Method for repairing nickel-zinc-copper or nickel-zinc alloy electroplating solutions from acidic waste solutions containing nickel and zinc ions and electroplating thereof

A method for preparing a nickel-zinc-copper or nickel-zinc alloy electroplating solution from at least one electroplating waste solution and/or at least one acidic leach solution of metal scrap containing nickel and/or zinc ions is disclosed. The method involves mixing two or more than two of solutions of the electroplating waste solutions and the acidic leach solutions, and optionally water, so that the ion concentrations of Ni, Zn, Cu, Fe, Cr and Pb of the resulting mixed solution are within the following ion concentrations: PA1 15 gdm.sup.-3 <Ni.sup.2+ <58 gdm.sup.-3, 28 gdm.sup.-3 <Zn.sup.2+ <44 gdm.sup.-3, 0<Cu.sup.2+ <1430 gm.sup.-3, 0<Fe.sup.2+ +Fe.sup.3+<5000 gm.sup.-3, 0<Cr.sup.3+ <1000 gm.sup.-3 and 0<Pb.sup.2+ <50 gm.sup.-3.

FIELD OF THE INVENTION 
The present invention relates generally to a method for preparing a 
nickel-zinc-copper or nickel-zinc alloy electroplating solution from an 
electroplating waste solution and/or an acidic leach solution of metal 
scrap containing nickel and/or zinc ions. 
BACKGROUND OF THE INVENTION 
Various methods have been utilized to treat a waste solution containing 
metallic ions. Ion exchange, membrane separation, solvent extraction, 
electrowining and precipitation are typical treatments for a waste 
solution containing a low concentration of metallic ions. As to the 
treatment of a waste solution containing a high concentration of metallic 
ions such as an electroplating waste solution and a thick leach solution 
of metal scrap, a complicated process involving several of those 
treatments is generally required, and thus the operation cost thereof is 
relatively high. When the waste solution contains different metallic ions 
of high concentrations, the separations of metallic ions from the waste 
solution become more difficult. Therefore, an ideal process for treating 
the waste solutions should be able to minimize the steps of separations, 
and preferably recycle useful products therefrom. 
Upon electroplating a single metal such as zinc and nickel metal, impurity 
control in the electroplating bath is severe C. Cachet, R. Wiart, "Zinc 
deposition and passivated hydrogen evolution in highly acidic sulphate 
electrolytes: depassitivation by nickel impurities", Journal of Applied 
Electrochemistry, 20 (1990), p. 1009-1014.; S. K. Gogia, S. C. Das, "The 
effect of Co, Cu, Fe and Fe during electrowining of nickel", Journal of 
Applied Electrochemistry, 21 (1991), p. 64-72!. However, there is no study 
on the effect of impurities on the newly developed nickel-zinc alloy 
electroplating A. Brenner, "Electrodeposition of Alloys", Two Volumes, 
Academic Press, Inc., New York (1963); R. Shula, S. K. Srivastava, and S. 
C. Srivastava, "The role of addition agents in the electrobath", Surface 
and Coating Technology, 28 (1986), p. 129-231!. 
SUMMARY OF THE INVENTION 
It is therefore the primary objective of the present invention to provide a 
method for preparing a nickel-zinc-copper or nickel-zinc alloy 
electroplating solution from waste solutions containing zinc and/or nickel 
ions. 
It is still another objective of the present invention to provide a method 
for electroplating a nickel-zinc or nickel-zinc-copper alloy with the 
nickel-zinc or nickel-zinc-copper electroplating solution which is 
prepared by the method of the present invention. 
In keeping with the principle of the present invention, the foregoing 
objectives of the present invention are attained by a method for preparing 
a nickel-zinc-copper or nickel-zinc alloy electroplating solution from an 
electroplating waste solution and/or an acidic leach solution of metal 
scrap containing nickel and/or zinc. 
The method of the present invention consists of the following steps of: 
(a) measuring ion concentrations of Ni, Zn, Cu, Fe, Cr and Pb in two or 
more than two solutions selected from the group consisting of an 
electroplating waste solution containing nickel, an electroplating waste 
solution containing zinc ions, an electroplating waste solution containing 
nickel and zinc ions, an acidic leach solution of metal scrap containing 
nickel ions, an acidic leach solution of metal scrap containing zinc ions, 
and an acidic leach solution of metal scrap containing nickel and zinc 
ions; and 
(b) mixing two or more than two of said measured solutions, and optionally 
water, so that the ion concentrations of Ni, Zn, Cu, Fe, Cr and Pb of the 
resulting mixed solution are in conformity with the ion concentrations 
specified as follows: 
15 gdm.sup.-3 &lt;Ni.sup.2+ &lt;58 gdm.sup.-3 
28 gdm.sup.-3 &lt;Zn.sup.2+ &lt;44 gdm.sup.-3 
0&lt;Cu.sup.2+ &lt;1430 gm.sup.-3 
0&lt;Fe.sup.2+ +Fe.sup.3+ &lt;5000 gm.sup.-3 
0&lt;Cr.sup.3+ &lt;1000 gm.sup.-3 
0&lt;Pb.sup.2+ &lt;50 gm.sup.-3 
wherein an electroplating solution suitable for depositing a nickel-zinc 
alloy is attained as the Cu.sup.2+ concentration is smaller than 500 
gm.sup.-3 ; and wherein an electroplating solution suitable for depositing 
a nickel-zinc-copper alloy is attained as the Cu.sup.2+ concentration is 
greater than 500 gm.sup.-3. 
Preferably, the Ni.sup.2+ concentration specified in the step (b) ranges 
from 18 to 24 gdm.sup.-3, the Zn.sup.2+ concentration specified in the 
step (b) ranges from 31 to 36 gdm.sup.-3, and the Pb.sup.2+ concentration 
specified in the step (b) is less than 20 gm.sup.-3. 
In addition to the method described above, the present invention discloses 
further an electroplating method for the nickel-zinc-copper alloy 
electroplating solution prepared by the method of the present invention. 
The electroplating method of the present invention consists of 
electrolysis, in which an article to be electroplated is used as the 
cathode for carrying out the electrolysis. In the meantime, the 
nickel-zinc-copper alloy electroplating solution is used as the 
electrolyte having a pH ranging between 2 and 5, preferably 4. The 
electrolysis is carried out at a current density ranging between 200 and 
500 Am.sup.-2. 
By using the nickel-zinc alloy electroplating solution prepared by the 
method of the present invention, another electrolysis can be carried out 
such that an article to be electro deposited is used as the cathode, and 
that the nickel-zinc alloy electroplating solution is used as the 
electrolyte. The current density of the electrolysis ranges between 200 
and 500 Am.sup.-2. The pH value of the electrolyte ranges between 2 and 5, 
preferably 4. 
It is recommended that a brightener is added to the electrolyte in the 
electroplating method of the present invention. The brightener may be 
glycine, glucose, or ascorbic acid, preferably glycine. The preferred 
concentration of the brightener added to the electrolyte is about 1000 
gm.sup.-3. 
The foregoing objectives, features, functions, and advantages of the 
present invention will be more readily understood upon a thoughtful 
deliberation of the following detailed description of the embodiments of 
the present invention.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention discloses a method for preparing a nickel-zinc-copper 
or nickel-zinc alloy electroplating solution from at least one 
electroplating waste solution and/or at least one acidic leach solution of 
metal scrap containing nickel and/or zinc ions. 
The electroplating waste solution suitable for use in the method of the 
present invention can be a nickel electroplating waste solution, for 
example, a black nickel electroplating waste solution and a Watts nickel 
electroplating waste solution; a zinc electroplating waste solution; a 
nickel-zinc alloy electroplating waste solution or a nickel-zinc-copper 
alloy electroplating waste solution. 
The acidic leach solution of the metal scrap is prepared by immersing metal 
scrap in an aqueous solution of a strong acid such as H.sub.2 SO.sub.4 and 
HNO.sub.3. The metal scrap may be a post-consuming zinc article having 
multiple electroplating layers of copper and nickel; a post-consuming zinc 
article having multiple electroplating layers of copper, nickel and 
chromium; a waste zinc cast article; secondary scrap of zinc casting in 
which zinc is previously melted away; used hooks in nickel electroplating; 
nickel scrap; a waste Raney nickel; and a nickel electrode of a 
post-consuming nickel hydrogen battery. 
The method of the present invention consists of the following steps of: 
(a) measuring ion concentrations of Ni, Zn, Cu, Fe, Cr and Pb in said at 
least one electroplating waste solution and/or said at least one acidic 
leach solution of the metal scrap; and 
(b) mixing two or more than two of said measured solutions, and optionally 
water, so that the ion concentrations of Ni, Zn, Cu, Fe, Cr and Pb of the 
resulting mixed solution are in conformity with the-ion concentrations 
specified as follows: 
15 gdm.sup.-3 &lt;Ni.sup.2+ &lt;58 gdm.sup.-3 
28 gdm.sup.-3 &lt;Zn.sup.2+ &lt;44 gdm.sup.-3 
0&lt;Cu.sup.2+ &lt;1430 gdm.sup.-3 
0&lt;Fe.sup.2+ +Fe.sup.3+ &lt;5000 gdm.sup.-3 
0&lt;Cr.sup.3+ &lt;1000 gm.sup.-3 
0&lt;Pb.sup.2+ &lt;50 gm.sup.-3 
A suitable method for measuring the ion concentrations of Ni, Zn, Cu, Fe, 
Cr and Pb is ICP-AES (Inductively Coupled Plasma-Atomic Emission 
Spectrophotometry). 
A solution suitable for electroplating a nickel-zinc alloy is attained if 
the CU.sup.2+ concentration of the resulting mixed solution is smaller 
than 500 gm.sup.-3. On the other hand, if the Cu.sup.2+ concentration of 
the resulting mixed solution is greater than 500 gm.sup.-3, a solution 
suitable for electroplating the nickel-zinc-copper alloy is obtained. 
The electroplating solutions obtained by the method of the present 
invention may serve as an electrolyte in electrolysis in which an article 
is electroplated with a Ni--Zn--Cu or Ni--Zi alloy layer. The electrolysis 
has a current efficiency as high as 90% and over. The electrolysis 
referred to above can be brought about by a current density ranging 
between 200 and 500 Am.sup.-2. In the meantime, the electrolyte (the 
electroplating solution) of the present invention has a pH value ranging 
between 2 and 5, preferably 4. It is recommended that a brightener, such 
as glycine, glucose, or ascorbic acid, be added-to the electrolyte such 
that the concentration of the brightener is about 1000 gm.sup.-3. The pH 
value of the electrolyte of the present invention can be kept in the range 
of 2-5 by adding an alkali, such as ammonium sulfate. The electroplating 
layer formed by the present invention is semilustrous and gray. According 
to the ASTM D 3359 test, both electroplating layers of the present 
invention have an excellent adhesive quality (0-grade). In addition, both 
electroplating layers formed by the present invention have a hardness and 
a corrosive resistance both superior to those of a pure nickel 
electroplating layer or a pure zinc electroplating layer. 
EXAMPLES 1-16 
H.sub.2 SO.sub.4 solutions containing a Ni.sup.2+ concentration of 22 
gdm.sup.-3 and a Zn.sup.2 + concentration of 35 gdm.sup.-3 and other metal 
ions having concentrations listed in Table 1 were used as an 
electroplating bath, and a fixed current density of 200-500 Am.sup.-2 was 
used in Ni--Zn alloy electroplating. The H.sub.2 SO.sub.4 solutions 
further contained 13.2 gdm.sup.-3 of ammonium sulfate so that a pH value 
of 4 was obtained. In addition, glycine was added as a brightener to each 
of the H.sub.2 SO.sub.4 solutions so that it had a glycine concentration 
of 1000 gm.sup.-3. The results are presented in the following Table 1. 
TABLE 1 
______________________________________ 
Current Hard- Corrosive 
Current 
Concentration (gm.sup.-3) 
density ness resistance 
efficien- 
Ex. Cu Fe Cr Pb (Am.sup.-2) 
(VHN) (Ohm) cy (%) 
______________________________________ 
1 100 960 835 18 200 250 260 92 
2 500 985 825 20 300 270 300 93 
3 100 230 5 400 290 300 90 
4 50 755 11 500 265 315 95 
5 50 100 200 260 117 94 
6 50 10 300 263 205 90 
7 50 5000 400 250 305 92 
8 50 1000 500 290 415 94 
9 50 90 200 263 120 93 
10 50 9 300 250 200 94 
11 50 900 400 320 303 90 
12 50 450 500 271 450 93 
13 50 5 200 280 125 90 
14 50 2 360 261 180 92 
15 50 20 400 234 301 90 
16 50 10 500 295 450 91 
17 361 660 0.3 300 270 300 91 
18 50 4960 5 400 320 305 93 
19 49 145 125 300 260 205 93 
______________________________________ 
On the basis of the data shown in Table 1, it is readily apparent that the 
hardness and the corrosive resistance of the electroplating layers of the 
Examples 1-16 are superior to those of the pure nickel electroplating 
layer and the pure zinc electroplating layer, which have respectively the 
hardness 130-200 (VHN) and the hardness 100-170 (VHN). The corrosive 
resistance of the pure nickel electroplating layer and the pure zinc 
electroplating layer are 180-250 (Ohm) and 140-180 (Ohm), respectively. 
In the following Examples 17-19, the leaching solutions and the 
electroplating waste solutions listed as follows were used for preparing 
the Ni--Zn alloy electroplating solutions: 
______________________________________ 
Concentration, gm.sup.-3 
Solution* 
Ni Zn Cu Fe Pb Cr 
______________________________________ 
A 21000 22000 400 730 
B 63000 7000 30 150 
C 10 120000 10 30 3 
D 112000 4800 
E 30000 70000 80 20 250 
F 300 140000 260 16 20 
______________________________________ 
*A: a black nickel electroplating waste solution; B: a Watts nickel 
electroplating waste solution; C:. a zinc electroplating waste solution; 
D: a leach solution of Raney nickel; E: a leach solution of a waste zinc 
cast article; F: a solution leached from secondary scrap of zinc casting 
EXAMPLE 17 
900 ml of A solution and 100 ml of C solution were mixed such that an 
electroplating solution containing a zinc ion concentration of 31.8 
gdm.sup.-3, a nickel ion concentration of 18.9 gdm.sup.-3, a copper ion 
concentration of 361 gm.sup.-3, an iron ion concentration of 660 
gm.sup.-3, and a Pb ion concentration of 0.3 gm.sup.-3 was obtained. To 
the electroplating solution glycine was added so that the electroplating 
solution had a glycine concentration of 1000 gm.sup.-3. The electroplating 
was carried out at room temperature and with a current density of 300 
Am.sup.-2. The hardness and the corrosive resistance of the nickel-zinc 
alloy electroplating layer were shown in Table 1 and are superior to those 
of the electroplating layers of pure zinc and pure nickel. 
EXAMPLE 18 
200 ml of D solution and 250 ml of E solution were mixed and then diluted 
by 550 ml of water such that an electroplating solution containing a zinc 
ion concentration of 35 gdm.sup.-3, a nickel ion concentration of 22.5 
gdm.sup.-3, a copper ion concentration of 50 gm.sup.-3, an iron ion 
concentration of 4960 gm.sup.-3, and a Cr ion concentration of 5 
gm.sup.-3, was obtained. To the electroplating solution glycine was added 
so that the electroplating solution has a glycine concentration of 1000 
gm.sup.-3. The electroplating was carried out at room temperature and with 
a current density of 400 Am.sup.-2 . The hardness and the corrosive 
resistance of the nickel-zinc alloy electroplating layer are shown in 
Table 1 and were superior to those of the electroplating layers of pure 
zinc and pure nickel. 
EXAMPLE 19 
300 ml of B solution and 500 ml of E solution were mixed and then diluted 
with 200 ml of water such that an electroplating solution containing a 
zinc ion concentration of 35 gdm.sup.-3, a nickel ion concentration of 19 
gdm.sup.-3, a copper ion concentration of 49 gm.sup.-3, an iron ion 
concentration of 145 gm.sup.-3, and a Cr ion concentration of 12.5 
gm.sup.-3 was obtained. To the electroplating solution glycine was added 
so that the electroplating solution has a glycine concentration of 1000 
gm.sup.-3. The electroplating was carried out at room temperature and with 
a current density of 300 Am.sup.-2. The hardness and the corrosive 
resistance of the nickel-zinc alloy electroplating layer are shown in 
Table 1 and were superior to those of the electroplating layers of pure 
zinc and pure nickel.