CA1044468A - Extracting of iron ore and chromium from nickel lateritic ores - Google Patents
Extracting of iron ore and chromium from nickel lateritic oresInfo
- Publication number
- CA1044468A CA1044468A CA233,856A CA233856A CA1044468A CA 1044468 A CA1044468 A CA 1044468A CA 233856 A CA233856 A CA 233856A CA 1044468 A CA1044468 A CA 1044468A
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- CA
- Canada
- Prior art keywords
- chromium
- ore
- iron
- nickel
- soluble
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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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
- C22B34/00—Obtaining refractory metals
- C22B34/30—Obtaining chromium, molybdenum or tungsten
- C22B34/32—Obtaining chromium
-
- 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
- C22B23/0407—Leaching processes
- C22B23/0415—Leaching processes with acids or salt solutions except ammonium salts solutions
- C22B23/043—Sulfurated acids or salts thereof
-
- 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
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
Abstract
Abstract of the Disclosure Chromium is removed from nickel lateritic ore by sizing the as-mined particulate ore to provide a size fraction of fines in which substantially all of the chromium is in the acid-soluble form and then leaching said soluble chromium from said fines fraction together with nickel and other associated metal values by high pressure leaching at an elevated temperature in an aqueous sulfuric acid solution, such that an iron ore tailings is produced very low in chromium suitable for the recovery of iron therefrom.
Description
~.0~68 This invention relates to the recovery of chromium together with nickel and associated metal values from nickel lateritic ores while producing an iron ore tailings having utility for the recovery of iron there-from.
State of the Art Generally speaking, chromium is recovered from high grade ores containing by weight 50% to 60% chromium as chromium oxide together with about 12% to 25% iron in the form of ferrous oxide. The recovery of chromium from low grade chromium ores has not been economically feasi~e.
- One method has been proposed for recovering ` chromium from nickel lateritic ores which generally contain less than 5% chromium. Such a method is disclosed in U.S.
Patent No. 3,082,080 (March 19, 1963) which describes a process for recovering chromium and nickel from iron con-tained in lateritic, limonite ores. The ore is mixed with a tetravalent manganic oxide mineral in an amount suffi-cient stoichiometrically to oxidize the chromium, the ore ' 20 being leached in an aqueous acid solution containing sul-} ~uric acid equalling at least 40/O of the dry weight of f - the ore, the amount of acid in the slurry being predeter-mined so as not to dissolve any substantial proportion of irsn present. A temperature of at leas~ about 475F is used at superatmospheric pressure and an iron or~ ~ailings results from the treatment.
~, t -2-,, , ~4~468 However, the foregoing treatment does not pro-duce an iron ore tailings sufficiently low in associzted metal values, such as chromium, among other elements, for use in the recovery of iron therefrom.
Relative to the foregoing problem, we have developed a method which enables the substantially com-plete removal of chromium, together with associated metal values, from nickel lateritic ores.
; We have found that chromium appears in the ore in two forms, soluble chromium and insoluble chromium.
Thus, the use of prior methods generally results in the insoluble chromium appearing in the iron tailings which decreases its utility in steel making.
Obiects of the Inv~ntion It is thus the object of the invention to pro-vide a method for recovering chromium from particulate iron-containing ores in an economical manner while produc-ing an iron ore by-product having utility in the manufac-ture of steel.
Another object is to recover chromium from nickel and cobalt containing lateritic ores which also ~ contain iron, wherein the nickel and cobalt are recovered ! together with chromium, and wherein the iron is recovered in the tailings suitable for use in the recovery of iron therefrom.
,. ..
, ,~ ~, , , , , ; " ' ' , ' : . , 1~44468 These and other objects will more clearly ap-pear from the following disclosure and the appended claims~
Statement of the Invention :`
Our discovery is based on the fact that substan-tially all of the soluble chromium appears in a size frac-tion of the particulate or comminuted ore of very fine average size which may comprise a size less than about 20 microns, preferably less than lO microns. By sizing the comminuted ore to produce a desired size fraction in which the chromium is substantially acid-soluble and then leaching the metal values therefrom, an iron ore tailing i9 obtained that is acceptable for use in the recovery of ' iron therefrom. It is preferred that the ore be one in .
which the size fraction containing the soluble chromium ., constitutes at least about 50~/O of the ore batch to be treated. Generally, the fines fraction may range from about 50/O to 85% by weight of the total ore batch. Tetra-,. ~ --1 -valent manganese ion, such as manganese dioxide tor MnO4 or S2O8 ), is preferably added to the size fraction as an oxidizing agent to oxidize the chromium to a higher ` valence and reduce its tendency to hydrolyze out of solu-tion. ~
., ,~ , i .
10~468 Thus, the invention resides in a method of separating chromium from particulate lateritic ores con-taining substantial amounts of iron, which comprises as a first step, sizing said ore to produce a fines fraction in which substantially all of the chromium is in the soluble form. In the case of ~ew Caledonia ore, it has been found that the fines fraction may be minus 20 microns, preferably minus 10 microns. As stated herein-- above, it is preferred to add an amount of tetravalent manganese oxide material or other of the aforementioned oxidizing agents in an amount at least stoichiometrically suficient to oxidize the chromium to a higher valence.
The additional steps comprise forming an aqueous slurry of the ore containing an amount of sulfuric acid corres-ponding to about 0.1 to 0.5 parts by weight of acid per part of dry ore, and then subjecting the ore to high pre~
sure leaching at an elevated temperature, thereby extract-ing said chromium and associated metal values from the iron which reports in the tailings, the tailings being , 20 very low in the associated metal values. The chromium in the tailings is reduced to less than 0.2% and generally less than 0.1%.
,~
Details of the Invention The cut size of the ore may depend upon the size distribution of the soluble and the insoluble forms of chromium. The size distribution may be determined by a procedure in which 0.5 gram of sample is mLxed with 1 cc of 36 ~ H2S04, 10 cc of 12 ~ HCl and 2 cc of io N HF
in a 100 cc polyprolyene flask. The ore sample is allowed to decompose for 1 hour at 100C in a water bath. Then 75 ml of 5% boric acid solution is added and the volume brought up to 200 cc. The soluble chromium analysis is determined by atomic absorption. The foregoing is carried out on various cuts to determine-that fines fraction in which substantially the chromium is acid-soluble. As sta-ted earlier, the fines fraction should preferably consti-tute at least about 50/0 by weight of the ore batch.
The total chromium content in the size fraction is dFtermined in the usual manner by ~a202 fusion and the percent soluble chromium in the fraction determined rela-tive to the total chromium content.
$ 20 The cut slze of the ore following the determina-tion of the soluble chromium distribution selected for the leach feed material generally contains about 100% of tbe soluble chromium. As stated above, in the case of J
~r, ' ' ' '' ," ", ... . .. . . . . . . . .
~044468 New Caledonia lateritic ores, the chromium in a cut size `~ of minùs 10 microns has been found to be ~ore than 9~h soluble chromium. This is important as it enables the production of iron ore tailings following leaching which contains very little or no chromium. The cut size or fines fraction is easily produced by using a hydrocyclone.
It was found relative to New Caledonia ore that a coarser cut, such as 400 mesh, generally lowers the soluble chromium relative to total chromium to about 60~/o `~ 10 to 70%. This should be avoided since the leach residue would then contain chromium higher than the maximum generally permitted for iron ore.
By determining the proper fines fraction in which substantially all of the contained chromium is soluble, an acceptable iron ore tailing is generally obtainable containing less than about 0.1% chromium.
In order to insure that the soluble chromium i leached stays in solution, it is preferred that the leaching be effected under oxidizing conditions by using, for - 20 exa~ple, tetravalent manganese oxide material containing MnO2 or its equivalent.
Since New Caledonia lateritic ores contain nickel and cobalt as valuable metal values together with associated metal values, such as chromium, then these metals are also recovered together with chromium. Fol-, ,;, .
, , :
~7~
r" ~ . . ; . ` . ;. . . : . .
lU4~468 lowing leaching, the various metal values can be separa-ted by well known chemical precipitation techniques.
The leaching temperatures generally range from about 200C to 300C, e.g. about 230C to 280C, the t~m-perature preferably being about 250C, the retention time being usually one hour and higher. The superatmospheric pressure under which the leaching is conducted generally ranges from about 400 psig to 1000 psig.
The ore is slurried in an aqueous acid solu-tion of sulfuric acid at a pulp density of over about
State of the Art Generally speaking, chromium is recovered from high grade ores containing by weight 50% to 60% chromium as chromium oxide together with about 12% to 25% iron in the form of ferrous oxide. The recovery of chromium from low grade chromium ores has not been economically feasi~e.
- One method has been proposed for recovering ` chromium from nickel lateritic ores which generally contain less than 5% chromium. Such a method is disclosed in U.S.
Patent No. 3,082,080 (March 19, 1963) which describes a process for recovering chromium and nickel from iron con-tained in lateritic, limonite ores. The ore is mixed with a tetravalent manganic oxide mineral in an amount suffi-cient stoichiometrically to oxidize the chromium, the ore ' 20 being leached in an aqueous acid solution containing sul-} ~uric acid equalling at least 40/O of the dry weight of f - the ore, the amount of acid in the slurry being predeter-mined so as not to dissolve any substantial proportion of irsn present. A temperature of at leas~ about 475F is used at superatmospheric pressure and an iron or~ ~ailings results from the treatment.
~, t -2-,, , ~4~468 However, the foregoing treatment does not pro-duce an iron ore tailings sufficiently low in associzted metal values, such as chromium, among other elements, for use in the recovery of iron therefrom.
Relative to the foregoing problem, we have developed a method which enables the substantially com-plete removal of chromium, together with associated metal values, from nickel lateritic ores.
; We have found that chromium appears in the ore in two forms, soluble chromium and insoluble chromium.
Thus, the use of prior methods generally results in the insoluble chromium appearing in the iron tailings which decreases its utility in steel making.
Obiects of the Inv~ntion It is thus the object of the invention to pro-vide a method for recovering chromium from particulate iron-containing ores in an economical manner while produc-ing an iron ore by-product having utility in the manufac-ture of steel.
Another object is to recover chromium from nickel and cobalt containing lateritic ores which also ~ contain iron, wherein the nickel and cobalt are recovered ! together with chromium, and wherein the iron is recovered in the tailings suitable for use in the recovery of iron therefrom.
,. ..
, ,~ ~, , , , , ; " ' ' , ' : . , 1~44468 These and other objects will more clearly ap-pear from the following disclosure and the appended claims~
Statement of the Invention :`
Our discovery is based on the fact that substan-tially all of the soluble chromium appears in a size frac-tion of the particulate or comminuted ore of very fine average size which may comprise a size less than about 20 microns, preferably less than lO microns. By sizing the comminuted ore to produce a desired size fraction in which the chromium is substantially acid-soluble and then leaching the metal values therefrom, an iron ore tailing i9 obtained that is acceptable for use in the recovery of ' iron therefrom. It is preferred that the ore be one in .
which the size fraction containing the soluble chromium ., constitutes at least about 50~/O of the ore batch to be treated. Generally, the fines fraction may range from about 50/O to 85% by weight of the total ore batch. Tetra-,. ~ --1 -valent manganese ion, such as manganese dioxide tor MnO4 or S2O8 ), is preferably added to the size fraction as an oxidizing agent to oxidize the chromium to a higher ` valence and reduce its tendency to hydrolyze out of solu-tion. ~
., ,~ , i .
10~468 Thus, the invention resides in a method of separating chromium from particulate lateritic ores con-taining substantial amounts of iron, which comprises as a first step, sizing said ore to produce a fines fraction in which substantially all of the chromium is in the soluble form. In the case of ~ew Caledonia ore, it has been found that the fines fraction may be minus 20 microns, preferably minus 10 microns. As stated herein-- above, it is preferred to add an amount of tetravalent manganese oxide material or other of the aforementioned oxidizing agents in an amount at least stoichiometrically suficient to oxidize the chromium to a higher valence.
The additional steps comprise forming an aqueous slurry of the ore containing an amount of sulfuric acid corres-ponding to about 0.1 to 0.5 parts by weight of acid per part of dry ore, and then subjecting the ore to high pre~
sure leaching at an elevated temperature, thereby extract-ing said chromium and associated metal values from the iron which reports in the tailings, the tailings being , 20 very low in the associated metal values. The chromium in the tailings is reduced to less than 0.2% and generally less than 0.1%.
,~
Details of the Invention The cut size of the ore may depend upon the size distribution of the soluble and the insoluble forms of chromium. The size distribution may be determined by a procedure in which 0.5 gram of sample is mLxed with 1 cc of 36 ~ H2S04, 10 cc of 12 ~ HCl and 2 cc of io N HF
in a 100 cc polyprolyene flask. The ore sample is allowed to decompose for 1 hour at 100C in a water bath. Then 75 ml of 5% boric acid solution is added and the volume brought up to 200 cc. The soluble chromium analysis is determined by atomic absorption. The foregoing is carried out on various cuts to determine-that fines fraction in which substantially the chromium is acid-soluble. As sta-ted earlier, the fines fraction should preferably consti-tute at least about 50/0 by weight of the ore batch.
The total chromium content in the size fraction is dFtermined in the usual manner by ~a202 fusion and the percent soluble chromium in the fraction determined rela-tive to the total chromium content.
$ 20 The cut slze of the ore following the determina-tion of the soluble chromium distribution selected for the leach feed material generally contains about 100% of tbe soluble chromium. As stated above, in the case of J
~r, ' ' ' '' ," ", ... . .. . . . . . . . .
~044468 New Caledonia lateritic ores, the chromium in a cut size `~ of minùs 10 microns has been found to be ~ore than 9~h soluble chromium. This is important as it enables the production of iron ore tailings following leaching which contains very little or no chromium. The cut size or fines fraction is easily produced by using a hydrocyclone.
It was found relative to New Caledonia ore that a coarser cut, such as 400 mesh, generally lowers the soluble chromium relative to total chromium to about 60~/o `~ 10 to 70%. This should be avoided since the leach residue would then contain chromium higher than the maximum generally permitted for iron ore.
By determining the proper fines fraction in which substantially all of the contained chromium is soluble, an acceptable iron ore tailing is generally obtainable containing less than about 0.1% chromium.
In order to insure that the soluble chromium i leached stays in solution, it is preferred that the leaching be effected under oxidizing conditions by using, for - 20 exa~ple, tetravalent manganese oxide material containing MnO2 or its equivalent.
Since New Caledonia lateritic ores contain nickel and cobalt as valuable metal values together with associated metal values, such as chromium, then these metals are also recovered together with chromium. Fol-, ,;, .
, , :
~7~
r" ~ . . ; . ` . ;. . . : . .
lU4~468 lowing leaching, the various metal values can be separa-ted by well known chemical precipitation techniques.
The leaching temperatures generally range from about 200C to 300C, e.g. about 230C to 280C, the t~m-perature preferably being about 250C, the retention time being usually one hour and higher. The superatmospheric pressure under which the leaching is conducted generally ranges from about 400 psig to 1000 psig.
The ore is slurried in an aqueous acid solu-tion of sulfuric acid at a pulp density of over about
2~/o so~ids and preferably from about 3~/O to 50~/O. The acid-to-ore ratio (dry ore) on the weight basis ranges from about 0.1 to 0.5. The MnO2 to ore ratio will vary with the ore but should be at least stoichiometrically sufficient to oxidize the chromium to the higher valence.
When the soluble chromium is leached from the nickel lateritic ores, the nickel and the cobalt extractions are very close to 100%, with the tails or leach residue meeting the specification requirements of iron ore. The iron tails can be subjected to such well known processes as pelletizing, roasting or other processes to produce acceptable iron ore material for the metallurgical produc-tion of steel.
Aa illustrative of the advantages of the in-vention, the following example is given:
, ,. ' ~
z , .
.
E
xample 1 An ore sample containing 1.44% Ni, 0.11% Co, 2.25% Cr, 0~80~o Mn, 44~2~/o Fe, each in the form of oxides and the balance oxides of silicon, aluminum, etc. is sized using a hydrocyclone to provide a size fraction of minus 10 microns, the size fraction constituting about ; 63% by weight of the total ore sample.
The chemical analysis of the size fraction as to the important metal values was as follows: 1.43% Ni, 0~04% CO, 0~90% Cr, 0.40% Mn and 48~0% Fe. The total chromium in the fines fraction includes both the soluble and insoluble chromium, the soluble chromium being over 90/O of the total chromium present.
A given weight of the fines fraction is formed into a leach pulp with a 35% solids content, the acid-to-`~ ore ratio being about 0~25 on the dry ore basis. The pulp was subjected to leaching in an autoclave for about one hour at 250C and a pressure of about 575 psig.
The soluble chromium leached out of the ore i 20 ~ corresponded to about 0.85% chromium in the fines frac-.
tion, the total chromium content in the fines fraction being 0.9/O. Thus, the ratio of the soluble chromium to the total chromium on the percent extraction basis cal-.
g , ,, , i , ,, . , i . , , ' ,' - , ' ' ~ ' ' ' ,. ' ', , , ' ' , , ' . ' ' ' .' ,,: . ' . ,, ' :, `
~044468 culates to about 94%. This results in an iron ore tail-ings containing 0.06% chromium, the iron content of the tailings being about 52%. This is acceptable ore grade.
By comparison, minus 400 mesh fraction of the ore was similarly treated. This fraction had a total chromium content of 1.32% of which 0.80% is soluble chro-mium. The ratio of soluble chromium to total chromium on the percent basis corresponds to only 61% of the total chromium. Leaching this fraction under the same condi-tions as above results in an iron ore residue assaying 0.57% chromium which is not acceptable grade where a substantially chromium-free product is desired.
In a size fraction ranging from about 65 to 400 mesh having a total chromium content of 7.48%~ of lS which 1~75% is soluble chromium, the iron ore residue ` resulting from the leach assayed about 6.3% chromium which renders the tailings even more unacceptable as iron ore for the recovery of iron therefrom.
In another fines fraction of minus 10 mi,~rons, all of the chromium was soluble, the amount assaying about 0.95%. The iron ore residue after leaching con-tained substantially no chromium.
The chromium in the ore is in the trivalent form and tends to hydrolyze when the emf values of the solution are reducing. However, hyflrolysis of Cr+3 czn be prevented at all pH vàlues if the solution emf values ,, ,,, ., .~, .. . . .
. , : ' ,,., " : :,. . . . . . . .
- . ... , ,.: , . : . . .
104~68 are sufficiently oxidizing, for example, by adding tetra-valent manganese ion (e.g. MnO2) or its equivalent, such as MnO4 or S208 . It takes 3 mols of Mn+4 to oxidize 2 mols of Cr+3 to 2 mols of Cr+6. Thus, the MnO2 addi-` 5 tion (or its equivalent) should be at least stoichio-metrically sufficient to oxidize the chromium to hexa-valent chromium. The ratio by weight of Mn to Cr may range from about 1.5:1 to 3:1. The stable chromium ion produced is Cr2O7 which is stable over a broad pH
range.
Thus, by leaching feed material in which sub-; ~tantially all of the chromium is soluble and by using oxidizing conditions to convert the chromium from the trivalent state to the hexavalent state, the leach resi-due will be practically free of chromium and provide an acceptable iron ore tailings. However, the chromium may be kept in the trivalent form where it is to be removed by precipitation following the chromium leaching step.
The foregoing method is applicable to nickel lateritic ores cQptaining: about 0.5% to 2.5% nickel;
about 0.05% to 1.0% cobalt; about 0.25% to 5.0/O manganese;
about 0.3% to 15% chromium; about 0.2% to 10% aluminum;
about 0.1% to 15% magnesium; about 2% to 45% silica (sio2);
and about 10% to 55% iron. The metal values are present as oxides.
. . .
,, , ... .. ,. ~ ......... .. .
. .
In removing the chromium by pressure leaching as described herein using an aqueous sulfuric acid solu-tion, generally at least 95% of the nickel and cobalt is removed with the soluble chromium together with amounts of manganese, aluminum, magnesium, etc. The chromium in this instance may be in the trivalent state.
The metal values are separated by methods well known in the art. For example, the pregnant liquor which has a low pH may be neutralized with coral mud to a pH
of about 2.5 to 2.8 and the nickel and cobalt removed by precipitation with H2S in an autoclave at about 122C and a pressure of about 150 psig. The sulfide precipitate is separated from the effluent chromium-containing solution for further treatment.
The effluent solution may then be adjusted to a pH of about 5.3 to precipitate chromium (trivalent), aluminum and any residual iron in solution. The chromium " can be recovered from the precipitate by any known method, such as by alumino-thermic smelting.
Any foreign ions remaining in solution following ~ ~he foregoing precipitation, such as lead, copper, zinc,-~ etc., can be separated by other precipitation techniques.
One method is to lower the pH of the solution to about l.S and then precipitate these metals as sulfides using H2S.
'J ' ' ' ' . , , " '', ' ,, ~,' ' ', ' ; ' , ' ' ' ' ' ' .
T~e important aspect of the invention resides in a technique for removing substantially all of the chromium from particulate ore which is first cut sized to provide a fines fraction in which substantially all S of the chromium is acid-soluble, such that the iron tail-ings remaining after the chromium leaching step is sub-qtantially chromium-free.
Where the chromium is recovered in the hexa-valent state (Cr2O7 ), it may be desirable to recover it selectively as a dichromate salt. One method for do-; ing this comprises passing the solution containing the chromium in the hexavalent state (to strip out such cations as Cr+3 and ~i+2) through cationic exchangers containing an ion exchange resin in which the active member is a ~;
; j 15 strongly acidic sulfonic acid type. Examples of such resins are: Dowex-50 which is a strongly acidic nuclea sulfonic acid type in a resin matrix of divinylbenzene;
Amberlite -200 which is defined as being strongly acidic sulfonated macroreticular, the resin being styrene divinyl-benzene; and Amberlite IR-120 which is a strongly acid ~ulfonic acid type cationic exchanger, with the resin a , polystyrene base. The effluent from this ion exchange sy~tem is then neutralized to pH 8, where the oxidizing potential of the solution is so low that little oxidation : ' .
' -13-. , , - 104~68 of an anion resin can occur. The neutralized solution is then treated with an anion exchange resin. When the anion resin is saturated with chromium, it is eluted with sodium hydroxide solution to produce a three percent solution of sodium chromate.
Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and the appended claims.
, .. .. .
When the soluble chromium is leached from the nickel lateritic ores, the nickel and the cobalt extractions are very close to 100%, with the tails or leach residue meeting the specification requirements of iron ore. The iron tails can be subjected to such well known processes as pelletizing, roasting or other processes to produce acceptable iron ore material for the metallurgical produc-tion of steel.
Aa illustrative of the advantages of the in-vention, the following example is given:
, ,. ' ~
z , .
.
E
xample 1 An ore sample containing 1.44% Ni, 0.11% Co, 2.25% Cr, 0~80~o Mn, 44~2~/o Fe, each in the form of oxides and the balance oxides of silicon, aluminum, etc. is sized using a hydrocyclone to provide a size fraction of minus 10 microns, the size fraction constituting about ; 63% by weight of the total ore sample.
The chemical analysis of the size fraction as to the important metal values was as follows: 1.43% Ni, 0~04% CO, 0~90% Cr, 0.40% Mn and 48~0% Fe. The total chromium in the fines fraction includes both the soluble and insoluble chromium, the soluble chromium being over 90/O of the total chromium present.
A given weight of the fines fraction is formed into a leach pulp with a 35% solids content, the acid-to-`~ ore ratio being about 0~25 on the dry ore basis. The pulp was subjected to leaching in an autoclave for about one hour at 250C and a pressure of about 575 psig.
The soluble chromium leached out of the ore i 20 ~ corresponded to about 0.85% chromium in the fines frac-.
tion, the total chromium content in the fines fraction being 0.9/O. Thus, the ratio of the soluble chromium to the total chromium on the percent extraction basis cal-.
g , ,, , i , ,, . , i . , , ' ,' - , ' ' ~ ' ' ' ,. ' ', , , ' ' , , ' . ' ' ' .' ,,: . ' . ,, ' :, `
~044468 culates to about 94%. This results in an iron ore tail-ings containing 0.06% chromium, the iron content of the tailings being about 52%. This is acceptable ore grade.
By comparison, minus 400 mesh fraction of the ore was similarly treated. This fraction had a total chromium content of 1.32% of which 0.80% is soluble chro-mium. The ratio of soluble chromium to total chromium on the percent basis corresponds to only 61% of the total chromium. Leaching this fraction under the same condi-tions as above results in an iron ore residue assaying 0.57% chromium which is not acceptable grade where a substantially chromium-free product is desired.
In a size fraction ranging from about 65 to 400 mesh having a total chromium content of 7.48%~ of lS which 1~75% is soluble chromium, the iron ore residue ` resulting from the leach assayed about 6.3% chromium which renders the tailings even more unacceptable as iron ore for the recovery of iron therefrom.
In another fines fraction of minus 10 mi,~rons, all of the chromium was soluble, the amount assaying about 0.95%. The iron ore residue after leaching con-tained substantially no chromium.
The chromium in the ore is in the trivalent form and tends to hydrolyze when the emf values of the solution are reducing. However, hyflrolysis of Cr+3 czn be prevented at all pH vàlues if the solution emf values ,, ,,, ., .~, .. . . .
. , : ' ,,., " : :,. . . . . . . .
- . ... , ,.: , . : . . .
104~68 are sufficiently oxidizing, for example, by adding tetra-valent manganese ion (e.g. MnO2) or its equivalent, such as MnO4 or S208 . It takes 3 mols of Mn+4 to oxidize 2 mols of Cr+3 to 2 mols of Cr+6. Thus, the MnO2 addi-` 5 tion (or its equivalent) should be at least stoichio-metrically sufficient to oxidize the chromium to hexa-valent chromium. The ratio by weight of Mn to Cr may range from about 1.5:1 to 3:1. The stable chromium ion produced is Cr2O7 which is stable over a broad pH
range.
Thus, by leaching feed material in which sub-; ~tantially all of the chromium is soluble and by using oxidizing conditions to convert the chromium from the trivalent state to the hexavalent state, the leach resi-due will be practically free of chromium and provide an acceptable iron ore tailings. However, the chromium may be kept in the trivalent form where it is to be removed by precipitation following the chromium leaching step.
The foregoing method is applicable to nickel lateritic ores cQptaining: about 0.5% to 2.5% nickel;
about 0.05% to 1.0% cobalt; about 0.25% to 5.0/O manganese;
about 0.3% to 15% chromium; about 0.2% to 10% aluminum;
about 0.1% to 15% magnesium; about 2% to 45% silica (sio2);
and about 10% to 55% iron. The metal values are present as oxides.
. . .
,, , ... .. ,. ~ ......... .. .
. .
In removing the chromium by pressure leaching as described herein using an aqueous sulfuric acid solu-tion, generally at least 95% of the nickel and cobalt is removed with the soluble chromium together with amounts of manganese, aluminum, magnesium, etc. The chromium in this instance may be in the trivalent state.
The metal values are separated by methods well known in the art. For example, the pregnant liquor which has a low pH may be neutralized with coral mud to a pH
of about 2.5 to 2.8 and the nickel and cobalt removed by precipitation with H2S in an autoclave at about 122C and a pressure of about 150 psig. The sulfide precipitate is separated from the effluent chromium-containing solution for further treatment.
The effluent solution may then be adjusted to a pH of about 5.3 to precipitate chromium (trivalent), aluminum and any residual iron in solution. The chromium " can be recovered from the precipitate by any known method, such as by alumino-thermic smelting.
Any foreign ions remaining in solution following ~ ~he foregoing precipitation, such as lead, copper, zinc,-~ etc., can be separated by other precipitation techniques.
One method is to lower the pH of the solution to about l.S and then precipitate these metals as sulfides using H2S.
'J ' ' ' ' . , , " '', ' ,, ~,' ' ', ' ; ' , ' ' ' ' ' ' .
T~e important aspect of the invention resides in a technique for removing substantially all of the chromium from particulate ore which is first cut sized to provide a fines fraction in which substantially all S of the chromium is acid-soluble, such that the iron tail-ings remaining after the chromium leaching step is sub-qtantially chromium-free.
Where the chromium is recovered in the hexa-valent state (Cr2O7 ), it may be desirable to recover it selectively as a dichromate salt. One method for do-; ing this comprises passing the solution containing the chromium in the hexavalent state (to strip out such cations as Cr+3 and ~i+2) through cationic exchangers containing an ion exchange resin in which the active member is a ~;
; j 15 strongly acidic sulfonic acid type. Examples of such resins are: Dowex-50 which is a strongly acidic nuclea sulfonic acid type in a resin matrix of divinylbenzene;
Amberlite -200 which is defined as being strongly acidic sulfonated macroreticular, the resin being styrene divinyl-benzene; and Amberlite IR-120 which is a strongly acid ~ulfonic acid type cationic exchanger, with the resin a , polystyrene base. The effluent from this ion exchange sy~tem is then neutralized to pH 8, where the oxidizing potential of the solution is so low that little oxidation : ' .
' -13-. , , - 104~68 of an anion resin can occur. The neutralized solution is then treated with an anion exchange resin. When the anion resin is saturated with chromium, it is eluted with sodium hydroxide solution to produce a three percent solution of sodium chromate.
Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and the appended claims.
, .. .. .
Claims (11)
1. A method of separating chromium from particulate lateritic ore containing substantial amounts of iron and pro-duce a purified iron ore tailing which comprises, sizing said particulate ore to provide a size fraction of fines of less than about 20 microns in size in which substantially all of the chro-mium therein is acid-soluble, forming an aqueous slurry of said ore contain-ing over 20% solids and an amount of sulfuric acid corresponding to about 0.1 to 0.5 parts by weight of said ore, subjecting said slurry to pressure leaching at an elevated pressure of about 400 to 1000 psig and temperature of about 200°C to 300°C for a time sufficient to remove said soluble chromium from said ore to provide an iron-containing residue and a pregnant liquor containing metal values, separating said pregnant liquor from said residue, and then washing said residue to produce a puri-fied iron ore-containing tailing with less than about 0.2% chromium.
2. The method of claim 1, wherein the ore con-tains nickel and cobalt, and wherein substantially all of said nickel and cobalt is leached from said ore together with the soluble chromium.
3. The method of claim 2, wherein said ore contains about 0.5% to 2.5% nickel, about 0.05% to 1.0% cobalt, about 0.25 to 5.0% manganese, about 0.3% to 15% chromium, about 0.2% to 10% aluminum, about 0.1% to 15% magnesium, about 2% to 45% silica (SiO2) and about 10% to 55% iron.
4. The method of claim 3, wherein the following said leaching, the nickel and cobalt are selectively separated from said solution to provide an effluent solution contain-ing said chromium.
5. The method of claim 4, wherein said chromium is then recovered from said effluent solution.
6. A method of separating chromium from particulate lateritic ore-containing iron and produce an iron ore tailing which comprises, sizing said particulate ore to provide a size fraction of fines of less than about 20 microns in size in which substantially all of the chromium therein is acid soluble, adding an oxidizing agent to said ore in an amount at least stoichiometrically sufficient to oxidize said chromium to the hexavalent state, forming an aqueous slurry of said ore containing over 20% solids and an amount of sulfuric acid corresponding to about 0.1 to 0.5 parts be weight of said ore, subjecting said slurry to pressure leaching at an elevated pressure of about 400 to 1000 psig and temperature of about 200°C to 300°C for a time sufficient to remove said soluble chromium from said ore to provide an iron-containing resi-due and a pregnant liquor containing metal values, separating said pregnant liquor from said residue, and then washing said residue to produce a purified iron ore tailing containing less than 0.2% chromium.
7. The method of claim 6, wherein the oxidizing agent is selected from the group consisting of Mn+4, Mno4-1 or S2O8-2.
8. The method of claim 7, wherein the ore con-tains nickel and cobalt, and wherein substantially all of said nickel and cobalt is leached from said ore together with the soluble chromium.
9. The method of claim 8, wherein said ore con-tains about 0.5% to 2.5% nickel, about 0.05% to 1.0% cobalt, about 0.25% to 5.0% manganese, about 0.3% to 15% chromium, about 0.2% to 10% aluminum, about 0.1% to 15% magnesium, about 2% to 45% silica (SiO2) and about 10% to 55% iron.
10. The method of claim 9, wherein following said leaching, the nickel and cobalt are selectively sepa-rated from said solution to provide an effluent solution containing said chromium.
11. The method of claim 10, wherein said chromium is then recovered from said effluent solution.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US50841974A | 1974-09-23 | 1974-09-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1044468A true CA1044468A (en) | 1978-12-19 |
Family
ID=24022671
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA233,856A Expired CA1044468A (en) | 1974-09-23 | 1975-08-21 | Extracting of iron ore and chromium from nickel lateritic ores |
Country Status (10)
| Country | Link |
|---|---|
| JP (1) | JPS5156720A (en) |
| BR (1) | BR7505992A (en) |
| CA (1) | CA1044468A (en) |
| CU (1) | CU34351A (en) |
| DE (1) | DE2542214A1 (en) |
| FR (1) | FR2285466A1 (en) |
| NO (1) | NO141657C (en) |
| PH (1) | PH16954A (en) |
| SE (1) | SE406775B (en) |
| ZA (1) | ZA755496B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5421858A (en) * | 1991-10-30 | 1995-06-06 | Novagold Resources Inc. | Ore feed heating |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP6661926B2 (en) * | 2015-09-08 | 2020-03-11 | 住友金属鉱山株式会社 | Method of treating ore slurry, method of hydrometallurgy of nickel oxide ore |
| US10583301B2 (en) | 2016-11-08 | 2020-03-10 | Cardiac Pacemakers, Inc. | Implantable medical device for atrial deployment |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3082080A (en) * | 1960-05-02 | 1963-03-19 | Freeport Sulphur Co | Leaching of chromium, nickel, cobalt and manganese from ores |
-
1975
- 1975-08-21 CA CA233,856A patent/CA1044468A/en not_active Expired
- 1975-08-27 ZA ZA00755496A patent/ZA755496B/en unknown
- 1975-09-16 PH PH17577A patent/PH16954A/en unknown
- 1975-09-17 BR BR7505992A patent/BR7505992A/en unknown
- 1975-09-19 FR FR7528710A patent/FR2285466A1/en active Granted
- 1975-09-22 NO NO753224A patent/NO141657C/en unknown
- 1975-09-22 DE DE19752542214 patent/DE2542214A1/en not_active Ceased
- 1975-09-22 SE SE7510577A patent/SE406775B/en unknown
- 1975-09-23 CU CU34351A patent/CU34351A/en unknown
- 1975-09-23 JP JP11435575A patent/JPS5156720A/en active Granted
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5421858A (en) * | 1991-10-30 | 1995-06-06 | Novagold Resources Inc. | Ore feed heating |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5156720A (en) | 1976-05-18 |
| FR2285466A1 (en) | 1976-04-16 |
| NO753224L (en) | 1976-03-24 |
| SE406775B (en) | 1979-02-26 |
| NO141657B (en) | 1980-01-07 |
| FR2285466B1 (en) | 1980-08-14 |
| AU8425875A (en) | 1977-03-03 |
| SE7510577L (en) | 1976-03-24 |
| JPS576501B2 (en) | 1982-02-05 |
| NO141657C (en) | 1980-04-16 |
| CU34351A (en) | 1980-10-30 |
| ZA755496B (en) | 1976-07-28 |
| PH16954A (en) | 1984-04-27 |
| BR7505992A (en) | 1976-08-03 |
| DE2542214A1 (en) | 1976-04-08 |
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