Electrolytic-ultrafiltration apparatus and process for recovering solids from a liquid medium

A process and apparatus for the recovery of suspended solids from a liquid medium is disclosed. The liquid medium containing suspended solids is circulated through an electrolytic cell and an ultrafiltration unit, the suspended solids being removed from the liquid medium as a uniform particulate mass of low liquid content while a proportionate amount of the liquid and dissolved components such as surfactants is removed through ultrafiltration to avoid a dilution of the liquid medium in a continuous process. The recovered solids, following evaporation of a small amount of remaining liquid, offers a more uniform particle size as well as substantially lower recovery costs when compared with conventional techniques, such as spray-drying, now used in the industry. The disclosed electrolytic-ultrafiltration process offers application to the treatment of industrial products and wastes (polymeric, e.g., PVC and PVC copolymers, rubber, paint, cellulose, paper sludge, food, etc.) and the recovery or concentrating of valuable materials from naturally occuring sources, e.g., whey protein.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
This invention relates to the electrolytic recovery of solids from liquid 
media where at least a portion of the liquid media may be simultaneously 
filtered, most preferably by circulation through an ultrafiltration unit 
to maintain a relatively constant solids concentration in the electrolytic 
cell; and to the apparatus used to achieve the separation of the 
above-mentioned solids from liquid media. 
(2) State of the Art 
The separation of suspended solids from a liquid has historically been 
achieved by such well-known methods as filtration or centrifuging. There 
are, however, a great number of solid-liquid compositions where these 
simple techniques do not achieve the desired separation or no separation 
at all. Examples of such solid-liquid compositions are polymer latex and 
emulsion compositions, particularly compositions containing polymer 
particles of small particle size (less that 1 to 2 microns), colloidal 
suspensions, compositions where solid particles have a high affinity for 
the liquid or solvent or where these more simple techniques cause 
processing problems such as agglomeration. Several processes have been 
proposed to effect the separation of these "special" solid-liquid 
compositions. Among these are freeze-thaw techniques, extrusion drying and 
spray-drying. Of these, spray-drying is probably the most effective and 
most widely used technique, particularly with emulsion resins. The 
spray-drying process, however, requires substantial amounts of energy in 
order to raise the material to the liquid vaporization temperature and 
also to overcome the heat of vaporization of the liquid, e.g., water. In 
this present era of dwindling energy supplies, a less energy intensive 
recovery and drying process would be extremely desirable. Another problem 
encountered with techniques such as spray-drying is that there is commonly 
a broad particle size distribution range for the dried solid. While this 
may not be critical in many applications, size classification is important 
in some of the more refined applications of the dried solids usage such as 
in PVC plastisols. Hence, a solids recovery process which would result in 
particles of more uniform size would be extremely useful for specialized 
applications such as the above-mentioned plastisols which generally 
require particle sizes less than about 2 microns. 
Electrophoretic techniques have been suggested for the recovery of 
suspended solids from liquid compositions to save energy, give better 
control of size classification and to provide a more economical recovery 
process. Electrophoretic techniques have long been used for depositing 
paint material coatings onto electrically conductive substrates, and more 
recently these techniques have been used in the electrolytic deposition of 
various solids on an anode. For example, British Pat. No. 1,525,103 
discloses a method of concentrating polyvinyl chloride (PVC) emulsion 
which comprises the steps of electrolytically attracting the solids 
towards an anode which is covered with a porous nonconductive element so 
that the solids of PVC are deposited on the element and then removing the 
deposited solids from the porous element. In this process, PVC, as in 
electrolytic depositions, is acidic and has to be neutralized in a 
separate step and vessel after removal from the membrane. U.S. Pat. No. 
3,664,938 illustrates the recovery of polymer fines, specifically 
polyacrylamide, by subjecting a water-in-oil suspension to an electrical 
field where the polymer fines deposit on an electrode and are removed. 
U.S. Pat. No. 4,146,455 teaches treating liquid whey by subjecting raw 
whey to forced flow electrophoresis to effect the separation of lactose 
and simultaneously concentrate the solids in the resulting product whey 
solution. U.S. Pat. No. 4,110,189 illustrates the electrokinetic 
separation of finely divided clay particles from an aqueous suspension 
thereof. 
U.S. Pat. No. 3,449,227 illustrates the manufacture of asbestos articles by 
electrodepositing asbestos fibers from a continuously circulated 
dispersion onto an electrode. U.S. Pat. No. 3,436,326 disloses the removal 
of waste solids from an aqueous system by electroplating said solids on a 
positively charged screen which screen must be removed to be cleaned. U.S. 
Pat. No. 3,424,663 teaches the electrophoretic deposition of a synthetic 
resin onto a metallic substrate from an aqueous solution to produce an 
adherent coating. The disclosed process requires the presence of a 
complexing agent, such as EDTA, in the aqueous disperson. 
The concentrating of polymer solids in an aqueous medium by ultrafiltration 
has been disclosed in the art in U.S. Pat. No. 3,956,114 and Japanese 
Kokai No. 18788/1977. The Japanese Patent further discloses that 
concentrating PVC solids by ultrafiltration requires further processing by 
spray-drying to obtain the desired separation of the solids from water. 
Effecting the separation of suspended solids from a liquid by employing 
either electrolysis or ultrafiltration alone has not yielded the desired 
separation. The practical problem is that ultrafiltration cannot remove 
all the liquid, and electrolysis does not remove all the suspended solids 
alone. Thus, both processes must be followed by some sort of additional 
processing, e.g., coagulation, filtrations, spray-drying, extrusion 
drying, etc. 
It is disclosed in U.S. Pat. Nos. 3,663,406 and 3,663,403 and Canadian Pat. 
No. 968,743 to use electrolysis in conjunction with ultrafiltration along 
with an additional processing step for electrodepositing coatings onto 
electrically conductive substrates where the function of the 
ultrafiltration step is to remove contaminates and generally to maintain 
stability in the electrodeposition bath. It is not found in the art where 
electrophoretic techniques are used in conjunction with ultrafiltration to 
recover suspended solids from a liquid medium. 
SUMMARY OF THE INVENTION 
In accordance with the invention, it has been discovered that unexpectedly 
high separation of suspended solids (e.g., approximately 80 percent PVC 
solids in a wet cake) can be achieved by combining an electrolytic process 
with ultrafiltration. It has been found, in accordance with the present 
invention, that the high and constant efficiency of the system is a result 
of the complimentary actions of electrolysis (E) and the ultrafiltration 
(UF). The electrolysis removes the suspended solids from the liquid, and 
the ultrafiltration removes the liquid from the low solids slurry 
resulting from the electrolysis to increase solids concentration for 
recycle to the electrolytic step. Without this complementary action, the 
efficiency of both processes diminishes rapidly, i.e., without liquid 
removal by ultrafiltration, the liquid containing suspended solids would 
be gradually depleted making the electrolysis proportionately more 
inefficient and expensive, and without electrolysis, the efficiency of the 
ultrafiltration drops exponentially with the increasing concentration of 
the suspended solids. 
Still further in accordance with the invention, a suspended solids recovery 
apparatus comprising an electrolytic cell alone or in combination with an 
ultrafiltration unit in a closed loop. The electrolytic cell comprises a 
container, an anode and a cathode parallel or coaxial thereto with such 
anode and cathode being electrically connected to a source of direct 
current external to the cell. This direct current to the cell may be 
continuous or interrupted. The container has inlet means for introducing 
the suspended solids-liquid composition. The container also has outlet 
means, if in combination with an ultrafiltration unit, for circulating 
depleted liquid through the ultrafiltration unit for removal of a portion 
of the liquid contained in the depleted suspended solids-liquid 
composition to raise the suspended solids concentration to optimum for 
return to the inlet means of the container portion of the electrolytic 
cell. 
Still further in accordance with the invention, the above-described 
electrolytic cell comprises a container having therein a cylindrical form 
anode rotating about a horizontal axis, said cylindrical anode being at 
least partially immersed in the liquid within the container. A coaxial, 
cylindrical or partially cylindrical cathode member which can be located 
inside the anode or outside the anode, is completely immersed in the 
liquid and spaced from the cylindrical anode member. Means for rotating 
the cylindrical anode are provided as is a scraper of some form, such as a 
"doctor blade," parallel to the axis of the cylindrical anode member for 
removing deposited solids from the anode as it rotates. 
Still further in accordance with the invention, the anode member as 
previously described comprises a solid cylindrical tube of sheet metal 
material, such as titanium sheet, and can have an electrocatalytic coating 
applied thereto. Still further in accordance with the invention, the 
cylindrical anode member as previously described is composed of an open 
mesh-type material and has a covering thereon of a flexible membrane or 
film which is impermeable to fluids and gases and resistant to degradation 
under the conditions of deposition. 
Still further in accordance with the invention, an ion exchange membrane 
can be used for (a) simltaneous in-situ neutralization of deposited acidic 
solids layer, (b) to exchange in-situ, if desired, the cations of the 
electrolyte in the deposited solids with a different cation, and (c) to 
protect the anode surface from wear. 
According to the present invention, the interior of said cylindrical member 
contains an ionic neutralizing substance which can pass through the ion 
exchange membrane to the deposited solids and neutralize its highly acidic 
condition. 
The anode member is a hollow cylindrical member having a continuous 
surface, or may be formed of a screen or mesh material having openings 
therethrough to the interior of the cylinder. When open mesh material is 
utilized, at least that part of the cylindrical member immersed in the 
latex must be tightly covered with a polymeric material having a surface 
which will retain the deposited solids. This polymeric material is tightly 
wrapped around the anode member, or it may be an endless loop passing 
around one or more pulley members external from the electrolytic cell. 
In accordance with the invention, deposition of suspended solids takes 
place at the anode surface when a direct current is applied to the anode 
and cathode of the electrolysis cell. As the anode is rotated in the 
latex, a layer of suspended solids forms on the surface thereof, where the 
thickness of such solids layer is dependent on the current density and the 
rotational speed of the anode. The solids layer is scraped from the anode 
member at a point above the surface of the liquid by a scraper member such 
as a doctor blade whereupon the solids layer of low water content is 
collected and passed on for further processing or drying as needed. Gases 
evolved at the electrodes during the electrolysis, such as when the liquid 
is water, are preferably vented so as to avoid any possibility of 
explosion. 
As discussed above, if the current efficiency of the above-described 
electrolysis cell decreases with decreasing solids concentration in the 
liquid, a portion of the liquid within the electrolysis cell may be 
constantly withdrawn and passed through an ultrafiltration unit to remove 
at least a portion of the liquid carrier from the liquid composition. The 
concentrated liquid composition is then passed back into the electrolytic 
cell at a higher concentration while the liquid filtrate may be either 
disposed of or reprocessed for use in some other process such as a 
polymerization reaction. 
Inlet means are also provided in the electrolytic cell for adding new 
suspended solids-liquid composition to keep the electrolyte level 
relatively constant while solids are removed electrolytically and where 
liquid filtrate can be removed by ultrafiltration or other means. The 
fresh liquid composition may enter into the system by way of either the 
ultrafiltration unit or the electrolytic cell at a rate to keep the level 
of the liquid composition in the cell constant, or the liquid composition 
may be supplied in split streams into both the ultrafiltration unit and 
electrolytic cell. This process then maintains the liquid composition at a 
relatively constant level and retains the required volume of liquid within 
the electrolytic cell for optimum current efficiency. 
It will be recognized by those skilled in the art that the process 
according to the present invention can have application in many areas such 
as treatment of industrial wastes, e.g., polymer and rubber latex, paper 
sludge, food, etc., and the recovery of valuable materials, e.g., the 
concentration of proteins in whey. It will also be recognized that because 
of the wide applicability of this invention, numerous solid-liquid 
compositions having widely varying requirements and properties will be 
treated. This will require variations and modifications to the process and 
apparatus of the present invention dictated by the particular 
solids-liquid composition. For example, a composition of high solids 
content where the solids have relatively large particle size, e.g., paper 
sludge, would not be ultrafiltered for reason of the obvious pumping 
problems as well as the problem of clogging the ultrafiltration unit. 
Thus, such variations and modifications to the present invention are 
considered to be within the scope of this invention. 
These and other aspects of the invention will become clear to those skilled 
in the art upon the reading and understanding of the specification.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings, FIG. 1 illustrates generally the apparatus 
used for the electrolytic recovery of suspended solids from a liquid 
medium comprising an electrolytic cell tank 10 having generally a box or 
trough form being at least partially filled with a suspended solids-liquid 
composition 12. A cylindrical-drum form anode 14 having a central axis 15 
is disposed horizontally within the trough and at least partially immersed 
in the solids-liquid composition 12. Means are provided for rotating at a 
varible speed, the drum anode about horizontal axis 15 in the direction of 
arrow A. Such means for rotating the drum are not shown but may be of any 
type such as a V-belt driven pulley system connected to an electric motor. 
Also disposed within the electrolytic cell tank 10 and completely immersed 
within the liquid composition 12 is a semi-cylindrical cathode saddle 16 
having a common axis with the drum anode 14. Cathode saddle 16 has a 
diameter which is greater than that of the anode drum 14 (note, however, 
FIG. 5) so that the cathode saddle 16 is displaced a small distance away 
from the rotating drum. The cathode 16 is displaced from the anode drum 14 
a distance sufficient so as not to shear off the solids layer deposited on 
the anode. Accordingly, it is desired to deposit a relatively thin layer 
of solids so that the cathode is as close as possible to the anode. This 
is accomplished by maximizing the rpm of the anode drum or belt to a speed 
at which the solids layer is not washed off by the friction of the liquid. 
The distance of the cathode from the anode while preferably being small is 
dependent upon several factors such as the speed of the anode contour, the 
current density, the solids content in the liquid medium, soap content (if 
a polymer, rubber, etc., composition), and pH vs. desirable or acceptable 
cell potential. 
Rotating drum anode 14 and cathode saddle 16 are electrically connected 
through conductor wires 18 and 20, respectively, to a source of direct 
current 22 which may be a rectifier, generator, battery or other such 
device. When anode drum 14 and cathode saddle 16 are electrically 
connected through conductors 18 and 20 to power source 22 and current is 
applied continuously or periodically, a layer of solids is deposited on 
the surface of drum form anode 14. As drum 14 rotates in the direction of 
arrow A, the layer of solids reaches scraper member 24 disposed parallel 
to and directed generally tangentially to the rotating drum and above the 
level of the suspended solids-liquid composition 12 in the electrolytic 
cell tank 10. As the solids layer approaches the scraper member 24, it is 
removed from rotating drum anode 14 and is deposited on means for removing 
the solids for further processing such as a conveyer belt 26. The cleaned 
rotating drum anode 14 then continues its rotation back into the suspended 
solids-liquid composition 12 within the electrolytic cell 10 and presents 
a clean surface for deposition of additional solids onto such surface. 
Drum form anode 14 may be made of any conductive metal such as nickel, 
iron, or stainless steel but, preferably, is made of valve metal such as 
titanium or tantalum or alloys thereof with a conductive coating applied 
thereto. If such metals as nickel or stainless steel or other like are 
utilized, a small amount of anode dissolution takes place during the 
electrolytic process and in the case with PVC recovery, results in a 
contamination of the PVC resin with metal ions such as nickel and/or iron. 
The presence of these metal ions in the PVC resin may cause heat 
instability and color differences in the resin. In applications with other 
solids material where heat stability or color are less important, it would 
then be possible to utilize these relatively inexpensive anode materials 
with continuous replacement of the degraded anodes being necessary. 
In the preferred embodiment, however, anode drum 14 is made of a valve 
metal material such as titanium and is coated with an electroconductive 
coating such as mixtures of precious metals and/or their oxides, oxides of 
valve metals, oxides of metals such as manganese, tin, antimony or the 
like or other known electroconductive coatings which are substantially 
insoluble under the anodic conditions of PVC and like solids deposition in 
this invention. 
In one preferred embodiment of the invention, the drum form anode 14 is 
constructed of solid metal sheet so that a continuous surface is presented 
to the liquid composition for deposition, and the suspended solids are 
deposited directly on the surface of the drum form anode 14. 
In another embodiment of the invention, the drum form anode 14 is 
constructed of an open mesh material such as a wire cloth or expanded mesh 
material. In this embodiment, a polymer film or membrane material is 
tightly wound around the drum anode. If the membrane material is a 
continuous belt, it covers at least the immersed portion of the drum form 
anode 14. The drum form anode 14 acts only as a current collector while 
the belt interrupts the deposition of the solids on the surface of the 
drum form anode 14, and the solids layer is built up on the surface of the 
membrane rather than on the surface of the drum form anode 14. If the 
membrane is used as a belt, then the scraper 24 may then be located at any 
point along the belt to remove the collected resin therefrom. Other 
embodiments of this invention utilizing the belt will be described 
hereinafter in conjunction with the other drawing figures. 
As the solids layer is deposited on the surface of the drum form anode in 
one embodiment, the liquid composition 12 becomes less and less 
concentrated with suspended solids, and as a consequence, the current 
efficiency of the electrolytic process is reduced. In order to keep the 
current efficiency at an optimum level, it is desirable to keep the solids 
concentration in the bulk of the liquid composition 12 in the range of 10 
to 60 percent solids and preferably between 35 and 50 percent solids. In 
order to keep the bulk liquid composition concentration at a desired 
level, a portion of the liquid composition 12 is drawn off through an 
orifice 28 disposed at the bottom of the electrolytic cell tank 10 and 
through conduit 30 by the action of pump 32 to be delivered to the inlet 
end of an ultrafiltration unit 34. The pump 32 may be of any type but is 
preferably of the diaphragm or helical type. Centrifugal pumps cause 
undesirable shear forces to be applied to the liquid composition causing 
coagulation in some cases, and it is difficult to keep the solids of the 
liquid medium away from the bearing surfaces which may eventually result 
in pump failure. 
Ultrafiltration unit 34 is of the type well-known to those skilled in the 
art and consists generally of an ultrafiltration membrane enclosed within 
a stainless steel or PVC tube. The liquid composition is passed into the 
ultrafiltration unit 34 where the liquid (e.g., water) and a portion of 
the dissolved species from the suspended solids-liquid composition are 
removed through the membrane, the thus concentrated solids-liquid 
composition passing out of the ultrafiltration unit by conduit 36 and is 
returned to opening 38 in electrolytic cell tank 10 for further 
processing. The liquid filtrate from ultrafiltration unit 34 is removed 
through conduit 40 to a remote point where it may be either reused as a 
process liquid or disposed of following treatment as needed. 
The ultrafiltration unit 34 may be of any suitable type which can 
effectively remove the liquid from the liquid composition. Generally, in 
the operation, the liquid composition fed to the ultrafiltration unit 34 
contains between about 10 and 40 percent suspended solids particularly in 
the case of PVC. After the emulsion is passed through the ultrafiltration 
unit 34, the liquid composition generally contains between about 30 and 55 
percent solids. This concentrated liquid composition is fed to the 
electrolytic cell 10 for removal and recovery of the solids. 
The ultrafiltration unit 34 which has been found effective is a unit 
consisting of a five (5) foot membrane placed in a one (1) inch ID PVC 
tube. The ultrafiltration units used according to the present invention 
include membranes of the HFD type manufactured by Abcor, Inc., of 
Wilmington, Massachusetts. These HFD type ultrafiltration membranes are 
characterized as having a minimum water flux of 200 gallons per square 
foot-day (GFD). 
If polymer resin, such as PVC, is being removed by the electrolytic process 
and water is the liquid being drawn through the ultrafiltration unit, it 
is necessary that the emulsion or latex be replenished from an external 
source such as a polymerization reactor or a solids-liquid composition 
reservoir 42 as illustrated in the figures. Pump 44 withdraws the required 
amount of emulsion from the reservoir 42 and passes the emulsion into the 
electrolytic cell tank 10 through conduit 46 at opening 48 in the side of 
the electrolytic cell tank 10. 
The rotation of drum form anode 14 will result in some mixing of the 
solids-liquid composition 12 within electrolytic cell tank 10. However, it 
may be advantageous to add some type of mixing or agitating means in order 
to maintain a relatively consistent bath composition throughout. Thus, 
agitation means such as air agitation or mechanical agitation in the form 
of a stirring propeller, paddle wheel, pumping, baffle walls or the like 
may be provided. It will also be understood that, for the purposes of 
illustration, the size of the tank 10 relative to the size of the drum 
form anode 14 has been reduced. Generally, a larger volume tank 10 would 
be utilized so that there would be a more uniform bath composition rather 
than areas of low concentration as may occur in a small volume bath. 
It is apparent that the amount of suspended solids deposited from the 
liquid composition as well as the overall efficiency of the process is 
directly related to the amount of surface area presented to the solution 
by the drum form anode 14. In the illustration shown in FIG. 1, the drum 
form anode 14 is only partially immersed in the deposition bath, and thus 
presents less than half of its surface area at any one time to the 
deposition process. FIGS. 2, 3, and 4 illustrate means by which a greater 
proportion of the drum form anode is immersed in the electrolysis bath 
thereby presenting a greater proportion of its surface area for deposition 
of suspended solids thereby increasing the efficiency of the apparatus and 
the process. 
In the embodiment shown in FIG. 2, a drum form anode 14 of the type 
previously described having a generally cylindrical form is nearly 
completely immersed in cell tank 10. Concentric cathode saddle 16 
surrounds the drum form anode 14 which may have a surface which is of a 
continuous sheet of conductive material such as a valve metal or alloys 
thereof and, more particularly a titanium surface upon which any 
electroconductive coating of the type previously described has been 
applied. Alternatively, the surface of the drum form anode 14 may be 
formed from screen material or expanded metal mesh, the surface being 
covered with an electrically conductive film or membrane material capable 
of passing at least some ionic species therethrough. This film or membrane 
may be a cation or anion exchange membrane which may be any of the 
membranes accepted in the electrochemical arts, such as NAFION, a membrane 
manufactured by E. I. DuPont De Nemours and Company of Wilmington, 
Delaware, and described in U.S. Pat. No. 3,909,378. 
Generally, the operating resistance of these ionic exchange membranes is 
distinctly different. That is, the cationic exchange membranes have a 
lower resistance to electric current than the anionic exchange membranes. 
Accordingly, in the use of the various membranes (i.e., cationic and 
anionic) a different potential is required to maintain the same current 
flow and the corresponding separation rate of solids. Thus, energy-wise, 
the cationic membrane is more economical. 
The cationic exchange membrane has ion exchange groups such as sulfonic, 
sulfuric and carboxylic groups. Similarly, the anionic exchange membrane 
has functional groups which contain nitrogen or phosphorous. For example, 
these functional groups are primary and secondary amines, quaternary 
ammonium groups, phosphoric groups, phosphonic groups and the like. 
In the embodiment shown in FIG. 2, a large amount of the surface area is 
exposed to the liquid composition bath 12. This arrangement allows for 
maximum use of the surface for deposition of latex and offers substantial 
cost savings since a greater proportion of the apparatus is working at any 
one time. 
Also shown in FIG. 2 are a plurality of liquid composition inlets 50. These 
inlets 50 may take the form of tubular members which are generally 
parallel to the rotational axis of drum form anode 14. Openings are 
provided in the side of the tubular members 50 so that a fresh supply of 
liquid composition either from a reservoir or from the discharge of the 
ultrafiltration unit or any combination thereof is provided. The plurality 
of tubular members 50 act to keep the concentration of the liquid 
composition more consistent throughout the bath and also provide a source 
for agitation for the bath. 
The deposition process when working with an aqueous medium involves the 
evolution of hydrogen at the cathode 16 and oxygen at the anode 14. These 
gases bubble to the surface of bath 12 and may be collected by hoods 52 
placed over the surface of the bath and adjacent to the rotating drum form 
anode 14. These gases are then removed and either exhausted or processed 
as necessary. The evolution of gases also performs some agitation of the 
bath. An alternative embodiment of the invention is shown in FIG. 3 
wherein a belt of flexible material preferably an ion exchange membrane 
belt 54 passes around rotating drum form anode 14 and around a remote 
pulley 56 disposed away from cell 10. This allows the removal of the 
deposited solids by scraper 24 at a point remote from the cell thereby 
avoiding the problems of scraped solids material falling back into the 
liquid composition within the cell. The belt returns to the area of the 
drum form anode passing around pulley member 58 prior to tangentially 
wrapping around drum form anode 14 to again pass through the bath. The 
remainder of the cell is substantially identical to that shown in FIG. 2 
and need not be further described. 
As stated previously, the rotating drum form anode offers only a limited 
amount of surface area to be exposed to the deposition process thereby 
limiting the efficiency of the system for a given size of bath. FIG. 4 
illustrates an embodiment of the invention which offers greatly increased 
surface area without an extreme increase in the size of the apparatus 
employed. As shown in the figures, the cell comprises a relatively deep 
tank 110 which is filled with solids-liquid composition 112. Immersed 
within the tank 110 is a cylindrical drum form pulley 114 completely 
immersed therein. A second pulley 156 is located above the liquid 
composition level outside the bath. A belt of conductive material such as 
metal mesh 154 is made nonconductive on the inside but conductive on the 
outside by an electroconductive coating, passes around both pulleys 114, 
156 and a drive means, not shown in the figures, turns the belt 154 and 
pulley system 114, 156 in the direction of arrow B. Belt 154 is preferably 
made of a flexible metal (e.g., stainless steel) having an 
electroconductive coating applied thereto. Optionally, this coated 
titanium mesh material may have an ion exchange membrane applied thereto 
from which the resin is more easily removed. 
A saddle of cathode material such as stainless steel mesh 116 follows the 
contour of belt 154 within the liquid composition. A plurality of liquid 
composition inlets 150 are disposed within the tank 110 to distribute the 
incoming latex evenly throughout the system. Depleted liquid composition 
is drawn out as in the other cells through opening 128 located in the 
bottom of the tank 110 and passed through an ultrafiltration unit as in 
the previously described processes. 
Optionally, if the inside of the moving belt anode is made conductive, 
means are provided to control the deposition and removal of the solids 
from that side of the anode. 
Preferably, the moving belt anode which is conductive only on its outside 
is embedded in an ion exchange resin continuous film and has one or more 
traveling insulated wire contacts for the DC feed. The wires are joined at 
one at a point 157 of equal distance from the bottom of pulley 114 and the 
top of pulley 156. The one wire leaves the cell through a conduit above 
the liquid composition level and ends in a sliding contact which allows a 
rotation of this contact on another contact of a DC source. The pulleys 
are made preferably of a dielectric, corrosion-resistant material such as 
PVC and the like. 
When an electrical potential is applied to the cathode 116 and the anodic 
belt 154, a solids layer is deposited on the portions of the belt which 
are immersed in the liquid compositon 112. Since the solids layer is only 
moderately adherent to the anode surface, it is preferred that the 
diameter of pulley 156 be significantly smaller than that of pulley 114. 
This allows the convergence of the belts as it rises vertically in the 
solution. This offers the advantage of having at least some of the forces 
tending to separate the solids from the anode surface to be overcome by 
gravitation which holds the solids against the belt. As the belt passes 
around pulley 156, a scraper member 124 removes the resin from the belt, 
and the material is then removed from the area of the cell by a conveyor 
belt 126. 
FIG. 5 illustrates another embodiment of the invention. In this embodiment, 
the cathode member 216 is located interior to drum form anode 214. The 
cathode 216 can be in the shape of a drum or the saddle form of the 
previously described embodiments, as long as it is completely immersed in 
the liquid composition 212. The cathode member 216 can be stationary or 
rotate in the liquid composition bath 212 as long as the cathode 216 is 
insulated from the means for rotating drum form anode 214 (not shown). The 
remainder of the cell is substantially identical to that shown in FIG. 2 
and need not be further described. 
It is readily apparent that other features of the other illustrated 
embodiments of the invention are applicable to the embodiment illustrated 
by FIG. 5. In this embodiment, however, the surface of the drum form anode 
214 must be formed from sheet material or expanded metal mesh, the surface 
being covered with a polymer film or membrane material capable of passing 
ionic species therethrough. The film or membrane may be a cation or anion 
exchange membrane, as previously described, depending upon the solids 
material being deposited thereon as well as other considerations. 
This embodiment offers the advantage of the cations in the liquid 
composition 212 migrating in only a single direction, namely: toward the 
cathode interior to the anode. This feature is of benefit when it is 
desirable to remove a particular cation or cations from the solids 
material such as in the case of de-watering paper sludge. The sodium ions 
present in paper sludge appear to cause the sludge to repeptize everytime 
it rains. Thus, the sludge never completely de-waters and the result is a 
"quick-sand" like landfill. Therefore, in using this embodiment to 
de-water paper sludge, the sodium ions "dragged" to the anode surface will 
pass on through the membrane to the cathode and can be removed from the 
electrolytic cell tank 210 under reduced pressure or by other means such 
as pumping. 
One of ordinary skill in the art will recognize that the specific 
embodiment and operating conditions employed will be dependent upon the 
particular solids-liquid composition being processed. As described 
previously, the embodiments of FIG. 5 would be particularly useful for the 
de-watering of paper sludge. Untreated paper sludge does not require the 
addition of surfactants nor is it necessary to neutralize the paper sludge 
solids being deposited on the anode. However, with PVC resin which can be 
produced in a water emulsion from vinyl chloride monomer, a surfactant is 
generally employed to keep the PVC resin dispersed in the emulsion. Such 
surfactants are generally referred to as "soaps," and they generally 
comprise sulfuric acid salts of a long chain fatty acid such as sodium 
lauryl sulfate. It has been found that in the depositon of PVC resin, it 
is necessary that at least some soap be present in the emulsion for 
deposition to take place. This has lead to the inference that the 
organosulfate anion is the migrating species in the applied 
electromagnetic field and that the associated polymer particles are 
carried along with this ionic species to the anode. This inference is 
further supported by the fact that the pH of the bulk latex increases 
while the pH of the deposited material tends to be acidic in nature. Other 
mechanisms may be possible, however, since some nonionic surfactants 
affect electrolytic deposition while cationic surfactants generally cause 
little deposition on either an anode or cathode. 
In the recovery of PVC solids from an emulsion or latex, the latex 
deposited on the anode is relatively acidic when compared to the remainder 
of the bath due to the presence of the acidic group associated with the 
surfactant used in the process. It is possible within the scope of the 
present invention to neutralize this acidic condition by the provision of 
a neutralizing substance such as sodium or potassium hydroxide located 
within a drum form anode having an open mesh structure and an ion exchange 
membrane covering its surface. Thus, during the electrolysis process, a 
neutralizing ionic species such as potassium ions or sodium ions will pass 
through the membrane toward the cathode and into the deposited resin 
material there to neutralize the acidic species within the resin. This 
technique only requires that an inlet to the interior of the drum form 
anode 14 be provided and that a source of neutralizing substance be 
supplied to such inlet at an adequate rate. In this situation, it is 
evident that the embodiments of FIGS. 2, 3 and 4 would be preferred. 
Still further in accordance with the invention, the process of the present 
invention is suitable for the separation of PVC and/or PVC copolymers from 
latices of various compositions having a polymer content of from about 5 
to 60 percent and from 0.3 to 5.0 percent of an anionic or nonionic 
surfactant (based on the polymer content). The polymer content is 
preferably between 35 and 45 percent, and the surfactant content is 
preferably between 0.5 and 1.0 percent. The pH can vary from 0 to 14, 
preferably from 3 to 12, and the temperature from 0.degree. to 90.degree. 
C. or preferably from 20.degree. to 40.degree. C. The electrolysis can be 
carried out at constant DC current at a current density (CD) varying from 
1 mA to 300 mA per cm.sup.2 electrode surface area, in which case the cell 
voltage may vary from 1 to 50 volts, or the electrolysis can be carried 
out at constant cell voltage and variable current. The DC current can be 
applied continuously or periodically. Since the rate of the electrolytic 
polymer deposition is proportional with the current density (CD) and the 
concentrations of polymer in the latex, the maintenance of the 
sufficiently high polymer concentration is necessary for an efficient 
operation of the process. This also being true for other solids-liquid 
compositions. While a constant current density (CD) can be set easily at 
any value on the power source, the maintenance of the polymer 
concentration is not possible without removing water from the latex. It 
has been found that equilibrium conditions between the electrolysis unit 
and ultrafiltration unit can be established in such a way that the 
ultrafiltration unit is able to remove the right quantity of water and 
maintain a constant and sufficiently high polymer concentration for an 
efficient and steady rate of electrolysis. 
In addition, it has been found to be advantageous to apply to the anode 
surface of the electrolytic cell certain metal oxide coatings such as 
manganese dioxide, ruthenium dioxide and tantalum dioxide or their 
combination. These current conductive oxides minimize surface corrosion 
and contamination of the solids material, particularly PVC, with metal 
particles. An electrode treated in a similar manner is disclosed in U.S. 
Pat. No. 3,878,083. According to the present invention, ion exchange 
membranes can be used advantageously in the process of the present 
invention to accomplish several desirable effects. For example, by 
covering a mesh anode with a cation exchange membrane, it is possible to 
simultaneously neutralize the deposited acidic solids in-situ, thus 
eliminating a separate post-neutralization process and the necessary 
equipment and labor. The same membrane can also be used for the in-situ 
exchange of cations of the surfactant in the deposited solids material. 
This type of a cation exchange is often desirable in order to improve the 
properties of such materials as PVC plastisols. The membranes on the anode 
protect the electrode surface from wear and damage also. These membranes 
can also be used as moving belts for carrying the deposited solids on them 
away from the cell for a more convenient removal. 
Further in accordance with the present invention, whey can be concentrated 
by the present electrolytic-ultrafiltration process. A wide variety of 
processes have been devised to achieve desirable concentration and 
separation of whey proteins including electrolytic techniques as 
illustrated by U.S. Pat. No. 4,146,455. Any one of the embodiments of the 
present invention previously described can be used in processing and 
concentrating whey. It may be necessary, however, to initially add 
sufficient acid or base to destroy the apparent electrical neutrality of 
the whey composition so as to obtain a much greater deposition of whey 
solids on the anode. The advantages of the present process for 
concentrating whey protein, over the process methods of the prior art 
presently being used, is that the present process does not require a need 
for extensive evaporating equipment, and also there is not the need to 
subject the whey to excess heat which can result in denaturation. 
As previously mentioned, the present invention has been found useful to 
dewater paper sludge. Presently the paper industry filters and dumps its 
sludge into a landfill. When it rains, the sludge repeptizes, forming a 
"quicksand"-like pond which also ferments and bubbles in the summer 
releasing pungent odors. Thus, an obvious environmental problem results, 
where the land cannot be reused since, in this state, the pond cannot be 
covered with dirt and planted over with grass. It would, thus, be 
desirable to reduce the repeptization of the dumped sludge when it rains. 
It has been found, in accordance with the present invention, that paper 
sludge can be dewatered by employing the electrolytic cell of the present 
invention, alone without ultrafiltration, and by pulling a vacuum in the 
cell, the sludge is deposited on the anode and the sodium ions present are 
removed at the cathode. It should be recognized that removal of ions, 
particularly sodium ions, present as well as the actual dewatering of the 
sludge is important to reducing the peptization action that occurs when it 
rains. As previously pointed out, the composition of the paper sludge does 
not readily lend itself to ultrafiltration, however, any of the 
electrolytic cells disclosed herein could be employed for the purposes of 
this special use where the cell of FIG. 5 is preferred. Also, most 
permeable membranes or films, previously mentioned, can be used as the 
belt covering the anode, however, a filter cloth is preferred. 
Thus, from the previous discussion, the apparatus and process of the 
present invention, as further illustrated in the examples below, is found 
to be advantageous over the prior art methods. The 
electrolytic-ultrafiltration system works under widely variable conditions 
and allows a great engineering flexibility without impairing the high 
efficiency. The following examples will serve to further illustrate the 
operation and advantages of the invention. These examples should not be 
considered, however, as a limitation upon the scope of the present 
invention where such scope is defined only by the claims. 
EXAMPLE 1 
PVC RECOVERY AT CONSTANT ELECTRIC CURRENT WITHOUT ULTRAFILTRATION (UF) 
This example is outside of the scope of the present invention and 
illustrates that the electrolytic process for PVC separation, as described 
in prior art processes (e.g., process of British Pat. No. 1,525,103) loses 
its efficiency proportionally with the decrease of PVC content in the 
latex during the separation. In an experiment, using a prior art process, 
electrolytic removal of PVC was performed at a constant electric current, 
weighed, dried and weighed again. Table 1, below, shows the reduction in 
PVC recovery in time as more and more PVC is removed and the increase of 
electrical energy for obtaining the same quantity of PVC. 
TABLE 1 
__________________________________________________________________________ 
PVC Recovery at Constant 
Electric Current Without Ultrafiltration (UF) 
__________________________________________________________________________ 
Time (minutes): 
10 20 30 
40 50 60 70 
80 90 100 
Approx. % PVC in latex: 
37 34 31 
29 27 25 23 
22 21 20 
PVC recovered (grams): 
168 155 -- 
127 118 105 -- 
88 71 -- 
Needed amp. hr/kg/PVC: 
0.53 
0.57 
-- 
0.70 
0.76 
0.85 
-- 
1.0 
1.26 
-- 
__________________________________________________________________________ 
As shown by the results of Table 1, the removal of PVC from a latex with a 
low PVC content (i.e., 1 to 5 percent) is uneconomical in the practice of 
prior art processes. Since some latices can be neither filtered, nor 
centrifuged and the cost of spray drying is prohibitive, the disposal of 
such dilute latex is, therefore, a liability on the prior art process. 
EXAMPLE 2 
PVC RECOVERY AT CONSTANT ELECTRIC CURRENT WITH ULTRAFILTRATION (UF) 
In contrast to Example 1, the following Examples A and B given here are 
within the scope of the present invention and they illustrate the decisive 
advantage of combining an unrelated process, namely ultrafiltration (UF) 
with the electrolytic (E) process. By utilizing ultrafiltration (UF), it 
is possible to remove water from the electrolytically depleted latex at a 
rate which corresponds to the quantity of removed PVC. By this combined 
process, the PVC concentration can be maintained at any desired 
concentration and have an efficient, constant rate of recovery of PVC. The 
results of the (E-UF) PVC recovery of Experiments A and B are provided 
below in Table 2. As indicated by the results, the recovery (i.e., 
removal) of PVC is at a generally constant rate. The results in Table 2 
show the amount of PVC recovered for each ten (10) minutes of operation at 
a constant electric current. For Experiment A, the PVC content was kept 
between 35 percent and 38 percent and for Experiment B, between 25 percent 
and 29 percent for a duration of two hours, each. The variance in PVC 
recovery between the experiments A and B is due to other differing 
conditions such as pH, type or quantity of surfactant. 
TABLE 2 
______________________________________ 
PVC Recovery at Constant 
Electric Current With Ultrafiltration (UF) 
PVC Recovered (grams) 
Ten-Minute Intervals 
Experiment A Experiment B 
______________________________________ 
1 95 128 
2 96 128 
3 99 134 
4 95 135 
5 95 133 
6 86 149 
7 94 143 
8 92 135 
9 91 138 
10 88 146 
11 88 156 
12 89 148 
______________________________________ 
EXAMPLE 3 
EFFICACY OF ELECTROLYTIC-ULTRAFILTRATION (E-UF) PROCESS FOR RECOVERY OF PVC 
The efficacy of the utilization of the present combined 
electrolytic-ultrafiltration (E-UF) process for a continuous and practical 
PVC recovery from latices was further illustrated by three experiments, 
i.e., C, D and E. The results of the experiments are provided, below, in 
Table 3. As indicated by the results, the maintenance of the PVC 
concentration by the E-UF system shows that the combined process is 
economically viable and superior to the prior art processes of Example 1. 
In these experiments, the apparatus used is illustrated by FIG. 1 and the 
anode of the electrolytic cell is a bare TIR-2000* coated Titanium (Ti) 
drum. The latex used in the three experiments was taken from three (3) 
different suitable sources. 
FNT *TIR-2000 is an anode of an electroconductive base of titanium with a 
coating of tantalum oxide and iridium oxide as described in U.S. Pat. No. 
3,878,083. 
TABLE 3 
______________________________________ 
Efficacy of Electrolytic-Ultrafiltration (E-UF) 
Process for Recovery of PVC 
Experiment C D E 
______________________________________ 
PVC concentration 
38 29 36.9 
(%) of latex 
Surfactant content (%) 
2.21 1.2 1.0 
Surfactant type TDS* NH.sub.4 --LS** 
SLS*** 
Electrolysis 
Time of experiment (hrs) 
7.0 2.5 4.0 
Cell V 11.3-8.2 12.4-10.3 16.6-16.3 
Current density: mA/sq in 
120 120 120 
Temperature, .degree.C. 
23-27 22-32 22-28 
pH 5.8-11.4 9.0-9.08 10.4-11.5 
Latex supply (automated), ml 
8200 5430 8500 
(approx.), g 9300 6000 9700 
PVC separated (wet cake), g 
4710 2742 4684 
PVC separated 
(wet cake), lb 10.4 6.05 10.3 
PVC content (%) 82 78.5 77.42 
PVC separated dry, g 
3860 2152 3626 
Used electricity, kwh 
0.129 0.059 0.131 
Efficiency, lb/kwh 
66 80.0 61.0 
Efficiency, lb/amp-hr 
0.61 1.1 1.0 
PVC g/hr-sq. in. anode area 
31 47.8 51 
PVC conc. in Latex 
at end (%) 35 24.5 36.5 
Ultrafiltration 
Tube inlet, psi .about.5 9.5 5.0 
Flow rate, ft/sec 
(calculated) .about.6.5 6.5 
Permeation rate, ml/min 
Avg. 26 142-100 23.2 (avg.) 
Permeate removed, ml 
5275 4100 5575 
pH 10.4-11.4 
9.5- 9.3 10.6-11.2 
Surfactant content (%) 
0.55 0.07-0.1 0.22 
______________________________________ 
*TDS-Sodium tridecyl sulfate 
**NH.sub.4 --LSAmmonium lauryl sulfate 
***SLSSodium lauryl sulfate 
As shown by the above results, these experiments, particularly Experiment 
C, demonstrate the feasibility of maintaining the PVC concentration in the 
cell latex by ultrafiltration, and sustaining a steady, efficient PVC 
separation by this combined E-UF process. 
EXAMPLE 4 
EFFICACY OF SURFACTANTS 
This example illustrates the effect of different surfactants on the 
electrolytic separation of PVC from latices. There is no, or little, 
separation of PVC without having ionic surfactants in the latex. A latex 
without a surfactant is not conductive to electric current, thus the 
process is ineffective. This example comprises a series of experiments in 
which 6 anionic, 5 nonionic and 2 cationic surfactants were tested. It is 
a fact that the conductivity of the latex as an essential condition for 
electrolytic PVC separation is due to an ionic surfactant (or soap). It, 
therefore, was unexpected to discover that certain nonionic surfactants 
not only were also effective, but were even more effective in aiding the 
efficiency of the process than the customary anionic surfactants. 
The procedure for the experiments and the list of tested surfactants are 
provided below and their effect on the efficiency of electrolytic PVC 
recovery is also provided below in Table 4. 
The PVC used for this study was recovered by the E-UF process from a 
commercial latex and the surfactant removed by extraction (residual 
surfactant 0.21 percent). This extracted PVC could neither be suspended in 
water nor electroplated without resupplying some of the surfactants 
tested. The experimental procedure was as follows: 
1. The surfactant, corresponding to 0.5 g 100 percent concentration (or one 
percent based on PVC) was dissolved in 150 ml deionized water, stirred 
until dissolved (i.e., 5 to 15 min.), and the pH determined; 
2. then, 50 g of PVC was gradually added to the soap solution while being 
stirred gently to avoid foaming, and after complete suspension; 
3. the suspension was sonified for 10 minutes and the pH determined; 
4. the obtained latex was moderately stirred while electrolyzed at a 
constant 0.4 amp. The total immersed surface area of the TIR-2000 coated 
Ti plate anode was 40 cm.sup.2. The cathodes of Ti mesh were 12 mm from 
the anode, on both sides, parallel with the anode; 
5. the electrolysis was maintained for 4 minutes at the same current 
density and the initial, half-time, and final cell potentials recorded; 
and 
6. finally, the deposited PVC was scraped off the anode, weighed, dried, 
and weighed again. 
The surfactants used in the experiment were: 
______________________________________ 
List of Surfactants 
No. Trade Name Generic Name Type 
______________________________________ 
1 SLS Sodium lauryl sulfate 
anionic 
2 MgLS Magnesium lauryl sulfate 
anionic 
3 NH.sub.4 LS Ammonium lauryl sulfate 
anionic 
4 TDS Sodium tridecyl sulfate 
anionic 
5 Aerosol OT-25 
Sodium dioctylsulfosuccinate 
anionic 
6 Igepon T-77 Sodium-N-methyl-N-oleyltaurate 
anionic 
7 Brij-30 Polyoxyethylene(4)lauryl ether 
non- 
ionic 
8 Tergitol 15-5-9 
Polyethyleneglycol ether of 
non- 
linear C.sub.11-5 alcohols 
ionic 
9 Igepal CO 30 
Nonylphenoxypolyethyleneoxy- 
non- 
ethanol ionic 
10 Triton X-100 
Octylphenoxypolyethoxyethanol 
non- 
ionic 
11 Hyonic Alkylphenoxy polyoxyethylene 
non- 
ethanol ionic 
12 Ethoduo- N, N'-polyoxyethylene-(15)-N- 
cat- 
meen T-25 tallow-1,3 diaminopropane 
ionic 
13 Emicol CC-9 Polypropoxylated quaternary- 
cat- 
ammonium chloride ionic 
______________________________________ 
The results of the runs are provided below in Table 4. 
TABLE 4 
______________________________________ 
Effect of Different Surfactants on 
Electrolytic Recovery of PVC 
Obtained PVC Avg. 
lb/ Cell 
No. Surfactant Type Grams amp-hr lb/kwh* 
V* 
______________________________________ 
1 SLS - 10.7 0.885 59.0 15 
2 MgLS - 6.5 0.538 28.1 19 
3 NH.sub.4 LS - 10.6 0.877 63.2 14 
4 TDS - 10.3 0.852 61.4 14 
5 Aerosol OT-25 
- 15.6 1.291 71.7 18 
6 Igepon T-77 - 5.5 0.455 50.6 9 
7 Brij-30 0 18.6 1.540 51.3 30 
8 Tergitol 15-5-9 
0 13.5 1.120 33.1 34 
9 Igepal CO 30 
0 19.1 1.582 47.0 33.6 
10 Triton X-100 
0 17.1 1.475 46.8 31.5 
11 Hyonic 0 16.8 1.336 53.4 26.0 
12 Ethoduomeen + none 
T-25 
13 Emicol CC-9 + Did not disperse PVC in H.sub.2 O. 
______________________________________ 
Type: - anionic; 0 nonionic; + cationic 
*approximate values 
From the results recorded in Table 4 above, it is evident that: 
1. Among the 6 anionic alkyl sulfate surfactants, those having a two-valent 
cation such as Mg, or having a nitrogen in the molecule cut the current 
efficiency to about half of those having the monovalent sodium; 
2. the tested nonionic surfactants provided to be more effective than most 
of the anionics as to the PVC deposit on the anode; and 
3. the cationic surfactants caused no deposition of PVC on the cathode and 
neither on the anode. 
EXAMPLE 5 
CURRENT EFFICIENCY FOR PVC DEPOSITION VS. SURFACTANT CONTENT 
The following experiments, i.e., F through N, were carried out to establish 
the influence of the quantity of the surfactant in an electrolysis type of 
PVC deposition process in which the electrodes were in direct contact with 
latex. 
In these experiments, the original surfactant was first removed by 
extraction from over 4 pounds of electrolytically separated, dried and 
milled PVC. In 200 ml volumes deionized water, 100 g quantities of this 
PVC were suspended. Before suspension, predetermined quantities of 
surfactant (i.e., sodium lauryl sulfate) ranging from less than 0.2 
percent to 2 percent were dissolved in the waters. The batches (each 300 
g) were magnetically stirred, then treated with ultrasonics for 10 minutes 
and immediately electrolyzed for 5 minutes at 0.5 amp. constant current. 
The current density was 10 mA/cm.sup.2. The anode was a TIR-2000-coated Ti 
plate with 50 cm.sup.2 of its surface immersed in the stirred latex. The 
initial and final pH of the batches and the temperatures were also 
measured. The "plated" PVC was removed from the anode, weighed, dried and 
weighed again. The dry weights of separated PVC and the initial pH of the 
latex batches vs. the surfactant content in the latex are recorded below 
in Table 5. 
TABLE 5 
______________________________________ 
Dry Weight of Separated PVC 
and pH of Latex 
as Based on Surfactant Content 
Dry Weight of PVC 
Surfactant (grams) per amp. 
Experiment 
Content (%) 
hour pH of Latex 
______________________________________ 
F 0.20 none 7.1 
G 0.25 629 8.2 
H 0.50 843 8.1 
I 0.75 829 8.9 
J 1.00 637 9.1 
K 1.25 605 9.2 
L 1.50 548 9.5 
M 1.65 428 9.3 
N 2.00 449 9.5 
______________________________________ 
The data provided above in Table 5 shows that the current efficiency as a 
function of quantity of surfactant goes through a maximum. While this is a 
general characteristic of the efficiency-surfactant quantity relation, the 
location of the maximum and its magnitude also depends on the type of 
surfactant present in the latex. 
EXAMPLE 6 
ION-EXCHANGE MEMBRANES IN ELECTROLYTIC SEATION OF PVC 
The application of different ion-exchange membranes in the electrolytic PVC 
separation has been illustrated in the following experiments, i.e., 
Experiments P, Q, R, S, T, U, V and W. 
A TIR-2000* coated mesh drum electrode was constructed with interchangeable 
membranes. These experiments were carried out under the same conditions 
with particular emphasis on the effect of various membranes (MB) on the 
rate of PVC deposition. Three anion and two cation exchange membranes (MB) 
were tested. The membranes (MB) covered the drum electrode which was 
charged with 250 ml distilled water or dilute sodium hydroxide solution to 
solubilize the surfactant if it crossed the membrane or quenched the 
generated hydrogen ion, respectively. 
At the end of the experiment, the solution from the drum electrode was 
recovered and analyzed. The PVC concentration in the circulated latex was 
maintained by simultaneous ultrafiltration. 
The electrolysis time was one hour for each experiment, except one (i.e., 
Experiment U) for one-half hour, at a constant one ampere or about 60 
mA/in.sq. current density (CD). 
Table 6 lists the tested membranes and records the experimental results, 
compared with a control experiment without a membrane (i.e., Experiment 
P). 
TABLE 6 
__________________________________________________________________________ 
Efficiency of E-UF Separation of PVC Using Various Membranes 
Final 
pH of Solution 
PVC, g 
In UF 
Experiment 
Membrane A** 
V*** 
Wet 
Dry 
Anode 
Permeate 
__________________________________________________________________________ 
P None, bare anode 
1 10.6 
993 
732 
-- 11.3 
Q MB-1 anion exchange 
1 19.0 
729 
556 
2.2 11.5 
(H.sub.2 O inside) 
R MB-2 cation exchange 
1 9.2 
851 
625 
3.1 11.5 
(H.sub.2 O inside) 
S MB-3 anion exchange 
1 14.6 
876 
655 
1.8 11.0 
T MB-4 cation exchange 
1 9.5 
764 
696 
2.6 11.3 
(H.sub.2 O inside) 
U MB-5 anion exchange 
1 40.0 
266 
191 
2.7 10.8 
(H.sub.2 O inside) 
V MB-3 anion exchange 
1 15.0 
797 
567 
12.7 
11.3 
(0.166N NaOH inside) 
W MB-4 cation exchange 
1 9.7 
766 
592 
12.1 
11.5 
(0.166N NaOH inside) 
__________________________________________________________________________ 
*TIR-2000 is an anode of an electroconductive base of titanium with a 
coating of tantalum oxide and iridium oxide as described in U.S. Pat. No. 
3,878,083. 
**amperes 
***operating voltage 
As shown by the last two experiments (i.e., Experiments V and W) above, 
unless a base (e.g., NaOH) is used for neutralization, an acidic 
environment is produced in the vicinity of the anode which makes the 
deposited PVC acidic also. 
EXAMPLE 7 
SIMULTANEOUS NEUTRALIZATION OF ELECTROLYTICALLY DEPOSITED PVC 
The usefulness of ion exchange membranes for the simultaneous 
neutralization of electrolytically deposited PVC has been demonstrated in 
the experimental series of Example 6. 
The electrodeposition of the PVC from a latex with a surfactant, for 
example, sodium lauryl sulfate CH.sub.3 --(CH.sub.2).sub.11 
--SO.sub.4.sup.- Na.sup.+ results in an acidic PVC of a pH of .about.2-3 
deposited on the anode due to the CH.sub.3 (CH.sub.2).sub.11 
SO.sub.4.sup.- H.sup.+ formation on the PVC, while sodium hydroxide forms 
at the cathode. The thermal stability of this acidic PVC is inadequate, 
therefore, such PVC must be neutralized in a separate operation with a 
base. The replacement of the acidic hydrogen with another sodium, ammonium 
or alkali metal ion became possible by depositing the PVC onto a membrane 
which has a basic solution on the opposite side of the membrane. A 
hydroxide concentration gradient of 0.05-0.2 equivalent higher over the 
bulk electrolyte was sufficient to maintain a simultaneous neutralization 
of the PVC deposit. The electrolysis was carried out at two amperes 
constant current. 
Table 7, below, shows 4 in-situ neutralization experiments (i.e., 
Experiments AA, BB, CC and DD) using a NAFION.RTM. cation exchange 
membrane described in U.S. Pat. No. 3,909,378 over a perforated drum anode 
into which a predetermined volume of base having experimentally determined 
concentration was metered during the electrolytic deposition of PVC. The 
cations of the base transfused from inside of the drum anode through the 
membrane into the PVC layer and replaced the acidic hydrogen of the alkyl 
hydrogen sulfate, thus neutralizing the half sulfuric acid surfactant 
forming a salt, the same or similar to the original surfactant. The pH's 
of the simultaneously neutralized PVC are compared with the pH of an 
unneutralized PVC in Experiment EE. 
The practical benefit from this in-situ simultaneous neutralization is that 
it eliminated the extra expenses for space, neutralizing equipment, power 
and labor, which are required for a post-neutralization of the acidic PVC. 
TABLE 7 
______________________________________ 
Simultaneous Neutralization of 
Electrolytically Deposited PVC 
Experiment AA BB CC DD EE 
______________________________________ 
Experiment using 
KOH LIOH NH.sub.4 OH 
NaOH None 
Cell voltage 
17.5 14.0 21.5 14.5 10.5 
Electrolysis time 
90 90 90 95 90 
(min.) 
Separated PVC 
951 780 1430 950** 1210 
(g) dried 
SLS surfactant 
17.5 14.3 26.3 31.5 31.0 
(meq)* 
MgLS surfactant 
7.2 5.9 10.8 -- -- 
(meq) 
Total surfactant in 
24.7 20.2 37.1 31.5 31.0 
latex (meq) 
Total base metered 
79.0 80 184 87 none 
into anode (meq) 
Recovered from 
22.0 6 53 97 none 
drum 
Net base used (meq) 
57.0 74 131 77.3 none 
(meq) of surfactant 
230 366 353 245 none 
equivalent 
Avg. pH of 5.25 10.2 8.0 8.7 2.1 
deposited PVC 
______________________________________ 
*(meq) = milliequivalent 
**This latex contained 33% PVCPVA and 1% sodium tridecyl sulfate 
surfactant. 
In the results of Table 7, above, the lower pH with the KOH is due to a 
slower injection rate of KOH during the first two-thirds of the experiment 
time. The increased rate during the last third of the time built up some 
KOH in the drum. 
EXAMPLE 8 
DISTRIBUTION OF NEUTRALIZING CATIONS IN PVC 
This example illustrates the in-situ and simultaneous cation replacement of 
the surfactant in the electrolytically deposited and neutralized PVC. 
The practical value of the method of in-situ cation replacement is in the 
option of tailoring the properties of the PVC such as foamibility, thermal 
stability, moisture sensitivity, and the like. For example, the thermal 
stability of surfactant containing PVC ranks with the surfactant's cations 
as follows: Ba.sup.&gt; Mg.sup.&gt; Li.sup.&gt; Na.sup.&gt; K.sup.&gt; NH.sub.4. Thus, 
while for polymerization, a specific surfactant cation combinations may 
have to be used, for thermal or other requirements, the cation can be 
changed during the electrodeposition. 
The PVC from the neutralization experiments in Example 7 has been analyzed 
for the distribution of the cations involved, mainly Na.sup.+, Mg.sup.2+, 
K.sup.+, Li.sup.+ and NH.sub.4.sup.+. 
The table below shows the quantity of these species in ppm. 
TABLE 8 
______________________________________ 
Distribution of Neutralizing Cations in PVC 
Elements in PVC (ppm) 
Total 
Elements Na Mg K Li NH.sub.3 
PPM 
______________________________________ 
In starting PVC 
423* 94* 517 
In KOH neutralized 
146 86 318 550 
PVC 
In LiOH neutralized 
207 79 237 523 
PVC 
In NH.sub.4 OH neutralized 
351 63 420 834 
PVC 
______________________________________ 
*The original Na and Mg contents are calculated. 
The applied cations were also present in the latex electrolyte and also in 
the ultrafiltration (UF) permeate. The permeates contained 9.8, 8.1 and 
22.0 ppm of K, Li and NH.sub.3, respectively, indicating that some of 
these ions had penetrated not only the membrane and the deposited PVC 
layer but also the UF membrane. 
In absence of this method of cation replacement, should such replacement be 
necessary, the surfactant from the separated PVC (by electrolysis or spray 
drying) must be removed by extraction with a proper solvent, and the new 
desired surfactant added back. Most of the surfactant must be dissolved 
first and the PVC suspended in this solution. This process would return 
the water also, thus requiring a second PVC separation. To obtain a good 
distribution of the surfactant many times, a special method such as 
sonification must be applied. Again, these procedures are costly and time 
consuming and may adversely affect the quality of the PVC or plastisols 
made of such PVC. 
EXAMPLE 9 
ELECTROLYTIC-ULTRAFILTRATION (E-UF) PVC SEATION ONTO VARIOUS ANODE 
COVERINGS 
It is evident from the foregoing examples that the combined E-UF process 
for the separation of PVC, or other suitable particulate matter (e.g., PVC 
copolymers) from their suspension, has appreciable advantages over the 
prior art methods of separation. 
The following experiments were performed to illustrate additional 
advantages which allow considerable flexibility in engineering design of 
equipment and operation. Among the options the operator can choose are: 
1. a bare drum or continuous belt anode; 
2. a cloth or mesh or an ion exchange membrane to protect the surface of 
the anode from wear; 
3. a cloth or mesh or a membrane as a continuous moving belt from which the 
PVC is removed at a remote point of the cell; and 
4. when using a membrane, it can also be used for the in-situ 
neutralization of the PVC and in-situ exchange of cations of the 
surfactants. 
The experiments below demonstrate the use of moving belts of dielectric and 
electrolytically conductive materials such as polypropylene mesh and ion 
exchange membranes, respectively. 
(9-1) PVC Recovery Using Polypropylene Mesh Belt 
A PVC-type latex containing 43.3 percent PVC with about 2.11 percent sodium 
tridecyl sulfate surfactant was subjected to electrolysis at one amp. 
constant current and 6-5.3 cell potential for 1 hour and 40 minutes. The 
anode drum, 45 percent of its surface immersed in the latex, served as one 
of the pulleys and a one-inch diameter Rulon rod as the second pulley. The 
Rulon pulley was situated about 12 inches from the cell in an 
approximately 45.degree. elevation. The traveling speed of the belt was 
about 3 inches/min. The deposited PVC was scraped off just at the 
down-turn of the belt from the Rulon pulley (FIG. 3). The electrodeposited 
PVC weighed 262 grams wet and 216 grams dry. 
(9-2) PVC Recovery Using Nafion Cation Exchange Membrane Belt 
The same type of PVC latex as in experiment (9-1) was electrolyzed at one 
ampere constant current and 6.3-5.3 V cell potential for one hour. The PVC 
scraped off the second pulley weighed 224 grams wet and 181 grams dry. 
(9-3) PVC Recovery Using Selemion AMV Anion Exchange Membrane Belt 
The same type of PVC as used in Experiments (9-1) and (9-2) was 
electrolyzed at one ampere constant current and 11-11.4 V cell potential 
for one hour. The separated PVC from the second pulley weighed 235 grams 
wet and 192 grams dry. 
Additional experiments were performed to further illustrate the various 
modes of operation listed above. These experiments were carried out using: 
(9-4) a solid drum anode bare 
(9-5) a solid drum anode covered with a polypropylene mesh; 
(9-6) a solid drum anode covered with a cation exchange membrane; 
(9-7) a mesh drum anode covered with a cation exchange membrane but not 
used for in-situ neutralization; and 
(9-8) a mesh drum anode covered with a cation exchange membrane and used 
for in-situ neutralization. 
The experiments were carried out at the same and constant electric current 
(i.e., one ampere) using the same type of polyvinyl chloride-polyvinyl 
acetate copolymer (PVC-PVA) latex and other conditions except those 
specified above. 
The results of the experiments are summarized below in Table 9. The data 
indicates that the efficiencies are comparable and permit the engineering 
options without an appreciable sacrifice in production rate. The lower 
current efficiency in the in-situ neutralization (i.e., Experiment 9-8) is 
expected since the first part of the current is used up to replace the 
Na.sup.+ ion in the soap with the H.sup.+ ion, and the second part to 
neutralize the acidic H.sup.+ ion on the surfactant with the Na.sup.+ ion 
supplied from across the membrane. 
TABLE 9 
__________________________________________________________________________ 
Electrolytic-Ultrafiltration (E-UF) 
PVC Separation Onto Various Anode Coverings 
Yield 
PVC-PVA g per 
pH of 
Obtained, g 
Applied 
amp/hr 
Experiment 
Electrolysis 
Temp., 
Latex % Charge, 
Elect. 
Permeate 
No. in min. 
V .degree.C. 
in Cell 
wet 
dry 
dry 
amp/hr 
Charge 
pH 
__________________________________________________________________________ 
(9-4) 30 16-14 
25 8.8-9.4 
674 
514 
76.3 
1.0 514 7.5 
(9-5) 30 17-13 
27 9.0-9.6 
725 
559 
77.1 
1.0 559 8.9 
(9-6) 30 16-27 
25 9.0-9.4 
669 
514 
76.9 
1.0 514 7.75 
(9-7) 36 22-15 
23 5.0-9.5 
798 
618 
77.5 
1.2 515 7.5 
(9-8) 50 13-10 
26 9.0-9.8 
752 
583 
77.6 
1.67 
349 9.35 
__________________________________________________________________________ 
EXAMPLE 10 
EFFECT OF CURRENT DENSITY (CD) AND PVC CONTENT IN LATEX ON RATE OF 
ELECTROLYTIC (E) RECOVERY OF PVC 
In order to determine the effect of current density (CD) on the rate of 
electrolytic (E) recovery of PVC, latices were electrolyzed at different 
current densities (CD). The surfactants used in the experiments (i.e., 
Experiments FF and GG) were different. The results of the electrolysis of 
the latices are provided below in Table 10. 
TABLE 10 
______________________________________ 
Effect of Current Density (CD) 
On Electrolytic (E) PVC Recovery 
CD Recovered 
Experiment (Surfactant) 
(mA/in.sup.2) 
PVC (g) 
______________________________________ 
FF (SLS) 5 9.4 
10 17.9 
15 29.3 
GG (Brij-30) 5 13.3 
10 30.7 
15 46.5 
______________________________________ 
As shown in the results of Table 10, as the current density (CD) increases, 
a greater amount of PVC is recovered. 
In a manner similar to that discussed above, the effect of the PVC content 
in latex on the electrolytic (E) recovery of PVC was determined by 
electrolyzing latices of different PVC content at the same current density 
(CD). 
In this experiment, the PVC content of a latex containing 35 percent 
initial PVC was reduced by incremental dilution, and the resulting batches 
were electrolyzed under identical conditions at 60 mA/inch.sup.2 current 
density (CD). 
The results of the experiments are recorded below in Table 11. The results 
record the rate of separation, i.e., recovery, of PVC per faraday. 
TABLE 11 
______________________________________ 
Effect of PVC Content In Latex 
On Electrolytic (E) PVC Recovery 
______________________________________ 
Percent PVC in Latex 
10 15 20 25 30 35 
PVC (g.) Recovered/ 
1206 2171 3281 4593 5741 6706 
Faraday 
______________________________________ 
As can be seen in the results of Table 11, with a larger PVC content in the 
latex, the greater the PVC recovery. 
EXAMPLE 11 
ELECTROLYTIC PVC RECOVERY WITH A MOVING BELT ANODE 
In this experiment, the electrolytic system illustrated in FIG. 4 was used. 
The advantages of the geometry of this electrolytic system are that a 
greater portion of the surface of the anode can be immersed and utilized 
for PVC separation, the anode requires a relatively smaller latex 
container, and a multiplication of the belt anode unit can be constructed 
into one latex container or several belt anode units can be connected to 
form one moving belt anode with several rising and immersing sections. 
The anode was an endless stainless steel mesh belt. The centers of the 
lower and upper pulley were about 24 inches apart. The diameter of the 
lower pulley was 9 inches and that of the upper pulley 3 inches. The lower 
one-foot length of the belt was immersed in the PVC latex. The inner side 
of the anode was insulated to prevent the deposition of PVC on that side. 
The active anode surface area facing the cathode was 74 sq. in. The 
cathode, made of expanded titanium sheet, was situated parallel to the 
anode at a distance of 3/4 inch. 
The adjustable speed of the anode was set at 2 in./min. The latex contained 
53 percent PVC and was electrolyzed at 2 amperes constant current and 
8.3-8.8 V cell potential (CD 27 mA/inch.sup.2). The thickness of the 
deposited layer was about 3/32 inch and has not fallen off the anode when 
turned under the lower pulley. Preliminary experiments indicated that the 
thicker the PVC deposit the larger the diameter of the lower pulley must 
be. The deposited PVC was scraped off the belt at the upper pulley on the 
down-turn side. 
A 20-minute electrolysis separated 278 grams of wet PVC which, when dried, 
weighted 195 grams. 
EXAMPLE 12 
The following experiments (i.e., Experiments 12-1, 12-2 and 12-3) 
illustrate the various materials, and coatings which can be used as anodes 
in the present electrolytic ultrafiltration (E-UF) PVC separation process. 
(12-1) MnO.sub.2 Coated Solid Ti Drum Anode 
A plant latex containing 42 percent PVC with sodium tridecyl sulfate soap 
was used for this experiment. 
No ultrafiltration was applied. 
The electrolysis was carried out at 1.4 ampere constant current and 14 to 
9.8 V. After the 2-hour and 20-minute operation, the PVC which was 
obtained and dried weighed 1545 grams, or 3.21 pounds. The consumed 
electricity was 3.27 amp-hr. The current efficiency is approximately 1 
lb/amp-hr. 
The PVC was analyzed and found to contain 3.2 ppm of Mn. 
(12-2) MnO.sub.2 Coated Mesh Drum Anode Covered With Nafion 
Plant PVC with a 38 percent solid content was used in this experiment. 
The drum anode was made of mesh and was covered with a Nafion membrane. 
During the process, the permeate from the ultrafiltration (pH 11.5) was 
led through the inside of the anode to see whether the base in the 
permeate could be utilized for an in-situ neutralization of the deposited 
PVC. The pH of the deposited PVC was at 3.3-4.6. Thus, the neutralization 
with the alkaline permeate could not be accomplished because of the much 
higher acid generation in the anode than the supply of base by the 
permeate. 
The electrolysis was carried out at a constant current of 2 amperes for 1 
hour and 15 minutes. The separated PVC was 542 grams wet, approximately 
424 grams dry=0.933 pound. The cell voltage was 11.5-9.1. Current 
efficiency 0.373 lb/amp-hr. 
(12-3) MnO.sub.2 Coated Mesh Drum Anode Covered With a Filter Cloth 
In this experiment, a glass filter cloth was used to cover the MnO.sub.2 
coated mesh drum anode. The latex obtained from a pilot run contained 0.74 
percent, a mixed surfactant of about 0.53 percent sodium lauryl sulfate 
(SLS), and 0.21 percent magnesium lauryl sulfate (mgLS). The PVC solid 
content in the latex was 24 percent. 
The electrolysis was conducted at one ampere constant current and the cell 
potential varied between 10 and 8.9 V. In a one-hour processing, the PVC 
obtained was 450 grams wet, 339 grams dry=0.748 pound. Current efficiency: 
0.75 lb/amp-hr. 
The experiment was continued under the same conditions except a vacuum was 
applied to the interior of the drum electrode. The purpose was to see 
whether a filtration would be possible while also electrodepositing the 
PVC. A moderate increase (17 percent over electrolysis alone) in PVC 
deposition was realized. The filtrate, however, was not clear due to some 
PVC content. 
EXAMPLE 13 
PAPER SLUDGE DE-WATERING 
In this example, the use of the process of the present invention to 
de-water paper sludge is demonstrated. For this experiment, a TIR-2000 
coated mesh drum electrode was covered with a filtering cloth. The cathode 
was a mesh Ti (expanded) strip about 1 centimeter away from the drum anode 
concentric with the anode. The apparatus was basically the same used in 
the previous examples for the recovery of PVC solids except an 
ultrafiltration unit is not employed. A DC current was supplied from a 
power source while the sludge was agitated by air sparging. 
Electrolysis of the paper sludge was commenced and the amperage was 
increased from 0.7 amps to 0.85 amps over a period of 10 minutes. The 
filtering cloth covering the anode became initially coated with sludge but 
there was no further deposition of sludge particles on the anode with 
time, i.e., there was no increase in the thickness of the coating on the 
filtering cloth with an increase in time. 
A vacuum was then applied to the electrolytic cell to draw sludge fluids 
through the filtering cloth to the interior of the drum anode. The 
application of the vacuum while electrolyzing was continued for an 
additional 50 minutes. The solid particulate contained in the sludge 
composition continuously deposited on the rotating drum anode and was 
continuously recovered during this time. 
The net solid recovery weighed 381 grams and the filtrate removed was 950 
ml. 
A 120-gram portion of the wet recovered solid was placed into an oven to 
dry at 115.degree. C. over a weekend. The dried sludge sample weighed 52 
grams. Therefore, the de-watered sludge dry content was 43.3 percent. This 
compares with the solids concentration in the initial unprocessed sludge 
as follows: 
The total amount of the processed sludge was: 
______________________________________ 
Solid 381 g 
Filtrate 950 ml 
Approx. total wgt. 1331 g 
______________________________________ 
The dry material being 381/120.times.52=165.1 g or 12.4 percent solids in 
the unprocessed sludge. 
EXAMPLE 14 
DE-WATERING PAPER SLUDGE USING THE EMBODIMENT DEFINED IN FIG. 5 
In this example, paper sludge is de-watered as described in the previous 
Example 13. The only difference is that the apparatus utilized is the one 
defined in FIG. 5 where the cathode is interior to the anode. The elements 
or components of the apparatus are the same as described in Example 13 
above and the same procedure is used as set out in Example 13 above. A 
vacuum is applied (note Examples 12 and 13) 10 minutes after the 
electrolysis is commenced. The solid sludge particulate is readily 
deposited on the anode and is recovered as described in Example 13 above. 
The results of this experiment are essentially the same as in Example 13.