WO2016198976A1 - Procédé de lixiviations chimique et bactérienne intégrées d'un métal de base - Google Patents

Procédé de lixiviations chimique et bactérienne intégrées d'un métal de base Download PDF

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Publication number
WO2016198976A1
WO2016198976A1 PCT/IB2016/052949 IB2016052949W WO2016198976A1 WO 2016198976 A1 WO2016198976 A1 WO 2016198976A1 IB 2016052949 W IB2016052949 W IB 2016052949W WO 2016198976 A1 WO2016198976 A1 WO 2016198976A1
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Prior art keywords
leachate
leaching
base metal
mineral
bioleaching
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PCT/IB2016/052949
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English (en)
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Brian Edward FELSKE
Pedro MORALES CERDA
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Felske Brian Edward
Morales Cerda Pedro
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Publication of WO2016198976A1 publication Critical patent/WO2016198976A1/fr

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    • 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
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/18—Extraction of metal compounds from ores or concentrates by wet processes with the aid of microorganisms or enzymes, e.g. bacteria or algae
    • 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
    • C22B11/00—Obtaining noble metals
    • C22B11/04—Obtaining noble metals by wet processes
    • 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
    • C22B13/00—Obtaining lead
    • C22B13/04—Obtaining lead by wet processes
    • 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
    • C22B15/00—Obtaining copper
    • C22B15/0063—Hydrometallurgy
    • C22B15/0065—Leaching or slurrying
    • C22B15/0067—Leaching or slurrying with acids or salts thereof
    • 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
    • C22B19/00—Obtaining zinc or zinc oxide
    • C22B19/20—Obtaining zinc otherwise than by distilling
    • C22B19/22—Obtaining zinc otherwise than by distilling with leaching with acids
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • the present invention relates to a method of leaching of a metal from minerals. More specifically, the method utilizes an integrated chemical and bacterial process to leach base metals from minerals.
  • the move to higher temperatures to increase recovery of copper is necessitated by the formation of a "passivation" layer on the surface of minerals, particularly chalcopyrite, at ambient temperature under conventional bacterial leaching conditions.
  • the passivation layer is believed to be composed of jarosite, a potassium or ammonium iron hydroxy-oxide mineral, and ⁇ or modified elemental sulfur (S°).
  • this passivation layer stops or substantially slows further bacterial actions.
  • This technical difficulty may have been exacerbated by the fact that the existing bacterial leaching process is based on the oxidation of Fe (II) to Fe (III), with Fe (III) oxidizing the mineral and releasing the copper.
  • the increase in iron content in the leachate results in a rise in the redox potential (Eh) which in turn contributes to the formation of jarosite. Therefore, the existing bacterial leaching processes are often described as self-limiting.
  • Bacterial leaching used in the existing technology is a slow process.
  • a typical operation needs a leaching time of about 8 to 12 months in processing chalcocite and covellite minerals.
  • the process is substantially slower in the leaching of bornite and chalcopyrite minerals.
  • the present invention is directed to a method of integrated chemical and bacterial leaching of a base metal from a mineral.
  • the method comprises leaching a base metal from a mineral with an ammoniacal thiosulfate chemical leaching solution having a pH from about 8.5 to about 10.5, thereby forming a first leachate having a first concentration of the base metal; subsequently adjusting the first leachate to a neutral pH in a range from about 6.0 to about 8.0; inoculating neutralized first leachate with one or more neutrophilic bacteria; and bioleaching the base metal from the mineral with inoculated first leachate containing one or more neutrophilic bacteria, thereby forming a second leachate having a second concentration of the base metal.
  • the method further comprises inoculating the second leachate with one or more chloride-tolerant acidophilic bacteria, when the second leachate reaches an acidic pH of 4.5 or less after the bioleaching with one or more neutrophilic bacteria, and further bioleaching the base metal from the mineral with inoculated second leachate containing one or more chloride-tolerant acidophilic bacteria at the acidic pH.
  • Fig. 1 is a schematic flow chart illustrating the method of integrated chemical and bacterial leaching in a heap leaching process in some embodiments of the present invention.
  • Fig. 2 shows pH and redox potential (Eh) of the leachate during the integrated chemical and bacterial leaching process illustrated in Example 1.
  • FIG. 3 shows the cumulative copper recovery at the end of each phase of the integrated chemical and bacterial leaching process illustrated in Example 1.
  • Fig. 4 shows pH and redox potential (Eh) of the leachate during the integrated chemical and bacterial leaching process illustrated in Example 2.
  • Fig. 5 shows the cumulative copper recovery at the end of each phase of the integrated chemical and bacterial leaching process illustrated in Example 2.
  • Embodiments of the present invention generally relate to a method of leaching a metal from minerals. Embodiments of the invention are described more fully hereinafter with reference to the accompanying drawings. The various embodiments of the invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Elements that are identified using the same or similar reference characters refer to the same or similar elements.
  • the method provides an integrated chemical and bacterial leaching process to leach base metals from minerals.
  • the method comprises the following steps:
  • the base metal includes, but is not limited to, copper, nickel, zinc, and lead.
  • the method of the present invention can be used for leaching the base metal from various minerals.
  • mineral includes ores, concentrates, process intermediates, and metallurgical products.
  • the method can be further used for leaching precious metal contained in the minerals, as described hereinafter.
  • the precious metal includes, but not limited to, gold, silver and platinum.
  • the mineral are copper oxides, primary sulfides and secondary sulfides, such as atacamite (Cu 2 CI(OH) 3 ), malachite (Cu 2 C03(OH) 2 ), copper wad (CuO Mn0 2 -7H 2 0), copper pitch (MnO(OH)CuSi0 2 nH 2 0), chrysocola (CuSi03.2H 2 0), covellite (CuS), chalcocite (Cu 2 S), bornite (CusFeS- , chalcopyrite (CuFeS 2 ); minerals containing nickel, such as pentlandite ((Fe,Ni)9S8); minerals containing zinc, such as sphalerite ((Zn,Fe)S); minerals containing gold, minerals containing silver, and minerals containing platinum, or combinations thereof.
  • atacamite Cu 2 CI(OH) 3
  • malachite Cu 2 C03(OH) 2
  • copper wad CuO Mn0 2 -7
  • the integrated chemical and bacterial leaching process described above includes two phases: phase 1 , including step (a) above, is a chemical leaching process using an ammoniacal thiosulfate chemical leaching solution; and phase 2, including steps (b) to (d) above, is a bacterial leaching process, which is also referred to as bioleaching.
  • ammoniacal thiosulfate chemical leaching solution refers to an aqueous solution containing ammonia under the alkaline pH described above and thiosulfate anion. The ammonia may be formed from ammonium cation in situ under the alkaline pH condition.
  • the ammoniacal thiosulfate chemical leaching solution is also referred to as chemical leaching solution interchangeably.
  • the ammoniacal thiosulfate chemical leaching solution used in phase 1 comprises one or more ammonium compounds.
  • the ammonium compound may include ammonium halide, ammonium hydroxide, ammonium thiosulfate, or a combination thereof.
  • a combination of ammonium chloride and ammonium hydroxide is used.
  • the chemical leaching solution comprises a thiosulfate salt.
  • the thiosulfate salt may include alkali metal thiosulfate, ammonium thiosulfate, or a combination thereof.
  • sodium thiosulfate is used.
  • the chemical leaching solution comprises sodium thiosulfate, ammonium chloride and ammonium hydroxide.
  • concentration of sodium thiosulfate in the chemical leaching solution can be from about 0.05 to about 0.5 molar (M), and preferably from about 0.1 to about 0.3 M.
  • concentration of ammonium chloride can be from about 0.05 to about 1.0 M, and preferably from about 0.1 to about 0.5 M.
  • concentration of ammonium hydroxide can be from about 0.05 to about 1.0 M, and preferably from about 0.1 to about 0.5 M.
  • the chemical leaching solution has an alkaline pH in a range from about 8.5 to about 10.5, preferably from about 9.0 to about 10.0.
  • the chemical leaching solution in the embodiment described above contains ammonium thiosulfate, which is formed in situ by reaction between sodium thiosulfate and ammonium chloride.
  • Ammonia/ammonium and thiosulfate anion are active agents in the chemical leaching of the base metal.
  • ammonium thiosulfate can be added directly in the chemical leaching solution.
  • the concentration of ammonium thiosulfate can be from about 0.02 to about 1.0 M, and preferably from about 0.05 to about 0.5 M.
  • Fig. 1 illustrates the integrated chemical and bacterial leaching process in some embodiments of the present invention.
  • the chemical leaching solution is recirculated through the mineral for a first predetermined period of time, or until the concentration of a base metal in the leachate reaches a first target concentration.
  • the first predetermined period of time, or chemical leaching time may be from 1 to about 60 days. In one exemplary embodiment, the chemical leaching time is about 7 days.
  • the first target concentration can be determined empirically depending on the minerals to be processed.
  • the leachate obtained from the chemical leaching in phase 1 is referred to as the first leachate
  • the concentration of the base metal in the first leachate is referred to as the first concentration.
  • the chemical leaching is carried out at an ambient temperature, and no heating is required.
  • the reaction temperature for chemical leaching in phase 1 is from about 5°C to about 40°C, preferably from about 15°C to about 35°C.
  • the reaction temperature refers to a temperature that the minerals are exposed to during the chemical leaching or bioleaching process inside heaps, dumps, or inside a vat or a tank.
  • the chemical leaching in phase 1 of the integrated process has two important functions. Firstly, chemical leaching in phase 1 partially releases the base metal from the mineral. Using the copper oxide and copper sulfide minerals described above as an example, the chemical leaching involves reactions of ammonia with the oxide and sulfide minerals to form copper-ammine complexes, as well as subsequent reactions of copper-ammine complexes with thiosulfate, resulting in various soluble copper compounds in the first leachate under the reaction condition described above. Moreover, during the chemical leaching process the minerals become more porous because of dissolution of the base metal. The porous minerals have a substantially larger surface area, which is beneficial for the subsequent bioleaching process using bacteria.
  • RISCs reduced intermediate sulfur compounds
  • the reduced intermediate sulfur compounds (RISCs) include, but are not limited to, thiosulfates, tetrathionates, trithionates, and polysulfides as well as elemental sulfur (S°). Therefore, in the integrated process, in addition to chemical leaching, phase 1 functions as an indispensable preconditioning step for the subsequent bacterial leaching process.
  • the first leachate is adjusted to a neutral pH in a range from about 6.0 to about 8.0, preferably from about 6.5 to about 7.5.
  • the pH of the first leachate is adjusted to about 7.0 using an acid.
  • acids compatible with the bacteria used for bioleaching can be used for adjusting the pH of the first leachate.
  • sulfuric acid and hydrochloric acid are used.
  • the neutralized first leachate is inoculated with one or more neutrophilic bacteria.
  • the neutrophilic bacteria are mesophilic and chemolithotrophic. Suitable bacteria include, but are not limited to, Alpha-Proteobacteria, such as Starkeya novella and Paracoccus pantotrophus, Beta Proteobacteria such as Thiobacillus denitrificans, various sulfur oxidizing Bacilli species, and other similar neutrophilic chemolithotrophic bacteria that possess the metabolic pathways which allow them to metabolize the reduced intermediate sulfur compounds, or combinations of the above mentioned bacteria.
  • a combination of Thiobacillus denitrificans, Starkeya novella, Paracoccus pantotrophus, and Bacillus subtilus is used for bioleaching in phase 2.
  • the above described neutrophilic bacteria are known sulfur oxidizers, which possess metabolic pathways that allow the bacteria to oxidize the reduced intermediate sulfur compounds (RISCs) formed in phase 1 to sulfates, and therefore, release copper and other base metals in a soluble form into the leachate.
  • RISCs reduced intermediate sulfur compounds
  • the above described neutrophilic bacteria do not oxidize iron, because these bacteria are obligatory sulfur oxidizers.
  • Thiobacillus denitrificans has the ability to oxidize iron in pyrite, however, this oxidation process is sufficiently slow such that the effect is minor under the leaching condition and for the leaching time used in the process of the present invention.
  • the above described neutrophilic bacteria do not contribute to the dissolution of iron, and consequently do not contribute to the formation of jarosite.
  • the neutralized first leachate inoculated with the above described neutrophilic bacteria is recirculated through the mineral for a second predetermined period of time, or until the concentration of the base metal reaches a second target concentration.
  • the second predetermined period of time, or bioleaching time may be from 1 day to about 60 days. In one exemplary embodiment the bioleaching leaching time is about 7 days.
  • the second target concentration can be determined empirically depending on the minerals to be processed.
  • the leachate obtained from the bioleaching in phase 2 is referred to as the second leachate
  • the concentration of the base metal in the second leachate is referred to as the second concentration.
  • the second concentration of the base metal is a cumulative concentration resulted from phase 1 and phase 2, which is higher than the first concentration resulted from chemical leaching in phase 1.
  • the bioleaching described above in phase 2 is carried out at an ambient temperature. No heating is required for the integrated chemical and bacterial leaching process.
  • the reaction temperature for bioleaching in phase 2 is from about 12°C to about 40°C, preferably from about 15°C to about 35°C, more preferably from about 20°C to about 30°C.
  • phase 1 the reactions of the chemical leaching solution with the minerals generate reduced intermediate sulfur compounds (RISCs) in the leachate, which serves as the energy source to the bacteria used in the bioleaching in phase 2, as such phase 1 functions as an indispensable preconditioning step to the bioleaching of phase 2.
  • RISCs reduced intermediate sulfur compounds
  • the chemical leaching solution containing a combination of sodium thiosulfate, ammonium chloride and ammonium hydroxide provides a more effective leaching, which results in a higher cumulative recovery of copper in the integrated process than a chemical leaching solution made of ammonium thiosulfate in the absence of ammonium chloride.
  • chloride assists in dissolving copper oxides, and it may also play a role in preventing precipitation of released copper in the leachates.
  • the present inventors discovered that in the above integrated chemical and bacterial leaching process iron concentration in the leachate remained extremely low in the context of metal leaching in the mining industry.
  • the iron concentration in the leachate at the end of phase 2 was at ppm level. At this low concentration, iron does not interfere with leaching of the base metal in the instant integrated process.
  • the iron concentration in the leachate of existing copper bioleaching processes is significantly higher, at a level of grams per liter. At this higher level, jarosite formation is a known major obstacle of the existing copper bioleaching processes, because it can render the copper bioleaching processes self- limiting. Similar to iron, aluminum and magnesium contents in the leachate of the instant integrated process also remain similarly low, such that these ions do not interfere with leaching of the base metal in the process.
  • the integrated chemical and bacterial leaching process is particularly advantageous for recovering base metals in mixed ores including both oxide and sulfide minerals.
  • the chemical leaching recovers most copper, or other base metals, in oxide minerals and a portion of copper in the sulfide minerals.
  • a portion or most of the remaining copper in the sulfide minerals are recovered by the bioleaching.
  • the integrated chemical and bacterial leaching process effectively recovers copper in ores with a complex composition.
  • the method may further include addition of a nitrate compound in the neutralized leachate in phase 2 for the above described bioleaching.
  • a nitrate compound in the neutralized leachate in phase 2 for the above described bioleaching.
  • Thiobacillus denitrificans metabolizes aerobically (with oxygen) and anaerobically (in an oxygen deficit) with different metabolic capabilities. Under an anaerobic condition, Thiobacillus denitrificans may oxidize reduced intermediate sulfur compounds (RISCs) and pyrite using nitrate as an electron receiver.
  • RISCs reduced intermediate sulfur compounds
  • anaerobic condition could be present in dumps.
  • anaerobic condition may potentially be micro-localized in certain parts of the heaps. Therefore, presence of nitrate may support metabolism of the bacteria under such a condition, and hence may further enhance efficiency of the bioleaching.
  • the nitrate compound may include sodium nitrate, ammonium nitrate, or other nitrate salts compatible with the neutrophilic bacteria used in the bioleaching.
  • the choice of a specific nitrate compound may also depend on the type of ore being leached.
  • the amount of nitrate may vary depending on how many reduced intermediate sulfur compounds need to be oxidized and may also depend on the content of iron in the mineral.
  • sodium nitrate is used.
  • the concentration of sodium nitrate may be about 0.05 to about 1.0 M, and preferably from about 0.1 to about 0.5 M.
  • the method of the integrated chemical and bioleaching may optionally include a further phase, phase 3, which involves an additional bioleaching at an acidic pH using acidophilic bacteria.
  • the method further comprises the following steps: inoculating the second leachate from phase 2 with one or more chloride- tolerant acidophilic bacteria, when the second leachate reaches an acidic pH of 4.5 or less during the bioleaching with the neutrophilic bacteria described above; and then further bioleaching the base metal from the mineral with the second leachate inoculated with the chloride-tolerant acidophilic bacteria at the acidic pH.
  • the acidophilic bacteria used are chloride-tolerant because of the chloride contained in the second leachate.
  • Acidithiobacillus thiooxidans is used for the additional bioleaching at an acidic pH.
  • the second leachate inoculated with the above described acidophilic bacteria is recirculated through the mineral for a third predetermined period of time, or until the concentration of the base metal reaches a third target concentration.
  • the leachate obtained from the additional bioleaching in phase 3 is referred to as the third leachate
  • the concentration of the base metal in the third leachate is referred to as the third concentration.
  • the additional bioleaching process in phase 3 is also carried out at ambient temperature. No heating is required.
  • the reaction temperature in phase 3 is from about 12°C to about 40°C, preferably from about 15°C to about 35°C, more preferably from about 20°C to about 30°C.
  • the additional bioleaching at an acidic pH using acidophilic bacteria can be used to further leach the base metal from the mineral if the chemical leaching and bioleaching with the neutrophilic bacteria described above have not sufficiently leached the base metal from the mineral to a desired extent. This is a situation as illustrated in Example 1 described hereinafter. However, as further shown in Example 2, with an extended leaching time applied to chemical leaching and bioleaching with the neutrophilic bacteria described above, the additional bioleaching at an acidic pH using acidophilic bacteria may not be needed.
  • the additional bioleaching with acidophilic bacteria functions as a safe guard, which can be implemented optionally to further improve an overall recovery of the base metal in the integrated leaching process.
  • the metals in the leachate may be recovered at the end of the entire integrated chemical and bacterial leaching process, or may be recovered during or at the end of a certain phase. For example, as illustrated in Fig.
  • the second leachate can be withdrawn at the end of phase 2, and copper or other base metals can be recovered by solvent extraction and electrowinning.
  • the leachate can be withdrawn at the end of phase 3, instead of at the end of phase
  • the base metal can then be recovered from the leachate as shown.
  • partial recovery during or at the end of phase 1 may also be contemplated. Reducing the overall concentration of a metal in the leachate may drive the chemical reaction toward the direction of further dissolving the metal, and may also decrease metal precipitation in the leachate. If a partial recovery occurs at phase 1 , the second concentration of the base metal at the end of phase 2 will be a partial cumulative concentration.
  • the integrated chemical leaching and bioleaching process of the present invention can be carried out in a form of heap leaching, tank leaching, vat leaching, or dump leaching.
  • Heap leaching is the most commonly utilized bacterial process for recovering base metal, such as copper.
  • the process involves stacking crushed ore onto a specially prepared impermeable pad.
  • the pad is designed so that the leachate draining from the heap collects at a point from which it is drained to a collection pond.
  • Air may be injected into the heap using various methods, such as with appropriate air blowing systems.
  • the base metal is recovered from the leachate, also commonly referred to as pregnant liquor solution, via precipitation, or solvent extraction and electrowinning.
  • the ore is crushed to proper sizes, typically from about 2 inches to about 0.25 inch. Furthermore, the crushed ore can be agglomerated with binders, acid or other reagent, and water prior to stacking, which results in a more uniform particle size. Heaps are irrigated with the chemical leaching solution and the leachate inoculated with the bacteria, respectively, as described above.
  • Dump leaching is similar to heap leaching and is generally reserved for lower grade ores. Typically, little or no crushing will be performed prior to stacking. Only a minimum pad preparation will be performed, and there will be no forced aeration.
  • the chemical leaching solution, the first leachate inoculated with the neutrophilic bacteria and the second leachate inoculated with the acidophilic bacteria, respectively, are recirculated through the stacked ore similarly as that carried out in heap leaching.
  • vat leaching the mineral to be treated is fully immersed in the chemical leaching solution without extensive agitation.
  • the process has the advantage over heap or dump leaching in that complete wetting of the mineral surfaces is achieved. Finer crush sizes can also be handled better in a vat. Aeration may be provided by submerged pipe, or could be accomplished by intermittently draining the vat and allowing air to be drawn into the ore by recirculating the leachate.
  • Tank leaching is carried out with aerated mineral slurries in agitated tanks.
  • the leaching solution, or inoculated leachate is circulated in the tanks in different phases.
  • the method of the present invention is further illustrated by examples in Examples 1 and 2.
  • crushed ore containing atacamite, chalcocite, covellite, bornite and chalcopyrite was used, which had a total copper content of 0.5%.
  • a chemical leaching solution containing 0.20M sodium thiosulfate, 0.40M ammonium chloride and 0.18M ammonium hydroxide, and having a pH of 9.5 was used in phase 1 for chemical leaching of copper.
  • a consortium of four neutrophilic bacteria namely, Thiobacillus denitrificans, Starkeya novella, Paracoccus pantotrophus, and Bacillus subtilus, was used to inoculate the first leachate at a neutral pH after phase 1.
  • the leachate inoculated by these neutrophilic bacteria was used for bioleaching copper from the minerals.
  • an acidophilic bacterium Acidithiobacillus thiooxidans
  • the second leachate inoculated by the acidophilic bacterium was used for further bioleaching of copper.
  • the entire leaching process was carried out at room temperature.
  • Example 1 the leaching time in both phases 1 and 2 was relatively short, and they were 2 days and 5 days, respectively. As shown in Fig. 3, the cumulative copper recovery at the end of each phase was 21.8%, 30%, and 39%, respectively. In this example, each phase of the integrated chemical and bacterial leaching process contributed to the overall recovery of copper.
  • Example 2 a substantially higher copper recovery was obtained by increasing leaching time in phase 1 and phase 2, which were 7 days in both phases. As shown in Fig. 5, the cumulative copper recovery at the end of phase 1 and phase 2 was 37.5% and 53.3%, respectively.
  • phase 1 and phase 2 achieved a significant recovery of above 50% copper content in the ore in merely about 15 days.
  • Such a high yield copper recovery in a short time is a major breakthrough in mining industry. This substantially exceeds the current copper recovery of about 30% to 40% over a period of about one year leaching time using the existing bioleaching technologies.
  • the concentrations of aluminum, magnesium and iron remain low in the leachate in both phase 1 and phase 2.
  • the content of iron in the second leachate was about 130 ppm
  • the content of aluminum and magnesium was less than 80 ppm.
  • the typical concentrations of these metals in the leachate of the existing bioleaching processes are from 7 to 18 g/L for aluminum, from 1 to 12 g/L for magnesium, and from 1 to 12 g/L for iron, respectively. At these concentrations, interferences from these metals have been major obstacles for bioleaching copper in the existing methods.
  • the integrated process of the present invention has successfully overcome a long time technical problem in the mining industry wherein various known bacterial base metal leaching processes have been rendered self-limiting by jarosite formed in these processes.
  • phase 1 three individual samples of 150 grams of the crushed ore were each placed in a 2 liter open-mouth bottle together with 450 ml of a chemical leaching solution.
  • the chemical leaching solution contained 0.20M sodium thiosulfate, 0.40M ammonium chloride and 0.18M ammonium hydroxide, and had a pH of 9.5.
  • phase 2 was started.
  • the pH of the first leachate in each bottle was adjusted to pH 7 using sulfuric acid, and the amount of the leachate was adjusted with deionized water to the volume before sampling.
  • the filtered ore was returned to each bottle.
  • the first leachate in each bottle was then inoculated with an inoculum containing Thiobacillus denitrificans, Starkeya novella, Paracoccus pantotrophus, and Bacillus subtilus, and the inoculated leachate had a bacteria concentration of about 5 x 10 7 per gram of mineral.
  • the bottles were placed back on the rotating roller table.
  • phase 3 was started.
  • the filtered ore and the second leachate were returned to each bottle, and the solution volume was adjusted with deionized water to compensate for the sample removed.
  • an inoculum containing Acidithiobacillus thiooxidans was added to the second leachate in each bottle with a concentration of this bacterium of about 5 x 10 7 per gram of mineral.
  • the bottles were placed back on the rotating roller table.
  • Fig. 2 shows the average Eh and pH of the solution in the three bottles during the experiment. As shown, at the beginning of phase 2 the initial pH was adjusted to 7. Then, the pH decreased during the bioleaching with the consortium of neutrophilic bacteria. On day 5, the pH of the solution in the bottles was below 4 at which Acidithiobacillus thiooxidans was inoculated for the additional bioleaching in phase 3.
  • Fig. 3 shows the recovery of copper at the end of each phase. As shown, at the end of phase 1 , the copper recovery was 21.8%; at the end of phase 2, the cumulative copper recovery was 30%; and at the end of phase 3, the cumulative copper recovery was 39%.
  • phase 1 three individual samples of 150 grams of the crushed ore were each placed in a 2 liter open-mouth bottle together with 450 ml of the same chemical leaching solution described above in Example 1. The three open-mouth bottles were placed on a rotating roller table.
  • phase 2 was started.
  • the pH of the first leachate in each bottle was adjusted to pH 7.1 using sulfuric acid.
  • a 20 ml inoculum containing Thiobacillus denitrificans, Starkeya novella, Paracoccus pantotrophus, and Bacillus subtilus was added into the first leachate in each bottle, and the inoculated leachate had a bacteria concentration of about 5 x 10 7 per gram of mineral.
  • the bottles were placed back on the rotating roller table.
  • redox potential increased gradually during phase 1 and phase 2.
  • Eh increased from 407 to 512 mV.
  • Eh further increased slightly to 532 mV. This Eh level remained below the range that would normally support the formation of jarosite.

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  • Geology (AREA)
  • Manufacture And Refinement Of Metals (AREA)

Abstract

La présente invention concerne un procédé de lixiviations chimique et bactérienne intégrées d'un métal de base à partir d'un minéral. Le procédé consiste à lixivier un métal de base à partir d'un minéral avec une solution de lixiviation chimique de thiosulfate ammoniacal ayant un pH d'environ 8,5 à environ 10,5 de façon à obtenir un premier lixiviat, ajuster ensuite le pH du premier lixiviat à un pH neutre sur une plage d'environ 6,0 à environ 8,0, puis inoculer au premier lixiviat neutralisé une ou plusieurs bactéries neutrophiles et extraire le métal de base du minéral par lixiviation biologique au moyen du premier lixiviat auquel ont été inoculées les bactéries neutrophiles afin d'obtenir un deuxième lixiviat. Le procédé peut en outre consister à inoculer au deuxième lixiviat des bactéries acidophiles tolérantes aux chlorures sous un pH acide, et à extraire davantage le métal de base du minéral par lixiviation biologique au moyen du deuxième lixiviat inoculé sous le pH acide.
PCT/IB2016/052949 2015-06-11 2016-05-19 Procédé de lixiviations chimique et bactérienne intégrées d'un métal de base WO2016198976A1 (fr)

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Cited By (2)

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Publication number Priority date Publication date Assignee Title
US20200190395A1 (en) * 2017-07-10 2020-06-18 Biotechnology Solutions, Llc Composition and method for controlling bacteria in formations
CN109250882A (zh) * 2018-10-12 2019-01-22 江西省科学院生物资源研究所 一种畜禽废弃物重金属脱除的方法

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