and the cathodic member and constructed of a
2
was consumed, the voltage drop across the electrolytic
cell was increased and the temperature of the electrolyte
increased with the result being the establishment of
an operating temperature range of approximately 25· C
5 to approximately 70· C. At the upper limit of this operating
temperature range, the loss of graphite as a result
of graphite oxidation was substantially increased and, in
some instances, cooling coils were included in the electrolytic
cell to cool the electrolyte in an attempt to
10 maintain the electrolyte temperature at a reduced level
(approximately 50· C, for example).
The erosion of the carbon bipolar electrodes caused
dimensional instability and resulted in a decreased current
efficiency as the carbon bipolar electrode was operated
over a period of time. Since the erosion of the
carbon bipolar electrodes was not uniform, current
density gradients were formed which caused further
deleterious effects on the operational characteristics of
the electrolytic cell.
20 In recent years, metal electrodes have been proposed
to be operated as anodes in bipolar electrolytic cells,
such bipolar electrodes also including a cathodic surface.
For example, anodic surfaces of titanium have
been proposed with cathodic surfaces bonded thereto
and such bipolar electrodes have been proposed for use
in chloride brines. A non-conductive film tends to form
on exposed titanium anodic surfaces in chloride brines;
however, this non-conductive film does not tend to
develop on precious metals, such as platinum, for example,
and platinum in combination with iridium or rubidium
coated titanium anodic surfaces have been utilized
in chlor-alkali electrolytic cell applications.
In the past, metal bipolar electrodes have been constructed
of titanium sheets bonded to steel plates, the
titanium sheets forming the anodic member and the
steel plate forming the cathodic member. One problem
encountered with such bi-metal bipolar electrodes was
that the titanium sheet was deformed via the action of
molecular hydrogen migrating through the cathodic
member to the anodic member forming an expanded
hydride with the titanium. This action resulted in a
weakening of the structural integrity of the bond between
the titanium sheet and the steel plate and, in many
instances, resulted in a separation of the titanium-steel
along the bonded surface.
Typical patents disclosing prior art devices of the
type generally referred to above are the U.S. Pat. Nos.
3,759,813, issued to Raetzsch, et ali 3,732,157, issued to
Dewitt; 3,043,757, issued to Holmes; 3,441,495, issued to
Colman; and 3,222,270, issued to Edwards.
4,085,027
1
BACKGROUND OF THE INVENTION
HYBRID BIPOLAR ELECTRODE
CROSS-REFERENCE TO RELATED
APPLICATIONS
Related subject matter is disclosed in the patent application,
Ser. No. 545,015, entitled "A BIPOLAR
ELECTRODE AND METHOD FOR CONSTRUCTING
SAME," filed on an even date with the
present application and assigned to the assignee of the
present invention.
1. Field of the Invention
The present invention relates generally to an im- 15
proved bipolar electrode and, more particularly, but not
by way of limitation, to an improved hybrid bipolar
electrode having an anodic member and a cathodic
member connected in a spaced apart relationship.
2. Brief Description of the Prior Art
In the past, many electrolytic cells have been proposed
for use in a variety of applications. Various electrodes
for use in electrolytic cell applications have also
been proposed in the past.
A typical prior art electrolytic cell included an anode 25
electrode and a cathode electrode immersed in an electrolyte
and an electrical power source connected to the
anode electrode and the cathode electrode, the positive
side of the power source being connected to the anode
electrode and the negative side of the power source 30
being connected to the cathode electrode. In this type
of electrolytic cell, the electrode functioning as the
anode and the electrode functioning as the cathode
were generally referred to in the art as "monopolar"
electrodes, i.e. each electrode functions as either an 35
anode or a cathode during electrolysis.
Another type of electrolytic cell included an anode
electrode and a cathode electrode and at least one electrode
interposed between the anode and the cathode
electrodes, each of the electrodes interposed between 40
the anode and the cathode electrodes having an anodic
member and a cathodic member and being referred to in
the art as "bipolar" electrodes. The cathodic member
and the anodic member of each bipolar electrode were
mechanically connected, and the cathodic member of 45
each of the bipolar electrodes was electrically in series
with the anodic members prior and subsequent thereto,
i.e. the current flowed through the electrolyte to the
cathodic member of the bipolar electrode, through the
bipolar electrode and from the anodic member of the 50
bipolar electrode through the electrolyte to the next
cathodic member of another bipolar electrode or to the
cathodic member of the monopolar cathode electrode
depending on the number of bipolar electrodes in the
electrolytic cell. 55
In the past, electrodes constructed of a carbon material
have been used in the construction ofboth monopolar
electrodes and bipolar electrodes. In some instances,
the anoclic surfaces were constructed of a carbon material
and the cathodic surfaces were constructed of a 60
ferrous material, this type of construction tending to
minimize contamination ofthe electrolyte which results
from the electrolytic erosion of many non-carbon anodes.
Bipolar electrodes have been constructed of graphite 65
and, in these instances, the graphite was continuously
consumed during electrolysis as a result of oxidation of
the graphite surfaces. As the graphite bipolar electrode
4,085,027
4
anodic member 12 is constructed of a titanium metal
sheet having a coating of a noble metal or oxide thereof
on the first face 20, such as platinum-iridium, platinum,
rubidium, ruthenium, osmium and oxides thereof and
the like, for example, the coating being electrically
conductive and forming the anodic surface on the anodic
member 12 (the coating forming the anodic surface
not being separately illustrated in the.drawings).
The cathodic member 14 is generally rectangularly
10 shaped and has a first face 34, a second face 36, a first
side 38, a second side 40, a third side 42 and fourth side
44. The cathodic member 14 is constructed such that
the first face 34 of the cathodic member 14 operates as
a cathodic surface in an electrolytic cell. In one preferred
embodiment, the hybrid bipolar electrode 10 is
utilized in an alkali metal chlorate or chlorine electrolyte
cell for the electrolysis of aqueous. solutions of
alkali metal chlorides in a manner mentioned before
with respect to the anodic member 12 and, in this one
preferred embodiment, the cathodic member 14 is constructed
of a carbon steel, stainless steel, or other ferrous
materials or non-ferrous materials such as copper,
nickel or molybdenum, for example, serviceable in chlorate
solutions.
A plurality of generally cylindrically· shaped depressions
46 are formed in the first face 34 of the cathodic
member 14. Each of the depressions 46 has an internal
diameter 48, as shown in FIG. 3, and forms an open
space SO extending a distance 52 generally into the first
30 face 34 of the cathodic member 14 terminating with an
end wall 56 (only some of the depressions 46 are specifically
designated in the drawings via a reference numeral
for clarity). Each of the depressions 46 forms a corresponding
raised portion on the second face 36 of the
cathodic member and each raised portion extends a
distance generally from the second face 36 terminating
with an end 54.
A plurality of openings 58 are formed through the
cathodic member 14, each opening 58 extending
through the cathodic.member 14 intersecting the first
face 34 and the second face 36 thereof. More particularly,
each of the openings 58 is formed through a central
portion of one of the depressions 46, each opening
58 intersecting the end wall 56 and the end 54 formed
via one of the depressions 46. The depressions 46 and,
more particularly, the openings 58 are spaced in accordance
.with a predetermined spacing pattern ·substantially
corresponding with the spacing pattern of the
openings 32 in the anodic member 12 and, in an assembled
position of the bipolar electrode . 10, each of the
openings 58· in the cathodic member 14 is substantially
aligned with one of the openings 32 in the anodic member
12.
The barrier member 18 is generally rectangularly
shaped and has a first face 60, a second face 62, a first
side 64, a second side 66, a third side 68 and a fourth side
70. A plurality of openings 72 are formed through the
barrier member 18 and each opening 72 extends through
the barrier member 18 intersecting the first face 60 and
the second face 62 thereof (only one of the openings 72
being shown in the drawings). The openings 72 are
spaced in accordance with a predetermined spacing
pattern corresponding with the spacing pattern of the
openings 32 in the anodic member 12 and corresponding
with the spacing pattern of the openings 58 in the
cathodic member 14. In an assembled position of the
bipolar electrode 10, each of the openings 72 in the
barrier member 18 is substantially aligned with one of
BRIEF DESCRIPTION OF THE DRAWINGS
3
material inhibiting the contact of hydrogen with the
anodic member in an electrolysis application.
FIG. 1· is an elevational view of the first face of an 5
anodic member of a hybrid bipolar electrode constructed
in accordance with the present invention.
FIG. 2 is an elevational view of the first face of a
cathodic member of the hybrid bipolar electrode.of the
present invention.
FIG. 3 is a fragmentary, partial sectional, partial
elevational view showing a typical first or second side
elevational view of the anodic member of FIG. 1 connected
via a fastener assembly to the cathodic member
of FIG. 2 forming the hybrid bipolar electrode of the 15
present invention, only two typical fastener assemblies
being shown in FIG. 3.
FIG. 4 is a fragmentary elevational view similar to
FIG. 3, but showing a typical third or fourth side elevational
view of the hybrid bipolar electrode of the pres- 20
ent invention, only two of the fastener assemblies being
shown in FIG. 4.
FIG. 5 is a fragmentary partial sectional, partial elevational
view showing the hybrid bipolar electrode of
the present invention in an electrolytic cell. 25
FIG. 6 is a fragmentary view similar to FIG. 3, but
showing a typical first or second side elevational view
of a modified hybrid bipolar electrode.
DESCRIPTION OF THE PREFERRED
EMBODIMENTS
Referring to the drawings and to FIGS. 1 through 4
in particular, shown therein and designated via the general
reference numeral 10 is a hybrid bipolar electrode
constructed in accordance with the present invention. 35
In general, the hybrid bipolar electrode includes an
anodic member 12, a cathodic member 14, a plurality of
fastener assemblies 16 connecting the anodic member 12
and the cathodic member 14 in a spaced apart relationship
(only some of the fastener assemblies being specifi- 40
cally shown in FIGS. 3 and 4, for clarity), and a barrier
member 18 disposed in the space between the anodic
member 12 and the cathodic member 14, the fastener
assemblies 16 also securing the barrier member 18 in an
assembled position supported between the anodic mem- 45
ber 12 and the cathodic member 14.
The anodic member 12 is generally rectangularly
shaped and has a first face 20, a second face 22, a first
side 24, a second side 26, a third side 28 and a fourth side
30.•A plurality of openings 32 are formed through the 50
anodic member 12 and each opening 32 extends through
the anodic member 12 intersecting the first face 20 and
the second face 22 thereof (only some of the openings
32 are specifically designated via a reference numeral in
the drawings for clarity). More particularly, each of the 55
openings 32 is sized and shaped to accommodate a portion
of one of the fastener assemblies 16, and, in one
preferred form, the openings 32 are spaced on the anodic
member 12 in accordance with a predetermined
spacing pattern arranged for cooperation with the fas- 60
tener assemblies 16 in a manner to be described below.
The anodic member 12 is constructed such that the
first face 20 of the anodic member 12. operates as an
anodic surface in an electrolytic cell. In one preferred
embodiment, the hybrid bipolar electrode 10 is utilized 65
in an alkali metal chlorate or chlorine electrolytic cell
for .the electrolysis of aqueous solutions of alkali metal
chlorides and, in this one preferred embodiment,. the
4,085,027
5 6
the openings 32 in the anodic member 12, each of the cathodic member 14 generally facing the second face 62
openings 72 in the barrier member 18 also being substan- of the barrier member 18. The cathodic member 14 is
tially aligned with one of the openings 58 in the ca- positioned such that the rod portions 78 of each of the
thodic member 14. bolt members 74 extends through one of the openings 58
Eachfastener assembly 16 includes a bolt member 72 5 in the cathodic member 14 and end face 88 of each of
having a head portion 76 and a threaded rod portion 78, the second spacers 84 generally faces the second face 36
only one of the fastener assemblies 16 being shown in of the cathodic member 14, a portion of each rod por-
FIGS. 3 and 4 for clarity. In a fastened position of the tion 78 extending a distance beyond the end wall 56
fastener assemblies 16, the rod member 78 of each bolt formed by one of the depressions 46 and being disposed
member 74 extends through one ofthe aligned openings 10 generally within one ofthe open spaces 50 formed in the
32 of the anodic member 12, through one of the aligned cathodic member 14 via the depressions 46. One of the
openings 72 of the barrier member 18, and through one nut members 80 is threadedly secured to the end portion
of the aligned openings 58 of the cathode member 14. of each rod portion 78 extending into the open space 50
Each of the fastener assemblies 16 also includes a nut formed via the depressions 46 and each of the nut memmember
80 having a threaded opening (not shown) 15 bers 80 is rotated in one direction threadedly engaging
extending a distance therethrough and sized to thread· one of the rod portions 78 and securing the hybrid bipoedly
engage the threaded rod portion 78 of one of the lar electrode 10 in an assembled position wherein the
bolt members 74, each nut member 80 being generally anodic member 12, the cathodic member 14 and the
disposed in one of the open spaces 50 formed in the barrier member 18 are disposed in generally parallel
depressions 46, in a fastened position of the fastener 20 extending planes in a spaced apart relationship, the ends
assemblies 16. 86 of each of the first spacers 82 are disposed generally
In one preferred embodiment, as shown in FIGS. 3 adjacent the second face 22 of the anodic member 12,
and 4, each fastener assembly 16 includes a first and a the ends 88 of each of the first spacers 82 are disposed
second spacer 82 and 84, respectively. The spacers 82 generally adjacent the first face 60 of the barrier memand
84 are similarly constructed and each spacer 82 and 25 ber 18, the ends 86 of each of the second spacers 84 are
84 has opposite end faces 86 and 88 and an opening 90 disposed generally adjacent the second face 62 of the
extending through a central portion thereof intersecting barrier member 18, and the ends 88 of each of the secthe
end faces 86 and 88. The first spacer 82 of each ond spacers 84 are disposed generally adjacent the secfastener
assembly 16 is disposed between the anodic ond face 36 ofthe cathodic member 14. Further, each of
member 12 and the barrier member 18 and the rod por- 30 the head portions 76 engages a portion of the first face
tion 78 of each of the bolt members 74 extends through 20 of the anodic member 12, each ofthe nut members 81)
the opening 80 formed through one of the first spacers engages a portion of the first face 34 of the cathodic
82, the bolt members 74 supporting the first spacers 82 member 14 and the rod portion ofeach ofthe bolt memin
an assembled position between the anodic member 12 bers 74 extends through the aligned openings 32, 58 and
and the barrier member 18. The second spacer 84 of 35 72 and through the openings 90 in the spacers 82 and 84.
each fastener assembly 16 is disposed between the ca- Thus, the fastener assemblies 16 mechanically connect
thodic member 14 and the barrier member 18 and the the anodic member 12, the cathodic member 14 and the
rod portion 78 of each of the bolt members 74 extends barrier member 18 in an assembled position with the
through the opening 90 formed through one of the second face 22 of the anodic member 12 spaced a dissecond
spacers 84, the bolt members 74 supporting the 40 tance 92 from the second face 36 of the cathodic memsecond
spacers 84 in an assembled position between the ber 14, and the first spacers 82 ofthe fastener assemblies
cathodic member 14 and the barrier member 18. 16 cooperate to secure the anodic member 12 in a
To assemble the hybrid bipolar electrode 10, the rod spaced apart relationship with respect to the barrier
portions 78 of the bolt members 74 are inserted through member 18 wherein the second face 22 of the anodic
the openings 32 in the anodic member 14 and each of 45 member 12 is spaced a distance 94 from the first face 60
the first spacers 82 are disposed on the rod portion 78 of of the barrier member 18, the second spacers 84 of the
one of the bolt members 74 with the rod portion 78 fastener assemblies 16 cooperating to secure the ca·
extending through the opening 90 in the first spacer 82, thodic member 14 in a spaced apart relationship with
the end face 86 of each of the first spacers 82 generally respect to the barrier member 18 wherein the second
facing the second face 22 of the anodic member 12. The 50 face 36 of the cathodic member 14 is spaced a distance
barrier member 18 is disposed near the anodic member 96 from the second face 62 of the barrier member 18. In
12 and positioned such that each of the openings 58 in a preferred form, each nut member 80 is sized and
the barrier member 18 is aligned with one of the open- shaped to be disposed in one of the open spaces 50
ings 32 in the anodic member 12, the first face 60 of the formed in the cathodic member 14 via the depressions
barrier member 18 generally facing the second face 22 55 46 and positioned therein such that the ends of each nut
of the anodic member 12. The barrier member 18 is member 80, opposite the ends engaging the end walls
positioned such that the rod portions 78 of each of the 56, are each disposed in a plane disposed generally
bolt members 74 extends through one ofthe openings 72 below and spaced a distance from the planar disposition
in the barrier member 18 and each of the second spacers of the first face 34 of the cathodic member 14. In one
84 is disposed on the rod portion 78 of one of the bolt 60 preferred embodiment, the bolt member 74 and the nut
members 74 with the rod portion 78 extending through member 80 of each of the fastener assembies 16 is conthe
opening 90 in the second spacer 84, the end face 86 structed of a material capable of conducting electrical
of each of the second spacers 84 generally facing the current or,mother words, an electrical conductor type
second face 62 of the barrier member 18. The cathodic of material, and, in this one preferred embodiment, a
member 14 is disposed near the barrier member 18 and 65 portion of each of the fastener assemblies 16, more parpositioned
such that each of the openings 58 mthe ticularly, is constructed ofan electrical conductor matecathodic
member 14 is aligned with one of the openings rial such as brass or copper, or example. In this embodi-
72 in the barrier member 18, the second face 36 of the ment ofthe present invention, the fastener assemblies 16
4,085,027
7
establish electrical continuity between the anodic member
12 and the cathodic member 14 in addition to mechanically
connecting the anodic member 12 and the'
cathodic member 14 in the spaced apart relationship.
The spacing of the fastener assemblies 16 with respect 5
to the anodic member 12 and the cathodic member 14 is
established to provide a uniform current density on the
cathodic member 14 and the anodic member 12 during
the operation of the hybrid bipolar electrode 10 in additin
to the mechanical connecting function of the fas- 10
tener assemblies 16, the spacing pattern of the fastener
assemblies 16 being a repetitive type of pattern as indicated
in FIGS. 1 and2'11
As mentioned before, the hybrid bipolar electrodes of
the present invention are particularly useful in an alkali 15
metal chlorate or chlorine electrolytic cell for the electrolysis
.of aqueous solutions of alkali metal chlorides.
Diagrammatically and schematically shown in FIG. 5 is
an electrolytic cell 100 comprising: a cell box 102 hav- 0
ing opposite side walls 104 and 106, opposite end walls 2
108 and 110 and a base 112 defining a space 114 for
retaining the electrolyte; a monopolar anodic electrode
116 connected via conventional means to the positive
side of an electrical power source 118 (more particu- 25
larly, a direct-current power source); a monopolar cathodic
electrode 120 connected via conventional means
to the negative side of the electrical power source 118;
and a plurality of the hybrid bipolar electrodes 10 disposed
between the anodic electrode 116 and the ca- 30
thodic electrode 120 (only the first hybrid bipolar electrode
10 next to the monopolar anodic electrode 116
and the last hybrid bipolar electrode 10 next to the
monopolar cathodic electrode 120 being shown in FIG.
~ ~
In one form, the cell box 102 includes a plurality of
openings 122 formed through the base 112 for introducing
the electrolyte into the space 114 formed in the cell
box ·102. A plurality of channels are formed in the side
wall 104, only four channels being shown in FIG. 5 and 40
designated therein via the reference numerals 124, 126,
128 and 130, and a plurality of channels are formed in
the side wall 106, each of the channels formed in the
side wall 106 being aligned with one of the channels
124,126, 128 and 130 formed in the side wall 104 (only 45
four channels being shown in FIG. 5 and designated
therein via. the reference numerals 132, 134, 136 and
138).
The monopolar anodic electrode 116 has opposite
sides 140 and 142 and a surface 144 operating as an 50
anodic surface during the operation. of the electrolytic
cell 100. The aligned channels 124 and 132 are sized and
positioned to slidingly receive the anodic electrode 116,
and the anodic electrode 116 is supported within the
space 114 and extends between the side walls 104 and 55
106, the anodic electrode 116 being at least partially
immersed in the electrolyte during the operation of the
electrolytic cell 100.
The monopolar cathodic electrode 120 has opposite
sides 146 and 148 and a surface ISO operating as a ca- 60
thodic surface during the operation of the electrolytic
cell 100. The aligned channels130 and 138 are sizedand
positioned to slidingly receive the cathodic electrode
120, and the cathodic electrode UO is supported within
the space 114 and extends between the side walls 104 6S
and 106. the cathodic electrode 120 beinS at least partially
immersed in the electrolyte dUrinS the operation
of the electrolytic cell 100.
8
Assuming the electrolytic cell 100 included only the
monopolar electrodes 116 and 120, the electrical power
source 118 would be connected to tne DlOnopolar electrodes
116 and 120, and the current would flow from
the anodic surface 144, through the electrolyte in the
space 114, and to the cathodic surface ISO. The anodic
surface 144 and the cathodic· surface ISO are spaced a
distance apart and the electrolyte is disposed generally
between the anodicsurface 144 and the cathodic surface
ISO. Further, the anodic monopolar electrode 116 is not
mechanically connected to the cathodic electrode 120.
Assuming further that the electrolytic cell 100 included
a plurality of monopolar anodic electrodes and a plurality
of monopolar cathodic electrodes, the monopolar
anodic electrodes would be connected in parallel to the
electrical power source and the monopolar cathodic
electrodes would be connected in parallel to the electrical
power source. This type of arrangement just described
would constitute a typical prior art monopolar
electrode type of electrolytic cell configuration.
The present invention is directed to an electrolytic
cell which includes at least one bipolar electrode, in
contrast to the electrolytic cell which includes only
monopolar electrodes described above. Thus, the electrolytic
cell 100, shown in FIG. 5, includes the monopolar
anodic electrode 116, the monopolar cathodic electrode
120 and one or more of the hybrid bipolar electrodes
10 of the present invention supported within the
cell box 102 space 114,generally between the monopolar
electrodes 116 and 118, and at least partially immersed
in the electrolyte during the operation of the
electrolytic cell 100.
The hybrid bipolar electrode 10 includes a seal member
152 (as shown in FIG. 5) extending generally about
the sides 24, 26, 28 and 30 of the anodic member 12 and
generally about the sides 38, 40, 42 and 44 of the cathodic
member 14. A portion of the seal member 152
sealingly engages the cathodic member 14 and a portion
of the seal member 152 sealingly engages the anodic
member 12 forming a fluid seal· between the anodic
member 12 and the cathodic member 14 to substantially
seal the electrolyte from the space between the second
face 22 of the anodic member 12 and the second face 36
ofcathodic member 14. Thus, a substantial portion of
the space between the second faces 22 and· 36 of the
anodic and the cathodic members 12 and 14 (depending
generally on the size, type and position of the sealmember
152, for example) is sealingly isolated from the electrolyte
solution during the operation of the electrolytic
cell 100. In addition to the seal member 152, each of the
openings 32 in the anodic member 12 and. each of the
openings 58 in the cathodic member 14 are preferably
sealed in a manner forming a seal between the fastener
assemblies 16 and the portions of the anodic member 12
and the cathodic member 14 generally near the openings
32 and 58. In one form, the engagement between
each of the head portions 76 and the first face 20 of the
anodic member 12 forms a seal for substantially inhibiting
the flow.of electrolyte through. the openings 32 in
the anodic member 12 into the space between the anodic
and the cathodic members 12 and 14, and the engagement
between each of the nut members 80 and the
first face 34 (the end walls 56) of the cathodic member
14 forms a seal for substantially inhibiting the flow of
electrolyte through the openings 58 in the cathodic
member 14 into· the space between the anodic and the
cathodic members 12 and· 14. It should be noted that
additional sealing material may be added to augmentthe
4,085,027
9 ro
mechanical seal formed via the engagement between formed on the first face 20 of the last hybrid bipolar
portions of the fastener assemblies 16 and the cathodic electrode 10 through the electrolyte to the cathodic
and the anodic members 14 and 12 if required in a par- surface 156 formed on the monopolar cathodic electicular
application. trode 120. It should be noted that the current flow to,
The aligned channels 126 and 134 in the cell box 102 5 through and from the hybrid bipolar electrodes 10 interare
sized and positioned to slidingly receive one of the mediate or disposed between the first and the last hyhybrid
bipolar electrodes 10 of the present invention brid bipolar electrode 10 has not peen referred to in
(the hybrid bipolar electrode 10 sometimes referred to detail in the foregoing description.
herein in connection with FIG. 5 as the first hybrid In summary, the cathodic surface on the cathodic
bipolar electrode 10), and the aligned channels 128 and 10 member 14 is mechanically connected to the anodic
136 in the cell box 102 are sized and positioned to slid- surface on the anodic member 12 of each hybrid bipolar
ingly receive another hybrid bipolar electrode 10 con- electrode, and the cathodic surface and the anodic surstructed
in accordance with the present invention (the face of each hybrid bipolar electrode 10 are in electrical
hybrid bipolar electrode 10 sometimes referred to series. In addition, the anodic surface of each hybrid
herein in connection with FIG. 5 as the last hybrid 15 bipolar electrode 10 generally faces and is spaced a
bipolar electrode 10). Each of the hybrid bipolar elec- distance from a cathodic surface of either the monopotrodes
10 is supported within the space 114 and extends lar cathodic electrode or one of the other hybrid bipolar
between the side walls 104 and 106. The channels 124, electrodes 10, and the current flows from the anodic
126, 128, 130, 132, 134, 136 and 138, are positioned to surface ofeach hybrid bipolar electrode 10, through the
support the electrodes 10, 116 and 120 in a spaced apart 20 electrolyte, to the cathodic surface of either the monorelationship.
The hybrid bipolar electrodes 10 are each polar cathodic electrode or one of the other hybrid
oriented such that the anodic surface formed on the first electrodes 10. The cathodic surface ofeach hybrid bipoface
20 of the anodic member 12 generally faces and is lar electrode 10 generally faces and is spaced a distance
spaced a distance from the cathodic surface formed on from an anodic surface of either the monopolar anodic
either the monopolar cathodic electrode 120 or the next 25 electrodes or one of the other hybrid bipolar electrodes
hybrid bipolar electrode 10 and the cathodic surface 10 and the current flows from the cathodic surface to
formed on the first face 34 of the cathodic member 14 the anodic surface via the fastener assemblies of each
generally faces and is spaced a distance from the anodic hybrid bipolar electrode 10.
surface formed on either the monopolar anodic elec- During the operation of the electrolytic cell 100, the
trode 116 or the next hybrid bipolar electrode 10, the 30 electrolyte is introduced into the space 114 of the cell
cathodic member 14 and the anodic member 12 of each box 102 via the openings 122, and the electrolyte is
hybrid bipolar electrode 10 being mechanically con· removed from the space 114 of the cell box 102 by
nected and in electrical series. For example, in an assem- overflowing over the top (not shown) of the cell box
bled position of the electrolytic cell 100, the anodic 102 or, in some instances, by passing the electrolyte
surface 144 formed on the monopolar anodic electrode 35 through openings (not shown) in the cell box 102 gener-
116 is spaced a distance 154 from the cathodic surface ally near the top thereof. In some applications, the cell
formed on the first face 34 of the first hybrid bipolar box 102 is supported within a larger cell tank (not
electrode 10 in a direction generally from the monopo- shown) and the electrolyte is retained within the cell
lar anodic electrode 116 toward the monopolar ca- tank circulated into the cell box 102 from the cell tank,
thodic electrode 120; the anodic surface formed on the 40 removed from the cell box 102 and circulated back into
first face 20 of the first hybrid bipolar electrode 10 is the cell tank, a cooling coil being disposed in the cell
spaced a distance from the cathodic surface formed on tank in contact with the electrolyte for maintaining the
the first face 34 of the next hybrid bipolar electrode 10 electrolyte at a predetermined temperature level during
(not shown in FIG. 5) in a direction generally from the the electrolysis operation. The construction and operamonopolar
anodic electrode 116 toward the monopolar 45 tion of cell boxes and cell tanks and the use of cell boxes
cathodic electrode 120jand the anodic surface formed in electrolytic applications is well known in the art, and
on the fIrst face 20 of the last hybrid bipolar electrode a further detailed description is not required herein.
10 in the electrolytic cell 100 is spaced a distance 156 As mentioned before, the hybrid bipolar electrode 10
from the cathodic surface 150 formed on the monopolar is particularly suitable for service in an alkali metal
cathodic electrode 120. During the operation of the 50 chlorate or chlorine electrolytic cell for the electrolysis
electrolytic cell 100 of the present invention the current of aqueous solutions of alkali metal chlorides, and, in
flows from the anodic surface 144 of the monopolar this one preferred embodiment the anodic member 12 is
anodic electrode 116 through the electrolyte to the constructed of a metal comprising or consisting essencathodic
surface formed on the first face 34 of the first tially of titanium and an anodic surface is formed on the
hybrid bipolar electrode 10; the current flows through 55 first face 20 ofthe anodic member 12 by coating the frrst
the first hybrid bipolar electrode 10 from the cathodic face 20 with a precious metal or oxide thereof. Further,
member 14 to the anodic member 12 via the fastener in this embodiment of the present invention, the caassemblies
16; the current flows from the anodic surface thodic member 14 is constructed of a metal comprising
formed on the first face 20 of the first hybrid bipolar or consisting essentially ofcarbon steel, stainless steel or
electrode 10 through the electrolyte to the cathodic 60 ferrous materials or non-ferrous materials serviceable in
surface formed on the frrst face 34 of the next hybrid chlorate solutions, the frrst face 34 of the cathodic memo
bipolar electrode 10 (not shown in FIG. 5); the current ber 14 operating as the cathodic surface of the hybrid
flows through the electrolyte to the cathodic surface bipolar electrode. In an alkali metal chlorate or chlorine
formed on the first face 34 of the last hybrid bipolar electrolytic cell application and utilizing an anodic
electrode 10; the current flows through the last hybrid 65 member 12 and a cathodic member 14 constructed as
bipolar electrode 10 from the cathodic member 14 to just described above, the barrier member 18 is conthe
anodic member 12 via the fastener assemblies 16; structed of a material operating to shield or provide a
and finally the current flows from the anodic surface hydrogen barrier for substantially inhibiting the migra4,085,027
11
tion of atomic hydrogen forming at the cathodic surface
provided via the first face 34 of the cathodic member 14
during the operation of the electrolytic cell, the migrationof
atomic hydrogen occurring through the ca·
thodic member 14 and tending to attack the titanium 5
anodic member,12 and the barrier member 18 substantially
preventing the atomic hydrogen from attacking
the anodic member 12 and forming titanium hydrides.
The formation of titanium hydrides on the' titanium
anodic member 12 caused warping and, in some applica- 10
tions, also caused disintegration of the anodic member
14, the formation of titanium hydrides also resulting in
titanium hydride embrittlement. It has been proposed to
clad the cathodic surface of a bipolar electrode constructed
of titanium with steel to prevent the formation 15
of titanium hydrides; however, it has been found that
the thickness of the steel necessary to prevent the hydrogen
from diffusing to the titanium was substantially
large and, in many applications, prohibitive as far as an
economically feasible or practical solution. In addition, 20
it was required that the cladding edges be sealed from
the anodic electrical potential, otherwise the steel
would be substantially dissolved in the electrolyte. The
hybrid electrode of the present invention provides a
bipolar electrode wherein the anOdic member can be 25
constructed •• of a metal comprising titanium and yet
substantially reducing the' possibility of titanium hy.
drides attacking the titanium anodic member 12.
In one preferred embodiment, the barrier member 18
is constructed of an inert material such as a polyvinyl 30
chloride (PVC or PVDC or CPVC or the like, for
example) type of material, for example. In this embodi·
ment, the barrier member 18 also operates to provide
the hydrogen barrier substantially insulating the anodic
member 12 from the cathodic member 14, except for the 35
fastener assemblies 16 which are constructed of an electrically
conductive material and establish electrical
continuity between the, anodic member .12 and the cathodic
member 14, in a preferred embodiment. In this
operational embodiment wherein the anodic member 12 40
is constructed of a metal consisting essentially of titanium,
the cathodic member 14 is constructed of a metal
providing a surface operating as a cathodic surface and
the barrier member 18 is constructed essentially of an
inert material; the bolt members 74 and the nut member 45
80 are each preferably constructed of an electrically
conductive material such as copper or brass or the like,
for example, the first spacer 82 is preferably constructed
of a metal consisting .essentially of titanium, and the
second spacer 84 is constructed of a metal comprising 50
carbon steel or a stainIess steel or other ferrous or nonferrous
materials or the like, for example.
It should also be noted that a plurality of depressions
could be formed in the anodic member 12 to accommodate
the head portions 76 of the bolt members 74 in a 55
manner similar to that described before with respect to
the depressions 46 in the cathodic member 14 and the
nut members 80.
In the embodiment of the invention shown in FIGS.
1 through 4, the first spacers 82 operate to space.the 60
second face 22 of the anodic member 12 a distance from
the first face 60 of the barrier member 18, and the second
spacers 84 operate to space the second face 36 of
the cathodic member 14 and the ends 54 portion of the
second face 36 of the cathodic member 14 a distance 65
from the second face 62 of the barrier member 18. The
first and second spacers 82 and 84 cooperate with the
barrier member 18 to space the second face 22 of the
12
anodic member 12 the distance 92 from the second face
36 of the cathodic member 14. Thus, the elements of the
hybrid bipolar electrode 10 which are constructed of a
metal comprising titanium are isolated and spaced from
the cathodic member 14 i.e. the hydrogen producing
member or elements as'in the case of the second spacer
84. The spacing of the elements constructed of a metal
comprising titanium from the hydrogen producing elements
(the cathodic member 14) and the disposition and
construction of the barrier member 14 cooperate to
substantially reduce the possibility of hydrogen attack·
ing the elements constructed of titanium and provide a
metal bipolar electrode having an anodic member constructed
of titanium which is serviceable in an alkali
metal chlorate or chlorine electrolytic cell application.
EMBODIMENT OF FIG. 6
Shown in FIG. 6 is a modified hybrid bipolar electrode
lOa which is constructed exactly like the hybrid
bipolar. electrode 10, except the hybrid bipolar electrode
lOa includes a modified barrier member 180 and
the fastener assemblies 160 do not include, spacers similar
to the spacers 82 and 84 of the hybrid bipolar electrode
10. Thus, the first face 60 of the barrier member
180 generally abuts the. second face 22 of the anodic
member 12 and the second face 62 of the barrier memo
ber 180 is disposed near and generally abuts the second
face 36 ofthe cathodic member 14, the second face 62 of
the barrier member 180, more particularly, abutting
ends 54 portions of the second face 36 of the cathodic
member 14 and the second face 62 of the barrier member
180 being spaced a distance 160 from. the second
face 36 of the cathodic member 14 via the raised portions
formed by the depressions 46 (not shown in FIG.
6) and the corresponding raised portions on the cathodic
member 14. It should be noted that, in this em·
bodiment of the invention, the second face 62 of the
barrier member 180 can abut the second face 36 of the
cathodic member 14 if the depressions 46 are eliminated.
In this embodiment of the invention, the barrier memo
ber 180 is constructed ofa material comprising graphite,
in one preferred form, and the barrier member 180,
more particularly, is constructed of an oil impregnated
type of graphite. The barrier member 180 operates to
provide a hydrogen barrier substantially inhibiting the
migration of atomic hydrogen to the anodic member 12
and the resulting formation of titanium hydrides in a
manner like that described before with respect to the
barrier member 18. However, in this embodiment of the
invention, the bamer member 180 is also constructed of
an electrically conductive material (graphite or oil impregnated
graphite, for example), and the barrier memo
~r 180 cooperates with the spacing pattern of the fastener
assemblies 16 to enhance the establishment of a
substantially uniform current density on the anodic
member 12 and the cathodic member 14:
The hybrid bipolar'electrode lOa provides a particularly
useful construction for converting the' bipolar
electrodes of existing electrolytic cells.to the type of
bipolar electrode construction of the present invention.
For example, some existing alkali metal chlorate or
chlorine electrolytic cells presently utilize bipolar electrodes
constructed essentially of graphite and each of
these existing graphite electrodes can be utilized to form
the barrier member 180. It should be noted that, in some
instances, it may be desirable to reduce the thickness of
the existing graphite electrodes to form the barrier
4,085,027
13
member 180. For example, some typical existing graphite
electrodes have a thickness of approximately I.1
inches and the thickness of the barrier member 18a of
the replacing hybrid bipolar electrode lOa would be
approximately ! inches, assuming the replacing hybrid 5
bipolar electrode lOa is intended to be utilized under
approximately equivalent operating conditions as the
replaced existing graphite electrodes.
The hybrid bipolar electrode lOa is assembled in a
manner similar to that described before with respect to 10
the hybrid bipolar electrode 10.except the assembly
steps do not include provisions for installing the spacers
82 and 84 since the necessity ofproviding the spacers 82
and 84 is eliminated via the construction of the hybrid
bipolar electrode lOa. The hybrid bipolar electrode lOa 15
is sealed via the seal member 152 in a manner like that
described before with respect to the seal member 152
and the hybrid bipolar electrode 10, and the hybrid
bipolar electrode lOa is installed and operates in an
electrolytic cell in a manner like that described before 20
with respect to the electrolytic cell 100 and the hybrid
bipolar electrodes 10. The hybrid bipolar electrode lOa
is shown in FIG. 5 assembled in the electrolytic cell
100; however, it should be noted that the barrier member
180 is shown in FIG. 5 spaced a slight distance from 25
the anodic member 12 and the cathodic member 14
merely for the purpose of diagrammatically illustrating
the various aspects of the present invention and it is not
required to space the barrier member 180 from the anodic
member 12 or the cathodic member 14 in this last 30
described embodiment of the invention.
Changes may be made in the construction and the
arrangement of the various parts or the elements of the
embodiments disclosed herein or in the steps of the
method disclosed herein without departing from the 35
spirit and the scope of the invention as defined in the
following claims.
What is claimed is:
1. A hybrid bipolar electrode, for use in an electrolytic
cell wherein the bipolar electrode is at least par- 40
tially immersed in an electrolyte, said bipolar electrode
comprising:
an anodic member having a first face and a second
face;
a cathodic member having a first face and a second 45
face;
means for supporting the anodic member and the
cathodic member in a spaced apart relationship
with the second face of the anodic member being
spaced a distance from the second face of the ca- 50
thodic member;
means engaging portions of the anodic member and
the cathodic member for substantially sealing electrolyte
from a substantial portion of the space between
the anodic and the cathodic members; and 55
means having a portion constructed of an electrically
conductive material and portions contacting the
anodic member and the cathodic member, said
means electrically connecting the anodic member
and the cathodic member in series. 60
2. The hybrid bipolar electrode of claim 1 defined
further to include:
a barrier member disposed in the space between the
anodic member and the cathodic member, the barrier
member shielding the anodic member from the 65
cathodic member.
3. The hybrid bipolar electrode of claim 2 defined
further to include:
14
at least one first spacer, each first spacer being disposed
between the anodic member and the barrier
member and spacingthe anodic member a distance
from the barrier member.
4. The hybrid bipolar electrode of claim 3 defined
further to include:
at least one second spacer, each second spacer being
disposed between the cathodic member and the
barrier member and spacing the cathodic member a
distance from the barrier member.
5. The hybrid bipolar electrode of claim 3 wherein
the anodic member is constructed ofa material comprising
titanium and the barrier member is constructed ofan
inert material, the barrier member inhibiting the migration
of hydrogen from the. cathodic member to the
anodic member.
6. The hybrid bipolar electrode of 2 wherein the
anodic member is constructed of a material comprising
titanium and the barrier member is constructed of a
material selected from a group consisting of graphite
and polyvinyl chloride.
7. The hybrid bipolar electrode of claim 6 wherein
the barrier member includes a first face and a second
face, the first. face. of the barrier member abutting a
portion ofthe second face ofthe anodic member and the
second face of the barrier member abutting a portion of
the second face of the cathodic member; and wherein
the means supporting the anodic member and the cathodic
member in a spaced apart relationship is defined
further as supporting the barrier member between the
second face of the anodic member and the second face
of the cathodic member, the second face of the anodic
member being spaced a distance from the second face of
the cathodic member.
8. The hybrid bipolar electrode of claim 2 wherein
the anodic member includes at least one opening, each
opening being formed through the anodic member intersecting
the first and the second faces of the anodic
member; and wherein the cathodic member includes at
least one opening, each opening being formed through
the cathodic member intersecting the first and the second
faces of the cathodic member, each opening in the
cathodic member being aligned with an opening in the
anodic member; and wherein the means supporting the
anodic member and the cathodic member in a spaced
apart relationship is defined further to include:
at least one fastener assembly, each fastener assembly
having a portion extending through one of the
openings in the anodic member and through one of
the openings in the cathodic member, and each
fastener assembly having a portion engaging the
anodic member and a portion engaging the cathodic
member, the fastener assemblies mechanically
connecting the anodic member and the cathodic
member in a spaced apart relationship.
9. The hybrid bipolar electrode of claim 8 wherein
the barrier member includes at least one opening, each
opening extending through the barrier member, and
each opening in the barrier member being aligned with
one of the openings in the anodic member and with one
of the openings in the cathodic member; and wherein
each fastener assembly is defmed further to include a
portion extending through one of the openings in the
barrier member, the fastener assemblies supporting the
barrier member in the space between the anodic member
and the cathodic member.
10. The hybrid bipolar electrode of claim 2 wherein
the means supporting the anodic member and the ca4,085,027
15
thodic member in a spaced apart relationship is defined
further to include:
at least one fastener assembly each fastener assembly
having a portion engaging the anodic member, a
portion engaging the barrier member and a portion S
engaging the cathodic member, the fastener assemblies
mechanically connecting the anodic member
and the cathodic member in the spaced apart relationship
and supporting the barrier member in the
space between the anodic member and the cathodic 10
member.
11. The bipolar electrode of claim 1 wherein the
means supporting the anodic member and the cathodic
member in a spaced apart relationship is defmed further
to include a plurality of fastener assemblies, each fas- IS
tener assembly having a portion connected to the anodic
member and a portion connected to the cathodic
member, each fastener assembly mechanically connecting
and establishing electrical continuity between the
anodic member and the cathodic member. 20
12. The hybrid bipolar electrode of claim 1 wherein
the anodic member is defined further to include a coating
on the fust face thereof operating as an anodic surface
in an electrolysis application, the second face ofthe
anodic member being spaced a distance from the second 2S
face of the cathodic member and the fust face of the
cathodic member operating as a cathodic surface in an
electrolysis application.
. 13. An improved electrolytic cell having electrodes
connected. to an electrical power source and at least 30
16
partially immersed in an electrolyte wherein the electrolyticcell
includes at least one bipolar electrode including.
an anodic member having. a •first face and a
second face and a cathodic member having a first face
and a second face, the improvement comprising:
at least one fastener assembly, each fastener assembly
haVing a portion connected to.the anodic member
and a portion connected to the cathodic member of
each bipolar electrode in the electrolytic cell, each
fastener assembly·.mechanically connecting the
anodic member and the cathodic member in a
spaced apart relationship with the second face of
the anodic member spaced a distance from the
second face of the cathodic member;
means engaging portions of the anodic member and
the cathodic member for substantially sealing electrolyte
from a· substantial portion ofthe space between
the anodic and the cathodic members; and
means having a portion constructed of an electrically
conductive material and portions contacting the
anodic member and the cathodic member, said
means electrically connecting the anodic member
and the cathodic member in series.
14. The electrolytic cell of claim 13 wherein the improvement
is defmed further to include:
a barrier member disposed in the space between the
anodic member and the cathodic member, the barrier
member shielding the anodic member from the
cathodic member. • • • • •
3S
4S
so
60
6S
rR��lg0�(D�xt-autospace:none'>14
contacting said extract phase with at least the stoichiometric
quantity of an aqueous alkaline solution
required to neutralize the chloride form of said
amine to selectively separate said platinum values
from said palladium values in said organic extract
phase. and form a platinum stripped organic extract
phase and an aqueous platinum containing strip
solution, and
isolating said aqueous solution from said platinum
extract phase.
14. A continuous process for the separation and selective
recovery of palladium dissolved in aqueous chloride
solutions with platinum which comprises:
reducing said solution to an emf between about -425
mvand -650 mv,
contacting said aqueous chloride solution for a predetermined
time period with an organic solvent containing
at least 1% by weight of an organically
substituted secondary amine compound of the general
formula:
wherein R1 and Rz are hydrocarbon groups and R1 +
Rzcontain between 18 and 35 carbon atoms, said compound
capable of forming complexes of platinum and
palladium that are preferentially soluble in the organic
xolvent and whereby said contacting results in the creation
of an organic extract phase and an aqueous raffinate
phase, •
separating said organic extract phase from said aqueous
raffinate phase,
contacting said organic extract phase with an aqueous
solution containing a reducing agent acidified to
between about 0.1 to about 3.0 N-HCl to strip
palladium values from said organic extract phase,
said contact resulting in the formation of a palladium
loaded aqueous phase and a stripped organic
phase containing said platinum,
separating said loaded aqeuous phase and said
stripped organic phase, and recovering palladium
from said loaded aqueous phase.
* * * * *
50
55
60
65
no<ĩet0�(D�e:none'>point of elemental sulfur.
* * * * *
14
ture between about 500 C and the melting point of
sulfur to convert substantially all of the sulfide
sulfur to elemental sulfur in solid form and to effect
conversion of the metal compounds to metal chlorides,
and recovering metal from the chlorides.
22. The process of claim 21 in which chlorination is
performed at a temperature between about 800 C and
the melting point of sulfur.
23. The process of claim 2] in which the minerals
10 contain silver.
24. The process of claim 23 in which the silver containing
mineral is tetrahedrite.
25. The process of claim 21 in which sulfur chlorides
formed during dry chlorination are reacted with the
15 metal sulfides to form metal chlorides and elemental
sulfur.
26. The process of claim 25 in which the process is
performed by introducing the metal sulfides and dry
chlorine gas countercurrently into the reaction zone
20 and an inert sweep gas is introduced into the reaction
zone to bring sulfur chlorides formed during the dry
chlorination into contact with metal sulfides entering
the reaction zone.
4,011,146
13
lead, silver recovered from the leach solution by cementation,
the leach solution after removal of lead and
silver therefrom recycled to the sodium chloride leaching
step, the improvement comprising preventing the
build-up of zinc in the leach solution in the leaching 5
step by removing a bleed stream from the lead and
silver depleted leach solution, removing zinc from the
bleed stream and recycling the bleed stream to the
leaching solution in the leaching step.
19. The process of claim 18 including subjecting the
bleed stream to electrolysis after removal of zinc therefrom
to produce chlorine gas and recycling the chlorine
gas to the dry chlorination step.
20. The process of claim 19 in which the zinc is removed
by precipitating it as zinc carbonate by the addition
of sodium carbonate, the sodium hydroxide produced
in the electrolyis is carbonated to sodium carbonate
and the sodium carbonate recycled to the zinc
precipitation step.
21. The process of recovering metal values from
minerals of the polymorphic series of complex metal
sulfides tetrahedrite-tennantite comprising:
a. subjecting the minerals to dry chlorination with
chlorine gas in the absence of oxygen at a tempera-
25
30
35
40
45
50
55
60
65