GB2125828A

GB2125828A - Extraction of copper from solutions

Info

Publication number: GB2125828A
Application number: GB08316410A
Authority: GB
Inventors: Donald Alan Arcilesi; Rebecca Mary Spearot; John V Peck
Original assignee: Occidental Chemical Corp
Current assignee: Occidental Chemical Corp
Priority date: 1982-06-16
Filing date: 1983-06-16
Publication date: 1984-03-14
Also published as: FR2528870A1; GB8316410D0; CA1214580A; NL8302161A; JPS596336A; IT8348501A0; DE3321451A1

Abstract

A process for removing copper ions from an aqueous solution particularly an industrial effluent where the copper is in complexed form, requires the solution to be adjusted to a pH value of less than 6, preferably 2 to 4, before it is contacted with steel wool. Apparatus comprises a solution reservoir to which acid is controllably supplied to maintain the desired pH value, and one or more replaceable canisters of steel wool through which the solution is pumped from the reservoir.

Description

SPECIFICATION Extraction of copper from solutions The present invention broadly relates to an apparatus and process for extracting copper ions from aqueous solutions, and more particularly to the treatment of such copper ion containing solutions to reduce the copper concentration therein to a level at which the discharge effluent can harmlessly be discharged as waste.

The enactment of various environmental regulations, particularly those designed to improve water quality has made it mandatory to reduce or eliminate the discharge of certain metal ions present in industrial effluents to waste systems. Copper is one such metal ion which has been found environmentally undesirable and various techniques have heretofore been used or proposed for use to reduce or entirely remove such contaminating copper ions enabling the solution to be harmlessly discharged to waste. One such technique is disclosed in United States Patent 3,674,466. Other techniques employ various chemical reagents to effect a precipitation of the copper ions in such industrial effluents or the use of ion exchange resins to extract the copper and other harmful ions from the waste solutions.

Certain industrial effluents such as those derived from electroless copper plating rinse waters include copper ion concentrations above the permissive level. In them, ions are held in solution by various complexing agents. For example, commonly used complexing agents such as substituted alkyl amines prevent the effective removal of copper ions from solution by conventional methods such as by precipitation in the form of copper hydroxide by the addition of sodium hydroxide. The use of ion exchange resin beds has also been found ineffective to extract such copper ions due to the strong complexing effect of the anionic complexing agents present.When lime is employed to treat the solution so as to raise the pH thereof to about 12, the copper concentration can be reduced to a level slightly less than about 1 milligram per litre (mg/l) but such treatment results in the generation of voluminous amounts of sludge which also must be disposed of and the handling and cleaning of the treating system is accordingly costly and time consuming.

The present invention overcomes many of the problems and disadvantages associated with prior art treating techniques providing an apparatus and a process by which industrial effluents containing copper ions even tightly complexed form may be effectively removed to levels as low as 1 mg/l (1 ppm) and lower.

The system has been found to be economical, simple to operate and flexible in use.

According to a first aspect of the present invention, there is provided an apparatus suitable for at least partially removing copper ions from an aqueous solution containing copper ions, the apparatus comprising a receptacle for aqueous solution, means for ensuring the pH of the solution in the receptacle is within a preselected range and means for contacting the solution with steel wool.

Preferably, the apparatus comprises a tank or receptacle to which the copper containing aqueous solution is fed at a controlled rate and which receptacle incorporates pH monitoring means for automatically adjusting the pH thereof by the addition of alkaline or acidic materials to within a preselected pH range. The pH adjustment tank may further be provided with agitation and a level sensing device for selectively energizing and deenergizing a pump which transfers the pH adjusted solution through a plurality of serially arranged canisters each containing a removable cartridge of steel wool which is effective upon coming in contact with the copper ions to effect an extraction thereof.The capacity of the pump may be controlled at a magnitude greater than the influx of copper containing solution into the tank whereby the flow of the pH adjusted solution through the canisters is initiated when a preselected maximum level of solution is attained in the tank and is terminated when a preselected minimum level is attained. The apparatus can further include a copper ion sensing device at the discharge of the downstream canister to monitor the concentration of residual copper ions in the effluent. Selector valve means can also be employed in the apparatus for selectively diverting the flow of pH adjusted solution and reversing the upstream and downstream dispositions of the plurality of canisters consistent with the magnitude of saturation and effectiveness of the cartridges therein.

According to a second aspect of the present invention, there is provided a process for at least partially removing copper ions from an aqueous solution, the process comprising ensuring that the pH of the solution is within a preselected range and contacting the solution with steel wool.

In accordance with a preferred process of the present invention, an aqueous copper ion containing solution is treated by first adjusting the pH thereof to a preselected range at which any complexes present will be of a reduced complexing magnitude whereafterthe solution is passed through one or a plurality of canisters containing a fine grade of steel wool such as "0" grade which is operative to extract the copper ions to levels as low as 1 ppm or below. In the treatment of copper rinse solutions from electroless copper plating baths, effective treatment may be achieved by adjusting the pH to within a range of about 2 to about 6 with optimum process conditions occurring at about pH 4.0.

The invention can therefore be seen to encompass a process for removing copper ions from an aqueous feed solution comprising passing the feed solution at a pH of less than 6 through steel wool having sufficient surface area to extract at least a portion of the copper ions from the feed solution thereby reducing the residual copper ion concentration in the feed solution downstream of the steel wool.

According to a third aspect of the present invention, there is provided an aqueous solution from which copper ions have been removed by a process according to the second aspect and/or using an apparatus according to the first aspect of the invention.

For a better understanding of the invention, and to show how it may be put into effect, reference will now be made, by way of Example, to the accompanying drawings, in which: Figure 1 is a perspective partly diagrammatic view of the apparatus constructed in accordance with the preferred embodiments of this invention in a modular form, Figure 2 is a fragmentary plan view of the tank portion of the apparatus as shown in Figure 1, Figure 3 is a fragmentary side elevational view of the tank portion of the apparatus of Figures 1 and 2, Figure 4 is a transverse vertical sectional view through one of the canisters of the apparatus as shown in Figure 1; and Figure 5 is a fragmentary schematic view of an alternative valving arrangement for controlling the flow through the two canisters of the apparatus as shown in Figure 1.

Referring now in detail to the drawings, and as may be best seen in Figure 1, the apparatus comprising the present invention is illustrated in the form of a modular construction adapted to be installed as a unit for treatment and removal of copper ions in waste solutions and the like. As shown, the apparatus comprises a base or platform 10 on which a rectangular tank or receptacle 12 is mounted along one edge thereof. A canister 14 and a second canister 16 is supported on the base 10 for receiving the solution to be treated and for extracting the copper ions therein. An electrical control panel 18 is supported on the base by a pair of legs 20 and angle braces 22 to which the various operating components are electrically connected and controlled.

A conduit 24 equipped with a valve 26 as shown in Figure 1 supplies the copper contaminated aqueous solution to the tank 12. The copper contaminated solution may be one such as derived from the overflow rinse solution for rinsing parts treated by a copper electroless plating solution in which the copper ions therein are complexed by organic complexing agents such as ethylenediaminetetraacetic acid or the like.

The copper containing solution can be derived directly from the rinse tank overflow or from an intervening surge or holding tank for such rinse solution from which it flows by a pump or by gravity into the conduit 24.

The tank 12 as best seen in Figures 1-3 is provided with an automatic pH control unit 28 which extends downwardly in continuous contact with the solution therein for sensing and monitoring the pH thereof. It has been observed in order to optimize the removal of copper ions in such effluents, that optimum results are obtained at selected pH levels depending upon the concentration of copper ions and the specific type or types of complexing agents present in addition to other contaminating constituents in the aqueous solutions being treated. Accordingly, the pH sensing unit 28 is preset to maintain the solution within the tank 12 within a preselected optimum range and a metering pump 32 mounted on a flange 30 extending around the upper edge of the tank 12 effectively introduces an acidic material or an alkaline material, as the case may be to maintain appropriate pH.For this purpose as shown in Figure 2, a supply tank 34 is provided which is connected by means of a conduit 36 to the metering pump for discharge into the solution within the tank 12.

In the case of the treatment of electroless copper rinse effluents, such effluents are normally of an alkaline pH and it has been found desirable to acidify such effluents because the sequestering power of the chelating agents employed to complex the copper ions, such as for example ethylenediaminetetraacetic acid, tetrasodium salt, is significantly reduced at relatively low pH values. Particularly satisfactory results have been obtained by adjusting the pH of such solutions to a level below about 6 with pH levels of about 2 to about 4 being preferred. The specific pH level selected is also influenced on the quantity of iron present in the waste effluent discharged after treatment wherein the iron level of such discharged effluents will increase due to the increased dissolution of iron in the treatment canisters as the pH is reduced.

In any event, the pH sensing unit 28 in combination with the metering pump 32 are operative to maintain continuously the solution in the tank 12 within the prescribed range by constant or intermittent introduction of acidic or basic materials as the liquid to be treated is continuously introduced into the tank through the feed conduit 24. The maintenance of a uniform mixture within the tank is achieved by a mechanical agitator including a motor drive 38 supported on the upper tank flange 30 having a shaft 40 and a propeller 42 secured to the lower end thereof as may be best seen in Figures 2 and 3.

The level of the pH adjusted solution in the tank 12 is continuously monitored by a level control unit 46 of any of the types well known in the art to maintain the solution within a maximum level as indicated at 48 in Figure 3 and a minimum level indicated at 50. The level control unit 46 is electrically connected to a pump 44 through the control panel circuitry 18 for energizing the pump 44 when the solution level in the tank approaches the maximum level 48, for activating an alarm (not shown) when the maximum level is exceeded and for deenergizing the pump 44 when the solution level falls to the minimum level 50. The output of the pump 44 is selected so as to be greater then the flow rate or feed rate of the copper containing solution into the tank through the feed conduit 24. In this manner, potential overflow of solution from the tank 12 is eliminated.

The pump 44 is provided with an outlet 52 as best seen in Figure 2 to which a check valve 54 is connected.

The check valve in turn, as best seen in Figure 2 is connected by a supply conduit 56 to a flow control valve 58 which in turn is disposed in communication with a flow meter 60 terminating at its upper end with a pressure gauge 62 for sensing in combination, the rate of flow and pressure of the pH adjusted solution being supplied to the canisters 14, 16. The pressure gauge 62 is connected by means of a conduit 64 to an inlet 66 in the base of canister 14 and out through an outlet 68 in the canister 14. The outlet 68 is preferably provided with a sample cock 70 for sampling the effluent from the canister to enable analysis of the copper ion concentration therein. Alternatively, an automatic copper ion sensing device can be employed for continuously measuring and reporting the copper ion concentration in the canister effluent.

The sample cock 70 is connected by a cross conduit 72 to an inlet 74 in the base of canister 16 and the solution from canister 16 passes out through an outlet 76 at the upper portion thereof which, as in the case of canister 14, can be provided with a sample cock 78, or alternatively, an automatic copper ion sensing device.

The sample cock 78 is in turn connected by means of a conduit 80 to a T-fitting 82 which is connected to a discharge conduit 84 through final waste treatment including neutralization and the like.

At such time that it becomes necessary to change the cartridges within either one or both canisters 14, 16 for the purposes to be more fully described hereafter, the operating components through the control panel 18 are deenergized and the flow of copper containing feed material is stopped by closing the valve 26 as shown in Figure 1. A drain conduit 86 connected to the inlet of canister 14 is provided while a second drain conduit 88 is connected to the inlet 74 of canister 16. A normally closed valve 90 in conduit 86 is moved to the open position while a normally closed valve 92 in conduit 88 similarly is opened whereby the solution flows through the conduits 86,88 and valves 90,92 to a T-fitting 94 from which it flows through a drain conduit 96 connected to the T-fitting 82 to the discharge conduit 84.

In order to purge the canisters and associated conduits preparatory to extraction and replacement of the cartridges therein, a water supply conduit 98 connected to a supply of fresh water such as a domestic water supply system is provided which includes a valve 100 as shown in Figure 1 which in turn is connected to a Tfitting 102 disposed at the base of the flow meter 60. During the purging of the canisters with fresh water, the flow control valve 58 from the pump outlet is closed whereby the water circulates up through the flow meter 60, pressure gauge 62, supply conduit 64 and into the inlet 66 of the canister 14 through the cross conduit 72 and through the canister 16 from which it is discharged through the conduit 80 to the discharge conduit 84.Drainage of the residual solution from the canisters through the drain conduit system is facilitated by loosening covers 97 removably secured to the top of each canister to permit air to bleed into the canister. Alternatively, air bleed valves can be provided in the covers 97 for this same purpose.

Referring now in detail to Figure 4, a cross section of the canister 14 is illustrated incorporating a removable and disposable cartridge 104 therein. The description of the canister 14 is equally applicable to the canister 16 which are of substantially identical construction and operation. As shown in Figure 4, the upper edge of the cylindrical sidewall of the canister 14 is formed with a radial flange 106 on which a sealing gasket 108 is positioned and against which the peripheral portion of the circular cover 97 is adapted to be seated in sealing relationship. A series of screw type clamping members 110 are secured to the radial flange 106 for removably securing the cover 97 over the circular gasket 108.

The interior of the canister 14 is provided with a circular perforated plate 112 which is supported by several support members 114 which also act to evenly distribute the inlet flow into the chamber below plate 112. The foregoing arrangement as shown in Figure 4 defines a chamber disposed in communication with the inlet 66 into which the pH adjusted solution to be treated is introduced. A solid rod 116 is secured to the central upper face of the plate 112 and is provided at its upper end with a knob or handle 118 removably and threadably secured thereto.

The removable cartridge 104 as shown in Figure 4 comprises a substantially liquid impervious tubular cylindrical core 120 disposed in sliding fitting relationship around the periphery of the rod 116. A fine sized steel wool 122 surrounds the periphery of the core in the form of a cylindrical mass extending in peripheral contact with the inner surface of the canister 14. The steel wool is preferably applied in the form of a continuous pad wrapped in spiral form around the central core 120 to form a circular cylindrical mass of the desired height and diameter. The tubular core 120 and the mass 122 of steel wool therearound is retained in the position as shown in Figure 4 by the clamping effect of the knob 118.

In order to maximize efficiency of the extraction of copper ions from the pH adjusted solution passing upwardly through the cartridge 104 as shown in Figure 4, it is preferred to employ steel wool of a fine sized grade such as "O" grade to maximize surface contact and deposition of the copper ions thereon.

Replacement of the cartridge as may be required from time to time after the canister has been drained and purged with fresh water is simply achieved in accordance with the arrangement illustrated in Figure 4, by loosening the clamping members 110 and removing the cover plate 97. The cartridge and the perforated plate 112 are removed as a unit by pulling upwardly on the knob 118 which thereafter is removed enabling the cartridge 104 to be withdrawn from the rod 116. A fresh cartridge of similar construction is replaced on the rod and the knob 118 again secured whereafter the assembly is installed in the canister and the cover plate is again secured. Because of the economy of the cartridge, it can be disposed of or can be subjected to extraction for recovery of copper values as may be desired.

In accordance with the arrangement as illustrated in Figure 1, the cartridge in the canister 14will require replacement before the cartridge in canister 16 which is serially disposed downstream and exposed to a solution which has already been partially depleted of the copper ion contaminants therein. It is contemplated, accordingly, that during replacement of a cartridge in the canister 14, the cartridge in canister 16 be removed and placed in canister 16 enabling resumption of the copper recovery operation.

In accordance with an alternative embodiment of this invention and as fragmentarily and schematically illustrated in Figure 5, the use of flow selector valves can be incorporated in the supply conduit system to the canisters whereby the upstream and downstream position of the canisters can be alternated following the replacement of a cartridge in either one of the two canisters. In this arrangement, the canister which formerly had been the upstream canister requiring replacement of its cartridge, can be functionally positioned as the downstream canister following cartridge replacement on a resumption of the treating operation. This arrangement achieves the same effect as previously described in connection with Figure 1 of replacing the upstream cartridge with the cartridge from the downstream canister into which the fresh replacement cartridge is positioned.

In accordance with the arrangement of Figure 5, the pH adjusted solution supplied through the conduit 64 enters a selectorvalve 124 which in the position as schematically illustrated in Figure 5 is directed into the inlet 66 of canister 14 whereafter it is discharged through the outlet 68 into a second selector valve 126. In th position of the selector valve 126 as shown in Figure 5, the solution is transferred through a cross conduit 28 back to the selector valve 124 from which it is directed into the inlet 74 of the canister 16 and is discharged from the outlet 76 at the upper end thereof. The discharge solution again is directed to the selector valve 126 through which it passes into the discharge conduit 84 as previously described in connection with Figure 1.B rotating the selector valves 124,126 degrees a reversal of the foregoing flow scheme is attained whereby the feed solution first passes through the canister 16 and thereafter into the canister 14 from which it is ultimately discharged through the selector valve 126 into the discharge conduit 84.

In operation, the apparatus operation is activated by opening the valve 26 permitting copper containing feed solution to enter the tank 12. The control panel 18 is turned on activating the several monitoring and operating components of the system. As the copper containing feed solution commences to fill the tank 12, the pH control unit 28 intermittently or continuously energizes the metering pump 32 to maintain the solution under constant agitation by the mechanical agitator within the appropriate pH range.When the maximum level is attained in the tank 12 as sensed by the level control unit 46, the pump 44 is energized effecting a supply of the pH adjusted solution through the canisters 14, 16. Since the capacity of the pump 44 is selectively controlled at a flow rate higher than the copper containing feed material supplied to the tank 12 the level of solution in the tank 12 slowly decreases until the minimum level as sensed by the level control unit is attained. At this point, the feed pump is deenergized and remains deenergized until the solution level again attains the maximum level as sensed by the level control unit and the cycle as hereinbefore described is again repeated.The size of the cartridges and the number of canisters employed is dictated in consideration of the quantity of copper ions in the solution being treated and the permissible concentration of the copper ions in the final discharge from the apparatus. Typically, the size of the cartridges and the number of canisters employed in consideration of the solution being treated is selected so as to provide a replacement of a cartridge in the upstream canister at various convenient times in order to maintain the copper concentration in the discharge treated solution at a level of about one part per million (ppm) or less.

Rinse water effluent from a Udique @ (Registered Trade Mark) 820 electroless copper plating process was treated in accordance with the following to illustrate the process of the present invention. Before treatment, the effluent contained 58 mg/I copper ion concentration, and had a pH of about 10.5. The effluent was treatec under room temperature conditions after the pH of the effluent was adjusted to about 4.0 by addition of sulphuric acid bv serially passing the effluent through first and second canisters of the construction disclosed herein before. Each canister contained 24 Ibs. of "0" grade steel wool. The rate of flow of effluent through the canisters was 5 gal. per minute. After each 8 hours, flow of effluent was stopped and the cannisters were rinsed with fresh water.Initially, effluent analysis for total copper and total iron ions was: after first canister: 0.5 mg/l copper, 60 mg/l iron after second canister: 0.05 mg/l copper, 60 mg/l iron After 40 hours of effluent flow through the canisters, about 5.8 Ibs. of copper had been removed from the effluent and effluent analysis was: after first canister: 1.5 mg/l copper, 60 mg/l iron after second canister: 0.10 mg/l copper, 60 mg/l iron Thus, as illustrated above, the present invention can be employed to remove copper ions from effluent in an effective and economical manner.

If desired, the iron containing effluent may be further treated to remove the iron. Typically, CaCI2 or CaO is added to the effluent, in approximately molar amounts with respect to the iron present. The pH of the effluent is then raised to within the range of 7 - 9 by the addition of NaOH. An iron precipitate is formed which may be removed by filtration. If desired, a suitable floculant may be added, such as polyacrylamide, to aid in the formation of a more filterable precipitate.

Claims

1. An apparatus suitable for at least partially removing copper ions from an aqueous solution containing copper ions, the apparatus comprising a receptacle for aqueous solution, means for ensuring the pH of the solution in the receptacle is within a preselected range and means for contacting the solution with steel wool.

2. An apparatus as claimed in Claim 1, wherein the apparatus comprises means for agitating solution in the receptacle.

3. An apparatus as claimed in Claim 1 or 2, wherein the apparatus comprises means for keeping the level of solution in the receptacle within pre-elected limits.

4. An apparatus as claimed in Claim 1, 2 or 3, the apparatus comprising one or more canisters downstream of the receptacle, the or at least one of the canisters containing the steel wool.

5. An apparatus as claimed in Claim 4, wherein the apparatus comprises two canisters in serial communication.

6. An apparatus as claimed in Claim 4 or 5, wherein the steel wool is in one or more removable cartridges.

7. An apparatus as claimed in Claim 4,5 or 6, the apparatus comprising means for purging the or each canister.

8. An apparatus as claimed in any one of Claims 1 to 7, wherein the means for contacting the solution with steel wool includes a pump.

9. An apparatus as claimed in any one of Claims 1 to 8, in which the means for ensuring the pH of the solution in the receptacle is within a preselected range includes pH monitoring means and presettable to provide a pH of less than about 6 and supply means operable for supplying an acidic material to the receptacle.

10. An apparatus as claimed in Claim 2, in which the pH monitoring means is presettable in operating conjunction with the supply means to maintain the pH of the solution in said tank between about 2 to about 4.

11. An apparatus as claimed in any one of Claims 4 to 7, the apparatus including flow sensing means in conduit means for monitoring the rate of flow of the solution to the canister(s).

12. An apparatus as claimed in Claim 1 further including pressure sensing means for monitoring the pressure of the solution in conduit means between the receptacle and the steel wool.

13. An apparatus as claimed in Claims 3 and 8 in which a solution level sensing means is operable to deenergize the pump in response to the solution level in the receptacle at and below a minimum level.

14. An apparatus as claimed in Claims 3 and 8 in which a solution level sensing means is operable to energize the pump in response to a solution level in the receptacle at a maximum level and to maintain the pump energized until a minimum level is attained.

15. An apparatus as claimed in Claim 8, the apparatus including flow control means in first supply means to maintain the flow of copper containing solution into the receptacle at a rate below the discharge capacity of the pump.

16. An apparatus as claimed in any one of Claims 1 to 15, the apparatus including copper ion sensing means, associated with a discharge outlet, for sensing the concentration of copper ions in solution discharged from the apparatus.

17. An apparatus as claimed in Claim 5, the apparatus including valve means for reversing the disposition of an upstream one of the canisters and a downstream one of the canisters to a downstream and an upstream position, respectively.

18. An apparatus as claimed in any one of Claims 4to 7, 11 and 17, in which the or each canister comprises a receptacle and a removable cover to enable a cartridge to be extracted and replaced.

19. An apparatus as claimed in any one of Claims 4 to 7, 11,17 and 18, in which the or each canister comprises a receptacle, a perforated plate in the canister's receptacle at a position spaced from the base thereof, a cartridge in the canister's receptacle above the perforated plate, an inlet in communication with the interior of the canister's receptacle at a position below the perforated plate and an outlet in the canister's receptacle at a position above the cartridge.

20. An apparatus as claimed in Claim 19, the apparatus including a rod affixed to a central portion of the perforated plate and, extending upwardly within the interior of the canister's receptacle, stop means removably secured to an upper portion of the rod, the canister including a mass of steel wool disposed radially around a central tubular core, the core removably lying around at least a portion of the rod and supported by the perforated plate.

21. A process for at least partially removing copper ions from an aqueous solution, the process comprising ensuring that the pH of the solution is within a preselected range and contacting the solution with steel wool.

22. A process as claimed in Claim 21, wherein the said contacting is carried out in one or more canisters.

23. A process as claimed in Claim 22, wherein the or at least one of the canisters contains a cartridge of steel wool.

24. A process as claimed in Claim 21,22 or 23, in which the step of ensuring that the pH of the solution is within a preselected range includes mixing the solution with an acidic material to provide a pH of less than 6.

25. A process as claimed in Claim 21,22 or 23 in which the preselected pH range is from 2 to 4.

26. A process as claimed in Claim 21,22 or 23, in which the step of ensuring that the pH of the solution is within a preselected range includes providing a pH of 4.0.

27. A process as claimed in Claim 22 or 23, the process including the step of controlling the flow rate of pH adjusted solution passing through the canister(s).

28. A process as claimed in any one of Claims 21 to 27, in which the copper ion concentration is reduced to a level less than 1 ppm.

29. A process as claimed in Claim 23 including the further step of periodically replacing the steel wool cartridge in the or each canister.

30. A process as claimed in any one of Claims 21 to 29, the process including sensing the residual copper ion concentration in effluent.

31. A process as claimed in Claim 22, 23 or 29, the process including periodically reversing the direction of flow of the solution through the canister(s).

32. A process as claimed in Claim 29, the process including purging the canister(s) with water prior to replacing said steel wool cartridge.

33. A process as claimed in Claim 22, 23,29,31 or 32 the process including sensing the pressure and flow rate of solution passing to the canister(s).

34. A process according to any one of Claims 21 to 33, wherein the pH of the solution is from 2 to 4.

35. A process as claimed in Claim 21, wherein the solution is passed through plurality of canisters containing the steel wool, the canisters being disposed in serial communicating relationship.

36. A process as claimed in any one of Claims 21 to 35, wherein the solution is subsequently further treated to remove iron by: a. adding CaC12 or CaO to the solution; b. adjusting the solution pH of from 7 to 9; and c. filtering the solution to remove iron containing precipitate so formed.

37. A process for removing copper ions from an aqueous feed solution comprising passing the feed solution at a pH of less than 6 through steel wool having sufficient surface area to extract at least a portion of the copper ions from the feed solution thereby reducing the residual copper ion concentration in the feed solution downstream of the steel wool.

38. a process as claimed in Claim 37, wherein the feed solution downstream from the steel wool is further treated to remove iron by the steps of: a. adding CaCI2 or CaO to the effluent; b. adjusting the effluent pH to from 7 to 9; and c. filtering the effluent to remove the iron containing precipitate formed.

39. An apparatus substantially as herein described with reference to the drawings.

40. A process substantially as herein described.

41. An aqueous solution from which copper ions have been removed by a process according to any one of Claims 21 to 38 and 40 and/or using an apparatus as claimed in any one of Claims 1 to 20 and 39.

42. An apparatus for removing copper ions from an aqueous feed solution comprising a tank for receiving the copper containing solution, first supply means for introducing the copper containing solution into the tank, pH monitoring means in said tank for sensing the pH of the solution therein, second supply means for supplying at least one of an acidic material and an alkaline material to said tank to adjust the pH of the solution therein within a preselected range and operable in response to said pH monitoring means, means for agitating the solution in said tank, solution level sensing means in said tank for sensing a preselected minimum and maximum level of the solution therein, pump means operable in response to said level sensing means for withdrawing the pH adjusted solution from said tank, one or a plurality of canisters disposed in serial communicating relationship each containing a removable cartridge of steel wool, the upstream one of said canisters formed with an inlet and the downstream one of said canisters formed with a discharge outlet, conduit means for connecting said pump means to said inlet of the upstream canister, and purging means disposed in communication with said conduit means and said canisters for introducing water to purge any residual solution therefrom preparatory to the removal and replacement of a cartridge therefrom.

43. A process for removing copper ions from an aqueous feed solution comprising the steps of sensing the pH of the feed solution, admixing at least one of an acidic material and an alkaline material with the feed solution to adjust the pH within a preselected range, passing the pH adjusted feed solution through one or a plurality of canisters disposed in serial communicating relationship and in contact with a steel wool cartridge contained in each said canister in a manner to effect an extraction of at least a portion of the copper ions from the solution and a deposition thereof on the steel wool to reduce the residual copper ion concentration in the effluent discharged from the downstream canister to a desired level.