CA1214580A

CA1214580A - Apparatus and method for copper recovery

Info

Publication number: CA1214580A
Application number: CA000430570A
Authority: CA
Inventors: Donald A. Arcilesi; John V. Peck; Rebecca M. Spearot
Original assignee: OMI International Corp
Current assignee: OMI International Corp
Priority date: 1982-06-16
Filing date: 1983-06-16
Publication date: 1986-11-25
Also published as: JPS596336A; GB8316410D0; IT8348501A0; FR2528870A1; DE3321451A1; NL8302161A; GB2125828A

Abstract

ABSTRACT OF THE DISCLOSURE
An apparatus and method for removing copper ions from aqueous solutions comprising a pH adjustment tank for receiving the copper containing solution incorporating a pH control unit for monitoring and adjusting the pH thereof within a preselected range.
The solution is agitated and a level sensing unit is provided for controlling the level of the solution in the receptacle between a preselected maximum and a minimum level. A pump operable in response to the level control unit is operative to pump the pH adjusted unit through a plurality of canisters disposed in serial communicating relationship each containing a removable cartridge of steel wool through which the pH adjusted solution flows at a controlled rate effec-ting an extraction of the copper ions therefrom to residual concentrations as low as one part per million and lower whereafter the treated solution is discharged to final treatment before discharge to waste. Each canister incorporates a steel wool cartridge which can readily be replaced and disposed of upon attaining saturation. The invention further contemplates the use of copper ion sensing means in the discharge out-let of the apparatus for signaling the concentration of copper ions in the discharge solution in addition to the use of selector flow valves for reversing the upstream and downstream positions of the plural canisters to maintain efficient operation.

Description

APPARATUS AND METHOD FOR COPPER RECOVERY

BACKGROUND OF TIE INVENTION
The present invention broadly relates to an apparatus and process for extracting copper ions from aqueous solutions, and more particularly to the treat-mint 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 rug-lotions, particularly those designed to improve water quality has made it mandatory to reduce or eliminate the discharge ox certain metal ions present in incus-trial effluents to waste systems. Copper comprises 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 tech-unique 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 and which ions are held in solution by various completing agents. For example, commonly used come flexing agents such as substituted alkyd amine pro-vent 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 lo also been found ineffective to extract such copper ions due to the strong completing effect of the anionic completing agents present When lime is employed to treat the solution so as to raise the pi thereof to about 12, the copper concentration can be reduced to a level slightly less than about 1 milligram per liter Mel but such treatment results in the generation of voluminous amounts of sludge which also must be disk posed 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 in tightly complexes form can be effectively removed to levels as low as l Mel (l Pam) and lower, which system is economical, simple to open-ate and flexible in use.

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SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, there is provided 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 contain-in solution into the tank, pi monitoring means in the tank or sensing the pi of the solution therein, second supply means for supplying at least one of an acidic material and an alkaline material to the tank to adjust the pi of the solution therein within a preselected range and operable in response to the pi monitoring means, means for agitating the solution in thy tank, solution level sensing means in the tank for sensing a preselected minimum and maximum level of the solution therein, and pump means operable in response to the level sensing means for withdrawing the pi adjusted solution from the tank. One or a plurality of canisters is disposed in serial communicating relationship each containing a removable cartridge of steel wool, the upstream one of the canisters being formed with an inlet and the down-stream one of the canisters formed with a discharge outlet. The apparatus further includes conduit means for connecting the pump means to the inlet of the up-I stream canister, and purging means disposed in come monkeyshine with the conduit means and the canisters for introducing water to purge any residual solution there-from preparatory to the removal and replacement of a cartridge therefrom.
The apparatus of the invention 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 select-lively diverting the flow of pi adjusted solution and reversing the upstream and downstream dispositions of the plurality of canisters consistent with the mahogany-tune of saturation and effectiveness of the cartridges therein The present invention also provides, in a further aspect thereof, a non-electrolytic process for removing copper ions from an aqueous feed solution which contains copper ions complexes with organic completing agents, which comprises the steps of sensing the pi of the feed solution, admixing at least one of an acidic material and an alkaline material with the feed solution to adjust the pi within a preselected range of about 2 to about 6, passing the pi adjusted feed solution through one or a plurality of canisters disposed in serial communique-tiny relationship and in contact with a steel wool cart-ridge contained in each of the canisters 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 concentra-lion in the effluent discharged Tom the downstream canister to a level which is not in excess of about 5 parts per million, without substantial dilution of the effluent. The passage of the pi adjusted feed solution in contact with the steel wool cartridge is carried out at a flow rate which provides sufficient contact with the quantity of steel wool in the cartridge to effect a no-diction of the residual copper ion concentration to at least the level specified.
Optimum process conditions generally occur at about pi 4.
additional benefits and advantages of the pro-sent invention will become apparent upon a reading of the Description ox the Preferred Embodiments taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF TOE DRAWINGS
Figure 1 is a perspective view partly diagram-matte 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 elevation Al 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 l; 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.

. 5 DESCRIPTION OF THE PREFERRED EMBODIMENTS
-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 fox extracting the copper ions therein. An elect tribal 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 contami-noted 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 complexes by organic complex-in 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 pi control unit 28 which extends downwardly in continuous contact with the solution therein for sensing and monitoring the pi thereof. It has been observed in order to optimize the removal of copper ions in such effluents, that optimum results are obtained at selected pi levels depending upon the concentration of copper ions and the specific type or types of completing agents pros-en in addition to other contaminating constituents in the assess solutions being treated. Accordingly, the pi sensing unit 28 is preset to maintain the soul-lion 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 effect lively introduces an acidic material or an alkaline material, as the case may be to maintain appropriate phi 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 pi and it has been found desirable to ,, 7 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 pi values. Particularly satisfactory results have been obtained by adjusting the pi of such solutions to a level below about 6 with pi levels of about 2 to about 4 being preferred. The specific pi level selected is also influenced on the quantity of iron present in the waste effluent disk charged 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 pi is reduced.
In any event, the ply sensing unit I in come bination with the metering pump 32 are operative to continuously maintain the solution in the tank 12 within the prescribed range by constant or intermittent introduction of acidic or basic materials as the liquid two 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 sup-ported 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.

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The level of the pi adjusted solution in the tank 12 is continuously monitored by a level con-trot 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 India acted at 50. The level control unit 46 is electrically connected to a pump 44 through the control panel air-quoter 1.8 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 than the flow rate or feed rate of the copper contain-in 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 pi 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 I., :

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 report-in 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 which the treated aqueous solution is transmitted to final waste treatment including neutralization and the like.
At such time that it becomes necessary to change the cartridges within either one or both cents-lens 14, 16 for the purposes to be more fully described hereafter, the operating components through the con-trot 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 assess-axed conduits preparatory to extraction and replace-mint 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 T-fitting 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 , 11 US

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 in corpora-tying a removable and disposable cartridge 104 therein.
The description of the canister 14 is equally apply-cable 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 Jo be seated in sealing relationship. A
series ox 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 support ted 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 pi adjusted solution to be treated is introduced. A solid rod issue secured to the central ' Lo upper face of the plate 112 and is provided at its upper end with a knob or handle 118 removably and thread ably secured thereto.
The removable cartridge 104 as shown in Figure 4 comprises a substantially liquid impervious - tubular cylindrical core 120 disposed in sliding fit-tying 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 extend-in in peripheral contact with the inner surface of Jo the canister 14. The steel wool is preferably applied in the form of a continuous pad wrapped ion spiral form around the central core 120 to form a circular Solon-Dracula mass of the desired height and diameter. The I tubular core 120 and the mass 122 of steel wool there-around 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 ox-traction of copper ions from the pi adjusted solution passing upwardly through the cartridge 104 as shown in Figure 4, it is preferred to employ steel wool of a fine size grade such as "O" grade to maximize sun-face 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 accord dance with the arrangement illustrated in Figure 4, by loosening the clamping members lo 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 thereafter the assembly is in-stalled 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 thus-treated in Figure 1, the cartridge in the canister 14 will require replacement before the cartridge in cents-ton 16 which is serially disposed downstream and ox-posed 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 14 and a fresh cartridge installed 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 soys-them to the canisters whereby the upstream and downstream ` : 14 .

2 3~1 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 car-txidge 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 pal adjusted solution supplied through the con-dull 64 enters a selector valve 12~ which in the position as schematically illustrated in Figure 5 is directed into the inlet 66 of canister 14 thereafter it is discharged through the outlet 68 into a second selector valve 126. In the position of the selector valve 126 as shown in Figure 5, the solution is trays-furred through a cross conduit 128 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 pro-piously described in connection with Figure ]. By Jo 15 .. . .
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rotating the selector valves 124, 126 90 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 to 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 I 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 pi 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 pi range.
When the maximum level is attained in the tank 12 as sensed by the level control unit 46, the pump 44 is i energized effecting a supply of the pi adjusted solution through the canisters 14,16. Since the capacity of the pump 44 is selectively controlled at a slow rate hither than the copper containing feed material sup-i plied to the tank 12, the level of solution in the i 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 de-energized until the solution level again attains the ; 16 maximum level as sensed by the level control unit and the cycle as herein before described is again repeated.
The size of the cartridge-s 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 car-trudge in the upstream canister at various convenient times I in order to maintain the copper concentration in the discharge treated solution at a level of about one part per million (Pam) or less.
Rinse water effluent from a Unique 820 elect trowels copper plating process was treated in accordance with the following to illustrate the process of the present invention. Before treatment, the effluent con-twined 58 Mel copper ion concentration, and had a pi of about10.5.The effluent was treated under room them-portray conditions after the pi of the effluent was adjusted to about 4.0 by addition of sulfuric acid by serially passing the effluent through first and second canisters of the construction disclosed herein before.
; 25 Each canister contained 24 lobs. us "O" 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 canisters were rinsed with fresh water. Initially, effluent analysis for total copper and total iron ions was:
after first canister- 0.5 Mel copper, 60 Mel iron after second canister 0.05 Mel copper, 60 Mel iron After 40 hours of effluent flow through the canisters, about 5.8 lobs. of copper had been removed from the effluent and effluent analysis was:
after first canister: 1.5 Mel copper, 60 Mel iron after second canister: 0.10 Mel copper, 60 Mel 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, Cluck or Coo is added to the effluent, in approximately molar amounts with respect to the iron present. The pi of the effluent is then raised to within the range of 7 - 9 by the addition of aye. on iron precipitate is formed which may be removed by filtration. If desired, a suit-able flocculent may be added, such as polyacrylamide, to aid in the formation of a more filterable precipitate.
While it will be apparent that the preferred embodiments of the invention disclosed are well calculated to fulfill the objects above stated, it will be apple-elated that the invention is susceptible to modification, variation and change without departing from thy proper scope or fair meaning of the subjoined claims.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. 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 pre-selected 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 down-stream 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.

2. The apparatus as defined in claim 1 in which said pH monitoring means is presettable to provide a pH of less than about 6 and said second supply means is operable for supplying an acidic material to said tank.

3. The apparatus as defined in claim 1 in which said pH monitoring means is presettable in operating conjunction with said second supply means to maintain the pH of the solution in said tank between about 2 to about 4.

4. The apparatus as defined in claim 1 further including flow sensing means in said conduit means for monitoring the rate of flow of the pH adjusted solution to said canisters.

5. The apparatus as defined in claim 1 further including pressure sensing means in said conduit means for monitoring the pressure of the solution therein.

6. The apparatus as defined in claim 1 in which said solution level sensing means is operable to deenergize said pump means in response to the solution level in said tank at and below said minimum level.

7. The apparatus as defined in claim 1 in which said solution level sensing means is operable to energize said pump means in response to a solution level in said tank at said maximum level and to main-tain said pump means energized until said minimum level is attained.

8. The apparatus as defined in claim 1 including flow control means in said first supply means to maintain the flow of said copper containing solution into said tank at a rate below the discharge capacity of said pump means.

9. The apparatus as defined in claim 1 further including copper ion sensing means associated with said discharge outlet for sensing the concen-tration of copper ions in the solution discharged from said apparatus.

10. The apparatus as defined in claim 1 including valve means for reversing the disposition of said upstream canister and said downstream canister to a downstream and an upstream position, respectively.

11. The apparatus as defined in claim 1 in which each said canister comprises a receptacle including removable cover means for extracting and replacing said cartridge therein.

12. The apparatus as defined in claim 1 in which each said canister comprises a receptacle, a perforated plate disposed in said receptacle at a position spaced from the base thereof, said cartridge disposed in said receptacle above said perforated plate, said inlet disposed in communication with the interior or said receptacle at a position below said perforated plate, and an outlet in said receptacle disposed at a position above said cartridge.

13. The apparatus as defined in claim 12 further including a rod affixed to the central por-tion of said perforated plate and extending upwardly within the interior of said receptacle, stop means removably secured to the upper portion of said rod, said canister comprising a mass of said steel wool disposed radially around a central tubular core, said core disposed in overlying removable relationship around at least a portion of said rod and supported by said perforated plate.

14. A non-electrolytic process for removing copper ions from an aqueous feed solution which con-tains copper ions complexed with organic complexing agents, which comprises 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 of about 2 to about 6, passing the pH adjusted feed solution through one or a plurality of canisters disposed in serial com-municating relationship and in contact with a steel wool cartridge contained in each of said canisters 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 con-centration in the effluent discharged from the downstream canister to a level which is not in excess of about 5 parts per million, without substantial dilution of said effluent, said passage of the pH adjusted feed solution in contact with said steel wool cartridge being carried out at a flow rate which provides sufficient contact with the quantity of steel wool in said cartridge to effect a reduction of the residual copper ion concentration to at least the level specified.

15. The process as defined in claim 14, in which the pH of the feed solution is adjusted to within the range of about 2 to about 4.

16. The process as defined in claim 15, in which the pH of the feed solution is adjusted to about 4.

17. The process as defined in claim 14, further including the step of controlling the flow rate of the pH adjusted feed solution passing through said plurality of canisters.

18. The process as defined in claim 14, in which the step of passing the pH adjusted feed solution through said plurality of canisters is performed to reduce the copper ion concentration in said effluent to a level less than about 1 ppm.

19. The process as defined in claim 14, further including the step of periodically replacing said steel wool cartridge in each said canister.

20. The process as defined in claim 14, further including the step of sensing the residual copper ion concentration in said effluent.

21. The process as defined in claim 14, further including the step of periodically reversing the direction of flow of the pH adjusted solution through said plurality of canisters.

22. The process as defined in claim 19, further including the step of purging the plurality of canisters with water prior to replacing said steel wool cartridge.

23. The process as defined in claim 14, further including the step of sensing the pressure and flow rate of said pH adjusted solution passing to said canisters.

24. The process of claims 14, 15 or 16, wherein the effluent from the downstream canister is further treated to remove iron by the steps of:
a. adding CaC12 or CaO to the effluent;
b. adjusting the effluent pH to from about 7 to about 9, and c. filtering the effluent to remove the iron containing precipitate formed.

25. The process of claim 18, wherein the feed solution downstream from the steel wool is further treated to remove iron by the steps of:
a. adding CaC12 or CaO to the effluent;
b. adjusting the effluent pH to from about 7 to about 9; and c. filtering the effluent to remove the iron containing precipitate formed.