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US20180237886A1 - Method for recovering zinc from solution - Google Patents

Method for recovering zinc from solution Download PDF

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Publication number
US20180237886A1
US20180237886A1 US15/764,059 US201615764059A US2018237886A1 US 20180237886 A1 US20180237886 A1 US 20180237886A1 US 201615764059 A US201615764059 A US 201615764059A US 2018237886 A1 US2018237886 A1 US 2018237886A1
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Prior art keywords
zinc
solution
ammonium carbonate
aqueous
extractant
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US15/764,059
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English (en)
Inventor
Nicholas James Welham
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Metaleach Ltd
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Metaleach Ltd
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Priority claimed from AU2015903957A external-priority patent/AU2015903957A0/en
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Abandoned legal-status Critical Current

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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
    • C22B19/20—Obtaining zinc otherwise than by distilling
    • C22B19/24—Obtaining zinc otherwise than by distilling with leaching with alkaline solutions, e.g. ammonia
    • C22B3/0068—
    • 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
    • C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
    • C22B3/12—Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic alkaline solutions
    • C22B3/14—Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic alkaline solutions containing ammonia or ammonium salts
    • 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
    • C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
    • C22B3/26—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds
    • C22B3/38—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds containing phosphorus
    • C22B3/384—Pentavalent phosphorus oxyacids, esters thereof
    • C22B3/3846—Phosphoric acid, e.g. (O)P(OH)3
    • 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
    • C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
    • C22B3/26—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds
    • C22B3/30—Oximes
    • 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 recovering zinc from an ammoniacal ammonium carbonate solution. More particularly, the present invention relates to a method for recovering zinc from an ammoniacal ammonium carbonate solution by way of solvent extraction.
  • Zinc is typically derived from the sulphide mineral sphalerite by roasting the ore to form zinc oxide, leaching the zinc oxide in sulphuric acid, purifying the solution by adding zinc dust and then electrowinning the zinc. Purification of the pregnant leach solution can also be undertaken through the use of a solvent extraction process.
  • a method for recovering zinc from an aqueous ammoniacal ammonium carbonate zinc solution comprising the steps of:
  • extraction or variations, will be understood to incorporate both chemical and physical transfer of the species undergoing extraction between the aqueous and organic phases.
  • the inventors of the present invention have discovered that the presence of carbonate in the aqueous ammoniacal ammonium carbonate zinc solution has an effect on the loading of the zinc onto the organic zinc extractant.
  • ammoniacal solutions are chemically distinct from acid solutions.
  • an acid leach solution the level of carbonate will be very low due to the low solubility of CO 2 under the acid conditions necessary for leaching.
  • the addition of carbonates to such a solution therefore results in the evolution of CO 2 .
  • the ammoniacal solutions there is a much higher solubility of bicarbonate/carbonate ions and so CO 2 does not evolve.
  • the method further comprises the step of:
  • the zinc-containing ore contains carbonate minerals.
  • the zinc-containing ore is a zinc carbonate (smithsonite, ZnCO 3 , or hydrozincite Zn 5 (CO 3 ) 2 (OH) 6 ) containing ore. With such ores, a portion of the carbonate present in the ore will be dissolved concomitantly with the zinc during leaching in an ammoniacal solution, which may initially contain no carbonate ions, to produce the aqueous ammoniacal ammonium carbonate zinc solution.
  • ammonium carbonate solution by the addition of carbon dioxide to a solution of ammonia or by the addition of ammonia to a solution of carbon dioxide or by the addition of ammonia and carbon dioxide to an aqueous solution.
  • the carbon dioxide evolved during step (iii) is absorbed into an aqueous solution containing ammonia. Still preferably, the carbon dioxide evolved during step (iii) is absorbed into the zinc- and carbonate-depleted aqueous ammoniacal ammonium carbonate solution produced during step (i).
  • step (i) is performed in a continuous manner, and at least a portion of the organic solution of a zinc extractant of step (i) is provided by the zinc-depleted organic solution of a zinc extractant provided by subsequent method steps.
  • the method more specifically comprises a method for recovering zinc from an aqueous ammoniacal ammonium carbonate zinc solution containing free ammonia, the method comprising the steps of:
  • the ammonia scrub solution preferably has a pH less than 2. More preferably, the ammonia scrub solution has a pH less than 3. Still preferably, the ammonia scrub solution has a pH less than 4. Still preferably, the ammonia scrub solution has a pH less than 5. Still preferably, the ammonia scrub solution has a pH less than 6. Still preferably, the ammonia scrub solution has a pH less than 7.
  • the ammonia scrub solution preferably has a pH in the range 2-8. Still preferably, the ammonia scrub solution has a pH in the range 3-8. Still preferably, the ammonia scrub solution has a pH in the range 4-8. Still preferably, the ammonia scrub solution has a pH in the range 5-8. Still preferably, the ammonia scrub solution has a pH in the range 6-8. Still preferably, the ammonia scrub solution has a pH in the range 7-8.
  • ammonia present in the zinc-enriched ammonia-enriched organic solution is present as weakly-held ammonium NH 4 + ions.
  • the weakly-held ammonium ions are displaced by the more strongly-held protons of the ammonia scrub solution.
  • the ammonia scrub solution is produced by dilution of the zinc-enriched aqueous acid solution produced in the process. More preferably, the ammonia scrub solution is composed of a dilute solution of a mineral acid, selected from the group: sulphuric acid, hydrochloric acid, nitric acid. In a highly preferred form the ammonia scrub solution is dilute sulphuric acid.
  • the ammonia scrub solution is carbonic acid, a solution of carbon dioxide in water. More preferably, the concentration of carbonic acid in solution is maintained by constant replenishment of carbon dioxide.
  • the method more specifically comprises a method for recovering zinc from an aqueous impurity-containing ammoniacal ammonium carbonate zinc solution, the method comprising the steps of:
  • the impurity scrub solution preferably has a pH less than 0. More preferably, the impurity scrub solution has a pH less than 1. Still preferably, the impurity scrub solution has a pH less than 2. Still preferably, the impurity scrub solution has a pH less than 3. Still preferably, the impurity scrub solution has a pH less than 4. Still preferably, the impurity scrub solution has a pH less than 5. Still preferably, the impurity scrub solution has a pH less than 6. Still preferably, the impurity scrub solution has a pH less than 7.
  • the impurities present in the impurity-enriched zinc-enriched organic solution are present in weakly-held forms. In the presence of protons, the weakly-held impurity ions are displaced from the impurity-enriched zinc-enriched organic solution by the more strongly held protons of the impurity scrub solution. As would be recognised by those skilled in the art, different impurities will be held with differing strength and some impurities will require a lower pH impurity scrub solution than other.
  • the impurity scrub solution preferably contains zinc ions
  • the concentration of zinc in the impurity scrub solution is preferably less than 1 g/L. More preferably, the concentration of zinc in the impurity scrub solution is less than 2 g/L. Still preferably, the concentration of zinc in the impurity scrub solution is less than 3 g/L. Still preferably, the concentration of zinc in the impurity scrub solution is less than 4 g/L. Still preferably, the concentration of zinc in the impurity scrub solution is less than 5 g/L.
  • the concentration of zinc in the impurity scrub solution is less than 7 g/L. Still preferably, the concentration of zinc in the impurity scrub solution is less than 10 g/L. Still preferably, the concentration of zinc in the impurity scrub solution is less than 15 g/L. Still preferably, the concentration of zinc in the impurity scrub solution is less than 20 g/L. Still preferably, the concentration of zinc in the impurity scrub solution is less than 30 g/L. Still preferably, the concentration of zinc in the impurity scrub solution is less than 50 g/L. Still preferably, the concentration of zinc in the impurity scrub solution is less than 60 g/L. Still preferably, the concentration of zinc in the impurity scrub solution is less than 75 g/L. Still preferably, the concentration of zinc in the impurity scrub solution is less than 100 g/L. Still preferably, the concentration of zinc in the impurity scrub solution is less than 150 g/L.
  • the impurities present in the impurity-enriched zinc-enriched organic solution are present in weakly-held forms. In the presence of zinc ions, the weakly-held impurity ions are displaced from the impurity-enriched zinc-enriched organic solution by the more strongly held zinc ions. As would be recognised by those skilled in the art, different impurities will be held with differing strength and some impurities will require a higher zinc concentration in the impurity scrub solution than others.
  • the method of the present invention may more specifically comprise both of:
  • the method of the present invention is performed at elevated temperature.
  • the method of the present invention is performed at 15-80° C. Still preferably the method of the present invention is performed at 15-70° C. Still preferably, the method of the present invention is performed at 15-60° C. Still preferably, the method of the present invention is performed at 15-50° C. Still preferably, the method of the present invention is performed at 15-40° C. Still preferably, the method of the present invention is performed at 15-30° C. Still preferably, the method of the present invention is performed at 15-25° C. Still preferably, the method of the present invention is performed at ambient temperature. As would be understood by a person skilled in the art, the performance of the method of the present invention at ambient temperature is advantageous as no additional operations costs are incurred by increasing the temperature of the method.
  • the method of the present invention is performed at 20-80° C. Still preferably the method of the present invention is performed at 20-70° C. Still preferably the method of the present invention is performed at 20-60° C. Still preferably the method of the present invention is performed at 20-50° C. Still preferably the method of the present invention is performed at 20-40° C. Still preferably the method of the present invention is at 20-30° C.
  • the method of the present invention is performed at 25-80° C. Still preferably the method of the present invention is performed at 25-70° C. Still preferably the method of the present invention is performed at 25-60° C. Still preferably the method of the present invention is performed at 25-50° C. Still preferably the method of the present invention is performed at 25-40° C. Still preferably the method of the present invention is performed at 25-30° C.
  • the method of the present invention is performed at 30-80° C. Still preferably the method of the present invention is performed at 30-70° C. Still preferably the method of the present invention is performed at 30-60° C. Still preferably the method of the present invention is performed at 30-50° C. Still preferably the method of the present invention is performed at 30-40° C.
  • the concentration of zinc in the ammoniacal ammonium carbonate solution is less than 0.1 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is less than 1 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is less than 2 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is less than 3 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is less than 4 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is less than 5 g/L.
  • the concentration of zinc in the ammoniacal ammonium carbonate solution is less than 7 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is less than 10 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is less than 15 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is less than 20 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is less than 30 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is less than 50 g/L.
  • the concentration of zinc in the ammoniacal ammonium carbonate solution is less than 60 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is less than 75 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is less than 100 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is less than 150 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is less than 250 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is less than 500 g/L.
  • the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 1 g/L.
  • the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 2 g/L.
  • the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 3 g/L.
  • the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 4 g/L.
  • the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 5 g/L.
  • the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 7 g/L.
  • the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 10 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 15 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 20 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 30 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 50 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 60 g/L.
  • the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 75 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 100 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 150 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 200 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 250 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 350 g/L. Still preferably, the concentration of zinc in the ammoniacal ammonium carbonate solution is between 0.1 and 500 g/L.
  • the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 0.1 g/L.
  • the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 1 g/L.
  • the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 2 g/L.
  • the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 3 g/L.
  • the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 4 g/L.
  • the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 5 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 7 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 10 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 15 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 20 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 30 g/L.
  • the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 50 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 60 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 75 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 100 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 150 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 200 g/L.
  • the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 250 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is less than 300 g/L.
  • the concentration of free ammonia in the ammoniacal ammonium carbonate solution is between 0.1 and 1 g/L.
  • the concentration of free ammonia in the ammoniacal ammonium carbonate solution is between 0.1 and 2 g/L.
  • the concentration of free ammonia in the ammoniacal ammonium carbonate solution is between 0.1 and 3 g/L.
  • the concentration of free ammonia in the ammoniacal ammonium carbonate solution is between 0.1 and 4 g/L.
  • the concentration of free ammonia in the ammoniacal ammonium carbonate solution is between 0.1 and 5 g/L.
  • the concentration of free ammonia in the ammoniacal ammonium carbonate solution is between 0.1 and 7 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is between 0.1 and 10 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is between 0.1 and 15 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is between 0.1 and 20 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is between 0.1 and 30 g/L.
  • the concentration of free ammonia in the ammoniacal ammonium carbonate solution is between 0.1 and 50 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is between 0.1 and 60 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is between 0.1 and 75 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is between 0.1 and 100 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is between 0.1 and 150 g/L.
  • the concentration of free ammonia in the ammoniacal ammonium carbonate solution is between 0.1 and 200 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is between 0.1 and 250 g/L. Still preferably, the concentration of free ammonia in the ammoniacal ammonium carbonate solution is between 0.1 and 300 g/L.
  • the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 0.1 g/L.
  • the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 1 g/L.
  • the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 2 g/L.
  • the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 3 g/L.
  • the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 4 g/L.
  • the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 5 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 7 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 10 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 15 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 20 g/L.
  • the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 30 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 50 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 60 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 75 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 100 g/L.
  • the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 150 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 200 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 300 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is less than 500 g/L.
  • the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 1 g/L.
  • the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 2 g/L.
  • the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 3 g/L.
  • the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 4 g/L.
  • the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 5 g/L.
  • the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 7 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 10 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 15 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 20 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 30 g/L.
  • the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 50 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 60 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 75 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 100 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 150 g/L.
  • the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 200 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 300 g/L. Still preferably, the concentration of ammonium carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 500 g/L.
  • the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 0.1 g/L.
  • the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 1 g/L.
  • the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 2 g/L.
  • the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 3 g/L.
  • the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 4 g/L.
  • the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 5 g/L.
  • the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 7 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 10 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 15 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 20 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 30 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 50 g/L.
  • the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 60 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 75 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 100 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 150 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 200 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 250 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 350 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is less than 500 g/L.
  • the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 1 g/L.
  • the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 2 g/L.
  • the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 3 g/L.
  • the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 4 g/L.
  • the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 5 g/L.
  • the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 7 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 10 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 15 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 20 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 30 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 50 g/L.
  • the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 60 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 75 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 100 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 150 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 200 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 250 g/L.
  • the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 350 g/L. Still preferably, the concentration of carbonate in the ammoniacal ammonium carbonate solution is between 0.5 and 500 g/L.
  • controlling will be understood to include any steps that could be taken to ensure that the molar ratio of carbonate to zinc in the aqueous ammoniacal ammonium carbonate zinc solution is within the required range.
  • methods of controlling the molar ratio of carbonate to zinc in the aqueous ammoniacal ammonium carbonate zinc solution include, but are not limited to:
  • the molar ratio of carbonate to zinc in the aqueous solution is less than 0.1.
  • the molar ratio of carbonate to zinc in the aqueous solution is less than 0.25.
  • the molar ratio of carbonate to zinc in the aqueous solution is less than 0.50.
  • the molar ratio of carbonate to zinc in the aqueous solution is less than 0.75.
  • the molar ratio of carbonate to zinc in the aqueous solution is less than 0.9.
  • the molar ratio of carbonate to zinc in the aqueous solution is less than 1.0.
  • the molar ratio of carbonate to zinc in the aqueous solution is less than 1.1. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is less than 1.25. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is less than 1.5. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is less than 2.0.
  • the molar ratio of carbonate to zinc in the aqueous solution is between 0.05 and 0.1.
  • the molar ratio of carbonate to zinc in the aqueous solution is between 0.05 and 0.25.
  • the molar ratio of carbonate to zinc in the aqueous solution is between 0.05 and 0.50.
  • the molar ratio of carbonate to zinc in the aqueous solution is between 0.05 and 0.75.
  • the molar ratio of carbonate to zinc in the aqueous solution is between 0.05 and 0.9.
  • the molar ratio of carbonate to zinc in the aqueous solution is between 0.05 and 1.0.
  • the molar ratio of carbonate to zinc in the aqueous solution is between 0.05 and 1.1. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.05 and 1.1. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.05 and 1.25. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.05 and 1.5. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.05 and 2.0.
  • the molar ratio of carbonate to zinc in the aqueous solution is between 0.1 and 1.0.
  • the molar ratio of carbonate to zinc in the aqueous solution is between 0.25 and 1.0. More preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.5 and 1.0. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.75 and 1.0. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.9 and 1.0. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.95 and 1.0.
  • the molar ratio of carbonate to zinc in the aqueous solution is between 0.1 and 1.1.
  • the molar ratio of carbonate to zinc in the aqueous solution is between 0.25 and 1.1. More preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.5 and 1.1. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.75 and 1.1. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.9 and 1.1. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.95 and 1.1.
  • the molar ratio of carbonate to zinc in the aqueous solution is between 0.1 and 1.5.
  • the molar ratio of carbonate to zinc in the aqueous solution is between 0.25 and 1.5. More preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.5 and 1.5. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.75 and 1.5. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.9 and 1.5. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.95 and 1.5.
  • the molar ratio of carbonate to zinc in the aqueous solution is between 0.1 and 2.0.
  • the molar ratio of carbonate to zinc in the aqueous solution is between 0.25 and 2.0. More preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.5 and 2.0. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.75 and 2.0. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.9 and 2.0. Still preferably, the molar ratio of carbonate to zinc in the aqueous solution is between 0.95 and 2.0.
  • the molar ratio of carbonate to zinc in the aqueous solution can be determined using any method available to those skilled in the art.
  • the content of zinc and carbonate in the aqueous phase can be determined by taking an aliquot of the solution and measuring the zinc concentration using, for example, an atomic absorption spectrometer.
  • Carbonate can be measured gravimetrically by precipitation using barium ions or by a pH titration.
  • the molar ratio of ammonia to zinc in the aqueous solution is less than 0.1.
  • the molar ratio of ammonia to zinc in the aqueous solution is less than 0.25.
  • the molar ratio of ammonia to zinc in the aqueous solution is less than 0.50.
  • the molar ratio of ammonia to zinc in the aqueous solution is less than 0.75.
  • the molar ratio of ammonia to zinc in the aqueous solution is less than 0.9.
  • the molar ratio of ammonia to zinc in the aqueous solution is less than 1.0.
  • the molar ratio of ammonia to zinc in the aqueous solution is less than 1.1.
  • the molar ratio of ammonia to zinc in the aqueous solution is less than 1.25.
  • the molar ratio of ammonia to zinc in the aqueous solution is less than 1.5.
  • the molar ratio of ammonia to zinc in the aqueous solution is less than 2.0.
  • the molar ratio of ammonia to zinc in the aqueous solution is less than 3.0.
  • the molar ratio of ammonia to zinc in the aqueous solution is less than 5.0.
  • the molar ratio of ammonia to zinc in the aqueous solution is less than 10.0.
  • the molar ratio of ammonia to zinc in the aqueous solution is less than 20.0.
  • the molar ratio of ammonia to zinc in the aqueous solution is less than 50.0.
  • the molar ratio of ammonia to zinc in the aqueous solution is less than 100.0.
  • the molar ratio of ammonia to zinc in the aqueous solution is between 0.05 and 0.1.
  • the molar ratio of ammonia to zinc in the aqueous solution is between 0.05 and 0.25.
  • the molar ratio of ammonia to zinc in the aqueous solution is between 0.05 and 0.50.
  • the molar ratio of ammonia to zinc in the aqueous solution is between 0.05 and 0.75.
  • the molar ratio of ammonia to zinc in the aqueous solution is between 0.05 and 0.9.
  • the molar ratio of ammonia to zinc in the aqueous solution is between 0.05 and 1.0.
  • the molar ratio of ammonia to zinc in the aqueous solution is between 0.05 and 1.1.
  • the molar ratio of ammonia to zinc in the aqueous solution is between 0.05 and 1.25.
  • the molar ratio of ammonia to zinc in the aqueous solution is between 0.05 and 1.5.
  • the molar ratio of ammonia to zinc in the aqueous solution is between 0.05 and 2.0.
  • the molar ratio of ammonia to zinc in the aqueous solution is between 0.05 and 3.0.
  • the molar ratio of ammonia to zinc in the aqueous solution is between 0.05 and 5.0.
  • the molar ratio of ammonia to zinc in the aqueous solution is between 0.05 and 10.0.
  • the molar ratio of ammonia to zinc in the aqueous solution is between 0.05 and 20.0.
  • the molar ratio of ammonia to zinc in the aqueous solution is between 0.05 and 50.0.
  • the molar ratio of ammonia to zinc in the aqueous solution is between 0.05 and 100.0.
  • the zinc extractant is selected from the group: liquid organophosphorus extractant, liquid oxime extractant, carboxylic acid extractant and combinations thereof.
  • the molecular formula of the carboxylic acid extractant contains 6-14 carbon atoms. In a preferred form of the invention, the molecular formula of the carboxylic acid extractant contains 8-12 carbon atoms.
  • the oxime extractant is selected from an aldoxime, a ketoxime or a mixture of both.
  • the organophosphorus extractant is a derivative of phosphoric, phosphonic, phosphinic or dithiophosphinic acid.
  • the organophosphorus extractant is Bis(2-ethylhexyl) hydrogen phosphate (also known as, Bis(2-ethylhexyl) phosphoric acid, Bis(2-ethylhexyl) phosphate, Bis(2-ethylhexyl) hydrophosphoric acid, BEHPA, BEHP, BEHHPA, BEHHP, Di-(2-ethylhexyl) phosphoric acid, D2EHPA, D2EHPA, (C 8 H 17 O) 2 PO 2 H and has the CAS Number 298-07-7).
  • Bis(2-ethylhexyl) hydrogen phosphate also known as, Bis(2-ethylhexyl) phosphoric acid, Bis(2-ethylhexyl) phosphate, Bis(2-ethylhexyl) hydrophosphoric acid, BEHPA, BEHP, BEHHPA, BEHHP, Di-(2-ethylhexyl) phosphoric acid, D2
  • the species extracted from other aqueous media has two molecules of the organic extractant per divalent metal ion
  • the species extracted from ammoniacal ammonium carbonate solution is understood to extract with only one molecule of the extractant, with the charge being balanced by another monovalent anion in the system, such as hydrogen carbonate (bicarbonate),
  • the inventors believe that if the complex RZnHCO 3 is present, then it will be notably shorter than R-Zn-R as there is only a single organic chain on the complex. This is less likely to become entangled than the R-Zn-R complex and therefore not have a substantially higher viscosity than the starting organic solution. This allows the use of a higher concentration of the organic extractant without practical difficulties such as increased separation time.
  • the molar ratio of ammonia to zinc in the aqueous ammoniacal ammonium carbonate zinc solution is four, or greater.
  • the molar ratio of ammonia to zinc in the aqueous ammoniacal ammonium carbonate zinc solution is four, or greater, the zinc in the aqueous ammoniacal ammonium carbonate zinc solution will be present as the tetraamine complex ion Zn(NH 3 ) 4 2+ .
  • the molar ratio of carbonate to zinc in the aqueous ammoniacal ammonium carbonate zinc solution is one, or greater.
  • At least 10% of the zinc species present in the organic solution is in the form of ZnRHCO 3 . More preferably, at least 20% of the zinc species present in the organic solution is in the form of ZnRHCO 3 . Still preferably, at least 30% of the zinc species present in the organic solution is in the form of ZnRHCO 3 . Still preferably, at least 40% of the zinc species present in the organic solution is in the form of ZnRHCO 3 . Still preferably, at least 50% of the zinc species present in the organic solution is in the form of ZnRHCO 3 . Still preferably, at least 60% of the zinc species present in the organic solution is in the form of ZnRHCO 3 .
  • At least 70% of the zinc species present in the organic solution is in the form of ZnRHCO 3 .
  • at least 80% of the zinc species present in the organic solution is in the form of ZnRHCO 3 .
  • at least 90% of the zinc species present in the organic solution is in the form of ZnRHCO 3 .
  • at least 95% of the zinc species present in the organic solution is in the form of ZnRHCO 3 .
  • at least 99% of the zinc species present in the organic solution is in the form of ZnRHCO 3 .
  • 100% of the zinc species present in the organic solution is in the form of ZnRHCO 3 .
  • the molar ratio of ammonia to zinc to carbonate in the aqueous ammoniacal ammonium carbonate zinc solution is about 4:1:1.
  • the zinc extraction reaction can be summarised as follows, the species in the organic solution are italicized.
  • the concentration of zinc extractant in the organic solution is less than 0.1 vol %.
  • the concentration of zinc extractant in the organic solution is less than 1 vol %.
  • the concentration of zinc extractant in the organic solution is less than 2 vol %.
  • the concentration of zinc extractant in the organic solution is less than 3 vol %.
  • the concentration of zinc extractant in the organic solution is less than 4 vol %.
  • the concentration of zinc extractant in the organic solution is less than 5 vol %.
  • the concentration of zinc extractant in the organic solution is less than 7 vol %.
  • the concentration of zinc extractant in the organic solution is less than 10 vol %.
  • the concentration of zinc extractant in the organic solution is less than 15 vol %. Still preferably, the concentration of zinc extractant in the organic solution is less than 20 vol %. Still preferably, the concentration of zinc extractant in the organic solution is less than 30 vol %. Still preferably, the concentration of zinc extractant in the organic solution is less than 40 vol %. Still preferably, the concentration of zinc extractant in the organic solution is less than 50 vol %. Still preferably, the concentration of zinc extractant in the organic solution is less than 60 vol %. Still preferably, the concentration of zinc extractant in the organic solution is less than 70 vol %. Still preferably, the concentration of zinc extractant in the organic solution is less than 80 vol %.
  • the concentration of zinc extractant in the organic solution is between 0.5 and 1 vol %.
  • the concentration of zinc extractant in the organic solution is between 0.5 and 2 vol %.
  • the concentration of zinc extractant in the organic solution is between 0.5 and 3 vol %.
  • the concentration of zinc extractant in the organic solution is between 0.5 and 4 vol %.
  • the concentration of zinc extractant in the organic solution is between 0.5 and 5 vol %.
  • the concentration of zinc extractant in the organic solution is between 0.5 and 7 vol %.
  • the concentration of zinc extractant in the organic solution is between 0.5 and 10 vol %.
  • the concentration of zinc extractant in the organic solution is between 0.5 and 15 vol %. Still preferably, the concentration of zinc extractant in the organic solution is between 0.5 and 20 vol %. Still preferably, the concentration of zinc extractant in the organic solution is between 0.5 and 30 vol %. Still preferably, the concentration of zinc extractant in the organic solution is between 0.5 and 40 vol %. Still preferably, the concentration of zinc extractant in the organic solution is between 0.5 and 50 vol %. Still preferably, the concentration of zinc extractant in the organic solution is between 0.5 and 60 vol %. Still preferably, the concentration of zinc extractant in the organic solution is between 0.5 and 70 vol %. Still preferably, the concentration of zinc extractant in the organic solution is between 0.5 and 80 vol %.
  • the method further comprises the step of:
  • the concentration of the phase modifier is less than 0.1 vol %.
  • the concentration of the phase modifier is less than 1 vol %.
  • the concentration of the phase modifier is less than 2.5 vol %.
  • the concentration of the phase modifier is less than 5 vol %.
  • the concentration of the phase modifier is less than 7.5 vol %.
  • the concentration of the phase modifier is less than 10 vol %.
  • the concentration of the phase modifier is less than 15 vol %.
  • the concentration of the phase modifier is less than 20 vol %.
  • the concentration of the phase modifier is 0.11-50 vol %. Still preferably, the concentration of the phase modifier is 1-50 vol %. Still preferably, the concentration of the phase modifier is 2.5-50 vol %. Still preferably, the concentration of the phase modifier is 5-50 vol %. Still preferably, the concentration of the phase modifier is 7.5-50 vol %. Still preferably, the concentration of the phase modifier is 10-50 vol %. Still preferably, the concentration of the phase modifier is 15-50 vol %.
  • the phase modifier is an organic alcohol.
  • the organic alcohol is selected from the group: 1-decanol, 2-ethyl hexanol, and p-nonyl phenol.
  • the phase modifier is isodecanol (1-decanol, decan-1-ol, CAS 112-30-1, C 10 H 22 O).
  • the phase modifier is trioctyl phosphine oxide (TOPO).
  • the phase modifier is tributyl phosphate (TBP, CAS 126-73-8, C 12 H 27 O 4 P).
  • the organic solution of a zinc extractant comprises a zinc extractant and a diluent.
  • the diluent is >50% aliphatic.
  • the diluent is >60% aliphatic.
  • the diluent is >70% aliphatic.
  • the diluent is >80% aliphatic.
  • the diluent is >90% aliphatic Still, preferably, the diluent is >95% aliphatic.
  • the diluent is 50-100% aliphatic. Still preferably, the diluent is 60-100% aliphatic. Still preferably, the diluent is 70-100% aliphatic. Still preferably, the diluent is 80-100% aliphatic. Still preferably, the diluent is 90-100% aliphatic. Still preferably, the diluent is 95-100% aliphatic.
  • the diluent is kerosene.
  • the molar ratio of carbonate to zinc in the organic solution is less than 0.1.
  • the molar ratio of carbonate to zinc in the organic solution is less than 0.25.
  • the molar ratio of carbonate to zinc in the organic solution is less than 0.50.
  • the molar ratio of carbonate to zinc in the organic solution is less than 0.75.
  • the molar ratio of carbonate to zinc in the organic solution is less than 0.9.
  • the molar ratio of carbonate to zinc in the organic solution is less than 1.0.
  • the molar ratio of carbonate to zinc in the organic solution is less than 1.1.
  • the molar ratio of carbonate to zinc in the organic solution is less than 1.25. Still preferably, the molar ratio of carbonate to zinc in the organic solution is less than 1.5. Still preferably, the molar ratio of carbonate to zinc in the organic solution is less than 2.0. Still preferably, the molar ratio of carbonate to zinc in the organic solution is less than 3.0. Still preferably, the molar ratio of carbonate to zinc in the organic solution is less than 5.0. Still preferably, the molar ratio of carbonate to zinc in the organic solution is less than 10.0. Still preferably, the molar ratio of carbonate to zinc in the organic solution is less than 20.0.
  • the molar ratio of carbonate to zinc in the organic solution is between 0.05 and 0.1.
  • the molar ratio of carbonate to zinc in the organic solution is between 0.05 and 0.25.
  • the molar ratio of carbonate to zinc in the organic solution is between 0.05 and 0.50.
  • the molar ratio of carbonate to zinc in the organic solution is between 0.05 and 0.75.
  • the molar ratio of carbonate to zinc in the organic solution is between 0.05 and 0.9.
  • the molar ratio of carbonate to zinc in the organic solution is between 0.05 and 1.0.
  • the molar ratio of carbonate to zinc in the organic solution is between 0.05 and 1.1.
  • the molar ratio of carbonate to zinc in the organic solution is between 0.05 and 1.25. Still preferably, the molar ratio of carbonate to zinc in the organic solution is between 0.05 and 1.5. Still preferably, the molar ratio of carbonate to zinc in the organic solution is between 0.05 and 2.0. Still preferably, the molar ratio of carbonate to zinc in the organic solution is between 0.05 and 3.0. Still preferably, the molar ratio of carbonate to zinc in the organic solution is between 0.05 and 5.0. Still preferably, the molar ratio of carbonate to zinc in the organic solution is between 0.05 and 10.0. Still preferably, the molar ratio of carbonate to zinc in the organic solution is between 0.05 and 20.0.
  • the molar ratio of carbonate to zinc in the organic solution is between 0.05 and 2.0. Still preferably, the molar ratio of carbonate to zinc in the organic solution is between 0.25 and 2.0. Still preferably, the molar ratio of carbonate to zinc in the organic solution is between 0.5 and 2.0. Still preferably, the molar ratio of carbonate to zinc in the organic solution is between 0.5 and 1.5. Still preferably, the molar ratio of carbonate to zinc in the organic solution is between 0.75 and 1.25. Still preferably, the molar ratio of carbonate to zinc in the organic solution is between 0.9 and 1.1. Still preferably, the molar ratio of carbonate to zinc in the organic solution is between 0.95 and 1.05.
  • the molar ratio of carbonate to zinc in the organic solution can be determined using any method available to those skilled in the art.
  • the content of zinc and carbonate in the organic phase can be determined by taking an aliquot of the organic solution and mixing it thoroughly with a larger volume of 150 g/L sulphuric acid, ensuring that any gaseous carbon dioxide evolved is captured.
  • the phases should then be allowed to separate and an analysis of the aqueous phase for zinc and carbonate ions using standard methods may be performed. To ensure that all of the zinc and carbonate have been stripped, further contacts with fresh 150 g/L sulphuric acid may be required. This method gives the zinc and carbonate concentrations in the organic directly and this data can be used to determine the molar ratio of Zn:CO 3 in the organic.
  • the molar ratio of ammonia to zinc in the organic solution is less than 0.001.
  • the molar ratio of ammonia to zinc in the organic solution is less than 0.005.
  • the molar ratio of ammonia to zinc in the organic solution is less than 0.01.
  • the molar ratio of ammonia to zinc in the organic solution is less than 0.05.
  • the molar ratio of ammonia to zinc in the organic solution is less than 0.1.
  • the molar ratio of ammonia to zinc in the organic solution is less than 0.25.
  • the molar ratio of ammonia to zinc in the organic solution is less than 0.50.
  • the molar ratio of ammonia to zinc in the organic solution is less than 0.75.
  • the molar ratio of ammonia to zinc in the organic solution is less than 0.9.
  • the molar ratio of ammonia to zinc in the organic solution is less than 1.0.
  • the molar ratio of ammonia to zinc in the organic solution is less than 1.1.
  • the molar ratio of ammonia to zinc in the organic solution is less than 1.25.
  • the molar ratio of ammonia to zinc in the organic solution is less than 1.5.
  • the molar ratio of ammonia to zinc in the organic solution is less than 2.0.
  • the molar ratio of ammonia to zinc in the organic solution is less than 3.0.
  • the molar ratio of ammonia to zinc in the organic solution is less than 5.0.
  • the molar ratio of ammonia to zinc in the organic solution is less than 10.0.
  • the molar ratio of ammonia to zinc in the organic solution is less than 20.0.
  • the molar ratio of ammonia to zinc in the organic solution is between 0.001 and 0.1.
  • the molar ratio of ammonia to zinc in the organic solution is between 0.001 and 0.25.
  • the molar ratio of ammonia to zinc in the organic solution is between 0.001 and 0.50.
  • the molar ratio of ammonia to zinc in the organic solution is between 0.001 and 0.75.
  • the molar ratio of ammonia to zinc in the organic solution is between 0.001 and 0.9.
  • the molar ratio of ammonia to zinc in the organic solution is between 0.001 and 1.0.
  • the molar ratio of ammonia to zinc in the organic solution is between 0.001 and 1.1.
  • the molar ratio of ammonia to zinc in the organic solution is between 0.001 and 1.25.
  • the molar ratio of ammonia to zinc in the organic solution is between 0.001 and 1.5.
  • the molar ratio of ammonia to zinc in the organic solution is between 0.001 and 2.0.
  • the molar ratio of ammonia to zinc in the organic solution is between 0.001 and 3.0.
  • the molar ratio of ammonia to zinc in the organic solution is between 0.001 and 5.0.
  • the molar ratio of ammonia to zinc in the organic solution is between 0.001 and 10.0.
  • the molar ratio of ammonia to zinc in the organic solution is between 0.001 and 20.0.
  • the molar ratio of zinc to the zinc extractant in the organic solution is less than 0.1.
  • the molar ratio of zinc to the zinc extractant in the organic solution is less than 0.25.
  • the molar ratio of zinc to the zinc extractant in the organic solution is less than 0.50.
  • the molar ratio of zinc to the zinc extractant in the organic solution is less than 0.75.
  • the molar ratio of zinc to the zinc extractant in the organic solution is less than 0.9.
  • the molar ratio of zinc to the zinc extractant in the organic solution is less than 1.0.
  • the molar ratio of zinc to the zinc extractant in the organic solution is less than 1.1.
  • the molar ratio of zinc to the zinc extractant in the organic solution is less than 1.25. Still preferably, the molar ratio of zinc to the zinc extractant in the organic solution is less than 1.5. Still preferably, the molar ratio of zinc to the zinc extractant in the organic solution is less than 2.0. Still preferably, the molar ratio of zinc to the zinc extractant in the organic solution is less than 3.0. Still preferably, the molar ratio of zinc to the zinc extractant in the organic solution is less than 5.0. Still preferably, the molar ratio of zinc to the zinc extractant in the organic solution is less than 10.0. Still preferably, the molar ratio of zinc to the zinc extractant in the organic solution is less than 20.0.
  • the molar ratio of zinc to the zinc extractant in the organic solution is between 0.05 and 0.1.
  • the molar ratio of zinc to the zinc extractant in the organic solution is between 0.05 and 0.25.
  • the molar ratio of zinc to the zinc extractant in the organic solution is between 0.05 and 0.50.
  • the molar ratio of zinc to the zinc extractant in the organic solution is between 0.05 and 0.75.
  • the molar ratio of zinc to the zinc extractant in the organic solution is between 0.05 and 0.9.
  • the molar ratio of zinc to the zinc extractant in the organic solution is between 0.05 and 1.0.
  • the molar ratio of zinc to the zinc extractant in the organic solution is between 0.05 and 1.1. Still preferably, the molar ratio of zinc to the zinc extractant in the organic solution is between 0.05 and 1.25. Still preferably, the molar ratio of zinc to the zinc extractant in the organic solution is between 0.05 and 1.5. Still preferably, the molar ratio of zinc to the zinc extractant in the organic solution is between 0.05 and 2.0.
  • the molar ratio of zinc to the zinc extractant in the organic solution is between 0.1 and 1.1.
  • the molar ratio of zinc to the zinc extractant in the organic solution is between 0.25 and 1.1.
  • the molar ratio of zinc to the zinc extractant in the organic solution is between 0.5 and 1.1.
  • the molar ratio of zinc to the zinc extractant in the organic solution is between 0.75 and 1.1.
  • the molar ratio of zinc to the zinc extractant in the organic solution is between 0.9 and 1.1.
  • the molar ratio of zinc to the zinc extractant in the organic solution is between 0.95 and 1.05.
  • FIG. 1 is a flow diagram representing the method of the embodiment, in the context of an aqueous ammoniacal zinc solution produced by the ammoniacal leaching of a zinc carbonate ore;
  • FIG. 2 is a graphical representation of the loading isotherms for Zn and CO 3 ions from the high carbonate solution of Example 1;
  • FIG. 3 is a graphical representation of the loading isotherms for Zn and CO 3 ions from the low carbonate solution of Example 2;
  • FIG. 5 is a graphical representation of the Zn/D2EHPA ratios for isotherms of FIG. 4 ;
  • FIG. 6 is a graphical representation of the zinc extraction as a function of equilibrium pH after 1, 2 and 3 contacts in the trials of Example 4.
  • a zinc ore 20 is leached 10 in an ammoniacal ammonium carbonate solution 62 to produce a slurry 27 comprising an aqueous zinc ammoniacal ammonium carbonate solution containing impurities and a zinc-depleted solid, the slurry is subjected to solid-liquid separation 11 , to produce a solid waste 41 , which is disposed of, and an impurity-containing zinc ammoniacal ammonium carbonate solution 30 .
  • the aqueous impurity-containing zinc ammoniacal ammonium carbonate solution 30 is then introduced into a solvent extraction loading stage 12 , in which the aqueous impurity-containing zinc ammoniacal ammonium carbonate solution 30 is contacted with an organic solution of a zinc extractant, in the form of D2EHPA, dissolved in an aliphatic 43 .
  • the zinc, some impurities and some ammonia are transferred into the organic phase, thereby producing a zinc-depleted impurity-depleted ammonia-depleted aqueous ammoniacal ammonium carbonate solution 60 and a zinc-enriched impurity-enriched ammonia-enriched organic solution of a zinc extractant 33 which are then separated.
  • the zinc-depleted impurity-depleted ammonia-depleted aqueous ammoniacal ammonium carbonate solution 60 is largely recycled back to the leach with a small volume 31 used to absorb the carbon dioxide 59 evolved during the zinc strip 15 forming a carbonic acid solution 32 .
  • the impurity-enriched ammonia-enriched zinc-enriched organic solution of a zinc extractant 22 proceeds to an ammonia scrub extraction 13 .
  • the impurity-enriched ammonia-enriched zinc-enriched organic solution of a zinc extractant 33 is contacted with an acidic solution of carbonic acid 32 , thereby producing an impurity-enriched ammonia-depleted zinc-enriched organic solution 47 and an ammoniacal ammonium carbonate solution 61 , which is combined with the raffinate 60 from the SX loading stage 12 to form an ammoniacal ammonium carbonate solution 62 which is recycled back to the leach stage 10 .
  • the impurity-enriched ammonia-depleted zinc-enriched organic solution 47 is then contacted with an acidic aqueous solution containing zinc 56 in an impurity scrub stage 14 forming an acidic aqueous solution containing zinc and impurities 58 , which can be disposed of and an impurity-depleted ammonia-depleted zinc-enriched organic solution of a zinc extractant 49 .
  • the impurity-depleted ammonia-depleted zinc-enriched organic solution of a zinc extractant 49 proceeds to a zinc strip stage 15 where it is contacted with a strongly acidic solution 51 producing a zinc-enriched acid aqueous phase 52 , an impurity-depleted ammonia-depleted zinc-depleted organic solution of a zinc extractant 43 and carbon dioxide 59 .
  • the zinc-enriched acid aqueous phase 52 proceeds to zinc electrowinning 16 where zinc cathodes 53 are produced.
  • the impurity-depleted ammonia-depleted zinc-depleted organic solution of a zinc extractant 43 is recycled back to the SX loading stage 12 .
  • the carbon dioxide 59 is absorbed into an aqueous solution 31 and the resultant solution 32 used in the ammonia scrub 13 .
  • a zinc silicate ore was leached with an ammoniacal ammonium carbonate solution consisting of ⁇ 25 g/L free ammonia and ⁇ 8 g/L of ammonium carbonate. After 24 h of leaching, the solution was separated by filtration, the zinc tenor of this solution was 4.67 g/L.
  • An organic phase comprising 100 mL of D2EHPA diluted to 1.00 L with aliphatic kerosene (Recosol V80), giving a solution containing 0.303 M D2EHPA, was made up.
  • the data points and best-fit Langmuir isotherms for zinc and carbonate ions resulting from this work are shown in FIG. 2 .
  • the carbonate data and isotherms are triangles and dashed line respectively.
  • the Langmuir isotherm indicates that the maximum zinc loading in the organic solution is 19.04 g/L, (0.291 M) and the maximum carbonate loading is 17.53 g/L (0.292 M).
  • Example 1 The leaching run in Example 1 was repeated using ⁇ 1 g/L of ammonium carbonate, this being the only difference between the two runs.
  • the solution tenor for zinc of 4.60 g/L is very close to that from Example 1, evidently, the level of carbonate ions in the leach solution has little effect on the extent of leaching from this ore.
  • the extraction process and analyses were also repeated to give the isotherms shown in FIG. 3 .
  • the isotherms for zinc and carbonate ions are shown in FIG. 2 .
  • Example 2 Simple comparison with Example 1 shows that reducing the molar ratio of carbonate ions to zinc ions in the aqueous feed solution from 1.18 to 0.15 reduced the maximum extraction of zinc from 19.04 g/L to 10.20 g/L, a very substantial reduction. Clearly, the presence of carbonate ions during the extraction have a very significant effect on zinc extraction.
  • the low level of ammonium carbonate in the aqueous solution (1.0 g/L, 0.010 M) is clearly insufficient to enable the transfer of more than ⁇ 6.4% (0.010/0.156 *100) of the zinc into the organic phase as the proposed ZnRHCO 3 complex.
  • the remaining ⁇ 93.6% of the zinc will be extracted as the well-known ZnR 2 complex.
  • a zinc bearing ammoniacal ammonium carbonate solution was made by leaching a dolomite ((Ca,Mg)CO 3 ) hosted smithsonite (ZnCO 3 ) ore in an ammoniacal solution for 24 h. After this time the solution was filtered to eliminate solids. The resultant solution contained 19 g/L of zinc, 30 g/L of total ammonia (i.e. ammonia+ammonium) and ⁇ 29 g of carbonate ions. This gives a carbonate to zinc molar ratio of 1.04.
  • FIG. 4 show the extraction isotherms for 40 and 60 vol % D2EHPA along with the isotherm for 10 vol % in high carbonate solution from Example 1.
  • the experimental data are shown as points, the lines show a Langmuir isotherm calculated from the data.
  • the composition of the species present in the organic solution at saturation can be determined from the maxima of the Langmuir isotherms.
  • the molar ratio of zinc to D2EHPA in the organic phase can be calculated. 40 vol % D2EHPA is ⁇ 1.21 M, 83 g/L Zn is 1.27 M, thus the molar ratio Zn/D2EHPA is 1.05. Similarly, in the 60 vol % D2EHPA run, the ratio is 1.02. Accordingly, it appears that the zinc species extracted from ammoniacal ammonium carbonate can be summarised as ZnR, which is significantly different to the ZnR 2 species extracted from other aqueous media.
  • the Langmuir isotherm can also be used to determine the Zn/D2EHPA ratio for any level of loading of the organic. This data is shown in FIG. 5 for all three isotherms from FIG. 3 .
  • the Zn/D2EHPA ratio for the individual data points shown in FIG. 4 ranges from 0.09 to 1.05. In the former case, only one in every eleven D2EHPA molecules present in the organic is attached to a zinc ion, the remaining ten are available to complex with other zinc ions as they are extracted in subsequent stages. This is made clear by the increasing Zn/D2EHPA ratio as the quantity of zinc in the organic phase increases with increasing numbers of contacts with the leach solution.
  • D2EHPA the most economic and efficient utilisation of the D2EHPA will be where the maximum number of D2EHPA molecules are associated with zinc ions, i.e. at the upper end of the D2EHPA saturation where the zinc concentration in organic as a percentage of the maximum possible zinc concentration is close to 100% and the Zn/D2EHPA ratio is highest. It would be possible, but economically poor to operate at much less than 50% saturation where the Zn/D2EHPA ratio is ⁇ 0.5.
  • the species extracted from ammoniacal ammonium carbonate solutions also contains a hydrogen carbonate.
  • the reason is twofold. Firstly, the valence of zinc is unchanged during extraction and a univalent anion is required to balance the charge in both aqueous and organic solutions. In the aqueous solution the only anion present at any useful concentration is carbonate. Secondly, between pH 6.2 and 10.2 the carbonate is predominantly present as hydrogen carbonate (bicarbonate), HCO 3 ⁇ . Thus it would seem that the zinc-bearing species present in the organic solution after extraction from ammoniacal ammonium carbonate is RZnHCO 3 .
  • the present system showed no apparent viscosity problems, even when using 60 vol % D2EHPA as the extractant. If the putative complex RZnHCO 3 is present, then it will be notably shorter than R-Zn-R as there is only a single organic chain on the complex. This is less likely to become polymerised than the R-Zn-R complex and therefore not have a substantially higher viscosity than the starting organic solution.
  • a large volume of zinc bearing aqueous solution was prepared by leaching 24 kg of 35% Zn ore in 300 L of ⁇ 35 g/L free ammonia solution to give a zinc tenor of ⁇ 16.7 g/L.
  • the ore also contained leachable lead and cadmium.
  • Fresh aqueous at a starting pH of 10.91 was contacted at a 1:1 volume ratio with fresh organic (40 vol % D2EHPA+10 vol % TBP in kerosene), the organic removed, the aqueous sampled and replaced with fresh organic. This was repeated three times.
  • FIG. 4 shows the zinc extraction as a function of equilibrium pH after 1, 2 and 3 contacts.

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CN110817930A (zh) * 2019-07-25 2020-02-21 重庆东群科技有限公司 一种生产碳酸锌铵的方法
CN113604678A (zh) * 2021-08-17 2021-11-05 云南锡业股份有限公司锡业分公司 一种通过氨浸-萃取工艺回收锡冶炼烟尘中锌的方法

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CN110817930A (zh) * 2019-07-25 2020-02-21 重庆东群科技有限公司 一种生产碳酸锌铵的方法
CN113604678A (zh) * 2021-08-17 2021-11-05 云南锡业股份有限公司锡业分公司 一种通过氨浸-萃取工艺回收锡冶炼烟尘中锌的方法

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