Recovery of nickel from waste materials

A method for recovering nickel from a waste material containing nickel and small amounts of iron or aluminum or a mixture thereof comprising the steps of: PA1 (a) removing the organic impurities from the waste material; PA1 (b) leaching the material with an acid after removal of organic impurities to provide an acid solution; PA1 (c) precipitating said iron and aluminum from the acid solution; and PA1 (d) recovering nickel from the acid solution.

BACKGROUND OF THE INVENTION 
This invention relates to a novel method for recovering nickel and 
ferronickel from waste materials and spent catalysts containing nickel and 
more particularly, to an inexpensive and novel method for improving the 
nickel content and/or production of ferronickel. 
As is well known to those skilled in the art, nickel-containing catalysts 
are used in many reactions such as hydrogenation reactions, alkylation 
reactions, hydroalkylation reactions, cracking processes, etc. Initially, 
these catalysts perform at a high level, but as the reaction proceeds, the 
catalyst becomes less active. Eventually, the activity of the catalyst 
decreases to a point where it is not sufficiently effective to be used in 
a commercial process. 
A wide variety of nickel catalysts and modifications thereof have been 
described in the art in which they are utilized. Nickel catalysts are used 
extensively in hydrogenation reactions such as in the hydrogenation of 
unsaturated organic compounds. Usually, catalysts which are used in 
hydroalkylation reactions will contain in addition to nickel, other metals 
such as tungsten. Nickel catalysts used in cracking operations often 
contain molybdenum and other elements. Other nickel catalysts may contain 
iron and/or aluminum in small amounts. 
Considerable research has been conducted on methods for regenerating spent 
catalysts and/or recovering nickel from spent catalysts and other 
nickel-containing waste materials since nickel is an expensive metal to be 
discarded and, moreover, the safe disposal of waste nickel requires 
consideration of environmental hazards. Several procedures have been 
described in the prior art for regenerating spent catalysts. U.S. Pat. 
Nos. 1,306,871; 3,926,842; 4,029,495 and 4,120,698 are examples of such 
disclosures. 
One of the difficulties involved in regenerating spent nickel catalysts 
results from the presence of reaction contaminants such as the various 
organic materials being treated by the catalyst systems. One method for 
removing the organic products which contaminate the spent catalysts is by 
burning off these organic materials at the same time that any nickel in 
elemental form is oxidized to form nickel oxide. U.S. Pat. No. 1,306,871 
describes such a process for oxidizing spent nickel catalysts to remove 
organic material and form nickel oxide. The patent also describes the 
transformation of the nickel oxide to nickel by reduction in a current of 
hydrogen at a temperature of about 300.degree. C. 
The regeneration of a nickel catalyst from spent catalyst is tedious, time 
consuming, and requires careful attention to the details of the procedure. 
Therefore, there continues to be a need for methods of recovering nickel 
from spent catalysts which provide for the inexpensive recovery of the 
nickel in a usable form. 
Nickeliferrous ores, in particular laterite ores containing nickel, have 
been treated pyrometallurgically to recover ferronickel. One example of a 
pyrometallurgical process for recovering ferronickel from nickel laterite 
ores involves operation steps whereby the ore is dried, ground to a 
powder, calcined, smelted, and finally subjected to reducing conditions to 
form ferronickel which is separated from the slag. 
The amount of ferronickel and the amount of nickel in the ferronickel 
obtained by such pyrometallurgical processes will depend upon a variety of 
factors such as the nickel content of the ore, the type and amount of 
impurities in the ore, and various process parameters, many of which can 
be varied in accordance with the techniques known to those skilled in the 
art. It generally is desirable to produce ferronickel having a high 
concentration of nickel. 
SUMMARY OF THE INVENTION 
This invention relates to a simplified process for recovering nickel or 
ferronickel from waste materials containing nickel, and more particularly, 
to an inexpensive method for recovering nickel from spent catalysts in a 
nickel or ferronickel producing operation. The nickel-recovery method of 
this invention comprises the steps of: 
(a) removing the organic impurities from waste material; 
(b) leaching the material with an acid after removal of organic impurities 
to provide an acid solution; 
(c) precipitating said iron and aluminum from the acid solution; and 
(d) recovering nickel from the acid solution. 
To recover ferronickel, the method of this invention comprises the steps 
of: 
(a) calcining the prepared waste material at a temperature of about 
200.degree.-600.degree. C.; 
(b) mixing an ore containing nickel and iron with the calcined material; 
(c) smelting the mixed ore and waste material in a smelting furnace; 
(d) reducing the smelted material in a metal reduction furnace; and 
(e) recovering the ferronickel from the furnace. 
The addition of nickel-containing ores to the nickel waste materials in 
accordance with the method of the present invention generally results in 
one production of ferro-nickel with increased nickel content.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Any waste materials containing nickel (in oxidized or oxidizable form) can 
be used in the process of the invention. Preferably the waste material 
contains material which is easily burned and produces substantial heat 
values on burning. Spent nickel catalysts particularly are useful in the 
method of the invention, and these may be any spent nickel catalysts 
available from any source and particularly from various industrial 
processes which utilize nickel catalyst systems. The nickel-containing 
spent catalysts may be obtained from hydrogenation, alkylation, 
hydroalkylation and cracking processes, and the degree to which the 
catalysts have been used in the processes is immaterial to their use in 
the method of the invention. The process of this invention is applicable 
to waste materials which are supported catalysts even though the presence 
of the inorganic support materials adds to the amount of impurities which 
must be separated from the nickel in accordance with the process of the 
invention. Moreover, the nature of the contaminants, most often organic 
compounds and products, does not deter from the use of the spent catalysts 
in the method of the invention. The organic compounds are burned away in 
the method of the invention. Samples of organic materials which often are 
present in spent catalyst products are fatty materials such as vegetable 
or fatty oils, and other edible or inedible oils. Nickel catalysts have 
been found to be useful and are used extensively in hydrogenation of 
unsaturated fatty oils. Thus, this commercial application of nickel 
catalysts provides a ready source of inexpensive spent catalysts for use 
in the method of the invention. 
Spent nickel catalysts containing oily contaminants have been found to be 
particularly useful since the heat values of the oils are utilized as a 
heat source in the process of the invention. Spent nickel catalysts 
contaminated with oils can be obtained from oil processors such as Armak 
Chemical Division, Morris, Illinois; Proctor and Gamble, Cincinnati, Ohio; 
Anderson Clayton Foods, Jacksonville, Illinois, and Cambra Foods, 
Lethbridge, Canada. Such waste materials contain, for example, from about 
4% to 20% or more nickel and have fuel values of up to about 11,000 
BTU/lb. preferably 6,000 to 11,000 BTU/lb. 
The method of recovering nickel or ferronickel in accordance with the 
invention is illustrated in the accompanying drawings. 
FIG. 1 illustrates a general method of the invention where the 
nickel-containing waste material is treated, as indicated by arrow 10 to 
remove any organic impurities which may be present in the waste material. 
Optionally, depending on the size of the starting waste material, the waste 
may be prepared as indicated by broken arrow 10A to reduce particle size 
and to provide increased surface area by any mechanical means and then 
treated to remove organic impurities as shown by broken arrow 10B. For 
example, the waste material may be processed through a pug mill or a 
hammer mill to the mesh size desired. Preferably, the screen size would be 
about a 10 mesh, although depending upon the waste material, screens 
providing more or less coarse waste material may be employed with the 
method of this invention. The appropriate screen and particle size of the 
waste material to be used in the method of this invention may be readily 
determined by one skilled in the art. 
Depending upon the consistency of the waste material and the amount of 
organic contaminants therein, the organic impurities may be removed by 
washing with a solvent, generally a Stoddard solvent, which is known to 
those skilled in the art. When the waste material is heavily contaminated 
with organic impurities, it has been found preferable to remove such 
organics by calcining the waste material at about 200.degree.-600.degree. 
C., preferably about 400.degree.-500.degree. C. It is not necessary to 
remove all of the organic impurities before acid leach because the acid 
leach will destroy residual organic material. 
After removal of the organic impurities, the waste material is advanced to 
the leaching step as indicated by arrow 11. The nickel is leached with an 
acid, preferably with sulfuric acid. The acid requirements of the leaching 
bath are dictated by the stoichiometry of the reaction 
EQU NiO+H.sub.2 SO.sub.4 .fwdarw.NiSO.sub.4 +HOH 
Preferably, the acid concentration of the leaching bath is in slight excess 
of the stoichiometric requirements, so as to provide a leaching bath with 
a pH of about 1. The temperature of the acid leaching bath during leaching 
is about 50.degree. to 100.degree. C. and preferably about 70.degree. C. 
Leaching is continued until no significant nickel concentration remains in 
the bath residue. The residual nickel concentrations may be determined by 
one skilled in the art using known techniques. During the final stages of 
leaching as indicated by arrow 12, iron and aluminum are precipitated by 
adjusting the pH of the acid leaching bath with a base, preferably sodium 
hydroxide, to about 2.5 to 3.5, and generally to about pH 3.0. One of the 
reasons why sodium hydroxide is preferred is that it can produce sodium 
sulfate which is needed for efficient electrowinning of nickel and reacts 
with ferric ions to precipitate sodium jarosite, Na.sub.2 
(Fe(OH).sub.2).sub.6 (SO.sub.4).sub.4 which entrains other impurities as 
well. In general, the base treated leach solution is stirred at an 
elevated temperature (100.degree.-200.degree. C.) in an oxygen atmosphere, 
preferably in an autoclave at an operating pressure of from about 100-200 
psig although other pressures and temperatures can be utilized. 
Alternatively, though not shown in the drawings, the base treated leach 
solution can be advanced directly to the electrowinning step and the 
impurities are removed after electrowinning. 
The leached nickel is recovered as indicated by arrow 13 such as by 
counter-current decantation which produces a pregnant electrolytic feed, 
from which electrolytic nickel is recovered by electrowinning. The residue 
from the nickel recovery is discarded as waste, as indicated by arrow 14 
and the spent electrolyte optionally is returned to the leaching step as 
indicated by broken arrow 14A. In an alternative procedure, the nickel 
waste material is not calcined following particle size reduction. 
Turning now to FIGS. 2 and 3 which illustrate the method of this invention 
for producing ferronickel, FIG. 2 depicts alternative methods for recovery 
of ferronickel from various types of nickel catalyst waste materials. For 
recovering ferronickel from spent nickel catalysts which have relatively 
low surface area, it has been found useful to reduce the particle size and 
to increase the surface area of the spent catalyst as indicated by broken 
arrow 20A followed by feeding the prepared catalyst, as indicated by 
broken arrow 20B, into a calciner. Alternatively, if the waste material is 
of suitable size and surface area, it is fed directly into the calciner as 
indicated by arrow 20. 
The spent catalyst is calcined at a temperature of about 200.degree. to 
600.degree. C., and preferably from about 400.degree. to 500.degree. C. 
The calcined material is advanced to hot ore bins as indicated by arrow 21 
or optionally is first briquetted 21A so as to reduce the generation of 
fine dust which otherwise could result due to the small particle size of 
the catalyst materials. If the calcined material is briquetted, the 
briquetting is followed by advancement of the material into hot ore bins 
(broken arrow 21B). Nickel-containing ores are added to the hot ore bins 
as indicated by arrow 22. 
The nickel-containing ores which are useful in the method of the invention 
for preparing ferronickel may be any of the naturally occurring ores which 
contain sufficient nickel to justify the expense of the recovery of the 
nickel. One of the most common nickel-containing ores are the 
nickeliferrous ores or the lateritic ores. The lateritic ores which are 
useful in the method of the invention are oxide complexes containing small 
amounts of nickel and cobalt while containing iron and substantially 
larger amounts of magnesia and silica. The nickel content of these 
lateritic ores varies over a wide range. While in the better deposits, the 
average nickel content may reach or even exceed 2 to 3% nickel, it is in 
the range of 1 to 2% nickel in the great majority of the known lateritic 
nickel ore reserves. An example of a nickeliferrous lateritic ore is the 
ore deposits found in the Riddle, Oregon region. A typical Riddle nickel 
laterite ore analysis by weight, after drying is about 0.7-1.8% nickel, 
0.01% cobalt, 0.3 to 1.0% chromium, 7 to 13% iron, 24 to 32% magnesium, 45 
to 50% silica and about 6 to 7.5% loss on ignition. The amounts of these 
components will vary somewhat depending upon the source of the ore and any 
preliminary benefication treatment. In general, the method of this 
invention can be conducted on nickeliferrous ores containing from 0.5 to 2 
or even 3% of nickel although the process can be conducted on ores 
containing higher amounts of nickel when available. 
The nickel-containing ores used in the method of the invention preferably 
are coarsely ground to the mesh size which is found to be suitable in the 
method of the invention. Because the natural ores recovered from the 
ground are wet, the ore generally will be dried prior to grinding to 
reduce the moisture content. The moisture content of the ore should be 
reduced to below about 5% and is preferably reduced to about 2-3%. The 
desired particle size is one which provides for ease of handling and for 
obtaining maximum nickel recovery. The optimum size for each particular 
ore is a function of the ore minerology and natural grain size 
distribution, and may be determined readily by one skilled in the art. 
The mixture of calcined waste material and nickeliferrous ore prepared in 
the hot ore bin is advanced to a smelting furnace (arrow 23) and smelted 
at an elevated temperature such as about 1670.degree. C. The smelted 
material is advanced, as indicated by arrow 24, to a metal reduction 
furnace. Reduction of the nickel is accomplished in the reducing container 
by adding a reducing agent as indicated by arrow 24A with vigorous mixing 
action to provide good contact between the reducing agent and the molten 
material from step 24. Alternatively the reducing agent, mixed ore and 
calcined spent catalyst can be briquetted or agglomerated and then fed to 
the smelting furnace. Examples of preferred reducing agents which may be 
added to the melt include silicon, ferrosilicons and an 
aluminum-iron-nickel-silicon alloy prepared from a spent nickel catalyst 
as described more fully below with respect to FIG. 3. Carbon may also be 
employed as a reducing agent particularly where a submerged arc furnace is 
used. Ferrosilicons containing about from 45 to 55% silicon particularly 
are useful. When the vigorous mixing is completed, the ferronickel is 
allowed to settle to the bottom of the container and slag is skimmed off 
the top and removed as indicated by arrow 26. As the reducing reaction 
continues, ferronickel accumulates in the reducing container and is 
removed as shown by arrow 25. 
FIG. 3 illustrates a method for recovering a reductant from nickel 
containing waste material which can be added to the metal reduction 
furnace as depicted by arrow 24A in FIG. 2. Either calcined or extruded 
spent nickel catalyst is fed 30 with other raw materials 31 to a 
ferrosilicon type furnace where the mixture is reduced and smelted at a 
temperature of about 1750.degree. C. The produced reductant, an 
aluminum-iron-nickel-silicon alloy is recovered 32 by techniques known to 
those skilled in the art. This metallic reductant can be added, as 
desired, to a metal reduction furnace as indicated by arrow 24A in FIG. 2 
during the recovery process for ferronickel, or may be added to any 
process in which an aluminum-iron-nickel-silicon reductant is useful. 
The following examples illustrate the procedure of the invention for 
removing organic impurities from the waste materials containing nickel and 
thereafter leaching the nickel from the material. 
EXAMPLE 1 
A spent nickel catalyst sample (50 grams) analyzing 14.5% Ni; 0.55% Fe; 28% 
SiO.sub.2 ; 4% Al.sub.2 O.sub.3 ; 16.9% C; 47.4% L.O.I.; and with a 
calorific power of 7,400 BTU/lb. is roasted at 400.degree. C. for 3 hours. 
The calcine containing about 27.5% Ni is leached at 70.degree. C. for 90 
minutes with H.sub.2 SO.sub.4 at a level of 1400 lb. of acid per short ton 
of calcine and at a 33% initial pulp density. The mixture is filtered and 
the filtrate is analyzed. The results are summarized in Table I. The assay 
of liquid is reported in gpl and solids in percent by weight. 
TABLE I 
______________________________________ 
Assay, % or gpl 
Extraction % 
Products Amount Fe Ni Ni 
______________________________________ 
Filtrate 500 cc 0.113 26.3 96.0 
Residue 27.2 g -- 2.02 
______________________________________ 
EXAMPLE 2 
Fifty grams of another silica matrix spent nickel catalyst is leached with 
Stoddard solvent at 75.degree. C. to remove the paraffin-like 
hydrocarbons. The leach residue, analyzing 5.7% Ni is then leached at 
70.degree. C. for 120 minutes with H.sub.2 SO.sub.4 at a level of 700 
lb/STon and 33% initial pump density. The mixture is filtered, and the 
filtrate and residue are analyzed. The results are summarized in Table II. 
TABLE II 
______________________________________ 
Assay, % or gpl 
Extraction % 
Products Amount Fe Ni Ni 
______________________________________ 
Filtrate 500 cc 0.032 5.86 96.7 
Residue 36.2 g -- 0.259 
______________________________________ 
EXAMPLE 3 
A leach solution obtained from leaching a calcined spent nickel catalyst 
with sulfuric acid is treated with sodium hydroxide to adjust the pH=3.2 
at 23.degree. C. A 500 ml sample is transferred into an autoclave and 
reacted for 30 minutes at 150.degree. C. under an operating pressure of 
150 psig of which about 100 psig is due to oxygen. After treatment the 
solution shows a pH=2.7 at 90.degree. C. The results of this test are as 
follows. 
TABLE III 
__________________________________________________________________________ 
Ni Fe Al SiO.sub.2 
__________________________________________________________________________ 
Feed Solution, 500 cc 
58.65 gpl 
1.734 gpl 
6.01 gpl 
0.119 gpl 
Purified Solution, 500 cc 
58.4 gpl 
0.172 gpl 
0.0128 gpl 
0.082 gpl 
Residue, 11.4 grams 
1.11 Wt. % 
6.85 Wt. % 
26.31 Wt. % 
0.162 Wt. % 
Impurities Removal: 
90.1 Wt. % 
99.8 Wt. % 
31.1 Wt. % 
__________________________________________________________________________ 
The embodiments of the invention in which an exclusive property or 
privilege is claimed are defined as follows: