WO2014000021A1 - Procédé de lixiviation de minerais de silicate de zinc - Google Patents

Procédé de lixiviation de minerais de silicate de zinc Download PDF

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Publication number
WO2014000021A1
WO2014000021A1 PCT/AU2013/000661 AU2013000661W WO2014000021A1 WO 2014000021 A1 WO2014000021 A1 WO 2014000021A1 AU 2013000661 W AU2013000661 W AU 2013000661W WO 2014000021 A1 WO2014000021 A1 WO 2014000021A1
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WIPO (PCT)
Prior art keywords
acid
solution
aqueous
zinc silicate
ore
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PCT/AU2013/000661
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English (en)
Inventor
Matthew Leslie Sutcliffe
Nicholas James Welham
Garry Mervyn Johnston
Original Assignee
Metaleach Limited
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Publication date
Priority claimed from AU2012902708A external-priority patent/AU2012902708A0/en
Application filed by Metaleach Limited filed Critical Metaleach Limited
Priority to EP13809302.6A priority Critical patent/EP2864510A4/fr
Priority to MX2014016126A priority patent/MX2014016126A/es
Publication of WO2014000021A1 publication Critical patent/WO2014000021A1/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
    • C22B19/00—Obtaining zinc or zinc oxide
    • C22B19/02—Preliminary treatment of ores; Preliminary refining of zinc oxide
    • 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
    • C22B19/24—Obtaining zinc otherwise than by distilling with leaching with alkaline solutions, e.g. ammonia
    • 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 for leaching zinc from zinc silicate ores. More particularly, the present invention relates to a method for leaching zinc from zinc silicate ores with an ammoniacal media.
  • the ammonia-based Schnabel process for the recovery of zinc from oxide ores was used for a number of years before being superseded by the acid-based roast-leach-electrowin process which could directly treat sulphides.
  • the Schnabel process feed was typically roasted sphalerite flotation concentrate, but selective mining also allowed processing of zinc oxide ores.
  • the Schnabel process is complex, as is evident from the summary by Harvey (Mineral Processing & Extractive Metallurgy Review, volume: 27, pages: 231-279, 2006), and it is perhaps unsurprising that there are few, if any Schnabel process plants in operation. In particular, the Schnabel process has several undesirable features:
  • the ore at Skorpion consists of a mixture of zinc minerals, smithsonite (ZnCOs), hemimorphite (Zn 4 Si 2 0 7 (OH) 2 'H 2 0) and the clay mineral sauconite (Nao.3Zn3(Si,AI) 4 Oi 0 (OH) 2 '4H 2 0).
  • the gangue minerals are primarily quartz, muscovite and orthoclase.
  • the ore is ground and then leached in sulphuric acid at 60°C, the high temperature is essential to maximise the solubility of the silicon dissolved from the silicate minerals.
  • the method of leaching of the present invention has as one object thereof to overcome the abovementioned problems associated with the prior art, or to at least provide a useful alternative thereto.
  • a method for leaching zinc from a zinc silicate ore comprising the method steps of: curing the zinc silicate ore to be leached through the application of a low volume of an aqueous acid solution having a pH of 0 or above, producing a cured ore more amenable to leaching through the application of an ammonium carbonate solution containing free ammonia; leaching the cured zinc silicate ore at atmospheric pressure through the application of an ammonium carbonate solution containing free ammonia, producing a pregnant leach solution; and passing the pregnant leach solution to a means for zinc recovery.
  • rendering the zinc silicate ore more amenable to leaching through the application of an ammonium carbonate solution containing free ammonia means effecting one or more of improved zinc recovery, in a shorter time, under milder leach conditions.
  • Milder leach conditions may include, but are not limited to, lower temperatures, lower pressures, lower concentrations of leaching agents or combinations thereof.
  • a given zinc recovery may be effected in a shorter time, or by using milder leach conditions, or both, as a result of the curing step of the method of the present invention.
  • rendering the zinc silicate ore more amenable to leaching through the application of an ammonium carbonate solution containing free ammonia provides one or more of the following leach conditions: lower temperatures, lower pressures and lower concentrations of leaching agents.
  • the term lower is used to describe a lower leach temperature, pressure or concentration relative to that required for leaching ores that had not undergone the curing step of the present invention.
  • Ammoniacal leaching is particularly attractive for high carbonate ores, which are generally not amenable to acid leaching-based processes for economic reasons, as the carbonate component consumes significant amounts of acid.
  • the scope of the present invention is not limited to high carbonate ores.
  • the present invention identifies a principle enabling the economical recovery of zinc from a wide range of zinc silicate ores, in that conventional, energy-intensive physical pre-treatment techniques such as grinding or roasting, used successfully or otherwise in ammoniacal leaching, can be replaced or enhanced by using chemical techniques, where application of the aqueous acid solution having a pH of 0 or above renders the zinc silicate ore amenable to the subsequent ammoniacal leaching.
  • the pH of the aqueous acid solution is 0 or above. In one form of the invention, the pH of the aqueous acid solution is 0.25 or above. In one form of the invention, the pH of the aqueous acid solution is 0.5 or above. In one form of the invention, the pH of the aqueous acid solution is 0.75 or above. In one form of the invention, the pH of the aqueous acid solution is 1 or above. In one form of the invention, the pH of the aqueous acid solution is 1.5 or above. In one form of the invention, the pH of the aqueous solution is 2 or above. In one form of the invention, the pH of the aqueous acid solution is 2.5 or above.
  • the pH of the aqueous acid solution is 3 or above. In one form of the invention, the pH of the aqueous solution is 3.5 or above. In one form of the invention, the pH of the aqueous acid solution is 4 or above. In one form of the invention, the pH of the aqueous solution is 4.5 or above. In one form of the invention, the pH of the aqueous acid solution is 5 or above. In one form of the invention, the pH of the aqueous solution is 5.5 or above.
  • the pH of the aqueous acid solution is 6 or below. In one form of the invention, the pH of the aqueous solution is 5.5 or below. In one form of the invention, the pH of the aqueous solution is 5 or below. In one form of the invention, the pH of the aqueous solution is 4.5 or below. In one form of the invention, the pH of the aqueous solution is 4 or below. In one form of the invention, the pH of the aqueous solution is 3.5 or below. In one form of the invention, the pH of the aqueous solution is 3 or below. In one form of the invention, the pH of the aqueous solution is 2.5 or below.
  • the pH of the aqueous solution is 2 or below. In one form of the invention, the pH of the aqueous solution is 1.5 or below. In one form of the invention, the pH of the aqueous solution is 1 or below. In one form of the invention, the pH of the aqueous solution is 0.75 or below. In one form of the invention, the pH of the aqueous solution is 0.5 or below. In one form of the invention, the pH of the aqueous solution is 0.25 or below.
  • the pH of the aqueous acid solution has a range with an upper limit selected from one of the following: 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7 and a lower limit selected from one of the following: 0, 0.5, 1 , 1.5, 2, 2.5, 3, 3.5, 4, 4.5 and 5, where the upper limit is greater than the lower limit.
  • the pH of the aqueous acid solution has a range with an upper limit selected from one of the following: 2, 2.5, 3, 3.5, 4, 4.5, 5, and a lower limit selected from one of the following: 0, 0.5, 1 , 1.5, 2, 2.5, 3, where the upper limit is greater than the lower limit.
  • the pH of the aqueous acid solution has a range with an upper limit selected from one of the following: 2, 2.5, 3, 3.5, 4, and a lower limit selected from one of the following: 0, 0.5, 1 , 1.5, 2, where the upper limit is greater than the lower limit.
  • the aqueous acid solution may be an aqueous solution of a weak acid or a strong acid, or a mixture of both. As would be understood by a person skilled in the art, for a given pH, an aqueous solution of a weak acid will be more concentrated than an aqueous solution of a strong acid.
  • aqueous acid solutions with pH below zero are stronger and/or more concentrated than the aqueous acid solutions of the methods of the present invention. It is generally understood that more concentrated solutions of stronger acids will have a greater chemical effect within a given time than more dilute solutions of weaker acids.
  • Aqueous acid solutions having a pH below zero, particularly aqueous solutions of strong acids are widely available and routinely used in the field of hydrometallurgy. Accordingly, the present invention represents a counter-intuitive discovery that better results may be achieved through the use of more dilute or weaker acid solutions than those conventionally used in the art.
  • the relatively low proton concentration of the aqueous acid solutions of the invention produces a chemical environment in which the zinc silicate minerals are intrinsically unstable and decompose without consuming either protons or acid anions. That is, the partially dissociated weak acids (or more dilute fully dissociated strong acids) produce a localised pH where zinc silicate minerals such as hemimorphite, willemite and sauconite are all intrinsically unstable and therefore dissolve in the solution until it is saturated whereupon the zinc then precipitates in another, more thermodynamically stable form. The more stable form is the phase which, again without wishing to be bound by theory, is subsequently dissolved in the ammoniacal ammonium carbonate leach solution.
  • a further advantage of the invention is that by avoiding high concentrations of strong acids, dissolution of gangue is decreased thereby substantially simplifying subsequent purification of the leach solution.
  • a further advantage of the invention is that by using ammonia as the leaching agent acid soluble elements, such as Fe, Ca, Al, Mg, Si, etc are not dissolved thereby substantially simplifying subsequent purification of the leach solution.
  • Zinc silicate ores Zinc silicate ores
  • the term "zinc silicate ore” or variations thereof will be understood to include, for example, the product of one or more pre-treatment steps, such as a roast or calcination steps, and / or one or more concentration steps, but is not limited thereto.
  • the scope of the present invention should not be understood to exclude ores that have been pre-treated by conventional methods, and in such circumstances, the method of the present invention may afford better recoveries than conventional methods. In many cases, the improved recoveries afforded by the method of the invention may render an ore body commercially viable.
  • the scope of the present invention includes methods where an aqueous acid solution having a pH of 0 or above is applied to a mixture of ores; at least one component of said mixture is a zinc silicate ore.
  • zinc silicate ore or variations thereof, will be understood to include ores comprising one or more of the following minerals: hemimorphite, sauconite and willemite.
  • the method of the present invention is particularly effective where the zinc silicate ore contains a significant quantity of hemimorphite.
  • the zinc silicate ore comprises hemimorphite.
  • the zinc content of the zinc silicate ore is predominantly in the form of hemimorphite. In one form of the invention, at least 10% of the zinc content of the zinc silicate ore is in the form of hemimorphite. In one form of the invention, at least 20% of the zinc content of the zinc silicate ore is in the form of hemimorphite. In one form of the invention, at least 30% of the zinc content of the zinc silicate ore is in the form of hemimorphite. In one form of the invention, at least 40% of the zinc content of the zinc silicate ore is in the form of hemimorphite.
  • At least 50% of the zinc content of the zinc silicate ore is in the form of hemimorphite. In one form of the invention, at least 60% of the zinc content of the zinc silicate ore is in the form of hemimorphite. In one form of the invention, at least 70% of the zinc content of the zinc silicate ore is in the form of hemimorphite. In one form of the invention, at least 80% of the zinc content of the zinc silicate ore is in the form of hemimorphite. In one form of the invention, at least 90% of the zinc content of the zinc silicate ore is in the form of hemimorphite.
  • the method of the present invention is particularly effective on sauconite where the aqueous acid solution having a pH of 0 or above is a concentrated solution of a weak acid
  • at least 10% of the zinc content of the zinc silicate ore is in the form of sauconite
  • the aqueous acid solution having a pH of 0 or above is a concentrated solution of a weak acid
  • at least 20% of the zinc content of the zinc silicate ore is in the form of sauconite
  • the aqueous acid solution having a pH of 0 or above is a concentrated solution of a weak acid.
  • At least 30% of the zinc content of the zinc silicate ore is in the form of sauconite, and the aqueous acid solution having a pH of 0 or above is a concentrated solution of a weak acid.
  • at least 40% of the zinc content of the zinc silicate ore is in the form of sauconite, and the aqueous acid solution having a pH of 0 or above is a concentrated solution of a weak acid.
  • at least 50% of the zinc content of the zinc silicate ore is in the form of sauconite, and the aqueous acid solution having a pH of 0 or above is a concentrated solution of a weak acid.
  • At least 60% of the zinc content of the zinc silicate ore is in the form of sauconite, and the aqueous acid solution having a pH of 0 or above is a concentrated solution of a weak acid.
  • at least 70% of the zinc content of the zinc silicate ore is in the form of sauconite, and the aqueous acid solution having a pH of 0 or above is a concentrated solution of a weak acid.
  • at least 80% of the zinc content of the zinc silicate ore is in the form of sauconite, and the aqueous acid solution having a pH of 0 or above is a concentrated solution of a weak acid.
  • at least 90% of the zinc content of the zinc silicate ore is in the form of sauconite, and the aqueous acid solution having a pH of 0 or above is a concentrated solution of a weak acid.
  • the minimum fraction of zinc present as a specific mineral required for the deposit to be economically treated will decrease as the zinc head grade increases.
  • those skilled in the art will recognise that such minerals can occur together and the economics will be a function of the combined fraction of zinc present as hemimorphite and / or willemite and /or sauconite.
  • a weak acid is an acid that dissociates incompletely in aqueous solution. That is, it does not release all of its protons when in solution, donating only a partial amount of its protons to the solution.
  • These acids have higher pKa than strong acids, which release all of their protons when dissolved in aqueous solution. Accordingly, weak acid solutions exhibit higher pH than solutions containing an equal concentrations of a strong acid.
  • the aqueous acid solution is an aqueous solution of an acid with a K a less than 1.8x10 ⁇ 16 .
  • the aqueous acid solution is an aqueous solution of a weak acid having a pKai of from 0 to 7.
  • the aqueous acid solution is an aqueous solution of a weak acid having a pKai of from 0 to 7 is selected from the list within the following lUPAC compilations:
  • the aqueous acid solution is an aqueous solution of an acid selected from the group: aliphatic mono- and di-carboxylic acids, phenyl substituted alkanoic acids, hydroxyalkanoic and hydroxyalkandoic acids, aromatic acids, aliphatic and aromatic sulfonic acids, [0039]
  • the aqueous acid solution is an aqueous solution of an acid selected from the group: acetic acid, phenylacetic acid, trifluoroacetic acid, acrylic acid, ascorbic acid, benzoic acid, chlorobenzoic acid, dinitrobenzoic acid, hydroxybenzoic acid, methoxybenzoic acid, methylbenzoic acid, o-acetoxybenzoic acid, napthalene-2-benzoic acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid isobutyric acid, phenylbutyric acid, ⁇ - hydroxybutyric
  • the aqueous acid solution is an aqueous solution of an acid selected from the group: citric acid, oxalic acid, tartaric acid, acetic acid.
  • the aqueous acid solution is an aqueous solution of an acid selected from the group: sulphuric acid, phosphoric acid, hydrochloric acid, nitric acid, perchloric acid.
  • Leaching describes a process by which a solution containing a leaching agent is contacted with an ore, the solution recovered and valuable metals extracted therefrom.
  • the curing step of the present invention renders the zinc silicate ore to be leached more amenable to the leaching process.
  • the process is one where there is dissolution of the ammonia insoluble mineral and precipitation of an ammonia soluble phase. No metal recovery is achieved during curing.
  • the scope of the present invention encompasses methods where the aqueous acid solution is collected after the step of curing the zinc silicate ore to be leached, and metal values recovered therefrom.
  • conventional aqueous leaching solutions do not fall within the meaning of aqueous acid solution , as they do not render the ore to be leached more amenable to the subsequent leaching process.
  • two stage ammoniacal leaching processes differ markedly from the method of the present invention as there is no enhancement of the second leaching stage by performance of the first.
  • the step of curing the ore to be leached through the application of aqueous acid solution more specifically comprises substantially retaining the aqueous acid solution in contact with the zinc silicate ore to be leached when the ammonium carbonate solution containing free ammonia is added.
  • aqueous acid solution in contact with the zinc silicate ore to be leached when the ammonium carbonate solution containing free ammonia is added.
  • the most desirable conditions under which the zinc silicate ore is cured vary as the composition, mineralogy and texture of the ore varies.
  • the temperature at which the curing step occurs, the pH at which the curing step occurs and the time for which the zinc silicate ore is exposed to the aqueous acid solution may all be varied in response to the composition, mineralogy, texture, particle size and pore volume of the zinc silicate ore.
  • the step of curing the zinc silicate ore to be leached takes place at atmospheric pressure.
  • the step of curing the zinc silicate ore to be leached takes place at ambient temperature.
  • the curing time will be a product of many factors, not least of which is the particle size of the zinc silicate ore, with smaller particle sizes enabling shorter curing time (at the expense, of course, of the energy associated with reducing the particle size of the ore).
  • the period preferably is within a range having a lower limit of 2 hours, and an upper limit selected from the group: 28 days, 20 days, 14 days, 7 days, 3 days, 2 days, 1 day, 18 hours, 12 hours, 8 hours, 4 hours and 3 hours.
  • the period preferably is within a range having a lower limit of 30 minutes, and an upper limit selected from the following group: 14 days, 7 days, 6 days, 5 days, 4 days, 3 days 2 days, 1 day, 18 hours, 12 hours, 8 hours, 4 hours, 3 hours, 2 hours and 1 hour.
  • pore space and "pore volume” refer to the space comprising the pores within the ore particles, as opposed to inter-particle pores created by any stacking process.
  • the volume of the aqueous acid solution having a pH of 0 or above is a function of a number of parameters including, but not limited to, the texture of the zinc silicate ore, the residence time (the time for which the zinc silicate ore is exposed to the aqueous acid solution having a pH of 0 or above prior to the leaching step), the concentration of the aqueous acid solution having a pH of 0 or above, desired zinc recovery and the leach conditions.
  • the volumes of cure solution exposed to the ore are as low as practicable. That is, preferred forms of the invention utilise low volumes of aqueous acid solution having a pH of 0 or above, and preferred methods for curing the zinc silicate ore to be leached through the application of aqueous acid solution having a pH of 0 or above are those adapted to utilise low volumes of aqueous solution of aqueous acid solution having a pH of 0 or above.
  • the ideal extent of saturation of the pore space of the zinc silicate ore with the aqueous acid solution having a pH of 0 or above will depend largely on the texture of the zinc silicate ore.
  • the step of curing the zinc silicate ore to be leached through the application of aqueous acid solution having a pH of 0 or above saturates at least 20% of the pore space with solution.
  • the step of curing the zinc silicate ore to be leached through the application of aqueous acid solution having a pH of 0 or above saturates at least 30% of the pore space with solution.
  • the step of curing the zinc silicate ore to be leached through the application of aqueous acid solution having a pH of 0 or above saturates at least 40% of the pore space with solution.
  • the step of curing the zinc silicate ore to be leached through the application of aqueous acid solution having a pH of 0 or above saturates at least 50% of the pore space with solution.
  • the step of curing the zinc silicate ore to be leached through the application of aqueous acid solution having a pH of 0 or above saturates at least 60% of the pore space with solution.
  • the step of curing the zinc silicate ore to be leached through the application of the aqueous acid solution having a pH of 0 or above saturates at least 70% of the pore space with solution.
  • the step of curing the zinc silicate ore to be leached through the application of the aqueous acid solution having a pH of 0 or above saturates at least 80% of the pore space with solution.
  • the step of curing the zinc silicate ore to be leached through the application of the aqueous acid solution having a pH of 0 or above or above saturates at least 90% of the pore space with solution.
  • Curing conditions application of the aqueous acid solution having a pH of O or above to the zinc silicate ore
  • the step of curing the zinc silicate ore to be leached through the application of aqueous acid solution having a pH of 0 or above more specifically comprises:
  • the method of the present invention may include the step of:
  • the method of the present invention includes the step of:
  • the invention comprises reducing the size of the zinc silicate ore to be treated by wet grinding, wherein the zinc silicate ore is ground in contact with water or a grinding aqueous solution
  • the aqueous grinding solution may be provided in the form of the aqueous acid solution having a pH of 0 or above.
  • the method comprises the steps of:
  • the method of the present invention may include a step of:
  • the method of the present invention includes the step of:
  • the invention comprises reducing the size of the zinc silicate ore to be leached by wet crushing, wherein the zinc silicate ore is crushed in contact with water or an aqueous crushing solution.
  • the aqueous crushing solution may be provided in the form of the aqueous acid solution having a pH of 0 or above .
  • the method comprises the steps of:
  • the step of curing the zinc silicate ore to be leached through the application of an aqueous solution of aqueous acid solution having a pH of 0 or above more specifically comprises:
  • the step of curing the zinc silicate ore to be leached through the application of an aqueous acid solution having a pH of 0 or above more specifically comprises:
  • the method of the present invention may include a step of:
  • the method of the present invention includes the step of:
  • agglomerating the zinc silicate ore to be leached by contacting the zinc silicate ore with water or an aqueous solution of an agglomerating agent.
  • the aqueous acid solution having a pH of 0 or above is also the aqueous solution of the agglomerating agent. That is, the aqueous solution contains both a curing agent and an agglomerating agent.
  • the curing agent is an agglomerating agent, such that the step of curing the ore to be leached through the application of an aqueous solution of a curing agent more specifically comprises:
  • the step of curing the zinc silicate ore to be leached through the application of an aqueous acid solution having a pH of 0 or above more specifically comprises:
  • the predetermined time for which the zinc silicate ore is rested prior to the step of leaching the cured zinc silicate ore at atmospheric pressure through the application of an ammonium carbonate solution containing free ammonia will be a function of a number of parameters including, but not limited to the particle size of the ore, the concentration of the curing agent and the texture of the ore.
  • the predetermined period is between 5 minutes and twenty eight days.
  • the predetermined period is between 2 hours and 14 days.
  • the predetermined period is between 1 day and 7 days.
  • the cured ore- aqueous acid solution having a pH of 0 or above mixture has a solids content not less than about 100 g/L. In a preferred form of the invention, the cured ore-aqueous acid solution having a pH of 0 or above mixture has a solids content not less than about 200 g/L. In a preferred form of the invention, the cured ore-aqueous acid solution having a pH of 0 or above mixture has a solids content not less than about 400 g/L. In a preferred form of the invention, the cured ore-aqueous acid solution having a pH of 0 or above mixture has a solids content not less than about 700 g/L.
  • the cured ore-aqueous acid solution having a pH of 0 or above mixture has a solids content not less than about 1000 g/L. In a preferred form of the invention, the cured ore-aqueous acid solution having a pH of 0 or above mixture has a solids content not less than about 2000 g/L. In a preferred form of the invention, the cured ore-aqueous acid solution having a pH of 0 or above mixture has a solids content not less than about 4000 g/L. In a preferred form of the invention, the cured ore-aqueous acid solution having a pH of 0 or above mixture has a solids content not less than about 7000 g/L.
  • the cured ore-aqueous acid solution having a pH of 0 or above mixture has a solids content not less than about 10000 g/L. In a preferred form of the invention, the cured ore-aqueous acid solution having a pH of 0 or above mixture has a solids content not less than about 20000 g/L. In a preferred form of the invention, the cured ore-aqueous acid solution having a pH of 0 or above mixture has a solids content not less than about 40000 g/L. In a preferred form of the invention, the cured ore-aqueous acid solution having a pH of 0 or above mixture has a solids content not less than about 50000 g/L.
  • the solids content of the cured ore-aqueous acid solution having a pH of 0 or above mixture falls within a range of contents having a lower limit of 100 g/L
  • the range of contents has a lower limit of 200 g/L.
  • the range of contents has a lower limit of 400 g/L.
  • the range of contents has a lower limit of 700 g/L.
  • the range of contents has a lower limit of 1000 g/L.
  • the range of contents has a lower limit of 2000 g/L.
  • the range of contents has a lower limit of 4000 g/L. In a preferred form of the invention, the range of contents has a lower limit of 7000 g/L. In a preferred form of the invention, the range of contents has a lower limit of 10000 g/L. In a preferred form of the invention, the range of contents has a lower limit of 20000 g/L. In a preferred form of the invention, the range of contents has a lower limit of 40000 g/L. In a preferred form of the invention, the range of contents has a lower limit of 50000 g/L.
  • the solids content of the cured ore-aqueous acid solution having a pH of 0 or above mixture falls within a range of contents having an upper limit of 100000 g/L. In one form of the invention, the solids content of the mixture falls within a range of contents having an upper limit of 50000 g/L. In one form of the invention, the solids content of the mixture falls within a range of contents having an upper limit of 40000 g/L. In one form of the invention, the solids content of the mixture falls within a range of contents having an upper limit of 20000 g/L. [0081] As would be obvious to those skilled in the art, the volume and concentration of the reducing solution will vary according to several factors.
  • the product of concentration and volume is the dose of reductant applied.
  • the specific dose required by an ore can be applied using a low volume of a high concentration or a high volume of low concentration.
  • the volume to be used is a function of the surface area of the ore. A large particle size will require a lower volume than a fine particle size as the surface area is smaller. An ore with a high cobalt headgrade will require more solution and / or higher concentration than an ore with a low cobalt headgrade.
  • Methods for leaching ore generally, although not zinc silicate ore specifically, at atmospheric pressure are well known to persons skilled in the art, and include heap leaching, vat leaching, tank leaching and dump leaching.
  • the step of leaching the cured zinc silicate ore at atmospheric pressure through the application of an ammonium carbonate solution containing free ammonia, producing a pregnant leach solution takes place at ambient temperatures.
  • Atmospheric leaching, particularly at ambient temperatures is one of the least energy-intensive leaching techniques available.
  • a curing step that is not energy intensive and that renders a zinc silicate ore amenable to an ammoniacal leaching step that is also not energy intensive has clear advantages over prior art methods.
  • Ammonium carbonate fixes the operating pH to a relatively narrow range and is, to some extent, self-regulating as the ammonium carbonate acts as a buffer.
  • the pH range buffered by the ammonium carbonate is a range in which zinc is soluble.
  • a second advantage of carbonate systems is that there is less prospect of gypsum scaling as the sulphate level is always too low for precipitation to occur. The calcium level will also be extremely low as the precipitation of CaC0 3 will occur whenever calcium ions are released into solution.
  • a third advantage is that at the operating pH many undesirable metals, including iron, calcium, magnesium, aluminium, silicon and manganese, have very low solubilities. This simplifies the overall process by eliminating or reducing the need to include unit operations designed to remove these metals from the zinc solution.
  • the ammonium carbonate concentration of the ammonium carbonate solution containing free ammonia is sufficient to prevent the pH decreasing below 8 during the step of leaching the cured zinc silicate ore at atmospheric pressure through the application of an ammonium carbonate solution containing free ammonia, producing a pregnant leach solution.
  • the ammonium carbonate concentration of the ammonium carbonate solution containing free ammonia is at least 0.1 g/L.
  • the ammonium carbonate concentration of the ammonium carbonate solution containing free ammonia is at least 1 g/L
  • the concentration of ammonium carbonate is at least 5 g/L.
  • the ammonium carbonate concentration of the ammonium carbonate solution containing free ammonia is at least 8 g/L.
  • the ammonium carbonate concentration of the ammonium carbonate solution containing free ammonia is at least 10 g/L.
  • the ammonium carbonate concentration of the ammonium carbonate solution containing free ammonia is at least 20 g/L.
  • the ammonium carbonate concentration of the ammonium carbonate solution containing free ammonia is at least 30 g/L.
  • the ammonium carbonate concentration of the ammonium carbonate solution containing free ammonia is between 0.1 g/L and 500 g/L.
  • the concentration of ammonium carbonate is between 1 g/L and 500g/L.
  • the concentration of ammonium carbonate is between 5 g/L and 500g/L.
  • the ammonium carbonate concentration of the ammonium carbonate solution containing free ammonia is between 8 g/L and 500g/L.
  • the ammonium carbonate concentration of the ammonium carbonate solution containing free ammonia is between 10 g/L and 500g/L.
  • the ammonium carbonate concentration of the ammonium carbonate solution containing free ammonia is between 20 g/L and 500g/L.
  • the ammonium carbonate concentration of the ammonium carbonate solution containing free ammonia is between 30 g/L and 500g/L
  • the ammonium carbonate concentration of the solution is about 10 g/L ammonium carbonate.
  • ammonia of the ammonium carbonate solution containing free ammonia may be generated in situ, such as by hydrolysis of urea.
  • the free ammonia concentration of the ammonium carbonate solution containing free ammonia may be tailored to the rate at which the zinc is leached from the cured zinc silicate ore, thereby minimising excess free ammonia and thus minimising ammonia losses due to evaporation.
  • the resulting pregnant leach solution preferably contains only a slight excess of free ammonia over that necessary to retain the zinc in solution. As there is little free ammonia in the pregnant leach solution, ammonia losses due to evaporation are low.
  • the ammonium carbonate solution containing free ammonia comprises about 30-70 g/L ammonia.
  • the level of ammonia in the solution applied in step (b) would be matched to the level of zinc in the ore and the rate at which it leaches. A low grade ore where the zinc leaches slowly would require a lower concentration of ammonia than a high grade ore where the leaching is rapid.
  • the concentration of acid is substantially dictated by the pH of the solution.
  • the relationship between the concentration of the acid and the pH is substantially determined by the K a (or K a s or Ka-i) of the acid.
  • the molar ratio of acid in the aqueous acid solution having a pH of 0 or above to zinc in the zinc silicate ore is less than 1 . In one form of the invention, the molar ratio of acid in the aqueous acid solution having a pH of 0 or above to zinc in the zinc silicate ore is less than 0.1.
  • the molar ratio of acid in the aqueous acid solution having a pH of 0 or above to zinc in the zinc silicate ore is less than 0.01. In one form of the invention, the molar ratio of acid in the aqueous acid solution having a pH of 0 or above to zinc in the zinc silicate ore is less than 0.001. In one form of the invention, the molar ratio of acid in the aqueous acid solution having a pH of 0 or above to zinc in the zinc silicate ore is less than 0.0001.
  • the molar ratio of acid to zinc for ores rich in sauconite is between 1 :1 and 4:1. In one form of the invention, the molar ratio of acid to zinc for ores rich in sauconite is between 1 :1 and 3:1. In one form of the invention, the molar ratio of acid to zinc for ores rich in sauconite is between 1.5:1. and 2.5:1 .
  • the means for metal recovery of the present invention may comprise one or more of the following: solvent extraction, ion exchange, precipitation and cementation.
  • Figure 1 is a schematic flow sheet of a method for leaching one or more target metals, at least one of which is zinc, from a zinc silicate ore in accordance with the present invention
  • Figure 2 shows the head grades of the ore samples in the examples
  • Figure 3 shows the relative abundance of the zinc minerals present in the samples of Figure 2;
  • Figure 4 shows the zinc dissolution for all of the samples after the leaching treatment of Example 1 ;
  • Figure 5 shows the recoveries as a function of dosage for the samples of Example 2.
  • Figure 6 shows the data of Figure 5 as function of citric acid dosage
  • Figure 7 shows the zinc dissolution for all of the samples after the treatment of Example 3;
  • Figure 8 shows the zinc dissolution for all the samples after being cured with strong acids at different doses
  • Figure 9 is a graph showing the extent of Direct leaching of the ores of example 5 ores in ammoniacal - ammonium carbonate solutions (AAC and SAC) and sulphuric acid;
  • Figure 10 is a graph showing the extent of Direct leaching of the ores of example 5 ores in ammoniacal - ammonium carbonate solutions (AAC and SAC) and sulphuric acid after a pretreatment step; and
  • Figure 1 1 is a graph showing the extent of Direct leaching of the ores of example 5 ores in ammoniacal - ammonium carbonate solution after the ores were pretreated using AAC and two different concentrations of citric acid.
  • the zinc silicate ore 1 is sprayed with a weakly acidic solution 2 sufficient to wet the pore volume of the ore.
  • the cured zinc silicate ore is then stacked 3 into a heap.
  • the heap is irrigated with an ammoniacal - ammonium carbonate solution 4, which is a combination of solution recycled from the solvent extraction and fresh solution.
  • the run off is collected and sent to solvent extraction 5, the zinc-depleted solids 6 are sent to tailings.
  • the zinc-rich ammoniacal solution 5 is contacted with a suitable solvent extraction reagent and zinc extracted.
  • the zinc-depleted ammoniacal solution 4 is recycled back to the heap leach stage.
  • the zinc-rich solution from the solvent extraction stage 7 is sent to a process for zinc recovery e.g. electrowinning. After recovery, the zinc- depleted solution 8 is recycled back to solvent extraction for reuse.
  • the zinc product 9 is sent for sale.
  • the other major minerals present in the ore were calcite (CaC0 3 ), dolomite (CaMg(C0 3 ) 2 ) and garnet
  • the acid neutralisation capacity of the ores were calculated to range from 10 to 850 kg H 2 SO 4 / 1 ore, the average being 440 kg H 2 SO / 1 ore. Economically, such high acid consumptions effectively discounts the use of acid as a leaching agent for these ores.
  • the samples were cured using a strong acid (sulphuric acid), and a weak acid, (citric acid), at two different dosages, by forming a paste.
  • the paste was slurried using 20 g/L ammonia + 20 g/L ammonium carbonate solution.
  • the solution was sampled and analysed for zinc.
  • Figure 4 shows the zinc dissolution for all of the samples.
  • the uncured sample is also shown after 24 h leaching in 20 g/L ammonia + 20 g/L ammonium carbonate solution.
  • the other disadvantage of acid leaching is that the leach solution will also contain other dissolved elements, notably iron, aluminium, silicon, calcium and magnesium, all of which will need to be removed and disposed of in an environmentally acceptable manner. None of these elements are soluble in the ammoniacal ammonium carbonate solution thereby greatly simplifying the overall process flowsheet and reducing the environmental impact.
  • the same ores were then pretreated by making up a paste by mixing a small volume of the same solutions as used for leaching with ore. The mixture was allowed to rest for 24h and then leached by adding the paste to a larger volume of AAC.

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Abstract

Conformément à la présente invention, il est prévu un procédé de lixiviation de zinc à partir d'un minerai, le procédé comprenant les étapes consistant : à durcir le minerai de silicate de zinc devant être lixivié par application d'une solution aqueuse d'un acide faible, à produire un minerai durci ; à lixivier le minerai durci à la pression atmosphérique par application d'une solution de carbonate d'ammonium contenant de l'ammoniac libre, à produire une liqueur-mère de lixiviation ; et à faire passer la liqueur-mère de lixiviation dans un moyen de récupération de zinc.
PCT/AU2013/000661 2012-06-26 2013-06-20 Procédé de lixiviation de minerais de silicate de zinc WO2014000021A1 (fr)

Priority Applications (2)

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EP13809302.6A EP2864510A4 (fr) 2012-06-26 2013-06-20 Procédé de lixiviation de minerais de silicate de zinc
MX2014016126A MX2014016126A (es) 2012-06-26 2013-06-20 Metodo para lixiviar minerales de silicato de zinc.

Applications Claiming Priority (4)

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AU2012902708 2012-06-26
AU2012902708A AU2012902708A0 (en) 2012-06-26 Method for Leaching Zinc Silicate Ores
AU2013202214A AU2013202214B2 (en) 2012-06-26 2013-03-28 Method for Leaching Zinc Silicate Ores
AU2013202214 2013-03-28

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Publication number Priority date Publication date Assignee Title
CN109022771A (zh) * 2018-08-01 2018-12-18 昆明理工大学 一种氧化锌矿酸性浸出剂及其浸出方法
CN110205489A (zh) * 2018-07-24 2019-09-06 重庆东群科技有限公司 一种以锌酸钡合成途径处理含锌原矿的方法
CN113528816A (zh) * 2021-07-23 2021-10-22 昆明冶金研究院有限公司 一种直接酸浸浮选氧化锌精矿的方法

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CN109371259B (zh) * 2018-11-13 2021-10-15 衡阳市大宇锌业有限公司 一种从硫酸锌溶液中去除氯的方法
CN110205482B (zh) * 2019-05-28 2021-01-12 西北矿冶研究院 一种锌冶炼有机物除钴渣的综合回收方法

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US20050069473A1 (en) * 2001-11-27 2005-03-31 De Souza Adelson Dias Integration processes of the treatments of zinc silicate concentrates or zinc silicate ore and roasted concentrates of zinc sulphides
US20100180728A1 (en) * 2007-07-13 2010-07-22 Metaleach Limited Method for ammoniacal leaching

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US20050069473A1 (en) * 2001-11-27 2005-03-31 De Souza Adelson Dias Integration processes of the treatments of zinc silicate concentrates or zinc silicate ore and roasted concentrates of zinc sulphides
US20100180728A1 (en) * 2007-07-13 2010-07-22 Metaleach Limited Method for ammoniacal leaching

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110205489A (zh) * 2018-07-24 2019-09-06 重庆东群科技有限公司 一种以锌酸钡合成途径处理含锌原矿的方法
CN110205489B (zh) * 2018-07-24 2020-12-11 重庆东群科技有限公司 一种以锌酸钡合成途径处理含锌原矿的方法
CN109022771A (zh) * 2018-08-01 2018-12-18 昆明理工大学 一种氧化锌矿酸性浸出剂及其浸出方法
CN113528816A (zh) * 2021-07-23 2021-10-22 昆明冶金研究院有限公司 一种直接酸浸浮选氧化锌精矿的方法

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AU2013202214A1 (en) 2014-01-16
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EP2864510A1 (fr) 2015-04-29
AU2013202214B2 (en) 2016-04-28
EP2864510A4 (fr) 2016-03-02

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