Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B23/00—Obtaining nickel or cobalt
  • C22B23/04—Obtaining nickel or cobalt by wet processes
  • C22B23/0476—Separation of nickel from cobalt
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling

Definitions

• This invention relates to the hydrometallurgical processing of nickeliferous oxide ores and, in particular, to acid leaching of nickeliferous oxide ores selected from the group consisting of limonite and saprolite, which jointly are called laterites.
• nickeliferous oxide ores e.g., limonite and saprolite
• One process for recovering nickel and cobalt is the well known Moa Bay process involving acid leaching at elevated temperatures and pressures at which iron oxide and aluminum oxysulfate are substantially insoluble.
• the leach solution pH which is quite low (e.g., between 0 and 0.5), is then neutralized with coral mud to a pH of about 2.4 in a series of four tanks at a total retention time of about 20 minutes and the thus-treated product liquor (containing about 5.65 gpl Ni, 0.8 gpl Fe and 2.3 gpl A1), after solid-liquid separation, is then subjected to sulfide precipitation.
• the leach liquor is preheated and the sulfide precipitation carried out using H2S as the precipitating reagent in an autoclave at about 120oC (250oF) and a pressure of about 150 psig.
• the solution containing nickel and cobalt was then neutralized with ammonia to a pH (5.35) sufficient to precipitate any residual iron, aluminum, and chromium present using air as an oxidizing agent.
• the precipitate was thereafter separated from the solution and the nickel and cobalt solution then adjusted to a pH of about 1.5. H2S was added to precipitate
• the precipitate was separated from the solution by filtration and the nickel recovered by various methods, one method comprised treating the nickel-containing solution with hydrogen at elevated temperature and pressure to produce nickel powder.
• the hydrometallurgical process employed involves the use of a chelating ion exchange resins in which nickel is preferentially separated from cobalt and impurities typically obtained in the sulfuric acid leaching of laterite ores. While chelating ion exchange resins are known for extracting nickel from solutions, it was not known that, under relatively high acidic conditions, nickel can be separated from cobalt present in laterite leach solutions and provide an eluate with a substantially high Ni to Co ratio, e.g., at least about 50:1 suitable for recovery of substantially pure nickel by electrolysis.
• Another object is to provide a process for
• Fig. 1 is a flowsheet illustrating the process as applied to nickel laterite ores
• Fig. 2 depicts two curves published by Dow Chemical showing the absorption characteristics for each of nickel and cobalt using a Dow ion exchange composition identified by the trade designation XFS-4195 in which an active ingredient thereof is comprised of bis-picolylamine;
• Fig. 3 is a curve depicting the absorption
• Fig. 4 is illustrative of cumulative loading of nickel
• Fig.5 depicts generally an ISEP configuration in the form
• Figs. 5A and 5B are schematics shown as flow sheets illustrating the use of said ISEP carousel configuration in carrying out the ion-exchange extraction of nickel from solution using the resin XFS-4915;
• Fig. 6 is illustrative of cobalt and nickel loading at room temperature as a function of the number of bed volumes (BVS/hr) passed through a column of XFS-4195 resin;
• Fig. 7 depicts curves illustrating the selective stripping of cobalt from the resin employed in extracting the cobalt
• Fig. 8 is a simplified schematic illustrating the counterflow operation of the ISEP configuration through a series of columns
• Fig. 9 illustrates the use of the ISEP configuration for carrying out the Ni + Co IX (i.e. nickel plus cobalt ion exchange).
• Fig. 10 is a flow sheet based on the use of a Recoflo apparatus in recovering the nickel from the pregnant leach liquor, Fig. 10A being a continuation of Fig. 10.
• laterite ores e.g. limonite and saprolite
• Ni, Co, Fe, Al, Mg, Mn, Cr, SiO 2 and a variety of impurity elements along with free and
• An example of a limonite ore is one containing by weight 1.72% Ni, 0.14% Co, 41% Fe, 2.5% Al, 1.58% Mg, 0.8% Mn, 2.05% Cr, 12.1% SiO 2 and 11.3% LOI (Loss on Ignition).
• nickel and cobalt important elements of interest are nickel and cobalt.
• Such ores will generally contain by weight about 0.5% to 3% nickel and about .005 to 0.5% cobalt.
• the oxide ores to which the invention is applied may contain by weight about 0.5% to 3% nickel, about
• the invention is directed to a process for the recovery of nickel from particulate nickel oxide ores, such as saprolites and limonites, by sulfuric acid leaching said ores to form a pregnant solution of metal values, e.g., nickel and cobalt, which are recovered directly by ionexchange.
• the ore may be either
• sulfuric acid leaching is carried out at a relatively high temperature and pressure, e.g., 270° and 810 psi.
• a relatively high temperature and pressure e.g., 270° and 810 psi.
• Another embodiment of the process comprises forming an aqueous slurry in the form of a pulp of particulate oxide ore containing by weight about 1.5% Ni and about
• the leaching may be carried out by either atmospheric or pressure leaching.
• the amount of sulfuric acid solution is at least stoichiometrically sufficient to dissolve
• the pulp is subjected to pressure leaching following injection of sulfuric acid at an elevated temperature of about 150oC to 300oC at a pressure ranging from about 150 psig to 1,000 psig to solubilize at least 80% nickel and at least about 80% of the cobalt present in the ore.
• a typical time of leaching may range from about 15 minutes to 120 minutes.
• a pregnant liquor is obtained containing said nickel and cobalt as sulfates and residual other elements and undissolved residue as tailings.
• the acid in the pregnant solution is adjusted to or provided at a pH of about 0.5 to 4 following which the slurry is subjected to countercurrent decantation to separate the pregnant nickel and cobalt solution from said tailings.
• the acid in the tailings is neutralized with lime or other base to a pH of about 9 and the tailings disposed of.
• cobalt is contacted with an ion exchange resin under pH conditions selective to the absorption of nickel, while providing a raffinate containing cobalt.
• the raffinate is thereafter prepared for the removal of cobalt plus any nickel remaining therein by an ion exchange resin under conditions selective to the absorption of cobalt and nickel.
• the invention provides a process for selectively recovering nickel by ion exchange
• the process comprises contacting the nickelcontaining acid solution at a pH ranging from about 0.3 to 6 with a bed of protonated ion exchange resin in which protons associated with said resin are exchangeable with nickel ions in the solution.
• the protonated resin selectively extracts the nickel in preference to cobalt from the solution at a pH of less than about 2.
• the low pH is generally achieved by proton ions entering the solution as the nickel ions are absorbed by the resin.
• the absorbed nickel is then stripped from the resin with sulfuric acid to form a nickel sulfate solution characterized by a nickel to cobalt ratio of at least about 50:1 suitable for the recover of substantially pure nickel by electrolysis.
• the pregnant nickel solution is passed serially through a plurality of moving columns of the resin which move countercurrently to the flow of the pregnant solution entering the first column and exiting through the last column thereof with the bulk of the nickel removed in the initial columns and the nickel-impoverished solution containing cobalt thereafter passing through the last column.
• the pregnant nickel solution may be passed serially through two stationary columns of resin in a Recoflo ® ion exchange system produced by Eco-Tec Inc. of Pickering, Ontario, Canada.
• the feed solution is stopped and the first column only is stripped of the loaded nickel with sulfuric acid solution.
• the feed solution is again passed through the two columns serially, except the second column now becomes the "lead” column for feeding the pregnant liquor.
• the feed solution is stopped and the second column is stripped. Then feeding commences once again with the first column as the lead column. This is
• the nickel absorbed by the resin is stripped with sulfuric acid to provide a pregnant solution from which substantially pure nickel is recovered, such as by
• the cobalt plus the remaining nickel absorbed in a second ion exchange step is recovered by stripping with a sulfuric acid solution and the mixed cobalt nickel solution then sent to nickel/cobalt
• An important economic advantage of the invention is that sulfide precipitation of nickel and cobalt is
• the invention takes a more simple and economic route in that following the leaching of the nickel oxide ore, e.g., pressure leaching in the
• the limonite ore contained by weight 1.7% Ni, 0.15% Co, 40% Fe, 4% Al, 2% Mg, 2% Mn, 2% Cr, 10% SiO 2 and 15% LOI (Loss On Ignition).
• the technology employed includes an ore preparation step (1) in which the coarse reject 1A thereof may be used for the neutralization of excess acid.
• Sulfuric acid pressure leaching (2) is carried out at about 270° C with a leaching time in the range of about 20-40 minutes and generally ranging up to 30 minutes
• CCD countercurrent
• tailings neutralization (5) with limestone and milk of lime, in which the pH is raised to about 9, the residue is disposed of at a tailings dam.
• the CCD overflow solution 6 is contacted with an ion exchange resin where only nickel (plus copper if present) and only minor quantities of cobalt are loaded (7). Because nickel replaces the proton or hydrogen ion in the active part of the resin, the pH of the solution decreases during ion exchange, whereby the nickel is extracted by the resin in preference to a cobalt at a pH of less than about 2.
• the nickel is stripped from the ion exchange resin (7) with sulfuric acid.
• the nickel-containing solution is neutralized at (8A) with limestone and the neutralized solution subjected to solid/liquid separation with the solids recycled to neutralization (3) and the nickel solution sent to nickel electrowinning (15).
• the raffinate 8 with only minor amounts of nickel plus most of the cobalt and other impurities is further neutralized at (9) with limestone to a pH of about 2 to 4.
• the solids and liquid are separated at (10), the solids sent to tailings disposal (5) and the nickel/cobalt solution (11) sent to cobalt recovery 12 with the
• the nickel/cobalt following ion exchange is substantially pure and free of the contained impurities.
• the purified cobalt solution is treated for recovery of cobalt as a salable commodity, either by soda ash precipitation, sulfide precipitation or electrowinning.
• the nickel loaded on the resin (7) may be stripped with spent electrolyte (16) from the nickel electrowinning circuit (15). Prior to returning the stripped resin to loading, the resin is washed with water which converts the resin from the bisulfate into the sulfate form, releasing sulfuric acid which can be reused for stripping.
• DOW's XFS-4195 as the resin both for nickel loading as well as cobalt/nickel loading.
• Other resins which may be used include Rohm and Haas IR-904, Amberlite XE-318, and DOW XFS-43084. As disclosed hereinafter, the DOW resins have picolylamines as active groups.
• copolymers onto which weakly basic chelating picolylamine derivatives have been attached onto which weakly basic chelating picolylamine derivatives have been attached.
• DOW resin XFS 4195 is a stronger and preferred completing agent for nickel than the other resins
• the functional groups in the XFS 4195 and XFS 4196 resin are more specifically referred to as bis(2-picolyl)amine and N-(2hydroxyethyl-2-picolylamine, respectively.
• the XFS 43084 resin is similar to the resins above, that is, the resin is a macroporous polystyrene copolymer with a weakly basic chelating picolylamine derivative attached, i.e., specifically N-(2-hydroxypropyl)-2-picolylamine.
• the absorption constant is really not a constant but a function of the pH, as shown in the attached Figure 2 published by DOW chemical.
• the importance of keeping the pH low will be apparent from Figure 3. This figure clearly shows that it is advantageous to keep the pH of the pregnant solution low if one wants to
• Ni/Co ratio in the product which is important. For example, if the Ni/Co ratio in the electro-winning of nickel is better than 50:1 and particularly better than 90:1 or 100:1,, a high quality nickel product is
• Co/Ni ratios are similarly important.
• An example of a desirable ratio is a ratio which is at least about 50:1 preferably 80:1 or 100:1.
• these solutions contain between 20 and 100 gpl Co and have a cobalt to nickel ratio of about 100 to 1.
• chromium, aluminum and iron present a problem.
• hexavalent chromium has to be limited to less than 10 ppm to maintain a good quality deposit.
• XFS-4195 has a disadvantage in that it has a very high affinity for hexavalent chromium
• XFS-4195 is also selective for copper.
• Laterite leach solutions have up to about 50 ppm Cu and up to 300 ppm total chromium, of which about 10% or more may be present as hexavalent Cr.
• a pretreatment step for removing both Cu and hexavalent Cr can be included as a preferred embodiment of the
• This pretreatment step can either be a metal cementation step using iron, zinc or even nickel to reduce hexavalent Cr to the trivalent state and to cement copper.
• an ion exchange column may be included that is specifically used to load both hexavalent Cr and Cu from the leach solution. After this treatment, the leach solution can then be treated by the ion exchange approach discussed herein.
• a novel aspect of the invention is the fact that the XFS4195 resin has the ability of being converted from the sulfate to the bisulfate form by taking up sulfuric acid as follows:
• RIP hot resin-in-pulp
• Equation (3) shifts completely to the right under all conditions of the acid leaching process.
• Equation (4) shifts only to the sulfate side at higher pH and lower temperatures.
• the bisulfate to sulfate ratio as a function of the temperature and pH is calculated as
• the ion exchange process can tolerate more free acid in solution as the process temperature is raised.
• the kinetics of nickel loading on the resin are rather slow at room temperature. It is not economically advisable to heat the solution to improve reaction kinetics.
• the leach discharge is generally near its boiling point and an advantage is obtained since the nickel loading will be done hot without the need for additional heating.
• the improved kinetics usually result in a significant increase in resin capacity in that, in carrying out the invention, the resin is capable of being loaded at a rate of at 30 Bed Volumes (BV) per hour while conventionally the maximum is about 5 BV/hr.
• electrowinning cell generally should be at a pH of 2.5 to 3.5 to obtain the best deposition characteristics.
• Test work in the laboratory has shown that raising the pH of the eluate going to the electrolytic cell not to 2.5-3.5, but to 4.5 to 5.5, removes any aluminum and chromium which pass through the ion exchange system, down to less than about 10 ppm levels. Little nickel will precipitate at this pH.
• Example 1 As illustrative of the invention, the following example is given: Example 1
• Particulate lateritic oxide ore is formed into a pulp with water and screened at 28 mesh (U.S. Standard).
• the composition is comprised of 1.5% Ni, 0.14% Co, 4% Al, 0.8% Mg and the balance substantially iron, i.e., 42% Fe, present as oxides or hydroxides.
• the coarse fraction (approximately +20 mesh) is separated from the ore and may be used for atmospheric leaching by
• the fines fraction of the ore which is passed to pressure leaching 2 of the flowsheet, is first pulped with water or an aqueous solution to a pulp density of about 35%.
• Sulfuric acid is added to provide an acid to ore ratio of 0.2:1 to 0.3:1 based on weight of
• the pulp is pressure leached in an autoclave at a temperature of about 270oC under a total pressure of about 810 psia, the sulfuric acid being added to the pulp in the autoclave by injection.
• the ore is leached in about 15 to 60 minutes and the nickel extracted to about 95% based on the amount of nickel in the ore.
• the iron and aluminum in the solution are substantially rejected and appear in the tailings as basic aluminum sulfate (alunite) and hematite (Fe 2 O 3 ).
• the pregnant nickel solution is passed on to acid neutralization at (3).
• the solution is neutralized with limestone to a pH of about 2, after which the neutralized slurry is subjected to solids/liquid separation at (4).
• the neutralized slurry is subjected to solids/liquid separation at (4).
• neutralization step (3) may be omitted.
• the separated solution is passed to an ion-exchange apparatus (7) containing an ion-exchange resin specific to the
• the ratio of nickel in the feed solution to the quantity of resin employed is such as to provide 95% of resin loading capacity while extracting 95% of the nickel. This helps to ensure complete “crowding" off of cobalt, that is, the preferential loading of nickel over that of cobalt.
• a particularly advantageous ion exchange resin is one identified as DOW XFS 4195 in which the active ingredient is bis-picolylamine.
• the raffinate remaining is subjected to acid neutralization at (9) with limestone to a pH of about 2 to 4.5, following which the slurry from acid neutralization is passed to solid-liquid separation at (10) and the solution
• Fig. 8 is a simplified illustration of the general operation of the ISEP configuration.
• Fig. 8 is a schematic of Figs. 5, 5A and 5B,
• a carousel as one embodiment, comprising a series of resin-loaded columns 1, 2, 3 and ranging up to the Nth column, arranged and adapted to provide a serial pathway for the solution 5 from the first column to the Nth column, the interruption in the system at 4 indicating that other resinloaded columns may be present in the system between the 3rd and Nth columns.
• the rotational arrangement of the columns shown in Fig. 5 is such that the flow direction 6 of the resin loaded columns of Fig. 8 (i.e., the direction of travel of the resin columns) is counter to the flow direction of the nickel pregnant solution through the columns as shown, i.e., countercurrent flow) whereby the resins of each succeeding column remove the nickel from solution with the raffinate solution 7 containing cobalt flowing out of the system for the subsequent recovery of said cobalt.
• FIG. 5A and 5B A more detailed schematic is shown in Figs. 5A and 5B to be discussed later.
• the acid pH is preferably maintained at a level selective to the absorption of nickel, the pH being such that the nickel crowds off or substantially inhibits the absorption of cobalt.
• the nickel to cobalt ratio in the resin following substantially complete recovery of nickel is at least about 50:1 or at least 90:1 or higher.
• substantially impoverished in nickel may then be treated after a pH adjustment, if necessary, to recover the cobalt using a resin and conditions selective to the absorption of cobalt, e.g., DOW FXS 4195.
• sulfate/cobalt sulfate solution having a Ni/Co ratio corresponding generally to that produced by leaching a typical limonite ore.
• the solution contained 12.5 gpl Ni and 1 gpl Co and had a pH of 3.
• the solution had a
• Co loading is suppressed because the resin is already loaded with substantial nickel which cannot be easily exchanged for Co, even at the higher pH of the feed solution.
• Florida It consists of a carousel of 30 ion exchange columns connected to a rotary valve arrangement at the top and bottom of the carousel as means for providing serial, flow through the columns of resin.
• Each rotary valve consists of a rotating disc attached to the columns and a stationary disc attached to reservoirs of the various process solutions.
• Each stationary disc has 20 internal ports.
• Each column on the carousel is connected to a port on the rotating disc at the top and the bottom of the carousel. (There are 30 columns and 30 ports in each rotating disc.)
• the carousel and rotating disc portions of.the top and bottom valve rotate continuously and the ports in the rotating disc are connected to the ports of the stationary disc in sequence.
• the solution pumped continuously into a port or ports of the stationary disc flows serially through each column in sequence as the carousel rotates.
• a countercurrent flow of solution and resin can thus be effected in this apparatus by the aforementioned indexing means.
• a second ion exchange system for carrying out the novel aspects of the invention is referred to as the
• Recoflo (trademark) system manufactured by Eco-Tec Inc. of Pickering, Ontario, Canada. In this system, two beds of resin are employed. A cyclic process is used (note Fig. 10) to provide in effect a partial countercurrent flow resin and solution. As will be clearly apparent from Fig. 10, there are eight distinct steps in each cycle,
• step 1 feed solution is passed through beds I and 2 in series.
• Bed 1 has already been partially loaded with nickel in the preceding step while bed 2 contains fresh resin because it was stripped and washed in the preceding steps.
• fresh feed solution is contacted with partially loaded resin and fresh resin is contacted with partially depleted and acidified solution as occurs in the ISEP contactor.
• the stationary ports of the ISEP apparatus are illustrated in the configuration shown in Fig. 5A.
• the carousel containing thirty 1 3/8 inch diameter by lm high columns of Dow XFS 4195 resin, was rotated at 0.2
• compositions of the various solution streams after 15 hours of continuous operation in grams/liter were as follows:
• the Ni and Co extractions from feed solution were 95% and 13%, respectively, producing a Ni/Co ratio in the eluate of >300:1.
• the feed solution composition of 6.6 g/L Mg and the eluate composition of 0.2 g/L Mg Based on the feed solution composition of 6.6 g/L Mg and the eluate composition of 0.2 g/L Mg, only 1.8% of the Mg in the feed was passed to the eluate by solution entrainment, indicating >98% washing efficiency in the load wash stage.
• the other impurities, including Al and Mn behaved similarly to Mg.
• Ni/Co ratio of 310 in the eluate is sufficient for direct electrowinning of good quality Ni cathodes, although not of so-called Class I quality (Ni/Co 1670:1). These cathodes would certainly be usable for stainless steel manufacture as the main source of Ni for the production of stainless steel is ferronickel, which typically has a Ni/Co ratio of only 30-40:1.
• Example 5 The advantage of higher solution temperatures is clearly seen by comparing this result with the result of Example 3.
• Example 5 The advantage of higher solution temperatures is clearly seen by comparing this result with the result of Example 3.
• the configuration of the ISEP for this test was only slightly different from Examples 3 and 4, as shown in Fig. 5B.
• the main difference is that the acidity of the feed solution was 25 g/L H 2 SO 4 , which is about the natural acidity expected for high pressure acid leach solution.
• the strip solution was a "synthetic" spent
• electrolyte as normally produced by electrowinning Ni directly from neutralized eluate, as shown in Fig. 1.
• Ni and Co extractions in this test were approximately 86% and 0.4%, respectively. Surprisingly, very good Ni extraction was achieved despite the high acidity of the feed solution.
• Nickel and sulfuric acid mass balances using the above data show that in the loading section net production of H 2 SO 4 was only 0.5 moles per mole of Ni loaded on the resin. This indicates that some sulfuric acid liberated by Ni loading actually reloads on the resin via reaction (1), thus limiting the free acid content of the raffinate and permitting substantial Ni loading despite the high acidity of the feed solution.
• a test was carried out with a Recoflo apparatus comprised of two 2 inch diameter columns 12 inches high containing DOW XFS 4195 resin. The two columns were connected in series and operated cyclically as illustrated in Fig. 10. The solution flow rates were maintained at about 0.4 L/min and each solution was heated to 70oC.
• the feed solution contained 9.75 g/L Ni, 0.94 g/L Co, 2.1 g/L Al, 5.5 g/L Mg, 2.05 g/L Mn and had a pH of about 2.
• the strip solution contained 100 g/L H 2 SO 4 .
• a steady state condition was achieved after 10 complete cycles of
• the eluate was collected as two separate fractions, the first fraction consisting mainly of displaced wash water.
• the stationary ports were arranged as shown in Fig. 9.
• the carousel was rotating at 0.13 revolutions per hour. All feed, wash and strip solutions were heated to 20oC prior to being fed to the ISEP apparatus.
• the flow rates of each solution were as follows:
• Ni + Co were loaded per liter of resin in the loading step.
• This example illustrates the ability of the ion exchange system to load both nickel and cobalt under conditions of relatively low acidity ( ⁇ 15 g/L H2so4) and a resin loading less than the resin maximum capacity (-0.65 moles Ni+Co per liter resin).
• a pure cobalt plus nickel solution is obtained which can be treated for cobalt recovery via methods apparent to those skilled in the art.
• a sample of limonite of 30% solids was batch leached with concentrated sulfuric acid in an autoclave at 270oC to produce a leach slurry.
• the pH of one liter of leach slurry was adjusted to 3.7 with calcium carbonate and the slurry was then mixed with 200 mL of Dow XFS 4195 resin for 2 hours at room temperature.
• the resin was recovered from the slurry by screening over a 50 mesh screen.
• the leach solution before and after treatment with the resin assayed as follows:
• Ni and Co recoveries were estimated at 96% and 88%, respectively. Iron and zinc were also extracted. It should be noted, however, that iron dissolution during leaching can be prevented by careful control of leaching conditions.

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• 1995
  • 1995-12-13 WO PCT/US1995/016118 patent/WO1996020291A1/en active Application Filing
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