AU1350100A - Treatment of titaniferous materials - Google Patents

Description

P/00/0 1 1 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Treatment of Titaniferous Materials The following statement is a full description of this invention, including the best method of performing it known to me/us: FHPMELC600367232.7 la- Treatment of Titaniferous Materials This invention relates to a process for facilitating the removal of impurities, especially but not only radionuclides such as uranium and thorium and their radionuclide daughters, from titaniferous materials, and is concerned in particular embodiments with the removal of uranium and thorium from weathered or "altered" ilmenite and products formed from the ilmenite.

Ilmenite (FeTiO 3 and rutile (TiO 2 are the major commercially-important, mineral feedstocks for titanium metal and titanium dioxide production. Although ilmenite and rutile almost invariably occur together in nature as components of "mineral sands" or "heavy minerals" (along with zircon (ZrSiO 4 and monazite ((Ce, La, Th)PO4)), ilmenite is usually the most abundant. Natural weathering of ilmenite results in partial oxidation of the iron, originally present in ilmenite in the ferrous state (Fe 2 to ferric iron (Fe 3 To maintain electrical neutrality, some of the oxidised iron must be removed from the ilmenite lattice. This results in a more porous structure with a higher titanium (lower iron) content. Such weathered materials are known as "altered" ilmenites and may have Ti02 contents in excess of 60%, compared with 52.7% TiO 2 in stoichiometric (unaltered) ilmenite. As weathering, or alteration, of the ilmenite proceeds, impurities such as aluminosilicates (clays) are often incorporated into the porous structure as discrete, small grains that reside in the pores of the altered ilmenite. It appears that uranium and thorium can also be incorporated into the ilmenite pores during this process.

Most of the world's mined ilmenite is used for the production of titanium dioxide pigments for use in the paint and paper industries. Pigment grade TiO 2 has been traditionally produced by reacting ilmenite with concentrated sulphuric acid and subsequent processing to produce a Ti0 2 pigment the so-called sulphate route.

However this process is becoming increasingly undesirable on environmental grounds due to the large volumes of acidic liquid wastes which it produces. The alternative process the so-called chloride route involves reaction with chlorine to produce volatile titanium tetrachloride and subsequent oxidation to TiO 2 Unlike the sulphate route, the chloride route is capable of handling feedstocks, such as rutile, which are high in TiO 2 content and low in iron and other impurities.

-2- Consequently the chloride-route presents fewer environmental problems and has become the preferred method for TiO 2 pigment production. Also whilst the sulphate route is capable of producing only TiO 2 pigments, both titanium metal and TiO 2 pigments can be produced via the chloride route. Natural rutile supplies are insufficient to meet the world demands of the chloride-route process. Thus there is an increasing need to convert the more plentiful ilmenites and altered ilmenites (typically 45 to 65 TiO 2 to synthetic rutile (containing over 90% TiO 2

A

number of different processes have been developed to upgrade ilmenite to synthetic rutile the most widely used, commercially, being the Becher process.

The Becher process involves reducing the iron in ilmenite (preferably altered ilmenite) to metallic iron in a reduction kiln at high temperatures to give so called reduced ilmenite, then oxidising the metallic iron in an aerator to produce a fine iron oxide that can be physically separated from the coarse titanium-rich grains forming a synthetic rutile. The product normally undergoes a dilute acid leach. Sulphur may be added to the kiln to facilitate removal of manganese and residual iron impurities, o by formation of sulphides which are removed in the acid leach. The titanium-rich synthetic rutile so produced contains typically 90% TiO 2 Whether ilmenite is marketed as the raw mineral or as upgraded, value- *'added, synthetic rutile, producers are being increasingly required to meet more stringent guide-lines for the levels of the radioactive elements uranium and thorium in their products. The Becher synthetic rutile process does not significantly reduce the levels of uranium and thorium in the product and so there exists an increasing need to develop a process for removal of uranium and thorium from ilmenite and other titaniferous materials synthetic rutile).

Frequently ilmenite concentrates contain low levels of thorium due to monazite contamination. It is not the purpose of this invention to remove macroscopic monazite grains from titaniferous materials, but rather to remove microscopic uranium and thorium originally incorporated into the ilmenite grains during the weathering process.

It has previously been disclosed in Australian patent applications 14980/92 and 14981/92 that uranium and thorium can be removed from titaniferous material by treatment with acid containing soluble fluoride or with base followed by an acid -3treatment, respectively. However, while these treatments were found to indeed remove uranium and thorium from titaniferous material, it has now been discovered that the radioactivity of the material is not reduced to the extent expected from the reduction in thorium and uranium content. Further investigation has shown that this is occurring because the prior treatments are primarily removing the parent uranium and thorium isotopes, and the radionuclide daughters are not being removed to the same extent. This finding is surprising because the observed differential behaviour is the opposite of what has generally been observed with leaching treatments of radioactive materials in other fields, where the radionuclide daughters are generally removed as well as or more readily than the parent.

More specifically, for the 232Th chain, we have found that none of the daughters are removed to the same extent as the parent 232Th. This observation .indicates that after, or as a result of, the transformation of 232Th to its immediate daughter 228Ra, a process takes place whereby 228Ra and all of its daughters, including 2Th, are made less accessible than the parent 232Th to removal by the processes described in the above patent applications. This conclusion is confirmed by the observation that, after applying the above processes to altered ilmenite, the 228Th isotope is often found to be in equilibrium with 228 Ra, but not with 232Th.

If the 228Th and 232Th isotopes were in the same physical environment, they would behave identically during chemical processing.

.It has been surprisingly found, in accordance with a preferred first aspect of Si:: the invention, that a heating treatment may be applied to the titaniferous material effective to enhance the accessibility of the radionuclides and/or at least one of the radionuclide daughters to subsequent removal processes, whether those described in Australian patent applications 14980/92 and 14981/92 or otherwise. Preferably, the parent isotope, eg 23 2 Th in the thorium decay chain, and its radionuclide daughters, eg 228Ra and 2 28 Th, are rendered substantially equally accessible to subsequent thorium and/or uranium removal processes.

In accordance with a first aspect of the invention, titaniferous material may be subject to a pretreatment effective to cause aggregation or concentration of the radionuclides and/or one or more of the radionuclide daughters into identifiable deposits or phases, whereby to enhance subsequent separation of the radionuclides and daughters from the material.

According to the first aspect, the invention provides a process for facilitating the removal of radionuclides and/or one or more of their radionuclide daughters from titaniferous material which comprises the step of treating the titaniferous material to cause aggregation or concentration of the radionuclides and one or more of their radionuclide daughters, to an extent effective to enhance the accessibility of at least one of the iradionuclide daughters to subsequent removal, wherein said treatment includes a heat treatment of said titaniferous material and contacting of the titaniferous material with one :o or more reagents selected to form a phase as a result of said heat treatment which disperses onto the surfaces of the titaniferous material and incorporates the radionuclides and said one or more radionuclide daughters. The radionuclides may be thorium and/or uranium and/or one or more of their radionuclide daughters.

This treatment preferably includes a heat treatment. Such heat treatment may be performed in an oxidising atmosphere, or in a reducing atmosphere or in an oxidising .o.•.atmosphere and then a reducing atmosphere or in a reducing atmosphere and then an oxidising atmosphere.

The reagent(s) are believed to be effective in providing in said phase a medium for S- •enhanced aggregation or concentration of the thorium and/or uranium, whereby to facilitate separation of the thorium and/or uranium and/or their radionuclides daughters during subsequent leaching. They also tend to lower the heating temperature required to achieve a given degree of radionuclide removal.

The heating temperature is preferably in excess of 500'C. Indeed it is found that in a first temperature range, eg between 500'C and 1000°C, there is an enhanced removal of 228 232 radionuclide daughters (eg 228Th) but diminished parent (eg 232Th) removal. In a second temperature range eg 1000'C to 1300 0 C, and especially at or above 1200'C, removal of the parent and daughter radionuclides improves and occurs to a similar extent, while for still higher temperatures, eg 1400'C, the total removal is high and the similar removal of the parent and daughter radionuclides is sustained, thereby achieving a good reduction in radioactivity.

The heating step may be optimised for either chemical or physical removal processes and can be performed in either an oxidising or reducing atmosphere, or a combination of both, in any appropriate oven, furnace or reactor. It will be appreciated that the optimal heating conditions will depend upon the process of the subsequent removal step.

The processes described in Australian patent applications 14980/92 and 14981/92 were found to be more effective at removing uranium and/or thorium from ilmenite than from synthetic rutile produced by the Becher process. We have now also found that a i heating treatment of the ilmenite prior to Becher processing, in accordance with the first aspect of the invention, renders the uranium and thorium in the synthetic rutile product more susceptible to subsequent leaching.

We have further found that a heat treatment of synthetic rutile, after Becher processing, also renders the uranium and thorium more susceptible to subsequent leaching.

•I •Prior to heat treatment the thorium was found to be distributed extremely finely in .t altered ilmenite grains (below the level of resolution of Scanning Electron Microscopy).

After heat treatment of the titaniferous material in accordance with the first aspect of the invention, to a temperature of about 1200'C or higher, thorium rich phases of up to several microns in size could be identified at and below the surface of the titaniferous grains. The aggregation and concentration of the thorium into discrete phases, which has been observed for both ilmenite and synthetic rutile, may allow physical (as well as chemical) separation of the thorium-rich phase from the titanium-rich phases by an appropriate subsequent process, eg attritioning. The temperatures required for optimal segregation of the thoriumrich phase are, however, higher than those necessary to render 232Th and its daughters equally accessible to chemical separation processes, eg leaching.

In a second aspect of the invention, there is provided a process for facilitating the removal of radionuclides, such as eg uranium and thorium, and/or one or more -6of their radionuclide daughters from titaniferous material which comprises contacting the titaniferous material with one or more reagents at an elevated temperature selected to enhance the accessibility of at least one of the radionuclide daughters in the titaniferous material, the reagent(s) being selected to form a phase at said elevated temperature which disperses onto the surfaces of the titaniferous material and incorporates the radionuclides and said one or more radionuclide daughters.

Usefully, the aforementioned phase incorporating the radionuclides. may take up other impurities such as silicon/silica, alumninium /alumina, manganese, and residual iron which can be removed along with the radionuclides on dissolution of the phase.

In a third aspect, the invention provides a process for facilitating the removal of one or more impurities from titaniferous material which comprises contacting the titanifeious material with one or more reagents at an elevated temperature, the reagent(s) being selected to form a phase at said elevated temperature which disperses onto the. surfaces of the titaniferous material and incorporates the impuitys).The impurities may comprise one or more of the group including silicon and/or silica, aluminium. and/or alumina, manganese and residual iron.

In the various aspects of the invention, the reagent, or reagents, preferably comprise glass forming reagents such as borates, fluorides, phosphates, and silicates. By glass forming reagent is meant a compound which at *an elevated temperature transforms to a glassy i.e. non-crystafline phase, comprising a three-dimensional network of atoms, usually including oxygen. The glass forming reagents may be added individually or in a combination or mixture of two or more of the. compounds. In addition, reagents that act as glass modifiers i.e. as modifier's of the aforementioned network phase, such as alkali and alkaline earth compounds, may also be added with the glass forming reagents. The glass modifiers may be added as, for example, an oxide, carbonate, hydroxide, fluoride, nitrate or sulphate compound. The glass forming reagents and glass modifiers added may be naturally occurring minerals, for example borax, ulexite, colemanite or fluorite, or chemically synthesised compounds.

Particularly effective glass forming reagents for the second and third aspects of the invention, in the sense that they achieve optimum incorporation of the -7radionuclides and radionuclide daughters in the glassy phase, include alkali and alkaline earth borates, more preferably sodium and calcium borates and calcium sodium borates. Examples of such borates include Ca 2

B

6

O

1 1 NaCaB 5 0 9 and Na 2

B

4 0 7 which are respectively represented by the minerals colemanite Ca 2

B

6

O

1 1 H20,ulexite NaCaB 5 0 9 .8H 2 0 and borax Na 2

B

4 0 7 .10H 2 0. Especially advantageous are calcium borates. An effective glass modifier in conjunction with these borates is fluorite (calcium fluoride).

A suitable elevated temperature effective to achieve a satisfactory or better level of radionuclide incorporation is in the range 900 to 1200 optimally 1050 to 1200 C.

In each of the:f~z aspects of the invention, the titaniferous material may be ilmenite, altered ilmenite, reduced ilmenite or synthetic rutile.

The radionuclide daughter(s) whose accessibility is enhanced preferably include 228Th and 2 28Ra.

The invention preferably further includes the step of separating radionuclide(s) from the titaniferous material.

The process, in any of its aspects, may further include treatment of the titaniferous material in accordance with one or both of Australian patent applications oo S 14980/92 and 14981/92, ie leaching the material with an acid containing fluoride or treatment with a basic solution followed by an acid leach, or treatment with an acid :or acids only. For example, the acid leach may be effective to dissolve the phase incorporating the radionuclides and radionuclide daughters, and to thereby extract the latter from the titaniferous material. The aforesaid reagent(s) may therefore be selected, inter alia, with regard to their solubility in acid, and borates are advantageous in this respect. An effective acid for this purpose is hydrochloric acid, e.g. of about IM but sulphuric acid may be preferable on practical grounds. If sulphuric acid is employed for the primary leach, a second leach with e.g.

hydrochloric acid may still be necessary, preferably after washing, to extract the radionuclide daughter radium 2 28Ra). When used as a second leach for this purpose rather than as the primary leach, the radium may be removed and the hydrochloric acid recirculated. The acid leach may be carried out with added fluoride, which may be advantageously provided by a fluoride reagent in the original 8 mixture of reagents. Effective fluoride reagents for this purpose include NaF and CaF 2 The leached solids residue may then be washed by any conventional means, such as filtration or decantation, to remove the radionuclide-rich liquid phase. This may be followed by drying or calcination.

An especially preferred application, embodying the aforedescribed- aspects of the invention, may be to the production of synthetic rutile (SR) from ilmenite by an iron reduction process such as the Becher process. As mentioned, in this process, iron oxides in ilmenite are reduced largely to metallic iron in a reducing atmosphere in a kiln, at a temperature in the range 900-1200°C, to obtain so-called reduced ilmenite. The aforementioned reagent(s) are also delivered to the kiln, and form(s) the phase which disperses onto the surfaces of the titaniferous material and incorporates the radionuclides and one or more of the radionuclide daughters. The cooled reduced ilmenite, or the synthetic rutile remaining after subsequent aqueous oxidation of the iron and separation out of the iron oxide, is subjected to an acid leach as discussed above to remove the thorium. A proportion of the radionuclides may also be removed at the aqueous oxidation stage.

The invention accordingly provides a process for treating iron-containing titaniferous material, eg an ore such as ilmenite, by reducing iron in the titaniferous material largely to metallic iron in a reducing atmosphere in a kiln, thereby producing a socalled reduced titaniferous material, comprising feeding the titaniferous material, a reductant, and one or more reagents selected to enhance the accessibility of at least one of the radionuclide daughters in the titaniferous material, to the kiln, maintaining an elevated temperature in the kiln, the reagent(s) being selected to form a phase at said elevated temperature which disperses onto the surfaces of the titaniferous material and incorporates the radionuclides and said one or more radionuclide daughters, recovering a mixture which includes the reduced titaniferous material and said phase from the kiln at a discharge port, and treating the mixture to remove thorium and/or uranium and/or one or more of the radionuclide daughters. The maintained elevated temperature is preferably in the range 900 to 1200 0 C, most preferably 1050 to 1200°C.

This process preferably incorporates one or more of the main steps of the Becher process as follows: -9- 1. Reduction, in the rotary kiln, of the iron oxides; contained in the ilmenite feed largely to metallic iron using coal as the heat source and the reductant.

2. Cooling of the mixture discharging from the reduction kihl 3. Dry physical separation of the reduced ilmenite and surplus char.

4. Aqueous oxidation (known as aeration) of the reduced ilmenite to convert the metallic iron to iron oide particles discrete from the Ti1) 2 rich mineral particles.

Wet physical separation to remove the iron oide from the Ti10 2 rc mineral partides.

6. An optional acid leaching stage to remove a portion of the residual iron and manganese.

7. Washing, dewatering and drying of the synthetic riitile product.

The treatment to remove thorium and/or uranium and/or one or more of their radionuclide daughters may advantageously be effected after and/or during step 4 and may be carried out simultaneously with step 6 by means of an acid leach, preferably with hydrochloric acid and preferably at a concentration of at least for exaple 0.5M. As previously mentioned, an initial sulphuric acid leach may be followed by a hydrochloric acid leach. The conventional acid leach in the Becher process is about 0.5M, typically of H 2 S0 4 Alternatively, the treatment to remove thorium and/or uranium and/or one :or more of their radionuclide daughters may be carried out by substituting step 4 above with an acid leach to remove the metallic iron and the radionuclides in one step. Again, HCl is preferred for this leach.

In another application, a mixture of the aforesaid reagents including one or more glass forming compounds, and perhaps one or more glass modifiers, are added to the ilmenite and heated at a temperature in the range 900 to 1200 "C before treatment by the process which includes the main steps of the Becher process as described above, and then a leach to remove thorium. and/or uranium and/or one or more of their radionculide daughters. Alternatively, the heated ilinenite with the added reagents may be leached to remove thorium. and/or uranium and/or one or more of their radionuclide daughters before treatment by the Becher process.

Removal of thorium and/or uranium and/or one or more of their 10 radionuclide daughters may also be carried out by treatment of the usual synthetic rutile (SR) product from the Becher process. In a particular application, a mixture of the aforesaid reagents including one or more glass forming compounds, and perhaps one or more glass modifiers, are added to the SR product and heated at 900 to 1200 0 C before a leach to remove thorium and/or uranium and/or one or more of the radionuclide daughters.

The invention is further described and illustrated by the following non-limiting examples. In the examples the Thyj,, value given is the 221 content of the material as determined by x-ray fluorescence spectrometry (XRF) while the T value is a 232 "M value calculated from a y-pectrometry measurement of the 228n in the sample assuming that the 23 2 Th and 22Th are in secular equiibriumn. When the two thoriumn isotopes are, in fact, in secular equilibrium then the Thyj~j and hr values are similar. When the ThypjF value is substantially less than the Thy value, as is observed in several of the examples given, this means that the parent 23 2 7h has been removed to a greater extent than the radionuclide daughters. When no Thy value is given in the Examples, qualitative measurements indicated that the activity of the sample had been reduced to a similar extent as the measured ThXRpj value.

The analytical data and activity values for the ilmenite and synthetic rutile examples in the following samples were as follows: 11 TABLE A

S

S

SYNTHETIC

SAMPLE ILMENITE

RUTILE

A B E F C D XRF Analysis Th (ppm) 375 357 240 118 421 306 TiO2 59.25 61.92 62.28 61.59 89.78 91.26 Fe 2 0 3 35.15 33.45 3233 32.62 6.43 4.54 Mn 3 0 4 136 131 131 1.12 1.72 1.09 SiO 2 1.22 0.98 0.55 0.79 132 1.46 Al2 0.61 0.70 136 1.14 1.15 1.19 CaO 0.00 0.00 0.00 0.01 0.00 0.02 Cr03 0.19 0.17 0.04 0.08 0.07 0.09 ZrO 2 020 0.19 0.05 0.22 0.93 0.21 Y-spectrometry 22Ra (Bqlg) 1.43 135 n.d. n.d. 1.6 1.27 228Th (Bq/g) 1.44 135 n.d. n.d. 1.7 1.26 Calc Th (ppm) 355 332 n.d. n.d. 395 310 332 3

S

5.5.5.

S

5* 4* 5-5 20 n.d. Not determined -12- EXAMPLE 1 The effect of a heating pre-treatment for the ilmenite on subsequent removal of thorium from the ilmenite by leaching is shown in this example.

Samples of Eneabba North ilmenite (SAMPLE with ThXR F and Thy assay values of 375 and 355 ppm Th, respectively, were heated at 500, 750, 1000, 1100, 1200, 1300 and 1400 C in a muffle furnace for 2 or 16 hours.

The heated ilmenite samples, and a sample of un-heated ilmenite, were reacted with 2 molar sodium hydroxide solution at a solids content of 40 wt% solids in a reactor fitted with a stirrer rotating continuously at 750 rev/min., a thermopocket containing a thermometer (or thermocouple) and a reflux condenser.

The reactor was heated by a heating mantle that was connected via a temperature 15 controller to the thermocouple. In this way, the reaction mixture could be maintained 0 at the desired temperature. The mixture was heated at 70 C for 1 h. The solid residue was then filtered, thoroughly washed with water and analysed.

0 The sodium hydroxide treated product was then returned to the reactor and leached with 6 molar hydrochloric acid containing 0.5 molar sodium fluoride solution at a solids content of 25 wt% solids at 85 °C for 2 h. The solid residue was again filtered, washed thoroughly with water, dried and analysed.

The thorium analyses for the un-heated and heated samples of SAMPLE A after the leaching with sodium hydroxide followed by hydrochloric acid containing sodium fluoride are given in Table 1.

13 TABLE 1 a HEATING HEATING ThXR F Th 7 TMERAT TIME (ppm Th) (ppm Th) ('OP (h) 89 307 500 2 98 302 750 2 156 270 1000 2 294 270 1100 16 258 248 1200 16 157 150 1300 16 205 182 1400 16 90 98 Unheated but otherwise treated sample of SAMPLE A. The ThXp and ThY values for SAMPLE A were 375 and 355 ppm Th respectively.

The results in Table 1 show that 20 1) Good leaching of 23 2 Th, but virtually no 228Th, is achieved at temperatures of 500 0 C and lower.

2) At intermediate temperatures of 750 and 1000 C, moderate leaching of 2 3 2 Th is obtained with increasing amounts of 2 28Th also being leached, but the total removal of thorium is less than with the unheated sample.

3) At higher temperatures in the range 1000-1300 C, especially at or above 1200 C, moderate amounts of both 23 2 Th and 2 28Th parent 2 3 2 Th and the radionuclide daughters) are equally removed, with the total thorium removal improving with increasing temperature.

4) At 1400 0C good total removal of thorium is achieved with both 23 2 Th and 2 2 8 Th being removed to a similar extent. The radioactivity of the resultant product was found to be substantially less than that of the unheated sample after leaching.

14- EXAMPLE 2 The effect of a heating pre-treatment before reduction and aeration of the ilmenite on subsequent removal of thorium from the resulting ilmenite by leaching is shown in this example.

Samples of Eneabba North ilmenite (SAMPLE A) were heated at 750, 1000, 1200, and 1400 C in a muffle furnace for 2 or 16 hours. The heated samples were reduced with char 0.5 mm) at 1100*C under conditions established in the laboratory to give a product similar to that produced in the reduction kiln in the Becher process.

The reduced ilmenite produced was aerated in an ammonium chloride medium under conditions similar to those used in the Becher process to remove 15 metallic iron and then leached with hydrochloric acid containing sodium fluoride at wt% solids at 90 *C for 2 hours. In some cases the acid leach was preceded with a leach with 2.5M NaOH at 25 wt% solids at 75 *C for 1 hour.

In Table 2, the results for the heated and reduced samples are compared with that for a sample that was not heated before reduction. The results show that as the temperature of the heating pre-treatment increases, the amount of thorium removed in the acid leach also increases. The results also show that the activity is removed to the same extent as the thorium.

15 TABLE 2 PRE-HiEAT REDUCTION ACID Th ip h, Tenp[ Time Temp~ Time EAH~ (ppm) (ppmh) 1100 1 A 305 295 750 2 1100 1 A 279 nd.

1000 2 1100 1 B 259 270 1200 16 1100 1 B 258 258 1400 16 1100 1.5 B 153 nd.

After aeration with NH 4 CI 02 to remove metallic iron, reduced samples were leached with 6M HCI 0.1M NaF(A), or 2.5M NaOH then 6M HCl 0.SM NaF p.

p p 'p q pp p 4p n.d. Not determined -16-

S

S

*5*S *5 S S *5 EXAMPLE 3 The enhanced leachability of thorium and its daughters from synthetic rutile after heating the synthetic rutile is shown in this example.

Samples of standard grade synthetic rutile (SR) from the Narngulu plant (SAMPLE C) were heated in a muffle furnace at temperatures of 1000-1400 °C for 16 hours. The heated SR samples were then leached with sodium hydroxide at wt% solids at 75 "C for 1 hour, followed by hydrochloric acid containing sodium fluoride at 25 wt% solids at 90 °C for 2 hours. The results in Table 3 show that the parent Th and the radionuclide daughters are removed to a greater extent from the SR samples as the temperature at which it is heated increases.

TABLE 3 Heating Heating time ThXRF Th Temperature (ppm Th) (ppmTh)

CC)

No heating 421 395 20 No heating but leached 302 300 1100 16 250 197 1200 16 223 221 1300 1 16 235 214 1400 16 170 160 17 EXAMPLE 4 The effect of the addition of silica alone, and with other reagents, to the ilmenite before a heat treatment is shown in this example.

Samples of Eneabba North ilmenite (SAMPLE A) were mixed with precipitated silica, and mixtures of precipitated silica and sodium fluoride or monosodium dihydrogen phosphate dihydrate, and heated in a muffle furnace at 1000 to 1300 *C for 1 to 2 hours. A sub-sample of the heated sample was leached with hydrochloric acid containing sodium fluoride at 25 wt% solids at 90 *C for 2 hours.

are..In Table 4, the results for the treated, heated and leached ilmenite samples are compared with those for ilmenite heated and leached but without addition of silica or the other reagents. The results shown that the addition of silica alone has little effect after heating at 1150 but that the addition of sodium fluoride is beneficial with the thorium removal increasing with increasing heating temperature.

The results show that the activity is removed to a similar extent as the thorium.

The addition of a phosphate with the silica results in better thorium removal and heating temperatures of only 1000 *C are required.

9 *9 9 9 9..

99 S 9 9 *9 9 9S* *9* 999 9 999 995 5 99 99 9e** 9 9 .9 9 9 9 999 9 5 995 9 999 9. 5 999 TABLE 4 Acid leach with 2.5M NaOH then 6M HCl 0.5M NaF or 6M HC1 0.5M NaF or 6M HCI 0.2M NaF n.d. =not determined 19 EXAMPLE The effect of the addition of a phosphate compound to the ilmenite before a heat treatment is shown in this example.

A sample of Eneabba North ilmenite (SAMPLE A) was mixed with analytical reagent grade (AnalaR) monosodium dihydrogen phosphate dihydrate or with commercial phosphate samples (1 to 5% by weight), wetted with water, mixed wet, dried in an oven at 120 'C and then heated in a muffle furnace at 1000 *C for 1 hour.

A sub-sample of the phosphate-treated and heated ilmenite was leached with an acid containing sodium fluoride at 25 wt% solids at 90 'C for two hours.

SIn Table 5, the results for the phosphate-treated, heated and leached ilmenite are compared with those for ilmenite that was heated and leached without addition 15 of phosphate before heating. The results indicate that the thorium removal is much greater from the material treated with phosphate. The results also indicate that an increased acid strength is needed to achieve a similar degree of thorium removal for a lower reagent addition.

TABLE REAGENT ADDITION HEATING ACID Tj Th W/W) Temp Time I II (PPM) YPPf (OC) (h) No additive 1000 2 A 294 270 AR Grade MSP 1 1000 1 B 164 nd.

MSP 2 1000 1 B 97 100 MSP 2 1000 1 C 136 204 MSP 5 1000 1 D 67 81 Commercial Grade MSP 2 1000 1 B 55 nd.

SPP 2 1000 1 B 55 nd.

TSP? 2 1000 1 B 50 n.I.

*e

C

C

C. C MSP SSP TSSp monosodium dihydrogen phosphate dihydrate sodium pyrophosphate tetrasodium pyrophosphate Acid leach with 2.5M NaOH then 6M HCI 0.5M Na? or 6M HCI 0.1M Na? or 3M H 2 S0 4 0.1M Na? or 1M HC1 0.1M NaB (D) n.d. Not determined 21 EXAMPLE 6 The effect of the addition of a fluoride salt alone, and with other reagents, to the ilmenite before a heat treatment is shown in this example.

Sodium or calcium fluoride, alone, or in combination with sodium carbonate, a phosphate, or borax, were added to one of two Eneabba North ilmenites (SAMPLE A or SAMPLE The samples were heated in a muffle furnace at 1000 or 1150 C for 1 hour and leached with hydrochloric acid or hydrochloric acid containing sodium fluoride at 25 wt% solids at 90 "C for 2 hours.

The results in Table 6 indicate that the addition of sodium fluoride alone, or **the fluorides in combination with the other reagents, resulted in a substantially greater removal of thorium in the heat and leach treatment compared with the 15 samples to which no reagents were added before the heat and leach.

9 a a oo *o *9 0 I I 00 0 0 0 0 00* 0** a

C

*00 000 0 C C. CO 0 *S* 0 0 0 0 0 a a 00 0 *0* TABLE 6 IADDITION HEATING ACID Th ILMENITE REAGENT LEACH (r LE) f*Total Ratio j~Temp [Time (Wt ~H (0c) A No additive 1000 2 A 294 B No additive 1000 2 B 255 A NaF 5 1000 1 B 76 A CaF.

2 5 1000 1 B 303 A [NaF Na 2 C~j 1000 1 1 B [CaFq Na 2 COq 5 1: B 11514111____ B j NaF +MSP J 5 1:9110001 1 1 B jCaF? TSPP J 2 1: 10 1 1 Jj136 ANaF borax 5 1:1 1000 1_ 110_ BE CaF 2 borax 5 i:1i 00 1 1105

*MSP=

monosodium dihydrogen phosphate dihydrate TSSP tetrasodium pyrophosphate Acid leach with 2.5M NaOH then 6M HMl 0.5M NaF 0.1M NaF or 1M HCl (D) or 6M HC1 0. 5M NaF or 6M HMl -23- EXAMPLE 7 The effect of the addition of borate minerals to the ilmenite before a heat treatment is shown in this example.

Naturally occurring borate minerals, in particular a sodium borate (borax, Na 2

B

4 07..1 H 2 a sodium calcium borate (ulexite NaCaB50 9 .8H 2 0) and a calcium borate (colemanite Ca 2

B

6 01 1

.H

2 0) were added at 2 to 5% by weight to Eneabba North ilmenite (SAMPLE heated in a muffle furnace at 900 to 1100 "C and leached with hydrochloric acid or hydrochloric acid containing sodium fluoride at 25 wt% solids at 60 or 90 C for 2 hours.

C

In Table 7 the results for the ilmenite treated with a borate mineral, heated and leached are compared with that for a sample that was heated and leached

C

15 without the addition of a borate. The results show that good removal of thorium was achieved with borax and ulexite after heating at 1000 and 1100 °C but that a heating temperature of 1100 °C is necessary when colemanite is added. This is in line with the higher melting temperature of colemanite compared with borax and ulexite. The results also show that more thorium is removed when the amount of borate added 20 is increased.

20 is increased.

24 TABLE 7 S S

S

S* SO S MEATING ACD Th~p REAGENT ADDITON Temp I Time (OP No additive 1000 2 A 255 pBorax 3 1000 1 134 Ulexite 3 1000 1 B 187 1100 1 B 78 _4 1100 1 B Colemanite 3 900 1 B 275 _3 1000 1 B247 3 11001 1 jB 98 2 11001 1 B 3 11001 1 B 98 I 5 1100 1 1 B 64 Acid Leach with 6M HCI 0.5M NaF(A), or IM HCl or 1M HOI 0.1M NaF (C)

S

S

0 S. S EXAMPLE 8 In this example, the effect of the addition of a borate mineral (borax or ulexite) and a calcium salt (fluu-ide, 1,,lroxide, or sulphate) to ilmenite before heating is shown.

A borate mineral and a calcium salt (3 to 4% by weight in the ratio 1:1 or 2:1) were added to Eneabba North ilmenite (SAMPLE B) and heated in a muffle furnace at 900 to 1100 °C for 1 hour and then leached with hydrochloric acid or hydrochloric acid containing sodium fluoride at 25 wt% solids at 60 or 90 °C for 2 hours.

0 The results in Table 8 show that good removal of thorium and activity was achieved, particularly with heating temperatures of 1000 and 1100 The results also show that, when calcium fluoride is added, a large amount of thorium can be removed in an acid leach with a low acid strength of 0.25M HCl.

see*S

S•

i" a S S* a a a..

a S. S* a a a a** a a a a S* a *5 S 9**a a Sa. a S *a a. a @6 a a a a a as S a a a a Sa S 555 TABLE 8

N

Acid leach with 6 i+O5MaF or 0.25M 1101 or 1M 111 C) n.d. not determined -27- EXAMPLE 9 The removal of thorium and uranium from a sample of ilmenite treated with borax and calcium fluoride (fluorite) by leaching after a heat treatment is shown in this example.

Samples of Eneabba North ilmenite (SAMPLE B) were mixed with borax and calcium fluoride (2 to 5% by weight in a 1:1 or 2:1 ratio) and heated in a muffle furnace at 1000 or 1150 *C for 1 hour and then leached with hydrochloric acid or hydrochloric acid containing sodium fluoride at 25 wt% solids at 60 "C for 2 hours.

The results in Table 9 show that the thorium (both the parent 232Th as indicated by ThxRF value and daughter 228Th as indicated by the Thy value) and :uranium in the ilmenite are removed by the heat and leach treatment. The results 15 show that the amount of thorium and uranium removed increases with increasing addition of borax and calcium fluoride with a heating temperature of 1000 °C for 1 o hour and a leach with 0.25M HC1. A higher heating temperature of 1150 °C and a leach with a stronger acid (2M HCI) results in removal of a larger amount of thorium and uranium.

0 C S 0O 'S TABLE 9 I ADDITION ii HEATING ACIDN ThXRF f Th y U REAGENT Ttl Rio Temp Time LEACH (pm) I(ppm) (ppm) No additive 357 332 10.4 No additive j 11!50 .1 A j 190 172 11.0 Borax CaF 2 2 1:1 1000 1 B 164 140 8.3 3 1:1 1000 1 B 123 118 7.3 4 1:1 1000 1. B 75 74 6.2 2:1 1000 1 B T 92 91 5.9 2:1 L 1150 1C 25 25 2.2 Acid leach with 6M HCl 0.5M NaF or 0.25M HMi or 2M HCM (C) -29- EXAMPLE The effect of the time ilmenite, treated with borax and calcium fluoride (fluorite), is heated at temperature is shown in this example.

Samples of Eneabba North ilmenite (SAMPLE B) were mixed with borax and calcium fluoride by weight in a 1:1 ratio) and heated in a muffle furnace at 1000 C for 0.25 to 4 hours and then leached with 0.25M hydrochloric acid at 25 wt% solids at 60 °C for 2 hours.

The results in Table 10 suggest that there is an optimum time for which the sample should be heated in order to remove the greatest amount of thorium in the acid leach. The results also indicate that the activity is removed along with the thorium. Heating for too long reduces the amount of thorium removed.

0 -o *oooo* *•go a a a a a a a. a a a a.

a a a a.

a a a a a S a.

*a .a .~aa TABLE REAGENT ADDITION HEATING ACID Th Th Rti 1ii1 LEACH *m PI No additive 100 ioo 2 A 255 253 Borax CaF 2 3 1:1 1000 0.25 B 140 147 3 1:1 1000 0.5 B 102 100 31:1 1000 1 B 123 118 3 1:1 1000 2 B 141 114 3 1:1 1000 4 B 166 160 Acid leach with 6M HC1 0.5M NaF or 0.25M HCi (B) -31- EXAMPLE 11 The effect of the addition of borate minerals to ilmenite before reduction is shown in this example.

Samples of Eneabba North ilmenite (SAMPLE A or SAMPLE B) were mixed with borate minerals (borax, ulexite, or colemanite) or borate mineral (borax or ulexite) and calcium fluoride (fluorite), wetted with water, mixed wet, and added with char 0.5 mm) to a silica pot. The sample was heated in a muffle furnace at 1000 or 1150°C for 1 to 4 hours to reduce the ilmenite and form reduced ilmenite. A sub-sample of the reduced ilmenite was either aerated to remove metallic iron and leached with hydrochloric acid containing sodium fluoride at wt% solids at 60 °C for 2 hours or treated directly with hydrochloric acid at 9.1 wt% solids at 60 C for 2 hours to dissolve the metallic iron, thorium and associated activity.

In Table 11 results for the borate treated, reduced and leached samples are compared with those for samples reduced and leached but without the addition of the borate minerals. The results show that the addition of the borate minerals results in greater thorium removal. Also the results indicate that a higher reduction temperature gives higher thorium removal in the acid leach. The rutile is in a more reduced state in the product from reductions at 1150°C than from reductions at 1100 °C.

S

S S S S S S S S*S S S *5 5* *5 S S S S S S S *S S 555 TABLE 11 ILMENITE REAGENT 11ADDITION

REDUCTION*I

II T ~ACID I ThXRF Total jRatio Temp Tie LEC (ppm) ANo additive 1100___ 1 A305 rNo additive 1100___ 1 A 223 ABorax 4 -1100 1 B 114 P ABorax 4 -1150 1 C 112 A Borax CaF 2 5 3.5:1.5 1100 4 D 249 A Borax CaF 2 5 3.5:1.5 1150 1.5 D EB Ulexite 5 -1100 1.5 D 99 B Ulexite 5 1150 1.5 D B Ulexite CaF 2 5 2:1 1150 1.5 D 78 B Colemanite 5 1100 1.5 D 53 B Colemanite 5 -1150 1.5 D Reduction in a silica pot with iljnenite:char 0.5 mm) 2:1 **Aeration and one or two acid leaches with 6M HCl 0. 5M NaF, 1.95M HMl and then 6M HM~ 0.5M NaF or 2M HMl or direct leach with -33- EXAMPLE 12 The effect of the addition of borate minerals to ilmenite before reduction with coal as a solid reductant and a heating profile similar to that existing in commercial Becher reduction kilns is shown in this example.

Samples of Eneabba North ilmenite (SAMPLE B) were mixed with borate minerals (borax, ulexite, or colemanite) or borax plus calcium fluoride (fluorite), mixed with coal (-10 5 rmm) and placed in a drum. The drum was roiled inside 10 a furnace and heated to a temperature of 1100 or 1150 °C using a heating profile •similar to that in commercial Becher reduction kilns to obtain a reduced ilmenite p sample of similar composition to that obtained in commercial plants. The reduced ilmenite was either aerated and leached with hydrochloric acid containing sodium fluoride at 25 wt% solids at 60 C for 2 hours or leached with hydrochloric acid directly at 9.1 wt% solids at 60 °C for 2 hours.

The results in Table 12 indicate that good thorium removal is achieved with borax and calcium fluoride and with ulexite with a reduction temperature of 1150 C,

S

while with colemanite this is achieved with a reduction temperature of 1100 The results indicate that the activity is removed along with the thorium.

p p

S.

S S 55.

S S.

I S o I

S

S S A

S

~50

A..

9 *5 S 555 S 50 S 0 5 Al S S S S S S Ce A TABLE 12 REAGENT ii ADDITION I REDUCTION ACID T hR Th Total Ratio Temp TieLEACH J (ppm) No additive -1100 10 A 256 246 Borax, 4 -1100 10 A 307 312 Borax CaF 2 5 2:1 1100 10 B 306 n.d.

2:1 1150 10 B 25 Ulexite 5 1100 10 a 191 n.d.

-1150 5 B 25 n.d.

Colemanite 3 -1100 11 B 89 96 C 88 113 D 88 103 Reduction in a rotating drum with ilmenite:coal (-10 to the required temperature.

**Aeration and a leach with 6M HC1 0.5M NaF or 1.75M H 2 S0 4 or aeration and a leach with 2M HCl n.d. =Not determined 5 mm) 1:1 with heating profile a direct leach with 2M HC1 or

(D)

EXAMPLE 13 The selective removal of the thorium and then radium from ilmenite by an acid leach after reduction of the ilmenite is shown in this example.

A sample of Eneabba North ilmenite (SAMPLE B) mixed with colemanite by weight) was reduced with coal (-10 5 mm) in a rotating drum at 1100 -C using a heating profile similar to that in commercial Becher reduction kilns to obtain a reduced ilmenite sample of similar composition to that obtained in commercial plants. The reduced ilmenite was either leached with hydrochloric acid at 9.1 wt% solids at 60°C for 2 hours or aerated in ammonium chloride solution and then leached with sulphuric acid at 25 wt% solids at 60 C for 1 hour followed by hydrochloric acid at 25 wt% solids at 60 C for 1 hour.

The results in Table 13 show that leaching the reduced inmenite with "hydrochloric acid removes the thorium (both the parent 2 32 Th and daughter MTh) and the radium (the daughter 228Ra). However, when sulphuric acid is used followed by hydrochloric acid, only the thorium is removed in the sulphuric acid leach and the radium is removed in the subsequent hydrochloric acid leach.

TABLE 13 TREATMENT ThXp Th22 228 (ppm) (Bq/g) (Bq/g) Reduction to RI* 399 344 1.40 1.39 Leach of RI with 2M HC 128 133 0.54 021 Aeration of RI in NH4Cl/air 415 408 1.66 1.02 Leach with 0.5M H 2 S0 4 145 165 0.67 1.00 Further Leach with IM HCI 128 123 0.50 0.15 Reduction of SAMPLE B with colemanite by weight) in a rotating drum with ilmenite:coal (-10 5 mm) 1:1 with heating profile to 1100 C 36 9 9 9**e 9 .9 EXAMPLE 14 The removal of thorium and uranium from ilmenite treated with colemanite by leaching after its reduction to reduced ilmenite is shown in this sample.

A sample of Eneabba North ilmenite (SAMPLE B) mixed with colemanite by weight) was reduced with coal (-10 5 mm) in a rotating drum at 1100 C using a heating profile similar to that in commercial Becher reduction kilns to obtain a reduced ilmenite sample of similar composition to that obtained in commercial plants. The reduced ilmenite was either leached with hydrochloric acid at 9.1 wt% solids at 60 C for 2 hours or aerated in ammonium chloride solution and leached with hydrochloric acid at 9.1 wt% solids at 60 *C for 2 hours.

The results in Table 14 show that both the thorium and uranium are removed 15 in a hydrochloric leach the reduced ilmenite either before or after aeration.

TABLE 14 TREATMENT ThF Th U (ppm) (pprh) (ppm) No treatment 357 332 10.4 Reduction* to RI with addition of 347 425 10.4 colemanite Leach of RI with 2M HC1 89 96 6.3 Aeration of RI with NH 4 Cl/air 458 442 13.5 Leach of with 2M HC1 88 103 Reduction of SAMPLE B plus colemanite by weight) in rotating drum with ilmenite:coal (-10 5 mm) 1:1 and 10 hours heating profile to 1100 C -37 EXAMPLE The effect of a heating pre-treatment before reduction on the removal of thorium in an acid leach is shown in tins example.

Samples of Eneabba North ilmenite (SAMPLE B) were mixed with ulexite or colemanite byweight) and heated at 1000 or 1100 *C for 1 hour. The heated sample was cooled and then reduced with coal (-10 5 mm) in a rotating drum at 1100 *C using a heating profile similar to that in commercial Becher reduction kilns to obtain a reduced ilmenite sample of similar composition to that obtained in commercial plants. The reduced ilmenite was leached with hydrochloric acid at 9.1 wt% solids at 60 C for 2 hours.

In Table 15 the results for ilmenite treated with ulexite or colemanite, heated, reduced and leached are compared with those for samples reduced, or heated and reduced, without the addition of the borate minerals. The results show that thorium is removed in the acid leach on the samples treated with ulexite or colemanite before heating.

S 0e** S S S S S S S S S S S 0 0. 46. 0* *S0 00 6% TABLE PRE-HEAT II REDUCTION REAGENT ADDITIO 1 ACID IIThXRF Temp Ti eCem Tim LEACH (ppm) No additie- 1 J 1100 10 2 HC1 350 No additive -1000 J 1 1100 2M HC1 379 Ulexite 3 1000 1 J1100 10 J2M HC1 172 Ulexite 3 1100 T 1 1100 10 2M HC1 187 Colemanite 3 1000 J 1 J1100 10 2M HC1 134 Colemanite 3 1100 1 1100 10 2M HC1 177 Reduction in rotating drum with heated ilmenite:coal (-10 heating profile to 1100*C 5 mmn) 1 and 10 hours 39

S*

S

EXAMPLE 16 The effect of the addition of borate minerals to ilmenite before reduction in an atmosphere of hydrogen and carbon dioxide is shown in this example.

Samples of Eneabba North ilmenite (SAMPLE A) were mixed with borate minerals (borax, ulexite, or colemanite), placed in a molybdenum boat and positioned inside a glass tube in the hot zone of a tube furnace. The sample was reduced at 1100 or 1150 *C for 2 or 4 hours in a flowing gas stream of a mixture of hydrogen and carbon monoxide of composition such as to give a similar oxygen partial pressure as in a Becher reduction kiln (PH 2

/PCO

2 34.68). The resulting reduced ilmenite was leached with hydrochloric acid at 9.1 wt% solids at 60 *C for 2 hours.

The results in Table 16 show that good thorium removal was achieved in the 15 acid leach in all cases.

TABLE 16

REDUCTION

ACID Thy 20 REAGENT ADDITION LEACH (ppmC W/w) Temp Time C) (h) No additive 1100 2 A 419 Borax 4 1150 2 A 1150 4 A 32 Ulexite 5 1100 2 A 91 ___1150 2 A Colemanite 5 1100 2 A 82 2 1150 2 A Reduction in molybdenum boat in flowing 2

CO

2 gas mixture with

S

5555

S

S

S.

.9

S.

PH

2

/PCO

2 34.68 equivalent to reduction potential kiln.

Acid leach with 2M HC1 (A) in a commercial Becher EXAMPLE 17 Removal of thorium from plant synthetic rutile after treatment with a borate mineral, heating, and leaching is shown in this example.

Samples of synthetic rutile from the plant at Narngulu (SAMPLE C) were mixed with borax, borax and calcium fluoride (fluorite), ulexite or colemanite and heated at 1000 or 1150 "C for 1 hour and then leached with hydrochloric acid at wt% solids at 60 or 90 °C for 2 hours.

In Table 17 results for plant synthetic rutile treated with borates, heated and leached are compared with those for the synthetic rutile either just leached or heated and leached without the addition of borate minerals. The results show that thorium 'is removed from the synthetic rutile by an acid leach when the borate minerals are 15 added.

*o *D i 7; S 155 S S S *S S S S S S S S S S S S S S S 555 5 5 S SO 55 SS.* S 55 5 5 S S S S S S S *S 55 5 TABLE 17 REAGENT ADDITION HEATING ACID ThXF T ITotal 1Ratio Temp Time EAH (ppm) (ppm) J (0c) j I1.

No additive 1 f -421 395_ lNo additive J J A f302 J300 No additive j I -1000 2 A 260 n.d.

Borax 5 -1150 1 B 103 n. d.

Borax CaF2 3 1:1 1000 1 C 187 n.d.

Ulexite 5 L1100 1 C 25 n.d.

Uolemaitej 5 JL1150 1 C 715 n.d.

Colemninte J 1100 C I <25 n2d Leach with 2.5M NaOH followed by 6M HC1 0.5M NaF or 6M CId or 2M IICl n.d. Not determined -42- EXAMPLE 18 In this example the selective removal of thorium and then radium from plant synthetic rutile by an acid leach after heating is shown.

A sample of synthetic rutile from the plant at Narngulu (SAMPLE D) was mixed with ulexite by weight) and heated at 1100 C for 1 hour. Sub-samples of the heated material were leached with hydrochloric acid at 25 wt% solids at 60 "C for 1 hour or with sulphuric acid followed by hydrochloric acid at 25 wt% solids at 60 C for 1 hour.

The results in Table 18 show that both the thorium and radium are removed when the heated material is leached with hydrochloric acid only but when sulphuric acid is used first and then hydrochloric acid, the thorium (parent 23 2 Th and daughter 15 228h) is removed in the first leach and the radium (228Ra) is removed in the second leach.

w a 4 *O *0 9 9 9* C C. BC 9 C C 9 B S 9 B* Ce CCC TABLE 18 I HEATING REAGENT ADDITION j ACID ThXRF Thy 28T 228 Ra Temp ITime LEACH (ppm) (ppm) (Bq/g) (Bqfg) No adiie- 100 1 1M 1HC1 276 n.d. n.d. n.d.- Ulexi te 3 1100 1 338 1.38 1.28 Ulexite 2 1100 j 1 1M HCi 109 120 10.49 0O.18 Ulexite 2 f1100 1 0.5M H 2 S0 4 99 f125 0.51__ 1.38__ .IM HC1 99 91 10.37 02 n.d. Not determined -44- EXAMPLE 19 The removal of thorium from different ilmenite samples from Western Australia is shown in this example.

A sample of ilmenite from different deposits in Western Australia (SAMPLES E and F) was mixed with colemanite by weight) and reduced with coal (-10 mm) in a rotating drum at 1100 C using a heating profile similar to that in commercial Becher reduction kilns to obtain a reduced ilmenite sample of similar composition to that obtained in commercial plants. The reduced ilmenite was leached with hydrochloric acid at 9.1 wt% solids at 60 *C for 2 hours to remove thorium.

In Table 19 the results for the two samples, with and without the addition of 15 colemanite, are compared with the corresponding values for an Eneabba North ilmenite (SAMPLE The results show that the thorium can be removed from other ilmenites as well as from Eneabba North ilmenite.

TABLE 19 I***t

I

I I

I.

I

I

*1*II.

I

III...

I

*1 U

*I

U.

REAGENT REDUCTION*

ACID

ILMENITE ADDITION LEACH ThxR

F

Temp Time (p B 0 1100 10 A 379 B 5 1100 10 A 47 E 0 1100 10 A 240 E 5 1100 10 A 96 F 0 1100 10 A 118 F 5 1100 10 A 74 Re uct n f imenirt in rt t r 1:1 and 10h heating profile to 1100 C Acid leach with 2M HC1 wi mnui tui ic.Loalj-10 T mm) EXAMPLE The removal of radium during the oxidation (aeration) of reduced ilmenite formed from ilmenite treated with colemanite is shown in this example.

A sample of Eneabba North ilmenite (SAMPLE B) was mixed with colemanite and reduced with coal (-10 5 mm) in a rotating drum at 1100 "C using a heating profile similar to that in commercial Becher reduction kilns to obtain reduced ilmenite. The reduced ilmenite was oxidised (aerated) to remove metallic iron in an ammonium chloride solution w/w) at 80 "C with air bubbling through the suspension (to saturate it with oxygen) for 16 hours.

GO60

S

055U 0 In Table 20 the results for two oxidised reduced ilmenite samples treated with ~colemanite are compared with the results for a sample without colemanite, and with 15 the initial ilmenite sample. It can be seen that the thorium and radium levels in the product are higher in the untreated sample compared with the initial ilmenite due to removal of iron in the reduction and oxidation treatments. Also it can be seen Ithat in the product from the ilmenite to which colemanite was added, the thorium has been concentrated to a similar degree as in the sample without colemanite but 20 that an appreciable amount of the radium has been removed.

9 9. 9 ~9* .9 9. 9 TABLE REDUCTION *1PRODUCT REAGENT ADDITION Tie OXIDATION1 (ppm) (ppm) (Bq/g) (Bq/g) No additive 1 110110 1NH, Cl/air 406 43 1.78-1 1.60 Colemanite 3 1 1100 110 1 NH 4 Cl/air 415 I408 1.66 1.02 Colemanite 5 1100 10 NHA CIL/air 1 .41.3 423 11.72 0.891 Reduction in rotating drum with ilmenite:coal (-10 5 mmn) 1:1 with profile to 1100*C **oxidation (aeration) in 1.2% NH 4 C1 solution at 80*C for 16 hours, through the suspension a 10 hour heating with air bubbling -47- EXAMPLE 21 The effect of the addition of borate minerals to ilmenite before reduction on the removal of impurities such as silicon/silica, aluminium/alumina, manganese, and residual iron in the acid leach is shown in this example.

Samples of Eneabba North ilmenite (SAMPLE B) were mixed with borate minerals (borax, ulexite, or colemanite) or borax plus calcium fluoride (fluorite), mixed with coal (-10 5 mm) and placed in a drum. The drum was rolled inside S 10 a furnace and heated to a temperature of 1100 0 C using a heating profile similar to that in commercial Becher reduction kilns to obtain a reduced ilmenite sample of similar composition to that obtained in commercial plants. The reduced ilmenite was *leached with hydrochloric acid at 9.1 wt% solids at 60 C for 2 hours.

The results in Table 21 show that good removal of impurities is achieved, with a corresponding increase in TiO 2 content, when borate minerals are added to ilmenite before reduction.

TABLE 21 REAGENT I ADDITION REDUCTION ACID ASSAY VALUES atal Rati Time LEACHI TotalRatioTemp Tim T10 2 Fe 2 0 3 MnO0 4 S102 Al1 2 0 3 No additive I 1100 10 2M IICi 92.4 3.22 1.55 1.55i 1.12 lBorax 4 1100 10 2M HC1 9.5. 5 1.36 1.26 1.12 0.41 Borax 5 J2:1 I1100 I10 I2M HC1 I93.1 I2.24 11.04 I1.65 0.35 CaF 2 IIII Ulexite 5 1100 10 2M HC1 9.5.7 1.47 0.90 1.42 0.61 Colemanite 3 1100 11i 2M HC1 195.81 2.91 1.24 1.27 0.51 lColemanite 5 JawI 10 11 J 2M HC1 193.8 I2.72 0.92 0.58 10.42

Claims (37)

1. A process for facilitating the removal of radionuclides, such as eg uranium and thorium, and/or one or more of their radionuclide daughters from titaniferous material which comprises contacting the titaniferous material with one or more reagents at an elevated temperature selected to enhance the accessibility of at least one of the radionuclide daughters in the titaniferous material, the reagent(s) being selected to form a phase at said elevated temperature which disperses onto the surfaces of the titaniferous material and incorporates the radionuclides and said one or more radionuclide daughters.

2. A process according to claim 1, wherein said reagent(s) include one or more glass forming reagents, for example selected from the group of glass forming reagents including borates, fluorides, phosphates, and silicates.

3. A process according to claim 2, wherein said glass forming reagent(s) is selected from the group consisting of alkali and alkaline earth borates.

4. A process according to claim 2, wherein said glass forming reagent(s) is selected from the group consisting of calcium and sodium borates, and calcium sodium borates. A process according to claim 4, wherein said glass forming reagent(s) comprises one or more of Ca 2 B 6 O 11 NaCaB 5 0 9 and Na 2 B 4 0 7

6. A process according to claim 5, wherein said glass forming reagent(s) comprise one or more of colemanite, ulexite and borax.

7. A process according to any one of claims 1 to 6, wherein said reagent(s) include one or more glass modifiers.

8. A process according to claim 7, wherein the glass modifier is fluorite.

9. A process according to any one of claims 1 to 8, wherein said elevated temperature is in the range 900 to 1200°C. A process according to claim 9, wherein said elevated temperature is in the range 1050 to 1200°C.

11. A process according to any preceding claim, wherein the heated titaniferous material is converted to synthetic rutile, which is subsequently leached to remove the radionuclides.

12. A process according to claim 11, wherein said titaniferous material is ilmenite and said conversion includes reduction of iron therein to metallic iron and then aqueous oxidation of the metallic iron to form a separable iron oxide.

13. A process according to claim 12, wherein the radionuclides are separated out during the oxidation step. a i 14. A process according to any one of claims 1 to 10, wherein said titaniferous material is synthetic rutile formed by treatment of ilmenite, which treatment includes reduction of iron therein to metallic iron and then aqueous oxidation of the metallic iron to form a S° separable iron oxide. A process for facilitating the removal of radionuclides and/or one or more of their radionuclide daughters from titaniferous material which comprises the step of treating the titaniferous material to cause aggregation or concentration of the radionuclides and one or more of their radionuclide daughters, to an extent effective to enhance the accessibility of at least one of the radionuclide daughters to subsequent removal, wherein said treatment includes a heat treatment of said titaniferous material and contacting of the titaniferous material with one or more reagents selected to form a phase as a result of said heat treatment which disperses onto the surfaces of the titaniferous material and incorporates the radionuclides and said one or more radionuclide daughters.

16. A process according to claim 15, wherein said reagent(s) include one or more glass forming reagents, for example selected from the group of glass forming reagents including borates, fluorides, phosphates, and silicates.

17. A process according to claim 16, wherein said glass forming reagent(s) is selected from the group consisting of alkali and alkaline earth borates.

18. A process according to claim 16, wherein said glass forming reagent(s) is selected from the group consisting of calcium and sodium borates and calcium sodium borates.

19. A process according to claim 18, wherein said glass forming reagent(s) comprise one or more of Ca2B 6 O, NaCaBsO 9 and Na 2 B 4 0 7 A process according to claim 19, wherein said glass forming reagent(s) comprise one or more of colemanite, ulexite and borax.

21. A process according to any one of claims 15 to 20, wherein said reagent(s) include one or more glass modifiers. 20 22. A process according to claim 21, wherein the glass modifier is fluorite.

23. A process according to any one of claims 15 to 22, wherein said heat treatment comprises heating the titaniferous material to a temperature in the range 900 to 1200 0 C.

24. A process according to claim 23, wherein said temperature is in the range 1050 to 1200 0 C. A process according to any preceding claim, wherein said titaniferous material is selected from the group including ilmenite, altered ilmenite, reduced ilmenite or synthetic rutile.

26. A process according to any preceding claim, wherein the radionuclide daughter(s) whose accessibility is enhanced include 228Th and 228Ra.

27. A process according to any preceding claim, further including the step of separating radionuclide(s) from the titaniferous material.

28. A process according to any preceding claim, further including subjecting the treated titaniferous material to an acid leach to remove the radionuclides. S 10 29. A process according to claim 28, wherein the acid is hydrochloric or sulphuric acid.

30. A process according to claim 28, wherein the leach comprises a primary leach with sulphuric acid and then a second leach with hydrochloric acid to remove radium. 15 31. A process according to claim 28, 29 or 30, wherein the acid leach is carried out with added fluoride. .32. A process for treating iron-containing titaniferous material, eg an ore such as ilmenite, by reducing iron in the titaniferous material largely to metallic iron in a reducing 20 atmosphere in a kiln, thereby producing a so-called reduced titaniferous material, comprising feeding the titaniferous material, a reductant, and one or more reagents selected to enhance the accessibility of at least one of the radionuclide daughters in the titaniferous material, to the kiln, maintaining an elevated temperature in the kiln, the reagent(s) being selected to form a phase at said elevated temperature which disperses onto the surfaces of the titaniferous material and incorporates the radionuclides and said one or more radionuclide daughters, recovering a mixture which includes the reduced titaniferous material and said phase from the kiln at a discharge port, and treating the mixture to remove thorium and/or uranium and/or one or more of the radionuclide daughters.

33. A process according to claim 32, wherein said elevated temperature is in the range 900 to 1200°C.

34. A process according to claim 33, wherein said temperature is in the range 1050 to 1200 0 C. A process according to claim 32, 33 or 34, further including aqueous oxidation of the metallic iron to form a separable iron oxide, wherein the radionuclides are separated out during the oxidation.

36. A process according to any one of claims 32 to 35, further including subjecting the treated titaniferous material to an acid leach to remove the radionuclides. :oooi S" 37. A process according to claim 36, wherein the acid is hydrochloric or sulphuric acid. A process according to claim 36, wherein the leach comprises a primary leach with sulphuric acid and then a second leach with hydrochloric acid.

39. A process for facilitating the removal of one or more impurities from titaniferous material which comprises contacting the titaniferous material with one or more reagents at an elevated temperature, the reagent(s) being selected to form a phase at said elevated temperature which disperses onto the surfaces of the titaniferous material and incorporates 20 the impurity(s). ooo 9 A process according to claim 39, wherein the impurities removed comprise one or more of the group consisting of silicon and/or silica, aluminium and/or alumina, manganese, residual iron, thorium and uranium.

41. A process according to claim 39 or 40, wherein said reagent(s) include one or more glass forming reagents, for example selected from the group of glass forming reagents including borates, fluorides, phosphates, and silicates.

42. A process according to claim 41, wherein said glass forming reagent(s) is selected from the group consisting of alkali and alkaline earth borates. 54

43. A process according to claim 41, wherein said glass forming reagent(s) is selected from the group consisting of calcium and sodium borates and calcium sodium borates.

44. A process according to claim 41, wherein said glass forming reagent(s) comprise one or more of Ca 2 B 6 O, NaCaBsO 9 and Na 2 B40 7 A process according to claim 44, wherein said glass forming reagent(s) comprise one or more of colemanite, ulexite and borax.

46. A process according to any one of claims 39 to 45, wherein said reagent(s) include one or more glass modifiers.

47. A process according to claim 46, wherein the glass modifier is fluorite.

48. A process according to any one of claims 39 to 47, wherein said elevated temperature is in the range 900 to 1200 0 C.

49. A process according to claim 48, wherein said elevated temperature is in the range 1050 to 1200 0 C.

50. A process according to any one of claims 39 to 49, further including subjecting the treated titaniferous material to an acid leach to remove the impurity(s).

51. A process according to claim 50, wherein the acid is hydrochloric or sulphuric acid.

52. A process according to claim 50 or 51, wherein the acid leach is carried out with added fluoride. ftQ a a.- Iluka Resources Limited By Freehills Patent Attorneys Registered Patent Attorneys for the Applicant 21 January 2000