WO2003097533A1 - Procede pour eliminer des impuretes radioactives dans des matieres contenant du zirconium - Google Patents

Procede pour eliminer des impuretes radioactives dans des matieres contenant du zirconium Download PDF

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Publication number
WO2003097533A1
WO2003097533A1 PCT/AU2003/000614 AU0300614W WO03097533A1 WO 2003097533 A1 WO2003097533 A1 WO 2003097533A1 AU 0300614 W AU0300614 W AU 0300614W WO 03097533 A1 WO03097533 A1 WO 03097533A1
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WIPO (PCT)
Prior art keywords
mineral
borate
zircon
impurities
borate salt
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PCT/AU2003/000614
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English (en)
Inventor
Halil Aral
Kenneth John Mcdonald
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Commonwealth Scientific And Industrial Research Organisation
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Publication date
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Priority to AU2003225340A priority Critical patent/AU2003225340A1/en
Publication of WO2003097533A1 publication Critical patent/WO2003097533A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
    • C22B3/06—Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic acid solutions, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions
    • C22B3/10—Hydrochloric acid, other halogenated acids or salts thereof
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/02—Roasting processes
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B34/00—Obtaining refractory metals
    • C22B34/10—Obtaining titanium, zirconium or hafnium
    • C22B34/14—Obtaining zirconium or hafnium
    • 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

  • This present invention relates to a process for reducing the amount of radioactive impurity components in a zirconium containing material without significantly altering the grain size distribution and mineralogy of the material.
  • the invention is particularly applicable to the removal of radioactive impurities such as U, Th, and Ra.
  • the process also can remove non-radioactive impurities such as Fe, Al, Ti and the rare earth elements.
  • the process of the invention is applicable to removal of impurities, from zirconium containing materials. While the process of the invention is applicable to any zirconium containing material, the following description will focus on its application to the mineral zircon. However, it is to be clearly understood that the invention is not limited to that application. BACKGROUND OF THE INVENTION
  • Zircon Zircon (ZrSiO 4 ) is an important component of most mineral sands or heavy mineral deposits. It is typically separated from the other heavy minerals (ilmenite, rutile, leucoxene, monazite) by wet concentration using gravity processes and then dry separation using magnetic and electrostatic processes.
  • Zircon finds major uses in foundries as sand moulds, refractories as lining for steel ladles and furnaces, and ceramics as glazes, pigments and enamels. More than half of the commercially produced zircon is consumed in the ceramic industry as an opacifier in glazes. When used as an opacifier it is added as frit or used directly in glazes, or in the body of granito type tiles. Zircon added as frit is ground to -45 micron size, while that added to glaze is micronised to a fine powder (generally less than 5 micron).
  • zircon industry is required to lower impurity levels to meet customer specifications as most impurities adversely affect the end use.
  • impurities in zircon is a problem in the magnetic and electrostatic separation stages of the concentration.
  • Zircon sand in foundry applications needs to be free of any alumina and clay which otherwise could cause sintering or fusion between cast metal and the zircon mould.
  • Light cream or white coloured ceramic grade zircon, typically low in iron oxides and titania, is preferred in many ceramics applications. All commercially available zircon sands contain impurities as surface coatings, discrete minerals, mineral inclusions and trace element substitutions.
  • Zircon sand concentrates are, in general, ginger to light brown in colour to the eye and appear mostly as clear, colourless, yellowish or reddish grains under the optical microscope.
  • the gingery or brownish colour is often related to iron- containing clayey surface coatings/stains but the removal of such material by attritioning or chemical-aided-leaching does not always eliminate the colour completely.
  • gangue minerals such as rutile, garnet xenotime, monazite, spinels, ilmenite, and aluminium silicates in the concentrate also add to the impurity levels in the zircon as well as imparting some colour to the concentrate.
  • Some zircon sands contain radioactivity levels well above the required level for transport as a non-radioactive material of 500 ppm U+Th, or 70 Bq/g activity limit.
  • the U+Th levels of Bangladeshi zircon sands can reach as high as 1500 ppm U+Th. This is about three times higher than the level in commercial zircon sands.
  • the fine-particle size zircon of the Horsham (Victoria, Australia) area contains about twice the level of U+Th than other commercial zircon sands. While the zircon sand potential of the Horsham area is up to 20 million tonnes, this zircon currently is not saleable due to its high radionuclide content.
  • the radiation-damaged zircon which is called metamict zircon, is amorphous to X- rays and is less resilient to attack by acid and alkali solutions.
  • Leachants such as mineral acids or alkalis can be used to dissolve or partly dissolve the metamict zircon while the crystalline portions of the grains remain intact. Radiation damage expands the crystal lattice and causes cracks in the grains.
  • commercial zircon sands are not metamict to such a degree that X-ray amorphous soluble zircon has formed.
  • any such "metamict" zircon is separated and discarded as a waste material.
  • the radiation-related damage is usually in the crystal lattice and no extensive fracturing is involved to channel leachants deep into the grain.
  • the required level of about 10 16 alpha events/mg for an effective amorphization is hard to achieve.
  • the radioactive impurities in zircon crystals are believed to be partly located in the crystal lattice and partly in the bands of zoned zircon grains.
  • the bands of zoned zircon grains are microporous and therefore expected to be accessible with some lixiviants.
  • the present invention provides a process for reducing the amount of impurities in a zirconium containing material, said process including the step of treating the zirconium containing material with a composition, substantially including a borate salt or mineral, at a temperature and for a period of time sufficient to collect at least part of said impurities into a borate phase.
  • the present invention also provides a purified zirconium containing material produced by a process as defined in the preceding paragraph.
  • the process further includes the step of leaching the borate phase produced above in order to dissolve the impurities.
  • the leachant is an acid, preferably a dilute acid.
  • a process for at least partially purifying a zirconium containing material especially zircon.
  • the zircon is typically mixed with a composition, at least largely comprised of a borate salt or mineral, and heated to a temperature and for a time sufficient to concentrate the impurity elements in a borate phase.
  • the borate phase is then generally subjected to leaching, preferably dilute acid leaching, which dissolves the impurities into solution, from which they may be later extracted.
  • the borate containing composition effectively functions as a sink for the impurities in the zirconium containing material.
  • the composition contains a minimum of 50 wt% of the borate salt or mineral.
  • the fluxing composition contains 70 wt% or higher of the borate salt or mineral.
  • the fluxing composition is substantially 100 wt% of the borate containing material.
  • the borate salt or mineral contains a minimum of 10 wt% B 2 O 3 .
  • the borate salt or mineral contains at least 50 wt% B 2 O 3 .
  • the borate salt or mineral is substantially 100 wt% B 2 0 3 .
  • the process of this invention may include a dilute caustic wash following the acid leach, rinsing with water and a drying step for removal of moisture.
  • the final product of the process of this invention is essentially a pale pinkish, cream to white coloured zircon sand containing substantially low amounts of impurities such as Fe, Ti, Al, U, Ra and Th.
  • the amount of impurities remaining in the final product is controlled by the initial impurity levels, intensity of the treatment conditions such as temperature of calcination, acid concentration, leach time and most importantly the amount of borate used in accordance to the amount of zircon sand.
  • the integrity of the grain size is largely protected when about ⁇ 20 wt% borate salt or mineral is added to the zircon sand.
  • the solids to be treated may be selected from any zirconium- containing minerals the use of zircon sand concentrate is preferred.
  • the particle size of the zircon sand concentrate could comprise any particle size but is generally in the average size range of less than 500 microns. However, the finer the grain size the better the impurity removal as a result of exposure of a higher surface area to the borate containing material and leach solution.
  • Processing zirconiferous material to a higher purity zircon product is particularly applicable on the fine-grained (dso ⁇ 50 microns) and U-Th-rich zircon sands of the Horsham area (Australia) and other fine-grained zircon sands, such as fine air table tails of commercial operations and metamict zircons.
  • the borate containing material is typically a borate salt or mineral or a mixture of borate salts and minerals.
  • the first step of the invention involves intimately mixing the zircon sand and the borate salt or mineral and calcining the mixture in a muffle furnace or rotary kiln or other suitable furnace.
  • the borate salt or mineral used in this invention is chosen preferably from sodium, calcium, ammonium, magnesium or lithium containing borate salts or naturally occurring borate minerals. Double salts of borates can also be used, in particular sodium calcium borate (e.g. the mineral ulexite) or hydroboracite (magnesium calcium borate).
  • the amount of borate relative to zircon sand could vary from 0.1 to 50 wt percent, such as from 1 to 20 weight percent, although the use of 5 to 15% borate salt or mineral may be found sufficient to obtain a good level of impurity removal.
  • the heating temperature for the borate calcination is chosen such that a complete or largely complete reaction between the borate salt or mineral and the impurities of the zircon sand is obtained.
  • Heating the zircon sand with the borate salt or mineral could be done in a furnace in the temperature range 700° to 1400°C, preferably 800°C to 1300°C, more preferably from 900°C to 1200°C. In one preferred embodiment, the temperature range is from 1200°C to 1250°C. Heating time is chosen to be long enough to assure a complete or largely complete reaction between the borate and the impurities of the zircon sand.
  • heating time 1 to 48 hours, preferably 2 to 24 hours, more preferably 2 to 6 hours would be sufficient for such reaction.
  • the heating process may be conducted in any suitable conventional manner, including utilising batch or continuous processing in a furnace.
  • the heating steps of the process may be conducted in a furnace of any size, shape or type including conventional and circulating type fluidised beds, microwave, and static, rotating or vibrating type furnaces. These furnaces may be heated by employing any suitable heat source.
  • the calcined product may be cooled in air or quenched quickly in water, acid or any other solution to provide rapid cooling and maximum disintegration of any aggregates formed during heating.
  • the calcined product may be stirred in the solution after quenching to promote a faster disintegration of lumps, aggregates and clusters.
  • the cooled product may require a gentle grinding and the calcined product could be passed through a roll or a ball mill to break down the lumps, aggregates and clusters formed during heating.
  • the acid leaching step according to the present invention may be conducted in any suitable conventional manner, including utilising batch or continuous processing in open vessels at any suitable temperature, preferably with agitation. Temperatures in the range of 10°C to 110°C may be used. However, leaching at a temperature below the boiling point of the acid is preferred.
  • the acid leach solution may be selected from mineral or organic acids or their mixtures.
  • Mineral acids such as hydrochloric, sulphuric, nitric, perchloric or hydrofluoric acids or organic acids including formic, citric, acetic, oxalic or tartaric acid or mixtures thereof may be used.
  • Preferred acids are mineral acids, such as HCI or HNO 3 , although HCI is more preferred because of its lower cost.
  • sulphuric acid may also be used, it has the disadvantage of forming insoluble RaSO as a by product of the leaching process.
  • Acid strength is chosen such that the bulk of the impurities dissolve at a maximum solids content within shortest reaction time. In general the required acid strength is low due to the selective removal of only trace amounts of impurities and added borate salt or mineral.
  • the concentration of the acid may be such that the content of the effective ion in the leaching solution to the minor impurities is slightly in excess amount.
  • a suitable acid concentration is from 0.1 molar to concentrated acid, preferably 0.2 to 2 molar, more preferably about 1.0 molar.
  • the solid content of the leach may be within the range 5 to 85% solids by weight, such as from 5 to 75% solids by weight, preferably from 10 to 50% solids by weight.
  • the reaction vessel may be agitated to promote the reaction rate. Agitation of the leaching vessel could be in the form of mechanical stirring or any other means to provide a rapid reaction between the impurities and the acid.
  • the acid leach step of the process according to the present invention may continue for a time sufficient for the dissolution of impurity elements in the acid solution. Although a leaching time in the range of 5 minutes to 24 hours may be used, in most cases 30 to 120 minutes, such as 30 to 60 minutes, leaching time is sufficient for the removal of impurities.
  • the solids may be separated from the leaching solution by filtration, flotation, centrifugation or by sedimentation.
  • the leach solution may be recycled for use with a fresh charge of zircon sand, usually following a regeneration step.
  • the dissolved borate in the acid may be extracted and also recycled.
  • the residue generated in the leach step may be reacted further with a fresh leaching composition under approximately the same or milder or stronger reaction conditions, but still remaining within the limits of the claims made in this application.
  • a second treatment can be expected to yield a product with lower impurity levels.
  • the recovered solids may be washed with water until the components of the leach solution are reduced to negligible levels.
  • a rinse with a dilute caustic solution before a water rinse may be found beneficial to neutralise and remove any residual acid remaining in the product. However, in most cases the use of a caustic leach step is found optional and may even be not necessary.
  • the water rinsed final product may be subjected to drying at a low (e.g. 100 to 200°C) temperature to remove the moisture.
  • This example demonstrates that the treatment of a (commercially) micronised zircon sand to a particle size of -5 micron gives a good impurity removal (see Example 1 in Table 1).
  • 50g of zircon sand was intimately mixed with 7.5 g of finely ground natural calcium borate mineral (colemanite) and the mixture was calcined in a muffle furnace at 1200°C for 4 hours.
  • the calcined product was cooled to ambient temperature.
  • the relatively soft but clustered product was crushed gently with pestle and mortar then leached with 1.2M HCI at a solids content of 10 weight% in a reaction vessel at 90°C for 30 minutes while being stirred.
  • the solids were recovered by filtration and washing using an additional 150 mL water.
  • the residue was dried at 110°C for several hours in an oven.
  • the product was an off white colour.
  • the particle size of the original product remained largely unchanged.
  • Example 1 in Table 1 shows that the ZrO 2 assay of the dry product was upgraded from 61.3% to 64.1 %. The reduction in impurity levels was significant. For example, the removal of AI 2 O 3 was 97%, Fe 2 0 3 82%, TiO 2 78%, Th 38% and U was 59%. The overall weight loss as a result of this treatment was about 7%. Table 1. Experimental and analytical data.
  • the test results show that the impurity levels were reduced significantly and a pale pinkish coloured product was obtained.
  • the AI 2 O 3 level in the sample was reduced from 4.6% to 0.28% which is equivalent to a 94% reduction.
  • the reduction in Fe 2 O 3 was 74% and in TiO 2 was 85%.
  • the U+Th content was reduced from 563 ppm to the required ⁇ 500 ppm level.
  • the ZrO 2 content was upgraded from 59.7% to 65.5% ZrO 2 . Particle size variation before and after the treatment was negligible as shown in Table 2.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Manufacturing & Machinery (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Geology (AREA)
  • Inorganic Chemistry (AREA)
  • Manufacture And Refinement Of Metals (AREA)

Abstract

L'invention concerne un procédé destiné à réduire la quantité d'impuretés dans une matière contenant du zirconium, ce procédé consistant à traiter ladite matière avec une composition, comprenant essentiellement un minéral ou un sel de borate, à une température et pendant une durée suffisantes pour recueillir au moins une partie des impuretés dans une phase borate.
PCT/AU2003/000614 2002-05-22 2003-05-21 Procede pour eliminer des impuretes radioactives dans des matieres contenant du zirconium WO2003097533A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2003225340A AU2003225340A1 (en) 2002-05-22 2003-05-21 Process for removal of radioactive impurities from zirconium containing materials

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AUPS2501 2002-05-22
AUPS2501A AUPS250102A0 (en) 2002-05-22 2002-05-22 Process for removal of radioactive impurities from zirconium containing materials

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WO2003097533A1 true WO2003097533A1 (fr) 2003-11-27

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005116277A1 (fr) * 2004-05-27 2005-12-08 The South African Nuclear Energy Corporation Limited Valorisation du zircon
CN107963913A (zh) * 2017-11-10 2018-04-27 中国天辰工程有限公司 一种硼钠钙石的洗涤装置及洗涤方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4067953A (en) * 1972-02-15 1978-01-10 Etienne Roux Process for upgrading ores containing baddeleyite
US4268485A (en) * 1975-12-05 1981-05-19 Dynamit Nobel Aktiengesellschaft Process for the separation of radioactive impurities of baddeleyite
US4361542A (en) * 1981-11-23 1982-11-30 General Electric Company Zircon retrieval
US5160482A (en) * 1989-03-02 1992-11-03 Teledyne Industries, Inc. Zirconium-hafnium separation and purification process

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4067953A (en) * 1972-02-15 1978-01-10 Etienne Roux Process for upgrading ores containing baddeleyite
US4268485A (en) * 1975-12-05 1981-05-19 Dynamit Nobel Aktiengesellschaft Process for the separation of radioactive impurities of baddeleyite
US4361542A (en) * 1981-11-23 1982-11-30 General Electric Company Zircon retrieval
US5160482A (en) * 1989-03-02 1992-11-03 Teledyne Industries, Inc. Zirconium-hafnium separation and purification process

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005116277A1 (fr) * 2004-05-27 2005-12-08 The South African Nuclear Energy Corporation Limited Valorisation du zircon
AU2005248159B2 (en) * 2004-05-27 2009-03-19 The South African Nuclear Energy Corporation Limited Upgrading of zircon
US7744847B2 (en) 2004-05-27 2010-06-29 The South African Nuclear Energy Corporation Limited Upgrading of zircon
CN107963913A (zh) * 2017-11-10 2018-04-27 中国天辰工程有限公司 一种硼钠钙石的洗涤装置及洗涤方法

Also Published As

Publication number Publication date
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