CA1210593A - Process for the sulfatization of non-ferrous metal sulfides - Google Patents
Process for the sulfatization of non-ferrous metal sulfidesInfo
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- CA1210593A CA1210593A CA000425215A CA425215A CA1210593A CA 1210593 A CA1210593 A CA 1210593A CA 000425215 A CA000425215 A CA 000425215A CA 425215 A CA425215 A CA 425215A CA 1210593 A CA1210593 A CA 1210593A
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- ferrous metal
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Abstract
PROCESS FOR THE SULFATIZATION OF
NON-FERROUS METAL SULFIDES
Abstract of the Invention In the extraction of certain non-ferrous metals from their sulfide ores by a process where these sulfides are converted to water soluble sulfates by roasting, alkali metal carbonate or bicarbonate, especially sodium carbonate, is added to the roaster feed to promote the sulfatization reaction. Ores containing copper, nickel, cobalt or zinc sulfides are concentrated by froth flotation, the concentrate mixed with carbonate or bicarbonate and roasted. the roasted product is mixed with water to separate these metals as soluble sulfates from iron compounds and other solid residue. The sulfate solution is filtered from the solids and the non ferrous metals recovered by precipitation or electrolysis.
NON-FERROUS METAL SULFIDES
Abstract of the Invention In the extraction of certain non-ferrous metals from their sulfide ores by a process where these sulfides are converted to water soluble sulfates by roasting, alkali metal carbonate or bicarbonate, especially sodium carbonate, is added to the roaster feed to promote the sulfatization reaction. Ores containing copper, nickel, cobalt or zinc sulfides are concentrated by froth flotation, the concentrate mixed with carbonate or bicarbonate and roasted. the roasted product is mixed with water to separate these metals as soluble sulfates from iron compounds and other solid residue. The sulfate solution is filtered from the solids and the non ferrous metals recovered by precipitation or electrolysis.
Description
- ~2~0593 .
.... 1 --PROC~S ~OR ~HE SU~FA~IZA~IO~ O~
: ~0~-~3RROUS M~TA~ SU~FlDES
~ield of the Invention This invention is concerned with the extraction o, certain non-ferrous metals from their ores and more particularly with a process for the sulfatization of such metal values from their sulfide ores.
~ac~ground of the In~ention Metals are commonly extracted from their ores by processes in which the minerals are concentrated and .the concentrate roasted to convert complex or otherwise difficult-to-extract metal compounds into compounds which can more easily be separated for recovery of the metal content.
In one such process, applicable to sul~ide minerals, sulfide~ are converted by roastlng into water soluble sulfates which may readily be recovered by leaching with water.
It is generally agreed that the mechanism involved in converting sulfides to sulfates proceeds via an oxide as follows:
MS + 3/2 2 ~ MO + S02 (1) S02 + 1/2 2 so3 -(2) MO + S03 ~ 4 wherein M represents metal. (See Palperi, M. and Aaltonen, O., Sul~atizing Roasting and ~eaching o~ Cobalt Ores at Outokumpu Oy, Journal o~ Metals, February 1971, pP--34~
. . For the sulfatization ~rocess to be economicaI, suf~iciently high ~per.centages o~ the metals must be converted under reasonable operating conditions to easily extractable water soluble sulfates while other, undesired materials remain insoluble. In particular, it is important that the iron content of the ore remains ~5 insoluble so that it can easily be disposed of as a solid by-product, rather than being leached as a water soluble ~210593 product which wculd require subsequent, difficult separation and disposal steps. ---Some of the desired non-ferrous metals in sulfide ores can be difficult to recover as water soluble sulfates in the sulfatization process. ~ickel in particular is difficult ~to sulfatize efficiently.
- Attempts to sulfatize nic~el sulfides were unsuccessful until ~hornhill, in U.~. Patents 2,81~,015 and 2,81~,016, showed that the addition of sodium sulfate to the roaster feed promoted the sulfatization of nickel sulfide. The sodium sulfate is used to control particle size in a fluidized bed and is said to render unstable the nickel ferrites in pyrrhotite according to the following equation:
~i~e204 + ~a2S4 ~ ~a~e204 + ~i~04 (4) - ., . -- . . . . . . . .
~hese patents also describe- sodium sulfate taking part in reactions providing sodium pyrosulfate, a strong sulfating agent, and sulfur trioxide for sulfatization of the metal oxide:
~a2S04 + ~03 ~ ~a2S2o7 (5) NiO + ~0 ` NiSO (6) ~ 4 lhus, these -patents demonstrate the addition of a sulfate material as a requirement to enhance the sulfatization of nickel. While the use of sodium sulf~te in the roast does provide significant improvement--in the-amount-o~ metal extracted as water soluble sulfate~ the percentage of such metal extracted from the raw material needs to be increased for improved process economics.
Unfortunately, the addition of sodium sulfate to the roaster increases the sulfur content of the roast and contributes to the generation of sulfur dioxide and sulfur trioxide gases during the roasting procedure.
~21059;~
. .
~his is undesirable because these gases are subject to pollution control regulations so tha~ increasing their quantity in the off gases increases the cost of pollution control and thereby 'also increases the cost of the extraction process.
At-tempts have been made to decrease the amount of toxic sulfur gases liberated in the sulfatization process. In U.S. Patent I~o. 3,791,812, copper, nic~el, cobalt and manganese are extracted as water soluble salts from sulfide oreæ by roasting the ore in the presence of sodium chloride. ~he use of sodium sul~'ate is'avoided and the amount of sulfur dioxide in the off gases is reduced by conducting the roasting in at least two stage~' ana using sulfur dioxide liberated in the first stage as a sulfatizing agent in a subsequent stage.
~nfortuna~ely, iron as well as~~the nsn-ferrous metals is extrac~ed as a ~water soluble s~alt, necessitating the expense of further separation steps to remove the iron.
Other alkali metal salts beside~ sodium sulfate and chloride have been used in the extraction o~ non-~errous metals from their ores~ U.~. Patent No. 2,775,517 discloses a process for separating nickel from low sulfur content iron oxide ores. The ore is roasted with alkali, such as sodium hydroxide, carbonate or bicarbonate and the roasted product leached with water to extract chromium and aluminum. ~he nickel remains in a water insoluble state and is subsequently removed by treatment in an auto~lave 'with ferric or ferrous chloride or ~ sulfate. ~his process'is not æ sulfatization process ~0 because t~e raw ma~eri'al is not a sulfide ore. The process suffers from the disadvantages that the nickel is not converted into a readily-leachable, water soluble - salt and that an autoclave is required, thereby increasing plant and operating costs and processing complexity.
, 32105~3 ~ here is, therefore, a need for a process or extracting non-ferrous metals from sulfide ores by sulfatization of such metals into readily leachable salts which extracts high percentages of the metals in the ore in an economical and environmentally acceptable process~
Summary of the Invention -We have now found that these objectives may be achie~ed by including alkali metal carbonate or bicarbonate in the sulfatizing roast. It is quite unexpected that the addition of carbonate should have this effect since ~hornhill's hypothesis, mentioned above, clearly requires the addition of sul~ate material. Moreover, we ha~e surprisingly found that the addition of carbonate material in this invention still forms water soluble sulfate3 in the sulfatizatiorl process rather than soluble carbonate-products. Utilization of a - carbonate or bicarbonate additive, instead of a sulfate, eliminates the addition of further sulfur to the roast and improves the sulfatization process and in doing so uses more of the natural sulfur in the sulfides in the ore and produces less sulfur-containin~ off gases. ln addition, the additives in this invention are less expensive~ ~oaium carbonate, for example, - is less expensi~e on a bulk scale than sodium sul~ate.
According to the invention there is provided a process for the sulfatization of non-ferrous metal sulfide which comprises roasting sulfide mineral containing said metal sulfide in the presence of alkali metal carbonate or bicarbonate and coverting at least a portion of saia metal suIf;ae into water soluble non-ferrous metal sulfate.
In one embodiment of the invention, the sulfatization process is used in a process for the extraction of non-ferrous metal from sulfide mineral containing non-ferrous metal sulfide. ~he extraction process ~o~sa comprises roasting the mineral in the presence of alkali metal carbonate or bicarbonate and converting at least a portion of the non-ferrous metal sullide into water soluble, non-ferrous metal sulfate. The roasted product containing the soluble sulfate is washed with water to leach out the soluble met~al sulfate from the solid materials and the non-ferrous metal content of the sulfate solution is recovered.
~he process - of the invention is particularly applicable to the sulfatization of at least one o~
cobalt, copper, nickel and zinc.
In the process of the invention, a sulfide ore, such as a low grade copper-nickel-cobalt ore, is milled to reduce the particle size of the ore and then, preferably, concen~rated such as by flotation. Alkali metal carbonate or bicarbonate is mixed with dried concentrate -- -~- or ore and the ~ixture is fed to a furnace for roasting.
Typical roasting conditions are a temperature of from about 400C. to 650C., ~enerally including a period at about 550C. to 630C., and a time of from 2 to 6 hours. ~he roasted material is allowed to cool and the soluble sulfates leached into solution by washing the roasted product with water. The sulfate solution is separated from insoluble residues by filtration and the metal values recovered by conventional means such as solvent extraction and electrowinning.
~rief Description of the Drawings - ~I&URE 1 is a flowsheet illustrating the steps in the p~ocess of the invention~
30FI~URE 2 is a flo~sheet illustra'ing representative changes in chemical composition of the products through the steps of the process of the invention;
~IGURE 3 is a graph showing the effect of roasting temperature on the extraction of copper, iron and nickel in the process of the invention.
~210S93 Detailed Description of the Preferred ~mbodiments Referring to ~igure 1, the process of the invention uses sulfide ore as the raw material. ~he ore contains one or more of the metals copper, cobalt, nickel and zinc and may be a high or low grade ore. ~he process is economically attractive for use on low grade ores and for this reason such ores are the preferred starting material. Preferred ores include copper-nickel-cobalt and copper-lead-zinc sulfide ores. A typîcal low grade copper-nic~el-cobalt ore is illustrated as the starting - material in Figure 2 and contains approximately 0.4%
copper, 0.4~ nickel, 0.04~ cobalt, 23% iron and 12%
sulfur. All percentages herein are by weight unless otherwise specified.
15The ore is milled by conventional methods to a suitable particle size and then--concentrated with respect - -to sulfide minerals. ~he concentration step is-- not , . . . ., . - . ..
necessary in order to achieve optimum response with the roasting process of the invention. While unconcentrated ores may be used in the process of this invention it is preferred that the ore be concentrated as shown in ~igure 1. ~he concentration process is simply a case of processing economics. Ideally, through the concentration process, a considerable P~ount of ore weight will be rejected with only a minor loss in metal values. In the process depicted in ~igure 2, flotætion concentration recovers 83% of the copper, 79% of the nickel and 79% of - the cobalt in 15% of the original ore weight. With the . .
concentrate representing onIy t5~- of~ the weight of the original feed ore, a considerable reduction in capital and operating costs in the subsequent treatment stages is realized. In the ore exemplified in ~igure 2, it can be seen that the concentration process substantially increases the percentage content of non-ferrous metals and therefore provides a material for subsequent ~210593 processing fro~ which it is easier to extract the desired metals. Of the yarious concentration techniques available, froth flotation has been found to yield the best metallurgical results with this particular ore.
~he concentrate may then be ground to further reduce the particle size and is aried, for example at about 120C. Alkali metal carbonate or bicarbonate is mixed with the dried concentrate, pre~erabl-y in an amou~t of from 5% to 50%, more preferably from about 10 to 20%, based on the weight of dry concentrate, or ore if the concentration step is omitted.
Sodium or potassium carbonates or bicarbonates may be - used as the al~ali metal additive. ~he sodium compounds are preferred, particularly sodium carbonate which has been found to provide optimum results while being ~elatively inexpensive and readily obtainable.
- The carbonate-concentrate mixture is fed to~a furnace for roasting to convert the metal sulfides to sulfates.
During roasting the roast may be rabbled periodically to maximize reaction.
Reactions for some typical sulfide minerals ores ar~e show~ below:
.... 1 --PROC~S ~OR ~HE SU~FA~IZA~IO~ O~
: ~0~-~3RROUS M~TA~ SU~FlDES
~ield of the Invention This invention is concerned with the extraction o, certain non-ferrous metals from their ores and more particularly with a process for the sulfatization of such metal values from their sulfide ores.
~ac~ground of the In~ention Metals are commonly extracted from their ores by processes in which the minerals are concentrated and .the concentrate roasted to convert complex or otherwise difficult-to-extract metal compounds into compounds which can more easily be separated for recovery of the metal content.
In one such process, applicable to sul~ide minerals, sulfide~ are converted by roastlng into water soluble sulfates which may readily be recovered by leaching with water.
It is generally agreed that the mechanism involved in converting sulfides to sulfates proceeds via an oxide as follows:
MS + 3/2 2 ~ MO + S02 (1) S02 + 1/2 2 so3 -(2) MO + S03 ~ 4 wherein M represents metal. (See Palperi, M. and Aaltonen, O., Sul~atizing Roasting and ~eaching o~ Cobalt Ores at Outokumpu Oy, Journal o~ Metals, February 1971, pP--34~
. . For the sulfatization ~rocess to be economicaI, suf~iciently high ~per.centages o~ the metals must be converted under reasonable operating conditions to easily extractable water soluble sulfates while other, undesired materials remain insoluble. In particular, it is important that the iron content of the ore remains ~5 insoluble so that it can easily be disposed of as a solid by-product, rather than being leached as a water soluble ~210593 product which wculd require subsequent, difficult separation and disposal steps. ---Some of the desired non-ferrous metals in sulfide ores can be difficult to recover as water soluble sulfates in the sulfatization process. ~ickel in particular is difficult ~to sulfatize efficiently.
- Attempts to sulfatize nic~el sulfides were unsuccessful until ~hornhill, in U.~. Patents 2,81~,015 and 2,81~,016, showed that the addition of sodium sulfate to the roaster feed promoted the sulfatization of nickel sulfide. The sodium sulfate is used to control particle size in a fluidized bed and is said to render unstable the nickel ferrites in pyrrhotite according to the following equation:
~i~e204 + ~a2S4 ~ ~a~e204 + ~i~04 (4) - ., . -- . . . . . . . .
~hese patents also describe- sodium sulfate taking part in reactions providing sodium pyrosulfate, a strong sulfating agent, and sulfur trioxide for sulfatization of the metal oxide:
~a2S04 + ~03 ~ ~a2S2o7 (5) NiO + ~0 ` NiSO (6) ~ 4 lhus, these -patents demonstrate the addition of a sulfate material as a requirement to enhance the sulfatization of nickel. While the use of sodium sulf~te in the roast does provide significant improvement--in the-amount-o~ metal extracted as water soluble sulfate~ the percentage of such metal extracted from the raw material needs to be increased for improved process economics.
Unfortunately, the addition of sodium sulfate to the roaster increases the sulfur content of the roast and contributes to the generation of sulfur dioxide and sulfur trioxide gases during the roasting procedure.
~21059;~
. .
~his is undesirable because these gases are subject to pollution control regulations so tha~ increasing their quantity in the off gases increases the cost of pollution control and thereby 'also increases the cost of the extraction process.
At-tempts have been made to decrease the amount of toxic sulfur gases liberated in the sulfatization process. In U.S. Patent I~o. 3,791,812, copper, nic~el, cobalt and manganese are extracted as water soluble salts from sulfide oreæ by roasting the ore in the presence of sodium chloride. ~he use of sodium sul~'ate is'avoided and the amount of sulfur dioxide in the off gases is reduced by conducting the roasting in at least two stage~' ana using sulfur dioxide liberated in the first stage as a sulfatizing agent in a subsequent stage.
~nfortuna~ely, iron as well as~~the nsn-ferrous metals is extrac~ed as a ~water soluble s~alt, necessitating the expense of further separation steps to remove the iron.
Other alkali metal salts beside~ sodium sulfate and chloride have been used in the extraction o~ non-~errous metals from their ores~ U.~. Patent No. 2,775,517 discloses a process for separating nickel from low sulfur content iron oxide ores. The ore is roasted with alkali, such as sodium hydroxide, carbonate or bicarbonate and the roasted product leached with water to extract chromium and aluminum. ~he nickel remains in a water insoluble state and is subsequently removed by treatment in an auto~lave 'with ferric or ferrous chloride or ~ sulfate. ~his process'is not æ sulfatization process ~0 because t~e raw ma~eri'al is not a sulfide ore. The process suffers from the disadvantages that the nickel is not converted into a readily-leachable, water soluble - salt and that an autoclave is required, thereby increasing plant and operating costs and processing complexity.
, 32105~3 ~ here is, therefore, a need for a process or extracting non-ferrous metals from sulfide ores by sulfatization of such metals into readily leachable salts which extracts high percentages of the metals in the ore in an economical and environmentally acceptable process~
Summary of the Invention -We have now found that these objectives may be achie~ed by including alkali metal carbonate or bicarbonate in the sulfatizing roast. It is quite unexpected that the addition of carbonate should have this effect since ~hornhill's hypothesis, mentioned above, clearly requires the addition of sul~ate material. Moreover, we ha~e surprisingly found that the addition of carbonate material in this invention still forms water soluble sulfate3 in the sulfatizatiorl process rather than soluble carbonate-products. Utilization of a - carbonate or bicarbonate additive, instead of a sulfate, eliminates the addition of further sulfur to the roast and improves the sulfatization process and in doing so uses more of the natural sulfur in the sulfides in the ore and produces less sulfur-containin~ off gases. ln addition, the additives in this invention are less expensive~ ~oaium carbonate, for example, - is less expensi~e on a bulk scale than sodium sul~ate.
According to the invention there is provided a process for the sulfatization of non-ferrous metal sulfide which comprises roasting sulfide mineral containing said metal sulfide in the presence of alkali metal carbonate or bicarbonate and coverting at least a portion of saia metal suIf;ae into water soluble non-ferrous metal sulfate.
In one embodiment of the invention, the sulfatization process is used in a process for the extraction of non-ferrous metal from sulfide mineral containing non-ferrous metal sulfide. ~he extraction process ~o~sa comprises roasting the mineral in the presence of alkali metal carbonate or bicarbonate and converting at least a portion of the non-ferrous metal sullide into water soluble, non-ferrous metal sulfate. The roasted product containing the soluble sulfate is washed with water to leach out the soluble met~al sulfate from the solid materials and the non-ferrous metal content of the sulfate solution is recovered.
~he process - of the invention is particularly applicable to the sulfatization of at least one o~
cobalt, copper, nickel and zinc.
In the process of the invention, a sulfide ore, such as a low grade copper-nickel-cobalt ore, is milled to reduce the particle size of the ore and then, preferably, concen~rated such as by flotation. Alkali metal carbonate or bicarbonate is mixed with dried concentrate -- -~- or ore and the ~ixture is fed to a furnace for roasting.
Typical roasting conditions are a temperature of from about 400C. to 650C., ~enerally including a period at about 550C. to 630C., and a time of from 2 to 6 hours. ~he roasted material is allowed to cool and the soluble sulfates leached into solution by washing the roasted product with water. The sulfate solution is separated from insoluble residues by filtration and the metal values recovered by conventional means such as solvent extraction and electrowinning.
~rief Description of the Drawings - ~I&URE 1 is a flowsheet illustrating the steps in the p~ocess of the invention~
30FI~URE 2 is a flo~sheet illustra'ing representative changes in chemical composition of the products through the steps of the process of the invention;
~IGURE 3 is a graph showing the effect of roasting temperature on the extraction of copper, iron and nickel in the process of the invention.
~210S93 Detailed Description of the Preferred ~mbodiments Referring to ~igure 1, the process of the invention uses sulfide ore as the raw material. ~he ore contains one or more of the metals copper, cobalt, nickel and zinc and may be a high or low grade ore. ~he process is economically attractive for use on low grade ores and for this reason such ores are the preferred starting material. Preferred ores include copper-nickel-cobalt and copper-lead-zinc sulfide ores. A typîcal low grade copper-nic~el-cobalt ore is illustrated as the starting - material in Figure 2 and contains approximately 0.4%
copper, 0.4~ nickel, 0.04~ cobalt, 23% iron and 12%
sulfur. All percentages herein are by weight unless otherwise specified.
15The ore is milled by conventional methods to a suitable particle size and then--concentrated with respect - -to sulfide minerals. ~he concentration step is-- not , . . . ., . - . ..
necessary in order to achieve optimum response with the roasting process of the invention. While unconcentrated ores may be used in the process of this invention it is preferred that the ore be concentrated as shown in ~igure 1. ~he concentration process is simply a case of processing economics. Ideally, through the concentration process, a considerable P~ount of ore weight will be rejected with only a minor loss in metal values. In the process depicted in ~igure 2, flotætion concentration recovers 83% of the copper, 79% of the nickel and 79% of - the cobalt in 15% of the original ore weight. With the . .
concentrate representing onIy t5~- of~ the weight of the original feed ore, a considerable reduction in capital and operating costs in the subsequent treatment stages is realized. In the ore exemplified in ~igure 2, it can be seen that the concentration process substantially increases the percentage content of non-ferrous metals and therefore provides a material for subsequent ~210593 processing fro~ which it is easier to extract the desired metals. Of the yarious concentration techniques available, froth flotation has been found to yield the best metallurgical results with this particular ore.
~he concentrate may then be ground to further reduce the particle size and is aried, for example at about 120C. Alkali metal carbonate or bicarbonate is mixed with the dried concentrate, pre~erabl-y in an amou~t of from 5% to 50%, more preferably from about 10 to 20%, based on the weight of dry concentrate, or ore if the concentration step is omitted.
Sodium or potassium carbonates or bicarbonates may be - used as the al~ali metal additive. ~he sodium compounds are preferred, particularly sodium carbonate which has been found to provide optimum results while being ~elatively inexpensive and readily obtainable.
- The carbonate-concentrate mixture is fed to~a furnace for roasting to convert the metal sulfides to sulfates.
During roasting the roast may be rabbled periodically to maximize reaction.
Reactions for some typical sulfide minerals ores ar~e show~ below:
2 CuFeS2 ~ 6 /2 2 -~ 2CuO ~ Fe203 + 4S02 (7) CuO + ~03 ~ CuS04 (8) 2(Ni,Fe)S + 4l/2 2 --~ 2~iO + Fe203 + 2S02 - (9) (assu~ing equiualent quantities of Ni and Fe) I~iO ~ S~ iS04 (tO~
,~0 ,. . ~ . . . . -2~eS ~ 3 /2 2~ 2 3 2 (11) Fe203 + ~SO~ ~ Fe2(S04)3 (12) . . .
~12~0593 Roasting temperature is dictated by the decomposition temperatures of the sulfates of the metals to be extractea. Optimwm temperatures for the conversion of the mineral sulfides to the sulfate state (for a given roasting time and atmospheric condition) exist when the decomposition temperatures are approached. ~y maintaining the reaction temperature either ~elow or above the decomposition temperature, more or less of the particular sul~ate can be obtained. ~his characteristic provides the means for setting conditions that theoretically will selectively sulfatize the non-ferreus metal values, such as Cu, Co, ~i and Zn9 while the iron sulfates are decomposed. However, when a sulfatizing roast is conducted on several different sulfide minerals, even under optimum roasting conditions, only a partial sulfatization is effected and the metallurgical response of the copper and cobalt sulfides is mu`ch more ~avorable than the response of the nickel sulfides. Similarly, in practice, decomposition of the iron sulfates is not ideal since decomposition is usually incomplete and therefore it is important that the leaching step extracts the maximum amount of non-ferrous wa~er soluble sulfates but the minimum amount of iron sulfates.
Accordingly, the temperatures used in the process of this inventibn depend on the metal or metals to be extracted. Where an individual m~tal is to be extracted, the temperature will approach the decomposition temperature of the sulfate of thæt metal. Where a number of metals are to be~ extracted~ as is usuall~ the case, the temperature will approach the lowest decomposition temperature of the metal sulfates in question. lhe energetic decomposition temperatures of ~eSO~, ZnS04~
CuS04, CoS04 and NiS04 are 480, 600 , 670 , 735 and 764C., respectively (~odgman, C.D. ed.
Handbook of Chemistry and Physics~ 37th edition, 1955, p.
~Z~0593 g 1812 and 48th edition, 1967 pp. ~-172, -241). Preferred roasting temperatures~ in th proces~ of the invention range from about 400 to 650C. Temperatures from about 400 to 500C. may be used for a proportion of the roasting period but a temperature greater than the decomposition temperature ~ of iron sulfate, about 500C., is required for a significant proportion of that period so as to promote con~ersion of the iron sulfate to insoluble iron oxide. More preferred roasting temperatures are from about 550C. to 650C., conveniently about 550 to 600C., - such as about 570C. As can be seen from Figure 3, high percentages of copper and nickel and low percentages of iron are extracted over a wide range of temperature.
Roasting time has a significant effect on the efficiency of the process ol -the invention. Generally longer roasting times convert more sulfide mineral to sulfate but long roasting times decrease the economy of the process. A preferred time is from two to six hours, for example about four hours.
~ he roasted product is allowed to cool and is then leached with water, convenientiy with suf~icient water to provide a 15 to 20% solid~ slurry. ~he slurry is then agitated, for example for about two hours, to maximize extraction of the water soluble sulfates. The slurry is filtered and optionally washed with more water to ensure that any residual water soluble sulfates are carried into the product solution. ~he liquid or filtrate portion - . . - - . ~ - . . - . .:. .-.
contains the wa~er soluble sulfates of nickel, cobalt~
copper or zinc. As can be seen ~rom Figure 2, on a laboratory scale high percentages of copper, nickel and cobalt are extracted into the filtrate with very little iron. The non-ferrous metals may be recovered from the solution by conventional means. For example, the sulfates may be recovered by precipitation or by solvent extraction and electrolysis.
~2~1S93 -- ,. .
Various parameters o~ the process of the invention were investigated in the laboratory to determine their effect on the efficiency of the process. In the tests which follow it is shown that the process of the invention enhances the extraction of nickel, cobalt, copper and zinc as wate~ soluble sulfates in the sulfatization of their sulfide ores while minimizing the extraction of iron as water soluble sulfate.
- ~ST SERI~S 1 In a first series of tests, numbers 1 to 4, a copper-nickel-cobalt sulfide concentrate was composited from products of various froth flotation tests. ~he composite assayed the following percentages: 0.69 Cu, 1.23 Ni, 5~.0 ~e~ and 30.4 S. ~he composite was wet ground to 200 mesh in a laboratory ball mill, dried at 120C, and split into 200 gram batches for comparison roasting tests. ~he specified amount of -additive was -blended into the sample with a mortar and pestle just prior to roasting. ~he sample was then placed in a refractory boat. The material in the boat had an approximate depth of 1 cm. The boat was then placed in an urlvented muffle furnace, which was at room temperature9 and the temperature controller was then set to 420C. ~he heating period to 420C was fairly linear and took approximately 40 minutes. The temperature was then held at 420 for 140 minutes.
Upon completion of this initial roasting period, the temperature controller was set to 610C. It took approximately 30 minutes to reach 610C and was then held at tni;s temperature for 210 minutes. Upon reaching 610C, the ore was rabbled e~ery 30 minutes for the duration of the roast. After the ore was subjected to this second stage roast, the furnace was turned off and allowed to cool before the boat was removed.
After completing the roasting procedure, the roasted material was removed from the refractory boat and 130 ~2~0sa3 grams were split out for leaching. ~he remainder of the material was submittea for chemical analysis. The leach sample was then placea in a 1 liter beaker containing 600 grams of distilled water. ~his slurry was then agitated for 2 hours. ~each tests were conducted in an open vessel beaker at room temperature. After 2 hours of agitation, the slurry was filtered and washed with ~00 gram~ of distilled water. The filtrate and wash solution was collected and its volume was measured. The filtered leach residue was dried and weighed. Both the filtrate solution and leach residue were submitted for chemical-analysis in order to evaluate the metal extractions.
Presented in Table 1 is a descriptive tabulation of the roasting tests performed. ~he four roasting tests were conducted in the exact same manner with the exception of types and amounts of additive.
: - Presented in ~able 2 is a partial chemical analysis of the leaching products and the metal extractions. ~he extractions represent the amount of metal (Cu, ~is Fe, 20 Co) that was leached from the roasted material which reports to the leach filtrate. The calculated head for each test represents an analysis of the roasted products calculated from the analyses of residue and filtrate material. ~he addition of sodium carbonate greatly increased the copper, nickel, and cobalt extractions over the test that was void of an additive and significantly increased the extractions, especially that of nickel, over those tests containing the sodium sul~ate additive.
.
- ~or exampIe, an extraction of ~4.8 percent nickel waq ~0 experienced when the ore was roasted with sodium carbonate. When the ore was roasted without an additive, a nickel extraction of 20.6 percent was experienced. ~he two tests that csntained sodium sulfate average an ~4.5 psrcent nickel extraction.
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~2~05~3 . .
-- ~4 --- T~ST S~RI~S 2 In a second series of tests, nu~bQrs 5 to 7, a copper-nickel-cobalt sulfide concentrate was again composited from products of various froth flotation tests. ~his composite assayed the following percentages: 1.80 Cu, 1.19 Ni, 51.2 ~e, 30.5 S, and 0.11 Co. ~he second test series of roasting tests were conducted in a similar manner as was the first series of r~asting tests. The composite was wet ground to 200 mesh in a laboratory ball mill, dried at 120C, and split into 150 gram batches ~or comparision roasting tests.
Again the specified amount of additive was blended into the sample with a mortar and pestle just prior to roasting. The sample was then placed in a refractory boat. In this test series, the ore was subjected a less severe, single stage roas~. -After the refractory boat wa8 placed in an unvented muf~le furnace, which was at .. . . ,, . - .
room temperature, the temperature controller was set to 610C~ The heating period was fairly linear and too~
approximately 70 minutes. The temperature was then held at 610C for 150 minutes with the ore being rabbled every ~0 minutes for the duration of the roast. After 150 minutes at 610C, the furnace was turned off and allowed to cool before the boat was removed.
The leaching procedure in test series 2 was conduc~ed in the exact manner as was the leaching procedure in test series 1 with the exception of a réduction in both the amount o~ roasted ma~erial and water used in the leaching - process The leach process consiste~ of 1~Q grams of 30 roasted material combinea and agi~ate~ with 500 grams of water.
Presented in Table- 3 is a descriptive tabulation of the roasting tests performed and a partial chemical analysis of the roasted products. The three roasting ~5 tèsts were conducted ih the exact same manner with the exception of types and amounts of additives.
1210S~3 . . .
1,5 Presented in ~able 4 is a partial chemical analysis of the leaching products and the metal extractions. ~he extractions represent the amount of metal (Cu, ~i, Fe) that was leac,hed from the roasted material which reports ~o the leach filtrate. Although cobalt extractions were succeæsful in both the sodium carbonate and sodium sulfate roast-leach, they were not accounted ~or because of the minor amount of cobalt present in the composite.
Again the addition of sodium carbonate greatly increased the copper, nickel, and cobalt extractions over the test that was void of an additive and increased the extractions over that test conducted with an equal amount of sodium sulfate.
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`` ~2~0593 ~ST SERI~S 3 In a third series of tests, numbers 8 to 20, various ores and concentrates were tested. One 150 gram batch was roasted per test. ~he specified amount of additive was blended into the sample with a mortar and pestal just prior to roasting. An unvented muffle furnace was heated to sioc and each sample, uniformly spread in -a refractory boat, was placed in the furnace for four hours. ~he samples were rabbled every 30 minutes during the roast. ~he refractory boat was removed from the ~urnace immediately upon completeion of the roast and allowed to cool. One hundred grams was split from the roasted sample, placed in a beaker and distilled water was added to produce a 15 percent solids solution. The slurry was agitated $or two hours at room temperature and then filtered and washed A~chemic~ nal~sis sf the -- residue and filtrate was -pérformed to determine the recovery of the metals in soluble form.
The various ores and concent~ates are listed in Table 5. Core samples were used as mineral æourceæ for ~ests 8 to 17. ~ince core samples are not homogeneous, samples for individual tests which are taken from different portions of a core sample will have slightly different assays~
Tests 8 to 17 were conducted on copper-nickel-cobalt ¢oncentrates and ores. Tests 8, 9 and 10 used concentrate from a core sample ~A) which was taken from the same ar~a as the sam~les used to prepare the concentrates in;~est-Series I and 2. Tests 11-to 15 were ~0 conducted on ~oncentràte from a differen~ core sampIe tB) but which had a mineralogy very similar to (A) and was taken from the same area as sample (A). Tests:16 a~d 17 were conducted on ore~ and concentrate respectively of a core sample (C) of a massive sul~ide ore containing quantities o$ copper, nickel and cobalt taken $rom a different area than samples (A) and (B).
~2~05g3 Tests 18, l9 and 20 were conducted on ore (D) which ~as a copper, lead and zinc bearing ore.
Presented in ~able 6 are the metallurgical results of ~ests 8 to 17. ~he results demonstrate the excellent extraction efficiencies achieved by the process of the invention and show that potassium carbonate as well as sodium carbonate gives good results. Test 16 shows that the process of the invention is applicable to ores as well as concentrates. Although extractions ~rom the concentrate, in Test 17, were better than from the ore, the tests demonstrate that sulfiae ores as well as concentrates are susceptible to the process of the invention. Unfortunately, the small quantity of ore (C) available did not allow optimization testing on this ore.
Presented in Table 7 are the metallurgical results of lests 18, 19 and 20 conducted-on copper, lead and zinc ; bearing ore (D). The results show not only-that- ores are susceptible to the process-o~ the invention but also that zinc may be extracted by the roast-leach process with high percentage extraction. ~ead sul~ide materials are not susceptiblé to the extraction process. Although lead sulfate may be produced in the roaæt, it is not water soluble and therefore is not extracted in the leach process.
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~210~93 ~ST ~RIES 4 ~aboratory roasting tests were performed on low grade copper-nickel concentrates. The effects on sulfatization of roasting time (one to six hours), roasting temperature (490 C to 650C) and additives (l~a2S04, ~a2C03, CaO, CaCO~, CaS04) were investigated.
A factorial design investigating levels of roasting temperature~ roasting time and, amount of sodium carbonate added to the roast was conducted. The results demonstrated that within the parameters of the experiment, the amount of sodium carbonate added to the roæst was the most significant factor for sulfatization followed by roasting time.
Several bench scale flotation concentrates were composited to provide enough material for several , roasting tests. Although fIotation composites varied '~ slightly between test series,, ~he dif~erence was not great enough to effect the results. The ore used to prepare the concentrates was from a 'core sample obtained in the same area as Sample (A) in Test Series 3.
The flotation composite was wet ground to 200 mesh in a laboratory ball mill, dried at 110C, and split into 150 gram batches for comparison roasting tests.
One 150 gram batch was ro~sted per test. The specified amount of additive was blended into the sample with a 'mortar and pestl~ just prior to roasting. The unvented ~uffle furnace was preheated to the specified ~ temperature. ~he concentrate sample was then uniformly - spread in a refractory boat and placed in the furnace.
Ihe sample was rabbled every 30 minutes for the duration of the roast. The -refractory boat was removed immediately upon completion of the roast and allowed to cool. In order to evaluate the degree of sulfatization, a standard leaching procedure was followed. One hundred grams was split from the roasted sample. The sample was ~2~0S93 .
placed in a beaker and distilled water wæs added to produce a 15 percent solids solution. ~he slurry was agitated for two hours at room temperature and then filtered and washed. A chemical analysis of the residue and filtrate solution was performed to determine recovery of copper, nickel and iron in soluble form.
In a first series of roasting tests, 21-26, an investigation was conducted in order to study the sulfatization effects of various additives: sodium sulfate, calcium sulfate, calcium oxide, calcium carbonate and soaium carbonate. The flotation composite used in this test series assayed the following percentages; 1.80 Cu, 1.19 Ni, 51.2 ~e, 30.5 ~, and ~.11 Co. In each test the specified additive was blended into the sample to equal 10 percent of the total weight. The sample was then roasted at 610~ for-150 minutes - Presented in Table 8 are the metallurgical results of these tests. A chemical analysis of the residues and filtrate solutions along with the metal distributions for each leach test is tabulated. The results of the tests indicate that sodium carbonate is the most effective promoter for the sulfatization of the Cu-~i values.
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~ æ N . N N N ~1 ~1 lZ'10593 The effect of temperature was investigated in ~ests 27-~5 when the roasting time was held constant employing a 10 percent by weight sodium carbonate addition.
Roasting temperatures between 490C and 650C were 5 investigated; a roasting time of 240 minutes was used.
~he flotation concentrates composited for this test work assayed the ~ollowing percentages: ~.22 Cu, 1.41 Ni, 54.5 ~e, and 29.4 S.
Presented in ~able 9 are the ro~sting conditions and 10 the metallurgical results of the temperature dependept roasting tests. A chemical analysis of the residues and filtrate solutions along with the metal distributions for each test is tabulated. Presented in ~igure 3 is a graph illustrating Cu~ e recoveries in soluble form as a 15 function of temperature. ~he results indicate that the copper recoverïes span a narrow range throughout the - -- range of~ temperatures. ~ickel recoreries are at a L
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maximum ~etween 550 and 590C and shærply decrease with ~
increasing temperatures. Iron recoveries span a narrow t 20 range and are inversely proportional to temperature.
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1 Tests were conducted in order to a~alyze the inter-active effects of the roasting variables; time, temperature and amount of additive. Again, several bench scale flotation concentrates were composited to provide enough material for the test series. The composite assayed the following percentages:
2.74 Cu, 1.49 Ni, 47.7 Fe, 27.3 S and 0.10 Co. The variables in this test series were quantified from the results of the previous tests and are listed in Table 10 as Tests 36-52~
Three levels each of roasting temperature, roasting time, and percent sodium carbonate addition were incorporated in this experiment. The temperatures selected were 550, 570 and 590C, which are above the decomposition temperature of iron (Fe++) sulfate but below the decomposition temperatures of copper ~Cu~+) sulfate and nickel (Ni++) sulfate. The roasting times selected were 2, 4, and 6 hours. The sodium carbonate addition levels were 0, 10, and 20 percent. With three levels each of roasting temperature, roasting time, and percent sodium carbonate additions, 27 combinations of roasting conditions are possible. The tests employed 0 and 20 percent sodium carbonate additions and were part of a limited factorial design series. The previous test work indicated that the addition of sodium carbonate is necessary to establish nickel sulfatization. However, increasing the sodium carbonate in excess of 10 percent was not determined to be a critical factor in the sulfatization process.
The roasting time appeared to be the most significant ~actor and was therefore emphasized in this investigation. Roasting times of 2, 4 and 6 hours were used at temperatures of 550, 570 and 590C.
The results of these tests indicate that there are interactions between the sodium carbonate addition ana the roasting time, and between the roasting temperature and roasting time.
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K ~3 v h a ~2~0sg3 Analyses were made of sulfide concentrates before and after roasting in the presence of alkali metal carbonate to determine whether sulfæte or carbonate products were formed.
~ach concentrate was blended with 20~ by weight of sodium carbonate and subjected to a four-hour roast at 570C.
~he analyses are presented in Table 11, and it can be seen that, surprisingly, while only a small amount of sulfate (S04) is present in the concentrate prior to roasting, esse~tially all the sulfur (S) is present as sulfate (-S0~) in thé roasted product~ ~he amount of carbon (C) present in the concentrates is reduced to only a trace amount by the roasting process. When roasted concentrate ~) was subjected to water dissolution, copper, nickel, cobalt, and iron extractions we~e 93.4%, - 72.4%, 88.8~, and 3.7%, respectlvely. When roasted concentrate (C) was subjected to water dissolution, copper, nickel, cobalt, and iron extractions were 96.7%, 85.6%, 92.0%, ~nd 12.8%, respectively.
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~210~3 ~ his invention is applicæble to the mining and metal industry. ~he process of the invention is useful in the extraction of non-ferrous metals from sulfide ores by sulfatization of such metals into water soluble salts which may readily be leached into aqueous solution for recovery of the metals.
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~12~0593 Roasting temperature is dictated by the decomposition temperatures of the sulfates of the metals to be extractea. Optimwm temperatures for the conversion of the mineral sulfides to the sulfate state (for a given roasting time and atmospheric condition) exist when the decomposition temperatures are approached. ~y maintaining the reaction temperature either ~elow or above the decomposition temperature, more or less of the particular sul~ate can be obtained. ~his characteristic provides the means for setting conditions that theoretically will selectively sulfatize the non-ferreus metal values, such as Cu, Co, ~i and Zn9 while the iron sulfates are decomposed. However, when a sulfatizing roast is conducted on several different sulfide minerals, even under optimum roasting conditions, only a partial sulfatization is effected and the metallurgical response of the copper and cobalt sulfides is mu`ch more ~avorable than the response of the nickel sulfides. Similarly, in practice, decomposition of the iron sulfates is not ideal since decomposition is usually incomplete and therefore it is important that the leaching step extracts the maximum amount of non-ferrous wa~er soluble sulfates but the minimum amount of iron sulfates.
Accordingly, the temperatures used in the process of this inventibn depend on the metal or metals to be extracted. Where an individual m~tal is to be extracted, the temperature will approach the decomposition temperature of the sulfate of thæt metal. Where a number of metals are to be~ extracted~ as is usuall~ the case, the temperature will approach the lowest decomposition temperature of the metal sulfates in question. lhe energetic decomposition temperatures of ~eSO~, ZnS04~
CuS04, CoS04 and NiS04 are 480, 600 , 670 , 735 and 764C., respectively (~odgman, C.D. ed.
Handbook of Chemistry and Physics~ 37th edition, 1955, p.
~Z~0593 g 1812 and 48th edition, 1967 pp. ~-172, -241). Preferred roasting temperatures~ in th proces~ of the invention range from about 400 to 650C. Temperatures from about 400 to 500C. may be used for a proportion of the roasting period but a temperature greater than the decomposition temperature ~ of iron sulfate, about 500C., is required for a significant proportion of that period so as to promote con~ersion of the iron sulfate to insoluble iron oxide. More preferred roasting temperatures are from about 550C. to 650C., conveniently about 550 to 600C., - such as about 570C. As can be seen from Figure 3, high percentages of copper and nickel and low percentages of iron are extracted over a wide range of temperature.
Roasting time has a significant effect on the efficiency of the process ol -the invention. Generally longer roasting times convert more sulfide mineral to sulfate but long roasting times decrease the economy of the process. A preferred time is from two to six hours, for example about four hours.
~ he roasted product is allowed to cool and is then leached with water, convenientiy with suf~icient water to provide a 15 to 20% solid~ slurry. ~he slurry is then agitated, for example for about two hours, to maximize extraction of the water soluble sulfates. The slurry is filtered and optionally washed with more water to ensure that any residual water soluble sulfates are carried into the product solution. ~he liquid or filtrate portion - . . - - . ~ - . . - . .:. .-.
contains the wa~er soluble sulfates of nickel, cobalt~
copper or zinc. As can be seen ~rom Figure 2, on a laboratory scale high percentages of copper, nickel and cobalt are extracted into the filtrate with very little iron. The non-ferrous metals may be recovered from the solution by conventional means. For example, the sulfates may be recovered by precipitation or by solvent extraction and electrolysis.
~2~1S93 -- ,. .
Various parameters o~ the process of the invention were investigated in the laboratory to determine their effect on the efficiency of the process. In the tests which follow it is shown that the process of the invention enhances the extraction of nickel, cobalt, copper and zinc as wate~ soluble sulfates in the sulfatization of their sulfide ores while minimizing the extraction of iron as water soluble sulfate.
- ~ST SERI~S 1 In a first series of tests, numbers 1 to 4, a copper-nickel-cobalt sulfide concentrate was composited from products of various froth flotation tests. ~he composite assayed the following percentages: 0.69 Cu, 1.23 Ni, 5~.0 ~e~ and 30.4 S. ~he composite was wet ground to 200 mesh in a laboratory ball mill, dried at 120C, and split into 200 gram batches for comparison roasting tests. ~he specified amount of -additive was -blended into the sample with a mortar and pestle just prior to roasting. ~he sample was then placed in a refractory boat. The material in the boat had an approximate depth of 1 cm. The boat was then placed in an urlvented muffle furnace, which was at room temperature9 and the temperature controller was then set to 420C. ~he heating period to 420C was fairly linear and took approximately 40 minutes. The temperature was then held at 420 for 140 minutes.
Upon completion of this initial roasting period, the temperature controller was set to 610C. It took approximately 30 minutes to reach 610C and was then held at tni;s temperature for 210 minutes. Upon reaching 610C, the ore was rabbled e~ery 30 minutes for the duration of the roast. After the ore was subjected to this second stage roast, the furnace was turned off and allowed to cool before the boat was removed.
After completing the roasting procedure, the roasted material was removed from the refractory boat and 130 ~2~0sa3 grams were split out for leaching. ~he remainder of the material was submittea for chemical analysis. The leach sample was then placea in a 1 liter beaker containing 600 grams of distilled water. ~his slurry was then agitated for 2 hours. ~each tests were conducted in an open vessel beaker at room temperature. After 2 hours of agitation, the slurry was filtered and washed with ~00 gram~ of distilled water. The filtrate and wash solution was collected and its volume was measured. The filtered leach residue was dried and weighed. Both the filtrate solution and leach residue were submitted for chemical-analysis in order to evaluate the metal extractions.
Presented in Table 1 is a descriptive tabulation of the roasting tests performed. ~he four roasting tests were conducted in the exact same manner with the exception of types and amounts of additive.
: - Presented in ~able 2 is a partial chemical analysis of the leaching products and the metal extractions. ~he extractions represent the amount of metal (Cu, ~is Fe, 20 Co) that was leached from the roasted material which reports to the leach filtrate. The calculated head for each test represents an analysis of the roasted products calculated from the analyses of residue and filtrate material. ~he addition of sodium carbonate greatly increased the copper, nickel, and cobalt extractions over the test that was void of an additive and significantly increased the extractions, especially that of nickel, over those tests containing the sodium sul~ate additive.
.
- ~or exampIe, an extraction of ~4.8 percent nickel waq ~0 experienced when the ore was roasted with sodium carbonate. When the ore was roasted without an additive, a nickel extraction of 20.6 percent was experienced. ~he two tests that csntained sodium sulfate average an ~4.5 psrcent nickel extraction.
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~2~05~3 . .
-- ~4 --- T~ST S~RI~S 2 In a second series of tests, nu~bQrs 5 to 7, a copper-nickel-cobalt sulfide concentrate was again composited from products of various froth flotation tests. ~his composite assayed the following percentages: 1.80 Cu, 1.19 Ni, 51.2 ~e, 30.5 S, and 0.11 Co. ~he second test series of roasting tests were conducted in a similar manner as was the first series of r~asting tests. The composite was wet ground to 200 mesh in a laboratory ball mill, dried at 120C, and split into 150 gram batches ~or comparision roasting tests.
Again the specified amount of additive was blended into the sample with a mortar and pestle just prior to roasting. The sample was then placed in a refractory boat. In this test series, the ore was subjected a less severe, single stage roas~. -After the refractory boat wa8 placed in an unvented muf~le furnace, which was at .. . . ,, . - .
room temperature, the temperature controller was set to 610C~ The heating period was fairly linear and too~
approximately 70 minutes. The temperature was then held at 610C for 150 minutes with the ore being rabbled every ~0 minutes for the duration of the roast. After 150 minutes at 610C, the furnace was turned off and allowed to cool before the boat was removed.
The leaching procedure in test series 2 was conduc~ed in the exact manner as was the leaching procedure in test series 1 with the exception of a réduction in both the amount o~ roasted ma~erial and water used in the leaching - process The leach process consiste~ of 1~Q grams of 30 roasted material combinea and agi~ate~ with 500 grams of water.
Presented in Table- 3 is a descriptive tabulation of the roasting tests performed and a partial chemical analysis of the roasted products. The three roasting ~5 tèsts were conducted ih the exact same manner with the exception of types and amounts of additives.
1210S~3 . . .
1,5 Presented in ~able 4 is a partial chemical analysis of the leaching products and the metal extractions. ~he extractions represent the amount of metal (Cu, ~i, Fe) that was leac,hed from the roasted material which reports ~o the leach filtrate. Although cobalt extractions were succeæsful in both the sodium carbonate and sodium sulfate roast-leach, they were not accounted ~or because of the minor amount of cobalt present in the composite.
Again the addition of sodium carbonate greatly increased the copper, nickel, and cobalt extractions over the test that was void of an additive and increased the extractions over that test conducted with an equal amount of sodium sulfate.
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`` ~2~0593 ~ST SERI~S 3 In a third series of tests, numbers 8 to 20, various ores and concentrates were tested. One 150 gram batch was roasted per test. ~he specified amount of additive was blended into the sample with a mortar and pestal just prior to roasting. An unvented muffle furnace was heated to sioc and each sample, uniformly spread in -a refractory boat, was placed in the furnace for four hours. ~he samples were rabbled every 30 minutes during the roast. ~he refractory boat was removed from the ~urnace immediately upon completeion of the roast and allowed to cool. One hundred grams was split from the roasted sample, placed in a beaker and distilled water was added to produce a 15 percent solids solution. The slurry was agitated $or two hours at room temperature and then filtered and washed A~chemic~ nal~sis sf the -- residue and filtrate was -pérformed to determine the recovery of the metals in soluble form.
The various ores and concent~ates are listed in Table 5. Core samples were used as mineral æourceæ for ~ests 8 to 17. ~ince core samples are not homogeneous, samples for individual tests which are taken from different portions of a core sample will have slightly different assays~
Tests 8 to 17 were conducted on copper-nickel-cobalt ¢oncentrates and ores. Tests 8, 9 and 10 used concentrate from a core sample ~A) which was taken from the same ar~a as the sam~les used to prepare the concentrates in;~est-Series I and 2. Tests 11-to 15 were ~0 conducted on ~oncentràte from a differen~ core sampIe tB) but which had a mineralogy very similar to (A) and was taken from the same area as sample (A). Tests:16 a~d 17 were conducted on ore~ and concentrate respectively of a core sample (C) of a massive sul~ide ore containing quantities o$ copper, nickel and cobalt taken $rom a different area than samples (A) and (B).
~2~05g3 Tests 18, l9 and 20 were conducted on ore (D) which ~as a copper, lead and zinc bearing ore.
Presented in ~able 6 are the metallurgical results of ~ests 8 to 17. ~he results demonstrate the excellent extraction efficiencies achieved by the process of the invention and show that potassium carbonate as well as sodium carbonate gives good results. Test 16 shows that the process of the invention is applicable to ores as well as concentrates. Although extractions ~rom the concentrate, in Test 17, were better than from the ore, the tests demonstrate that sulfiae ores as well as concentrates are susceptible to the process of the invention. Unfortunately, the small quantity of ore (C) available did not allow optimization testing on this ore.
Presented in Table 7 are the metallurgical results of lests 18, 19 and 20 conducted-on copper, lead and zinc ; bearing ore (D). The results show not only-that- ores are susceptible to the process-o~ the invention but also that zinc may be extracted by the roast-leach process with high percentage extraction. ~ead sul~ide materials are not susceptiblé to the extraction process. Although lead sulfate may be produced in the roaæt, it is not water soluble and therefore is not extracted in the leach process.
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~210~93 ~ST ~RIES 4 ~aboratory roasting tests were performed on low grade copper-nickel concentrates. The effects on sulfatization of roasting time (one to six hours), roasting temperature (490 C to 650C) and additives (l~a2S04, ~a2C03, CaO, CaCO~, CaS04) were investigated.
A factorial design investigating levels of roasting temperature~ roasting time and, amount of sodium carbonate added to the roast was conducted. The results demonstrated that within the parameters of the experiment, the amount of sodium carbonate added to the roæst was the most significant factor for sulfatization followed by roasting time.
Several bench scale flotation concentrates were composited to provide enough material for several , roasting tests. Although fIotation composites varied '~ slightly between test series,, ~he dif~erence was not great enough to effect the results. The ore used to prepare the concentrates was from a 'core sample obtained in the same area as Sample (A) in Test Series 3.
The flotation composite was wet ground to 200 mesh in a laboratory ball mill, dried at 110C, and split into 150 gram batches for comparison roasting tests.
One 150 gram batch was ro~sted per test. The specified amount of additive was blended into the sample with a 'mortar and pestl~ just prior to roasting. The unvented ~uffle furnace was preheated to the specified ~ temperature. ~he concentrate sample was then uniformly - spread in a refractory boat and placed in the furnace.
Ihe sample was rabbled every 30 minutes for the duration of the roast. The -refractory boat was removed immediately upon completion of the roast and allowed to cool. In order to evaluate the degree of sulfatization, a standard leaching procedure was followed. One hundred grams was split from the roasted sample. The sample was ~2~0S93 .
placed in a beaker and distilled water wæs added to produce a 15 percent solids solution. ~he slurry was agitated for two hours at room temperature and then filtered and washed. A chemical analysis of the residue and filtrate solution was performed to determine recovery of copper, nickel and iron in soluble form.
In a first series of roasting tests, 21-26, an investigation was conducted in order to study the sulfatization effects of various additives: sodium sulfate, calcium sulfate, calcium oxide, calcium carbonate and soaium carbonate. The flotation composite used in this test series assayed the following percentages; 1.80 Cu, 1.19 Ni, 51.2 ~e, 30.5 ~, and ~.11 Co. In each test the specified additive was blended into the sample to equal 10 percent of the total weight. The sample was then roasted at 610~ for-150 minutes - Presented in Table 8 are the metallurgical results of these tests. A chemical analysis of the residues and filtrate solutions along with the metal distributions for each leach test is tabulated. The results of the tests indicate that sodium carbonate is the most effective promoter for the sulfatization of the Cu-~i values.
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~ æ N . N N N ~1 ~1 lZ'10593 The effect of temperature was investigated in ~ests 27-~5 when the roasting time was held constant employing a 10 percent by weight sodium carbonate addition.
Roasting temperatures between 490C and 650C were 5 investigated; a roasting time of 240 minutes was used.
~he flotation concentrates composited for this test work assayed the ~ollowing percentages: ~.22 Cu, 1.41 Ni, 54.5 ~e, and 29.4 S.
Presented in ~able 9 are the ro~sting conditions and 10 the metallurgical results of the temperature dependept roasting tests. A chemical analysis of the residues and filtrate solutions along with the metal distributions for each test is tabulated. Presented in ~igure 3 is a graph illustrating Cu~ e recoveries in soluble form as a 15 function of temperature. ~he results indicate that the copper recoverïes span a narrow range throughout the - -- range of~ temperatures. ~ickel recoreries are at a L
.. , ..... .. . . ...... .. , . .. , .. , .. . . ,_ . . ,.. ,.,, .. ,. .. . ...... . I
maximum ~etween 550 and 590C and shærply decrease with ~
increasing temperatures. Iron recoveries span a narrow t 20 range and are inversely proportional to temperature.
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1 Tests were conducted in order to a~alyze the inter-active effects of the roasting variables; time, temperature and amount of additive. Again, several bench scale flotation concentrates were composited to provide enough material for the test series. The composite assayed the following percentages:
2.74 Cu, 1.49 Ni, 47.7 Fe, 27.3 S and 0.10 Co. The variables in this test series were quantified from the results of the previous tests and are listed in Table 10 as Tests 36-52~
Three levels each of roasting temperature, roasting time, and percent sodium carbonate addition were incorporated in this experiment. The temperatures selected were 550, 570 and 590C, which are above the decomposition temperature of iron (Fe++) sulfate but below the decomposition temperatures of copper ~Cu~+) sulfate and nickel (Ni++) sulfate. The roasting times selected were 2, 4, and 6 hours. The sodium carbonate addition levels were 0, 10, and 20 percent. With three levels each of roasting temperature, roasting time, and percent sodium carbonate additions, 27 combinations of roasting conditions are possible. The tests employed 0 and 20 percent sodium carbonate additions and were part of a limited factorial design series. The previous test work indicated that the addition of sodium carbonate is necessary to establish nickel sulfatization. However, increasing the sodium carbonate in excess of 10 percent was not determined to be a critical factor in the sulfatization process.
The roasting time appeared to be the most significant ~actor and was therefore emphasized in this investigation. Roasting times of 2, 4 and 6 hours were used at temperatures of 550, 570 and 590C.
The results of these tests indicate that there are interactions between the sodium carbonate addition ana the roasting time, and between the roasting temperature and roasting time.
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K ~3 v h a ~2~0sg3 Analyses were made of sulfide concentrates before and after roasting in the presence of alkali metal carbonate to determine whether sulfæte or carbonate products were formed.
~ach concentrate was blended with 20~ by weight of sodium carbonate and subjected to a four-hour roast at 570C.
~he analyses are presented in Table 11, and it can be seen that, surprisingly, while only a small amount of sulfate (S04) is present in the concentrate prior to roasting, esse~tially all the sulfur (S) is present as sulfate (-S0~) in thé roasted product~ ~he amount of carbon (C) present in the concentrates is reduced to only a trace amount by the roasting process. When roasted concentrate ~) was subjected to water dissolution, copper, nickel, cobalt, and iron extractions we~e 93.4%, - 72.4%, 88.8~, and 3.7%, respectlvely. When roasted concentrate (C) was subjected to water dissolution, copper, nickel, cobalt, and iron extractions were 96.7%, 85.6%, 92.0%, ~nd 12.8%, respectively.
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~210~3 ~ his invention is applicæble to the mining and metal industry. ~he process of the invention is useful in the extraction of non-ferrous metals from sulfide ores by sulfatization of such metals into water soluble salts which may readily be leached into aqueous solution for recovery of the metals.
~0 :
~5
Claims (7)
1. A process for the sulfatization of at least one.
non-ferrous metal sulfide selected from the group consisting of copper, nickel, cobalt and zinc sulfides which com-prises mixing alkali metal carbonate or bicarbonate with sulfide mineral containing said metal sulfide and con-verting a high percentage of said metal sulfide into water soluble, non-ferrous metal sulfate by roasting the mixture at a temperature greater than the decomposition temperature of iron sulfate but less than the decomposition temperature of the water soluble, non-ferrous metal sulfate.
2. A process for the extraction of at least one non-ferrous metal selected from the group consisting of copper, nickel, cobalt and zinc from sulfide mineral containing at least one sulfide of the non-ferrous metal which comprises:
mixing alkali metal carbonate or bicarbonate with said mineral;
roasting said mixture at a temperature above the decomposition temperature of iron sulfate but below the decomposition temperature of the sulfate of the non-ferrous metal to be extracted;
sulfatizing a high percentage of said metal sulfide to form water soluble non-ferrous metal sulfate in the roasted product;
non-ferrous metal sulfide selected from the group consisting of copper, nickel, cobalt and zinc sulfides which com-prises mixing alkali metal carbonate or bicarbonate with sulfide mineral containing said metal sulfide and con-verting a high percentage of said metal sulfide into water soluble, non-ferrous metal sulfate by roasting the mixture at a temperature greater than the decomposition temperature of iron sulfate but less than the decomposition temperature of the water soluble, non-ferrous metal sulfate.
2. A process for the extraction of at least one non-ferrous metal selected from the group consisting of copper, nickel, cobalt and zinc from sulfide mineral containing at least one sulfide of the non-ferrous metal which comprises:
mixing alkali metal carbonate or bicarbonate with said mineral;
roasting said mixture at a temperature above the decomposition temperature of iron sulfate but below the decomposition temperature of the sulfate of the non-ferrous metal to be extracted;
sulfatizing a high percentage of said metal sulfide to form water soluble non-ferrous metal sulfate in the roasted product;
Claim 2 continued.,.
leaching the roasted product with water to form a solid residue and an aqueous solution containing a high percentage of the non-ferrous metal sulfate;
separating said aqueous solution from the solid residue; and recovering non-ferrous metal from the aqueous solution.
3. A process for the extraction of at least one non-ferrous metal selected from the group consisting of copper, nickel, cobalt, and zinc from sulfide ore containing sulfide mineral comprising at least one sulfide of said non-ferrous metal which comprises:
reducing the particle size of the ore;
concentrating the sulfide mineral by froth flotation to form a sulfide mineral concentrate and solid residue;
separating the concentrate from the residue;
substantially drying the concentrate;
adding alkali metal carbonate or bicarbonate to the concentrate to form a mixture;
roasting the mixture to convert a high percentage of said non-ferrous metal sulfide into water soluble non-ferrous metal sulfate and provide said sulfate in the roasted product;
treating the roasted product with water to dissolve a high percentage of said soluble sulfates from the solids into solution;
leaching the roasted product with water to form a solid residue and an aqueous solution containing a high percentage of the non-ferrous metal sulfate;
separating said aqueous solution from the solid residue; and recovering non-ferrous metal from the aqueous solution.
3. A process for the extraction of at least one non-ferrous metal selected from the group consisting of copper, nickel, cobalt, and zinc from sulfide ore containing sulfide mineral comprising at least one sulfide of said non-ferrous metal which comprises:
reducing the particle size of the ore;
concentrating the sulfide mineral by froth flotation to form a sulfide mineral concentrate and solid residue;
separating the concentrate from the residue;
substantially drying the concentrate;
adding alkali metal carbonate or bicarbonate to the concentrate to form a mixture;
roasting the mixture to convert a high percentage of said non-ferrous metal sulfide into water soluble non-ferrous metal sulfate and provide said sulfate in the roasted product;
treating the roasted product with water to dissolve a high percentage of said soluble sulfates from the solids into solution;
Claim 3 continued...
separating the sulfate solution from the solids; and recovering non-ferrous metal from the solution.
separating the sulfate solution from the solids; and recovering non-ferrous metal from the solution.
4. A process as claimed in claim 1, 2 or 3 wherein the alkali metal carbonate or bicarbonate comprises sodium carbonate.
5. A process as claimed in claim 1, 2 or 3 wherein the alkali metal carbonate is present in an amount of from 10 to 20% by weight of the mineral roast feed.
6. A process as claimed in claim 1, 2 or 3 wherein the sulfide mineral is roasted at a temperature of from 550° to 650°C.
7. A process as claimed in claim 1, 2 or 3 wherein the sulfide mineral is roasted at a temperature of from 550° to 650°C for from two to four hours.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US36515282A | 1982-04-05 | 1982-04-05 | |
| US06/365,152 | 1982-04-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1210593A true CA1210593A (en) | 1986-09-02 |
Family
ID=23437685
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000425215A Expired CA1210593A (en) | 1982-04-05 | 1983-04-05 | Process for the sulfatization of non-ferrous metal sulfides |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU1126783A (en) |
| CA (1) | CA1210593A (en) |
| FI (1) | FI831108L (en) |
-
1983
- 1983-02-09 AU AU11267/83A patent/AU1126783A/en not_active Abandoned
- 1983-03-30 FI FI831108A patent/FI831108L/en not_active Application Discontinuation
- 1983-04-05 CA CA000425215A patent/CA1210593A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| FI831108A0 (en) | 1983-03-30 |
| AU1126783A (en) | 1983-10-13 |
| FI831108L (en) | 1983-10-06 |
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