FR2520760A1 - Electrode container for metal recovery cell - having lightweight structure and easily replaced electrode bag - Google Patents

Abstract

Container, for use in electrolytic recovery of metals, comprises two elements which cooperate to form a three-sided structure having an open face. An electrolyte-permeable bag surrounds the structure and is stretched around the structure by stretching devices positioned between the elements. The container has a much more lightweight construction than conventional containers and the bag is easy to fix and replace.

Description

The present invention relates to a container or a
box improved for application in the deposit by elec
trolysis of metals from aqueous solutions.

The recovery of nickel, copper, lead,
zinc, silver and other metals from solutions
aqueous by electrolytic processes is practiced with
success on an industrial scale for many years.

Basically, in such processes, we do
pass an electric current between an anode and a cathode
inserted into a suitable aqueous electrolyte. The metal to
collect is removed by plates at the cathode, while
various reactions can occur at the anode, for example
dissolving the anode or releasing a gas like
oxygen or chlorine.

In some cases; the cathode and the anode are
through a permeable membrane or diaphragm
electric. So in recovering nickel from
impure nickel anodes, a diaphragm is required to
prevent the impure electrolyte from reaching the cathode where the
impurities such as copper, lead or zinc could
remove by plates and contaminate the pure nickel plated with
cathode. The interposition of a diaphragm between the anode and the
cathode is commonly done by enclosing each cathode
in a cathode box "consisting of a wooden frame
rigid with a fabric membrane.
backflow of impure electrolyte into the canister
holds a positive flow of purified electrolyte from the compartment
from the cathode to the anode compartment, maintaining a
positive electrolyte head in the cathode compartment.

The frame of the box has the important function of maintaining
the membrane stretched to resist its tendency to project towards the anode by virtue of the flow of electrolyte.

 In other cases, it may be necessary to surround both the cathode and the anode with separate diaphragms, as described in Canadian Patent No. 463,573. The wooden electrode container described in this patent is always commonly used and a similar structure made of polypropylene is described in Canadian Patent No. 981,212.

In these two devices, permeable diaphragms are stretched taut on each side of an open rectangular frame. The edges of each diaphragm are forced into a continuous groove formed in each arm of the frame.

A caulking bead or bead is forced into the groove (on the diaphragm) to ensure the integrity of the seal between the diaphragm and the groove and to keep the tissue taut.

 This type of electrode container suffers from a number of drawbacks. In order to fix the diaphragm in the groove, you have to press it violently with your hand.

This process, which requires a lot of work, is both tiring for the worker and an important cause of usurpation for the box. In addition, the need to keep the diaphragm tight restricts the choice of tissue that can be successfully caulked to heavy, roughly dressed tissue. This excludes a large number of otherwise excellent diaphragm fabrics, such as polyester and polypropylene fabrics.

 The use of wooden frames has other drawbacks, in that the metal to be recovered may tend to deposit on the wooden frame, and as the metal's dentritic growth continues, short circuits may occur. appear between an adjacent cathode and anode, resulting in lower current efficiency and damaging the diaphragm. In addition, organic impurities can leak from the wooden frame into the electrolyte.

 Another disadvantage of the wooden frame is still the amount of work required to build a box. As anyone with experience in woodworking knows, the construction of a solid wooden frame (especially in the light of the harsh conditions of use in an electrolytic installation) with joints requires skill and time.

Wooden containers have yet another disadvantage
in that, given their inherent buoyancy, they tend to float in the electrolyte. This makes it difficult to immerse them in the plating cell and hold them securely in position. Substantial means are therefore necessary to immobilize the box in the tank.

 According to the invention, an electrode container for use in recovering metal from an electrolyte comprises two elements which cooperate to form a three-sided structure with an open face; an electrolyte permeable bag enveloping the structure; and a stretching means arranged between the elements to maintain the bag in a stretched state around the structure.

 Such a container can be of a much lighter construction than those described above, and the bag is easy to fix and replace.

 Interestingly, the cooperating elements and the stretching means, which is conveniently a stretching bar disposed at the open top of the container, are made of a polymeric material, preferably polyurethane. The advantages are that the metal to be collected does not accumulate on the plastic elements and the stretching bar, the organic impurities do not leak from the polymer box as they do from a wooden box, and that the manufacturing the box does not require much labor. In addition, if a polymer material of suitable density is used, the box does not float in the electrolyte.

An electrode container form according to the invention will now be described by way of example with reference to the accompanying drawings, where
Figure 1 is an elevation of the assembled container;
Figure 2 is an elevation of the cooperating elements;
Figure 3 is a plan seen from above of the drawing means;
Figure 4 is a view of Figure 3 taken along line 4-4.

 Figure 5 is a partial perspective view of the upper part of the assembled container, showing the means for attaching the bag.

 As shown in the drawings, the container 10, which can be used to accommodate either a cathode or an anode (not shown) comprises a permeable bag 12 tightly suspended above a frame 14. The frame consists of two elements 16A and 16B in polymeric material connected by a hinge at 18 and forming an open support structure with 3 sides 32. The hinge 18, which is also preferably made of polymeric material, allows the elements 16A and 16B to rotate by an arc A.

 The upper ends of the elements 16A and 16B are kept apart by a stretching bar 20 which pushes them against the bag 12 to keep it taut. The bar 20 includes two protrusions 22A and 22B which fit into channels 24A and 24B at the top of the elements 16A and 16B respectively. Grooves 26 are formed in the bar 20, and a fastener, such as a cord 28 surrounding the upper end of the bag 12 and being fixed there by loops of the bag 34, is threaded in a sinuous way through the grooves 26, to suspend securely the bag 12 to the bar 20 and prevent it from dislodging from the box 10. The elements 16A and 16B are formed with extensions 30A and 30B to suspend the box 10 in a complementary groove formed in an electrolytic tank (not shown ).

 As shown in more detail in FIG. 5, the loops 34 are arranged precisely against a hem 38 around the upper edge of the bag 12 The loops 34 like the hem 38 can be fixed to the bag 12 by an appropriate stitch 36.

 The elements 16A and 16B and the bar 20 are preferably made of high modulus polyurethane molded by a reaction injection process, and to increase their strength and durability they can be reinforced inside by a fiber bar glass. Polystyrene and propylene are less satisfactory in terms of dimensional stability (warping and elongation) and their resistance. The polyurethane elements have good physical properties, are satisfactory in use and can be easily mass produced. The density of the polymer prevents the box 10 from floating in the tank, so that the previous practice of fixing the box 10 to the tank is not necessary.

 Since it is not necessary to strike and caulk to attach it to the frame, it is no longer necessary for the bag 12 to be made of a rough material. On the contrary, it can be made of smooth materials readily available such as polyester or polypropylene. In addition, since the elements 16A and 16B and the bar 20 can be easily and quickly molded, the labor-intensive prior art of manufacturing the boxes 10 with wood is also eliminated.

 To assemble the container 1 we join the two elements 16A and 16B to the hinge 18. We simply slide the bag 12 onto the box 10, and when it is in position, we move aside by forcing the two elements 16A and 16B by means of a stretching tool, thereby stretching the bag 12 taut over the box 10. While the elements are forcibly separated, the stretching bar 20 is inserted into the two channels 24A and 24B to maintain the tensile force on the elements 16A and 16B and the bag 12.

The tool is then released and removed. The rope 28 is then wound through the grooves 26 to ensure the precise fixing of the bag 12 against the elements 16A and 16B.

 The container is then placed in the electrolyte tank and the electrode is suspended in the box 10 by known means. The purified electrolyte is introduced into the box 10 to maintain a slightly positive head above the impure electrolyte flowing outside the box 10 in the tank (not shown).

Claims (10)

1. An electrode container for application in the recovery of metal from an electrolyte, comprising two elements (16A, 16B) cooperating to form a three-sided structure having an open face; an electrolyte permeable bag (12) enveloping the structure; and stretching means (20) disposed between the members for maintaining the bag in a stretched state around the structure. 2. Container according to claim 1 wherein the elements are connected to each other by a hinge at the base of the structure. 3. Container according to one of claims 1 or 2 wherein the elements are a pair of identical L-shaped elements connected to each other by a hinge at the center of the base of the structure. 4. Container according to any one of the preceding claims, in which the drawing means is a drawing bar. 5. Container according to claim 4 wherein the drawing bar is detachable from the structure. 6. Container according to one of claims 4 or 5 wherein the bag comprises means (28) for fixing the bag to the drawing bar, and the drawing bar comprises means (26) for accepting the fixing means . 7. Container according to claim 6 wherein the fixing means is a rope (28) attached to the bag and the acceptance means consists of several grooves (26) in the bar in which the rope is inserted. 8. Container according to any one of claims 4 to 7 wherein the elements and the bar are made of a polymeric material. 9. Container according to claim 8 wherein the polymeric material is polyurethane. 10. A container according to any one of the preceding claims wherein the bag is made of polyester or polypropylene.