AU2015310078A1 - Method for separating scandium - Google Patents

Abstract

Provided is a method for separating scandium, the method comprising a step for: mixing an acid or an alkali with an aqueous raw solution containing at least scandium, titanium and zirconium to adjust the pH to the range of 1.0-2.0, thereby obtaining an aqueous scandium-containing suspension which contains scandium in the liquid phase, and titanium and zirconium in the solid phase. The aqueous scandium-containing suspension can be separated, by liquid-solid separation, into titanium and zirconium, and an acidic solution containing scandium.

Description

DESCRIPTION

Title of Invention METHOD FOR SEPARATING SCANDIUM Technical Field [0001] The present invention relates to methods for separating scandium, and titanium and zirconium, from an aqueous stock solution containing at least scandium, titanium, and zirconium and recovering crude scandium. The present invention also relates to methods for producing high purity scandium from the crude scandium by a chelating resin adsorption step and an organic solvent extraction step.

Background Art [0002] Scandium is one of transition metal elements and is classified, together with yttrium, as a rare earth element. For example, scandium is not only used as an additive for aluminum alloys and a modifier for positive electrodes of nickel alkaline storage batteries, but also used for metal halide lamps containing scandium iodide and used as a stabilizer for zirconium oxide, etc. Scandia-stabilized zirconia is used as an electrolyte for solid oxide fuel cells.

[0003] Scandium is a relatively rare metal and is contained in thortveitite etc. However, since the output of thortveitite etc. is limited, scandium is separated and recovered from a residue of titanium ore, nickel oxide ore, etc. For example, Patent Literature 1 describes that high purity scandium is recovered by leaching a solid residue of chlorinated titanium ore into an acid solution and filtering the resultant solution to remove an insoluble residue to produce a scandium-containing solution, then bringing the scandium-containing solution into contact with an organic solvent containing tributyl phosphate (TBP) to selectively extract scandium, stripping scandium into hydrochloric acid, and adding an ammonia solution to the resultant hydrochloric acid solution to precipitate scandium (Example l).

[0004] Patent Literature 2 describes a method for recovering nickel and scandium from oxide ore containing nickel and scandium, characterized by 1 including (l) a leaching step of leaching oxide ore into an acid at high temperature and high pressure to produce a leachate containing nickel and scandium, (2) a first neutralization step of adding a neutralizer to the leachate to adjust the pH to the range of 2 to 4 to remove, as precipitates, iron and aluminum from the leachate, (3) a second neutralization step of adding a neutralizer to the solution resulting from removing the precipitates in the first neutralization step to adjust the pH to the range of more than 4 to 7.5 to recover, as a precipitate, scandium from the solution, and (4) a third neutralization step of further adding a neutralizer to the resultant solution to adjust the pH to the range of more than 7.5, to recover, as a precipitate, nickel from the solution.

Citation List

Patent Literatures [0005] Patent Literature V Japanese Unexamined Patent Application Publication No. H03-115534

Patent Literature 2- Japanese Unexamined Patent Application Publication No. 2000-313928

Summary of Invention Technical Problem [0006] Patent Literature 1 discloses a method for selectively extracting scandium by leaching a solid residue of chlorinated titanium ore into an acid solution and then bringing the resultant scandium-containing solution into contact with an organic solvent containing tributyl phosphate (TBP). However, since the scandium-containing solution contains impurities such as titanium and zirconium derived from titanium ore, scandium is not selectively extracted into the organic solvent. Accordingly, high purity scandium is not produced even if the subsequent processes are performed. In Patent Literature 2, a neutralizer is added to a leachate to adjust the pH to the range of 2 to 4 to precipitate iron and aluminum. Subsequently, the 2 pH is adjusted to the range of more than 4 to 7.5 to precipitate scandium. If titanium and zirconium derived from ore are present, scandium is coprecipitated with titanium and zirconium when the pH is adjusted to 2 to 4. This causes disadvantages such as a reduced yield of scandium and contamination with impurities such as iron (ferrous) and manganese derived from ore even if the pH is subsequently adjusted to the range of more than 4 to 7.5.

Solution to Problem [0007] The inventors studied efficient and easy methods for separating or recovering scandium from a solution containing scandium, and found that scandium, and titanium and zirconium, is efficiently separated by mixing an alkali with an aqueous stock solution containing at least scandium, titanium, and zirconium ions to adjust the pH to the range of 1.0 to 2.0 to precipitate titanium and zirconium or by mixing an acid with an aqueous stock solution containing at least precipitates of scandium, titanium, and zirconium to adjust the pH to the range of 1.0 to 2.0 to dissolve scandium (titanium and zirconium separation step). The suspension produced by the titanium and zirconium separation step (the suspension containing scandium in a liquid phase and titanium and zirconium in a solid phase) is herein also referred to as the “scandium-containing aqueous suspension.” [0008] The inventors also found that a precipitate of scandium is separated by subsequently separating the scandium-containing aqueous suspension into solid and liquid fractions and mixing an alkali with the solution resulting from the solid-liquid separation (acidic solution containing scandium) to adjust the pH to the range of 3.5 to 7.0 to precipitate scandium, and then separating the resultant solution into solid and liquid fractions (first scandium precipitation and separation step). This scandium precipitate is a low purity crude scandium compound.

[0009] The inventors also found that, since adsorption species that are less selective with respect to scandium, such as titanium and zirconium, have been separated in the scandium-containing aqueous suspension and the scandium-containing acidic solution, which are produced by the above steps, and in a water-based solution of the scandium precipitate (first water-based solution), bringing one of the scandium-containing aqueous suspension, the scandium-containing acidic solution, and the first water-based solution into 3 contact with a chelating resin to cause facilitating adsorption of scandium on the chelating resin, whereby purity of scandium is increased.

[0010] Moreover, the inventors found that purity of scandium is increased by selectively performing the following steps,

Chelating resin adsorption and elution step of bringing the scandium-containing aqueous suspension, the scandium-containing acidic solution, or the water-based solution of the scandium precipitate (first water-based solution) which are produced by the above steps into contact with the chelating resin to cause adsorption of scandium on the chelating resin, and then eluting the adsorbed scandium into a water-based solvent to produce a second water-based solution,

Organic solvent extraction step of bringing the scandium-containing aqueous suspension, the scandium-containing acidic solution, or any of the water-based solutions, which are produced by the above steps, into contact with an organic solvent containing an extractant to extract scandium into the organic solvent to produce a scandium-containing organic solution, Stripping step of stripping scandium contained in the scandium-containing organic solution into a water-based solvent to produce a third water-based solution, and

Second scandium precipitation and recovery step of bringing the scandium-containing aqueous suspension, the acidic solution containing scandium, any of the water-based solutions, or the scandium-containing organic solution, which are produced by the above steps, into contact with a water-based solvent containing a precipitant to precipitate scandium and then recovering scandium by solid-liquid separation.

The inventors thus completed the present invention.

[0011] Namely, the present invention is directed to methods such as (1) a method for separating scandium, including the steps ofi preparing an aqueous stock solution containing at least scandium, titanium, and zirconium; and mixing an acid or an alkali with the aqueous stock solution to adjust the pH to a range of 1.0 to 2.0 to produce a scandium-containing aqueous suspension containing scandium in a liquid phase and titanium and zirconium in a sohd phase, (2) first preferred embodiment: the method for separating scandium, further including the steps ofi removing titanium and zirconium from the 4 scandium-containing aqueous suspension by solid-liquid separation to produce an acidic solution, and mixing an alkali with the acidic solution to adjust the pH to a range of 3.5 to 7.0 to precipitate scandium; and separating the precipitated scandium by solid-liquid separation, (3) second preferred embodiment: the method for separating scandium, further including the steps of: bringing the scandium-containing aqueous suspension, the acidic solution produced by solid-liquid separation of the scandium-containing aqueous suspension, or a first water-based solution of the precipitated scandium into contact with a chelating resin to cause adsorption of scandium on the chelating resin; and eluting the scandium adsorbed on the chelating resin into a water-based solvent to produce a second water-based solution, (4) third preferred embodiment: the method for separating scandium, further including the steps of: bringing the scandium-containing aqueous suspension, the acidic solution produced by solid-liquid separation of the scandium-containing aqueous suspension, the first water-based solution of the precipitated scandium, or the second water-based solution containing the eluted scandium into contact with an organic solvent containing an extractant to extract scandium into the organic solvent to produce a scandium-containing organic solution; and stripping scandium contained in the scandium-containing organic solution into a water-based solvent to produce a third water-based solution, and (5) fourth preferred embodiment: the method for separating scandium, further including the steps of: bringing the acidic solution produced by solid-liquid separation of the scandium-containing aqueous suspension, the first water-based solution of the precipitated scandium, the second water-based solution containing the eluted scandium, the scandium-containing organic solution containing the extracted scandium, or the third water-based solution containing the stripped scandium into contact with a water-based solvent containing a precipitant to precipitate scandium; and recovering scandium by solid-liquid separation.

Advantageous Effects of Invention [0012] According to the method for separating scandium of the present invention, scandium, and titanium and zirconium, is efficiently separated 5 by using the aqueous stock solution containing at least scandium, titanium, and zirconium. This reduces contamination with impurities, namely titanium and zirconium, and scandium are efficiently and easily separated. An alkali is mixed with the scandium-containing acidic solution produced by solid-liquid separation to adjust the pH to the range of 3.5 to 7.0 so as to precipitate scandium, and the resultant solution is then separated into solid and liquid fractions, whereby a precipitate of scandium is separated. This reduces contamination with impurities such as iron (ferrous) and manganese, and scandium is efficiently and easily separated. Crude scandium produced by these methods contains a small amount of impurities. Such low impurity content of the crude scandium reduces the burden in removing impurities when performing the subsequent steps such as the chelating resin adsorption and elution step, the organic solvent extraction step, the stripping step, and the scandium precipitation step, and these steps are efficiently performed. In particular, since impurities such as titanium and zirconium are removed in advance, adsorption of scandium on the chelating resin is facilitated, and as a result, purity of scandium is increased.

[0013] The method of the present invention is optimal for separating and recovering scandium by using a water suspension of a residue of chlorinated titanium ore or a water suspension of a residue resulting from leaching titanium ore into an acid.

Brief Description of Drawings [0014] [Fig. l] Fig. 1 is a graph showing scandium adsorption isotherms of Example 3 and Comparative Example 1.

Description of Embodiments [0015] The present invention is a method for separating titanium and zirconium, and scandium, by mixing an acid or an alkali with an aqueous stock solution containing at least scandium, titanium, and zirconium to adjust the pH to the range of 1.0 to 2.0 and thus producing a scandium-containing aqueous suspension containing scandium in a liquid phase and titanium and zirconium in a solid phase. 6 [0016] (l) Step of preparing an aqueous stock solution

The aqueous stock solution is an aqueous solution containing scandium, such as a solution containing scandium ions or slurry containing scandium hydroxide or scandium oxide, and contains titanium and zirconium in addition to scandium. Titanium and zirconium may be either in the form of ions or in the form of compounds such as hydroxides or oxides. The aqueous stock solution may contain a rare earth element other than scandium (yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, or lutetium), may contain a transition metal element such as vanadium, chromium, manganese, iron, cobalt, nickel, copper, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, or silver, may contain a radioactive element such as thorium or uranium, or may contain a main group element such as an alkali metal element, an alkaline earth metal element, a Group 12 element in the periodic table such as zinc or cadmium, a Group 13 element in the periodic table such as boron, aluminum, gallium, or indium, a Group 14 element in the periodic table such as silicon, germanium, or tin, a Group 15 element in the periodic table such as phosphorus, arsenic, antimony, or bismuth, a Group 16 element in the periodic table such as selenium or tellurium, or a Group 17 element in the periodic table such as fluorine or chlorine. An aqueous stock solution containing, in addition to titanium and zirconium, at least one kind of metal selected from rare earth elements other than vanadium and scandium is preferred because desired effects of the present invention tend to be obtained. The scandium concentration of the aqueous stock solution is not particularly limited, and an aqueous stock solution having desired scandium concentration may be used. Scandium generally tends to be recovered at a high yield by using an aqueous stock solution having high scandium concentration (about 500 to 50,000 mg/L). According to the method of the present invention, scandium is sufficiently refined, separated, and recovered even by using an aqueous stock solution having low scandium concentration (about 1 to 500 mg/L). The concentrations of elements other than scandium are also not particularly limited. Scandium is generally easily refined by using an aqueous stock solution containing a small amount of impurity components at low 7 concentrations (e.g., containing titanium, zirconium, and vanadium at about 1,000 mg/L or less each). According to the method of the present invention, scandium is sufficiently refined, separated, and recovered even by using an aqueous stock solution containing impurity components (such as titanium, zirconium, and vanadium) at relatively high concentrations (more than 1,000 mg/L). The concentrations of the rare earth elements other than scandium are also not particularly limited, but are preferably about 0 to 1,000 mg/L each. An aqueous stock solution in any pH range is used. If the stock solution has a pH of 6 or more, it is preferable to mix an acid with the stock solution in advance to adjust the pH to 6 or less, and more preferably to 2 or less. If the stock solution has a pH of 2 or more, the stock solution is in the form of slurry containing precipitates of hydroxides etc. of scandium, titanium, and zirconium. However, if the pH of the stock solution is in a strong acid range of 2 or less, the stock solution is a solution with scandium, titanium, zirconium, etc. dissolved therein and therefore is easy to handle. The stock solution having a pH of 1 or less is more preferred, and the stock solution having a pH of 0.5 or less is even more preferred due to greater stability of quality.

[0017] The aqueous stock solution contains at least scandium, titanium, and zirconium. Examples of the aqueous solutions are shown below. As used herein, the “acidic solution” refers to a solution having a pH of approximately 6 or less, the “neutral solution” refers to a solution having a pH of approximately 6 to 8, and the “alkaline solution” refers to a solution having a pH of approximately 8 or more. In the present invention, it is more preferable to use a solution of an ore in an acid, specifically a water suspension of a residue of chlorinated titanium ore, or a solution of a residue of an ore in an acid, specifically a water suspension of a residue resulting from leaching titanium ore into an acid. (1) An acidic solution of a material containing scandium such as an ore in an acid, or an acidic, neutral, or alkaline solution produced by mixing an alkali with this acidic solution. (2) An acidic solution resulting from hydrolyzing or neutralizing a solution of a material containing scandium such as an ore in an acid and thus removing other metal components therefrom by refining, an acidic solution produced by dissolving in an acid a residue resulting from 8 removing other metal components from the solution by refining, or an acidic, neutral, or alkaline solution produced by mixing an alkali with this acidic solution. (3) An alkaline solution of a material containing scandium such as an ore in an alkah, or an acidic, neutral, or alkahne solution produced by mixing an acid with this alkaline solution. (4) An alkaline solution resulting from hydrolyzing or neutrahzing a solution of a material containing scandium such as an ore in an alkali and thus removing other metal components therefrom by refining, or an acidic, neutral, or alkaline solution produced by mixing an acid with this alkaline solution. (5) An alkaline, neutral, or acidic solution produced by dissolving a residue in an alkah or an acid, the residue is resulting from hydrolyzing or neutralizing a solution of a material containing scandium such as an ore in an alkali and thus removing other metal components therefrom by refining. (6) An acidic, neutral, or alkaline solution resulting from roughly purifying scandium contained in any of the acidic or alkahne solutions (l) to (5) by adsorbing and eluting scandium by an ion exchange resin (chelating resin), by precipitating and separating scandium, etc. (7) An alkahne, neutral, or acidic solution produced by mixing an alkah or an add with slurry containing scandium hydroxide, scandium oxide, etc. resulting from roughly purifying scandium contained in any of the acidic or alkahne solutions (l) to (5) by adsorbing and eluting scandium by an ion exchange resin (chelating resin), by precipitating and separating scandium, etc.

[0018] Examples of the material containing scandium include, in addition to various ores and residues resulting from removing other metal components from ores by refining, various materials and waste materials such as aluminum alloys containing scandium, positive electrodes of nickel alkahne storage batteries, metal halide lamps, electrolytes for sohd oxide fuel cehs, and ceramics like scandia-stabilized zirconia. Examples of the ores include thortveitite, gold ore, silver ore, copper ore, lead ore, bismuth ore, tin ore, antimony ore, mercury ore, zinc ore, iron ore, chromium ore, manganese ore, tungsten ore, molybdenum ore, arsenic ore, nickel ore, cobalt ore, uranium ore, thorium ore, phosphate ore, sulfur ore, barium ore, 9 calcium ore, magnesium ore, strontium ore, beryllium ore, aluminum ore, and titanium ore. Ores with high scandium content such as iron ore, nickel ore, titanium ore, manganese ore, tin ore, and aluminum ore are preferred. The acid that dissolves a material such as an ore therein or the acid that makes a solution acidic is not limited. Examples of the acid that dissolves a material such as an ore therein or the acid that makes a solution acidic include: inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, and aqua regia; and organic acids such as acetic acid. The acid that dissolves a material such as an ore therein or the acid that makes a solution acidic may be a solution resulting from hydrolyzing or neutralizing a solution of a material such as an ore in an acid and thus removing other metal components therefrom by refining. Examples of the solution resulting from hydrolyzing or neutralizing a solution of a material such as an ore in an acid and thus removing other metal components therefrom by refining include: a leachate produced by pressure leaching of a mixture of nickel oxide ore, which is laterite ore, and sulfuric acid; and a solution resulting from removing nickel components from the leachate. Other examples of the acid that dissolves a material such as an ore therein or the acid that makes a solution acidic include^ a solution of titanium ore or iron ore such as rutile ore or ilmenite in an inorganic acid such as sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, or aqua regia or in an organic acid such as acetic acid; and a solution resulting from hydrolyzing or neutralizing the solution of titanium ore or iron ore in an inorganic or organic acid and thus removing titanium components and iron components therefrom. The acid that dissolves a material such as an ore therein or the acid that makes a solution acidic may be a solution produced by dissolving in an acid a residue resulting from chlorinating other metals in an ore and thus removing the chlorinated metals in the form of gas. Examples of the solution produced by dissolving a residue in an acid include: a solution produced by dissolving, in an inorganic acid such as sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, or aqua regia or in an organic acid such as acetic acid, a residue resulting from chlorinating titanium ore or iron ore such as rutile ore or ilmenite by chlorine gas and thus removing titanium chloride or iron chloride therefrom; and a solution resulting from hydrolyzing this solution produced by dissolving a residue in 10 an inorganic or organic acid and thus removing titanium components and iron components therefrom. The alkah that is used for pH adjustment is not limited. Examples of such an alkali include: alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkali metal compounds such as sodium carbonate and potassium carbonate; alkaline earth metal hydroxides such as calcium hydroxide (slaked lime), magnesium hydroxide, and barium hydroxide; alkaline earth metal oxides such as calcium oxide (quick lime), magnesium oxide, and barium oxide; alkaline earth metal compounds such as calcium carbonate, magnesium carbonate, and barium carbonate; ammonia; and amines. The alkali that is used for pH adjustment may be a solution of a material such as an ore in an alkah, or a solution resulting from hydrolyzing or neutralizing the solution of a material such as an ore in an alkali and thus removing other metal components therefrom by refining.

[0019] In the case where a material such as an ore is dissolved in an alkali, this alkaline solution, an alkaline solution resulting from hydrolyzing or neutralizing this alkaline solution and thus removing other metals therefrom, etc. may be mixed with an acid to produce an acidic, neutral, or alkaline solution. The alkali that dissolves a material such as an ore therein or the alkah that is used for pH adjustment is not limited. Examples of the alkah that dissolves a material such as an ore therein or the alkah that is used for pH adjustment include: alkah metal hydroxides such as sodium hydroxide and potassium hydroxide; alkah metal compounds such as sodium carbonate and potassium carbonate; alkaline earth metal hydroxides such as calcium hydroxide (slaked hme), magnesium hydroxide, and barium hydroxide; alkaline earth metal oxides such as calcium oxide (quick hme), magnesium oxide, and barium oxide; alkaline earth metal compounds such as calcium carbonate, magnesium carbonate, and barium carbonate; ammonia; and amines. The alkah that dissolves a material such as an ore therein or the alkah that is used for pH adjustment may be a solution of a material such as an ore in an alkah, or a solution resulting from hydrolyzing or neutralizing the solution of a material such as an ore in an alkah and thus removing other metal components therefrom by refining. The acid that makes the pH acidic is not hmited. Examples of this acid include: inorganic acids such as 11 hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, or aqua regia, and organic acids such as acetic acid. The acid that makes the pH acidic may be an acidic solution of a material such as an ore mentioned above.

[0020] The aqueous stock solution may be a solution resulting from roughly purifying scandium. Roughly purification of scandium is performed by a conventional method by using the acidic solution or the alkaline solution produced to prepare the acidic solution. For example, scandium contained in the acidic solution or the alkaline solution is adsorbed on an ion exchange resin (chelating resin) and then eluted from the ion exchange resin (chelating resin) or is precipitated and separated by pH adjustment etc. to produce scandium hydroxide, scandium oxide, etc., and scandium hydroxide, scandium oxide, etc. thus produced is dispersed in water, whereby scandium concentration is increased. A solution produced by adding an acid or an alkali to the solution resulting from the rough purification to adjust the pH may be used as the aqueous stock solution. A solution produced by adjusting the pH of a scandium-containing solution to 7 or more to precipitate scandium hydroxide and mixing an acid or an alkali with slurry containing the precipitate of scandium hydroxide to adjust the pH may be used as the aqueous stock solution. It is preferable to use a fractionated one of the aqueous stock solutions having a pH adjusted as necessary.

[0021] (2) Titanium and Zirconium Separation Step

In the present invention, an alkali is mixed with an aqueous stock solution containing at least scandium, titanium, and zirconium to adjust the pH to the range of 1.0 to 2.0 to produce a scandium-containing aqueous suspension containing titanium and zirconium in a solid phase and scandium in a liquid phase. Titanium and zirconium are precipitated by adjusting the pH of the aqueous stock solution from less than 1.0 to the range of 1.0 to 2.0. If the pH is adjusted to less than 1.0, titanium and zirconium are not sufficiently precipitated and a large amount of titanium and zirconium remains in the aqueous stock solution. If the pH is adjusted to more than 2.0, a precipitate of scandium is present together with precipitates of titanium and zirconium, whereby recovery of scandium is reduced. The alkah that is used for pH adjustment is not limited. Examples of this alkali include: alkali metal hydroxides such as sodium hydroxide and potassium hydroxide! alkali metal compounds such as 12 sodium carbonate and potassium carbonate; alkaline earth metal hydroxides such as calcium hydroxide (slaked lime), magnesium hydroxide, and barium hydroxide; alkaline earth metal oxides such as calcium oxide (quick lime), magnesium oxide, and barium oxide; alkaline earth metal compounds such as calcium carbonate, magnesium carbonate, and barium carbonate; ammonia; and amines. The alkali that is used for pH adjustment may be a solution resulting from hydrolyzing or neutralizing a solution of a material such as an ore in an alkali and thus removing other metal components therefrom by refining. The temperature for pH adjustment is set as appropriate. For example, the temperature for pH adjustment is preferably about 2 to 100°C, and more preferably about 5 to 70°C.

[0022] In another method of the present invention, an acid is mixed with an aqueous stock solution containing at least scandium, titanium, and zirconium to adjust the pH to the range of 1.0 to 2.0 to dissolve scandium therein. By adjusting the pH of the aqueous stock solution from more than 2.0 to the range of 1.0 to 2.0, scandium is dissolved therein and precipitates of titanium and zirconium are allowed to remain as they are. If the pH is adjusted to less than 1.0, precipitates of titanium and zirconium dissolve in the aqueous stock solution. A large amount of titanium and zirconium thus dissolves in the aqueous stock solution. If the pH is adjusted to more than 2.0, a precipitate of scandium remains in the aqueous stock solution and is present together with precipitates of titanium and zirconium, whereby recovery of scandium is reduced. The acid that makes the pH acidic is not limited. Examples of this acid include: inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, or aqua regia; and organic acids such as acetic acid. The acid that makes the pH acidic may be an acidic solution of a material such as an ore mentioned above. The temperature for pH adjustment is set as appropriate. For example, the temperature for pH adjustment is preferably about 2 to 100°C, and more preferably about 5 to 70°C.

[0023] (3) First scandium precipitation and separation step (first preferred embodiment)

It is preferable to separate the scandium-containing aqueous suspension produced by the titanium and zirconium separation step into 13 solid and liquid fractions to remove titanium and zirconium, and to mix an alkali with the aqueous solution resulting from removal of titanium and zirconium (acidic solution) to adjust the pH to the range of 3.5 to 7.0. By adjusting the pH of the acidic solution containing scandium to 3.5 to 7.0, scandium is precipitated, and the resultant solution containing the precipitate of scandium is separated into solid and hquid fractions. If the pH is adjusted to less than 3.5, scandium is not sufficiently precipitated and a large amount of scandium remains in the acidic solution. If the pH is adjusted to more than 7.0, iron (ferrous), manganese, etc. is precipitated, and the precipitate of iron (ferrous), manganese, etc. is present together with a precipitate of scandium, whereby purity of scandium is reduced. The above pH range is therefore preferred. The alkali that is used for pH adjustment is not limited. Examples of such an alkali include^ alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkali metal compounds such as sodium carbonate and potassium carbonate; alkaline earth metal hydroxides such as calcium hydroxide (slaked lime), magnesium hydroxide, and barium hydroxide; alkaline earth metal oxides such as calcium oxide (quick lime), magnesium oxide, and barium oxide; alkaline earth metal compounds such as calcium carbonate, magnesium carbonate, and barium carbonate; ammonia; and amines. The temperature for pH adjustment is set as appropriate. For example, the temperature for pH adjustment is preferably about 2 to 100°C, and more preferably about 5 to 70°C. The solid-liquid separation of the scandium-containing aqueous suspension and the solid-liquid separation of the solution containing the precipitate of scandium are performed by a normal method. For example, a filter, a standing separator, a centrifugal separator, etc. are used for the solid-liquid separation. The precipitate recovered by the solid-liquid separation is dried and/or fired as needed. In the case where the aqueous suspension is separated into solid and hquid fractions, powder of titanium oxide and zirconium oxide etc. are recovered by drying and/or firing the precipitates. In the case where the solution containing the scandium precipitate is separated into solid and liquid fractions, powder of scandium oxide is recovered by drying and/or firing the precipitate.

[0024] (4) Chelating resin adsorption and elution step (second preferred 14 embodiment)

The scandium-containing aqueous suspension produced by the titanium and zirconium separation step, the acidic solution resulting from the solid-liquid separation of the scandium-containing aqueous suspension, or a first water-based solution produced by dissolving the scandium precipitate produced by the scandium precipitation step in a water-based solvent is brought into contact with a chelating resin to cause adsorption of scandium on the chelating resin. The scandium thus adsorbed is then eluted in a water-based solvent to produce a second water-based solution. The water-based solvent that dissolves the scandium precipitate is a known acid such as a sulfuric acid aqueous solution, a hydrochloric acid aqueous solution, or a nitric acid aqueous solution, or a known alkali such as a sodium carbonate aqueous solution or an ammonium carbonate aqueous solution. Acids are preferred as the water-based solvent in terms of cost and ease in handling. The concentration of the water-based solvent is not particularly limited as long as scandium is soluble enough in the water-based solvent. If scandium is to be recovered at higher concentration, the water-based solvent with higher concentration is preferred. For example, 70% of sulfuric acid is more preferred.

[0025] The chelating resin is a conventionally known chelating resin, and a chelating resin capable of adsorbing a large amount of scandium is preferred. Examples of a functional group of the chelating resin capable of adsorbing a large amount of scandium include iminodiacetic acid, thiourea, polyamines, aminophosphoric acid, methylglucamine, amino oxime, phosphonic acid, sulfonic acid, and carboxylic acid. A chelating resin having one or more kinds of these functional groups is used. The chelating resin having scandium adsorbed thereon is transferred to an elution tank as needed so as to be in contact with a known eluent such as sulfuric acid, hydrochloric acid, nitric acid, acetic acid, sodium carbonate, or ammonium carbonate, whereby scandium is eluted in the water-based solvent. A scandium adsorption tank and the elution tank are a normal reaction tank, column, etc., and a liquid passage method etc. is selected as appropriate. The hquid temperature of the adsorption tank and the elution tank is set as appropriate. For example, the hquid temperature is preferably about 2 to 80°C, and more preferably about 5 to 50°C. The water-based solvent that 15 is used to elute scandium from the chelating resin is water or water mixed with an organic solvent such as alcohol as necessary. The content of the organic solvent is preferably about 10 mass% or less.

[0026] (5) Organic solvent extraction step and stripping step (third preferred embodiment)

The scandium-containing water-based solution produced in the steps (2) to (4) (the scandium-containing aqueous suspension produced by the titanium and zirconium separation step, the acidic solution resulting from solid-liquid separation of the scandium-containing aqueous suspension, the first water-based solution, or the second water-based solution) is brought into contact with an organic solvent containing an extractant to extract scandium into the organic solvent, whereby a scandium-containing organic solution is produced. Scandium contained in the scandium-containing organic solution is then stripped into a water-based solvent to produce a third water-based solution.

[0027] In the case where a solution of a scandium precipitate in a water-based solvent (first water-based solution) is used as the water-based solution containing scandium, it is preferable to mix an acid or an alkali with the water-based solution as necessary to adjust the pH to the range of 4.0 to 7.0, because extraction of scandium is increased. By adjusting the pH of the water-based solution to the above range, scandium is mainly extracted and almost no impurity elements are extracted. Scandium can thus be separated. The pH less than 4.0 is not preferred as extraction of scandium is reduced and thus yield of scandium is reduced. The pH higher than 7.0 is also not preferred as extraction of impurity elements is increased and thus separation efficiency is reduced. The preferred pH is 5.0 to 6.5. The acid that makes the pH acidic is not limited. Examples of this acid include: inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, or aqua regia; and organic acids such as acetic acid. The acid that makes the pH acidic may be an acidic solution of a material such as an ore mentioned above. The alkali that is used for pH adjustment is not limited as long as it exhibits alkaline properties. Examples of such an alkali include: alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkali metal compounds such as sodium carbonate and potassium carbonate; alkaline earth metal hydroxides such as calcium 16 hydroxide (slaked lime), magnesium hydroxide, and barium hydroxide; alkaline earth metal oxides such as calcium oxide (quick lime), magnesium oxide, and barium oxide; alkaline earth metal compounds such as calcium carbonate, magnesium carbonate, and barium carbonate; ammonia; and amines. The alkali that is used for pH adjustment may be a solution of a material such as an ore in an alkali.

[0028] An organic solvent containing an extractant is mixed with the water-based solution containing scandium to extract a complex of scandium and the extractant into the organic solvent. The extractant is a conventionally known extractant. For example, a carboxylic acid and/or a carboxylate (hereinafter also referred to as the “carboxylic acid extractant”) are preferred. The carboxylic acid is an organic acid having a carboxyl group, and examples of the carboxylate include sodium, potassium, and ammonium salts of a carboxylic acid. Any extractant that forms a complex with scandium is used. Specific examples of the carboxylic acid extractant include known extractants such as a neodecanoic acid extractant, a Versatic acid extractant, a naphthenic acid extractant, an oleic acid extractant, and a lauric acid extractant. Naphthenic acid and/or neodecanoic acid are preferred. The proportion of the extractant is set as appropriate. The organic solvent contains preferably 1 to 50 mass% of the carboxylic acid extractant, and more preferably 5 to 20 mass% of the carboxylic acid extractant. The organic solvent may further contain an interface adjusting agent (modifier) in order to restrain production of a third phase at the interface between an organic phase and an aqueous phase. Examples of the interface adjusting agent include: long-chain alkyl compounds such as nonylphenol, l decanol, isodecanol, l octanol, and 2-ethylhexanol; and alkyl phosphate compounds such as tributyl phosphate (TBP). The content of the interface adjusting agent is set as appropriate. Normally, the organic solvent contains preferably 1 to 50 mass% of the interface adjusting agent, and more preferably 5 to 40 mass% of the interface adjusting agent. The operation of extracting scandium into the organic solvent is performed by keeping the solution containing scandium (the aqueous suspension, the acidic solution, the first water-based solution, or the second water-based solution) in liquid-liquid contact with the organic solvent containing the extractant and as necessary the interface adjusting agent at an appropriate 17 temperature for a certain period of time by known procedures by using a desired liquid-liquid contactor, and then separating the resultant solution into an extractant phase and a liquid phase by standing separation or centrifugal separation. Examples of the liquid-liquid contactor include a centrifugal extractor, a mixer, a shaker, a separatory funnel, and a multi-stage liquid-liquid contactor, more specifically a counter-current mixer settler, and either a continuous extraction process or a batch extraction process may be used. The processing temperature is preferably set so as to maintain the temperatures of the various water-based solutions and the organic solvent containing the extractant before extraction operation. Normally, it is preferable to keep the processing temperature at 20 to 70°C in view of the flash point of the organic solvent, the phase separation rate, stability of the extractant phase, etc. Extraction with the solvent need not necessarily be performed in a single step, but may be performed in a plurality of steps.

[0029] The organic solvent is not particularly hmited. Examples of the organic solvent include: aromatic hydrocarbon compounds such as toluene, benzene, xylene, ethylbenzene, diethylbenzene, isopropylbenzene, amylbenzene, diamylbenzene, amyltoluene, chlorobenzene, bromobenzene, o-dichlorobenzene, o-chlorotoluene, and p-chlorotoluene; aliphatic hydrocarbon compounds such as kerosene, n-pentane, n-hexane, isohexane, nheptane, isoheptane, n-octane, isooctane, n-decane, n-dodecane, cyclohexane, chloroform, tetrachloromethane, chloroethane, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, l,l,2trichloroethane, 2-chloropropane, 1,2-dichloropropane, 1,2,3'trichloropropane, 1-chlorohexane, petroleum ether, petroleum benzine, ligroin, and n paraffin; and industrial diluents such as Isopar (registered trademark of Exxon Mobil Corporation) and Solvesso (registered trademark of Exxon Mobil Corporation). A mixture of one or two kinds of these organic solvents may be used.

[0030] The scandium-containing organic solution containing extracted scandium is mixed with a water-based solvent to strip scandium contained in the scandium-containing organic solution into the water-based solvent to produce a third water-based solution. The water-based solvent that is used for stripping is water or water mixed with an organic solvent such as alcohol 18 as necessary. The content of the organic solvent is preferably about 10 mass% or less. The water-based solvent that is used for stripping is preferably made acidic by using an inorganic acid such as hydrochloric acid, sulfuric acid, or nitric acid, or an organic acid such as acetic acid. The operation of stripping scandium is performed by keeping the organic solution in liquid-liquid contact with the water-based solvent at an appropriate temperature for a certain period of time by known procedures by using the liquid-liquid contactor and then separating the resultant solution into an extractant phase and a liquid phase by standing separation or centrifugal separation. Examples of the liquid-liquid contactor include a centrifugal extractor, a mixer, a shaker, a separatory funnel, and a multi-stage liquid-liquid contactor, more specifically a counter-current mixer settler or centrifugal extractor, and either a continuous stripping process or a batch stripping process may be used. Stripping need not necessarily be performed in a single step, but may be performed in a plurality of steps. The organic solvent extraction step and the stripping step need not necessarily be performed only once. It is preferable to repeat the organic solvent extraction step and the stripping step a plurality of times as the scandium concentration is increased. Scandium with purity of 99.0 mass% or more, and preferably 99.5 mass% or more, is obtained by performing the organic solvent extraction step and the stripping step in this manner.

[0031] (6) Second scandium precipitation and recovery step (fourth preferred embodiment)

The scandium-containing solution produced in the steps (2) to (5) (the acidic solution resulting from solid-liquid separation of the scandium-containing aqueous suspension, the first water-based solution, the second water-based solution, the scandium-containing organic solution, or the third water-based solution produced by stripping) is mixed with a solution (water-based solvent) containing a precipitant to precipitate scandium, and scandium is recovered as a precipitate by solid-liquid separation. For example, it is preferable to mix the scandium-containing organic solution with the precipitant to precipitate scandium. Scandium with purity of 99.0 mass% or more, and preferably 99.5 mass% or more, is obtained even if the precipitation step is thus performed immediately after 19 the organic solvent extraction step.

[0032] A conventionally known precipitant is used as the precipitant. For example, a carboxylic acid and/or a carboxylate (hereinafter also referred to as the “carboxylic acid precipitant”) are preferred. The carboxylic acid is a carboxylic acid having a carboxyl group, and examples of the carboxylate include sodium, potassium, and ammonium salts of a carboxylic acid. Any precipitant that precipitates scandium is used. Specific examples of the carboxylic acid precipitant include: fatty acids such as formic acid (methanoic acid), acetic acid (ethanoic acid), propionic acid (propanoic acid), butyric acid (butanoic acid), valeric acid (pentanoic acid), caproic acid (hexanoic acid), enanthic acid (heptanoic acid), and caprylic acid (octanoic acid); hydroxy acids such as lactic acid (2-hydroxypropanoic acid), malic acid (2-hydroxybutanedioic acid), and citric acid (2-hydroxypropane tricarboxylic acid); dicarboxylic acids such as oxalic acid (ethanedioic acid), malonic acid (propanedioic acid), succinic acid (butanedioic acid), glutaric acid (pentanedioic acid), adipic acid (hexanedioic acid), fumaric acid ((E)-but-2-enedioic acid), and maleic acid ((Z)-but-2-enedioic acid), etc., and their salts. Dicarboxybc acids such as oxalic acid and/or their salts are preferred. The proportion of the precipitant is set as appropriate. The proportion of the carboxylic acid precipitant to scandium is preferably 1.0 to 5.0 mol, and more preferably 1.5 to 3.0 mol. The operation of precipitating scandium is performed by keeping scandium in contact with the precipitant at an appropriate temperature for a certain period of time by known procedures by using a precipitation device so as to cause reaction therebetween. The precipitate thus produced is a compound such as scandium carboxylate. The precipitate is fractionated and recovered as necessary. The fractionation operation is performed by using a normal device. A filter, a standing separator, a centrifugal separator, etc. are used for the fractionation operation. It is preferable to dry and/or fire the recovered precipitate as necessary because powder of scandium oxide etc. is recovered. Drying conditions and firing conditions are set as appropriate. For example, an appropriate drying temperature is about 80 to 150°C, and an appropriate drying time is about 1 to 24 hours. For example, a firing temperature is about 300 to 1,200°C, and an appropriate firing time is about 1 to 24 hours. Scandium with purity of 99.3 mass% or more, 20 preferably 99.7 mass% or more, and more preferably 99.9 mass%, is obtained by performing the organic solvent extraction step, the stripping step, and the carboxyhc acid precipitation step in this manner. In particular, scandium is separated with high purity from an aqueous stock solution containing thorium, uranium, etc.

[0033] In the case where scandium thus recovered is scandium carboxylate, scandia-stabilized zirconia is produced by dissolving scandium carboxylate in an acid so that scandium carboxylate forms coprecipitates with a zirconium compound, and firing the coprecipitates. Scandia-stabilized zirconia is also produced by mixing powder of scandium hydroxide, scandium oxide, etc. recovered by drying and/or firing with zirconium oxide and firing the mixture. Since recovered scandium contains only a small amount of impurities, namely has high purity, scandia-stabilized zirconia produced by using the recovered scandium is useful as an electrolyte for solid oxide fuel cells. Scandium oxide is reduced to a metal, or scandium is iodized so as to be used as a compound such as scandium iodide.

Examples [0034] The present invention will be described below based on examples and comparative examples. The present invention is not limited to these examples.

[0035] Example 1 A residue of chlorinated titanium ore was suspended in water to a pH of less than 1 to produce 13 L of an aqueous stock solution of scandium (Sample A). Sodium hydroxide was then mixed with the aqueous stock solution to a pH of 1.5, and the mixture was stirred at 70°C for 15 minutes. Subsequently, the mixture was cooled to room temperature, whereby an aqueous suspension containing scandium was produced. This scandium-containing aqueous suspension was vacuum filtered to remove solids, whereby 14 L of an acidic solution containing scandium (Sample B) was produced. Sodium hydroxide was added to the scandium-containing acidic solution (Sample B) at room temperature to adjust the pH to 4, and the resultant solution was then stirred for one hour. This solution was vacuum filtered through a Buchner funnel to recover solids, and pure water was added to the Buchner funnel to continue the filtration. The solids were thus washed until filtrate conductivity was less than 1 mS/cm. 21 [0036] The solids thus washed were added to 70% sulfuric acid and dissolved therein, and the resultant solution was finely adjusted to the final pH of 0.7 with sulfuric acid, whereby 3 L of a water-based solution containing scandium (first water-based solution) (Sample C) was produced.

[0037] The concentration of each element in the aqueous stock solution and the scandium solutions after removal of titanium and zirconium (Samples A, B, and C) was analyzed with an inductively coupled plasma atomic emission spectrometer (ICP-AES or MP-AES). The results are shown in Table 1. The results show that impurity elements are separated and scandium is concentrated by the process of the present invention.

[0038] [Table l]

Sc Ti V Y Zr Fe Mn Cr A1 Sample A 43 3400 1500 20 1775 30000 4700 640 2700 Sample B 40 100 1300 19 48 29000 4600 580 2500 Sample C 158 440 4800 14 191 1700 10 2300 9100

Unit : mg/L

[0039] Example 2 A residue of chlorinated titanium ore was suspended in water to a pH of less than 1 to produce 10 L of an aqueous stock solution of scandium (Sample D). Calcium carbonate was then mixed with the aqueous stock solution to a pH of 4, and hydrochloric acid (10%) was added to the mixture at 40°C to a pH of 1. Subsequently, the resultant mixture was cooled to room temperature, whereby an aqueous suspension containing scandium was produced. This scandium-containing aqueous suspension was vacuum filtered to remove solids, whereby 15 L of an acidic solution containing scandium (Sample E) was produced. Calcium hydroxide was added to the scandium-containing acidic solution (Sample E) at room temperature to adjust the pH to 4, and the resultant solution was then stirred for one hour. This solution was vacuum filtered through a Buchner funnel to recover solids, and pure water was added to the Buchner funnel to continue the filtration. The solids were thus washed until filtrate conductivity was less than 1 mS/cm.

[0040] The solids thus washed were added to hydrochloric acid and dissolved therein, and the resultant solution was finely adjusted to the final 22 pH of 0.7 with hydrochloric acid, whereby 1 L of a water-based solution containing scandium (first water-based solution) (Sample F) was produced.

[0041] The concentration of each element in the aqueous stock solution and the scandium solutions after removal of titanium and zirconium (Samples D, E, and F) was analyzed with an inductively coupled plasma atomic emission spectrometer (ICP-AES or MP-AES). The results are shown in Table 2. The results show that impurity elements are separated and scandium is concentrated by the process of the present invention.

[0042] [Table 2]

Sc Ti V Y Zr Fe Mn Cr A1 Sample D 21 3600 980 127 1220 14700 2520 810 1820 Sample E 10 50 456 70 0 8100 1660 450 1740 Sample F 158 1370 6740 31 242 2100 0 6600 24600

Unit : mg/L

[0043] Impact of chelating resin on scandium concentration process Efficiency of known separation processes such as extraction with a chelating resin or a solvent is improved by reducing impurities that coexist with scandium by the above method. Example 3 shows an example of scandium adsorption properties of a chelating resin.

[0044] Example 3

The scandium-containing water-based solution (first water-based solution) (Sample F) produced in Example 2 and a known chelating resin (functional group: aminophosphoric acid) were placed in a sealed container at each volume ratio shown in Table 3 and were mixed with a bottle roller for 24 hours to cause adsorption of scandium etc. After the adsorption process, the chelating resin was separated from the solution, and the scandium concentration of the solution was analyzed with an inductively coupled plasma atomic emission spectrometer (ICP-AES or MP-AES). Scandium adsorption capacity per liter of the chelating resin was calculated based on the scandium concentrations of the solution before and after the adsorption process. The results are shown in Table 3.

[0045] [Table 3]

Experiment Examples 1 2 3 23

Chelating Resin [ml] 20 5 2 Sample F (Scandium Concentration 158mg/L) [ml] 80 100 100 Scandium Concentration of Solution after Adsorption [mg/L] 5 55 102 Adsorption per Liter of Resin [g/L resin] 0.6 2.1 2.8 [0046] In Example 4, an application test to various known chelating resins was conducted in order to confirm that the scandium solution after separation of titanium and zirconium according to the present invention is widely applied to refining processes using the various known chelating resins.

[0047] Example 4 A scandium-containing acidic solution (Sample H) was produced by performing a process similar to that of Example 2 except that an aqueous stock solution of scandium, titanium, zirconium, etc. (Sample G, pH: less than l) was used instead of Sample D. Sample H is a solution that had not been subjected to scandium precipitation, filtration, washing, and redissolution in an acid by pH adjustment. Sample H corresponds to Sample E in Example 2.

[0048] Sample H and each of various known chelating resins shown in Table 4 were placed in a sealed container at the volume ratio of 20 : 1 and were mixed with a bottle roller for 24 hours to cause adsorption of scandium etc. (Samples I, J, and K). After the adsorption process, the chelating resin was separated from the solution, and the scandium concentration of the solution was analyzed with an inductively coupled plasma atomic emission spectrometer (ICP-AES or MP-AES). Scandium adsorption capacity per liter of the chelating resin was calculated based on the scandium concentrations of the solution before and after the adsorption process. The results are shown in Table 5.

[0049] [Table 4]

Solution after Adsorption Functional Groups of Chelating Resin Sample I Phosphonic Acid, Sulfonic Acid, and Carboxylic Acid Sample J Aminophosphoric Acid 24 [0050] [Table 5]

Solution Composition Sc Adsorption Capacity per Liter of Resin Sc Ti Zr [mg/L] [g/Lresin] Sample G Aqueous Stock Solution 18 1740 600 — Sample H Sc-Containing Acidic Solution 18 <10 <10 — Sample I Solution after Absorption on Resin 2 <10 <10 0.32 Sample J Solution after Absorption on Resin 6 <10 <10 0.24 Sample K Solution after Absorption on Resin 2 <10 <10 0.32 [0051] Comparative Example 1

Sample K

Iminodiacetic Acid

The aqueous stock solution of scandium (Sample D) of Example 2 which had not been subjected to the separation process of the present invention and a known chelating resin (functional group: aminophosphoric acid, the same chelating resin as used in Example 3) were placed in a sealed container at each volume ratio shown in Table 6 and were mixed with a bottle roller for 24 hours to cause adsorption of scandium etc. After the adsorption process, the chelating resin was separated from the solution, and the scandium concentration of the solution was analyzed with an inductively coupled plasma atomic emission spectrometer (ICP-AES or MP-AES). Scandium adsorption capacity per liter of the chelating resin was calculated based on the scandium concentrations of the solution before and after the adsorption process. The results are shown in Table 6.

[0052] [Table 6]

Experiment Examples 4 5 6 Chelating Resin [ml] 20 5 2 Sample D (Scandium Concentration 21mg/L) [ml] 80 100 100 Scandium Concentration of Solution after Adsorption [mg/L] 2 17 19 Adsorption per Liter of Resin 0.08 0.08 0.1 25 [g/L resin] [0053] In a concentration process using a chelating resin, maximum adsorption of a target element (in this example, scandium) on the resin serves as one index of concentration efficiency. Fig. 1 shows scandium adsorption isotherms of Example 3 and Comparative Example 1. In Example 3, the maximum adsorption of scandium is 2.8 g/LRESiN. Example 3 has a tendency that adsorption of scandium increases as the amount of scandium-containing water-based solution (first water-based solution) that contacts the chelating resin increases. Comparative Example 1 shows that the scandium adsorption capacity is saturated at 0.1 g/ Lresin if the step of removing titanium and zirconium of the present invention is not performed. This is because a large amount of adsorption species (titanium and zirconium) that are less selective with respect to scandium is contained in the solution and adsorption of scandium on the chelating resin is therefore inhibited.

[0054] Table 5 shows that all of Samples I, J, and K have Sc adsorption capacity of 0.2 g/LRESiN or more. This is sufficiently higher than 0.1 g/LRESiN, which is the Sc adsorption capacity of Comparative Example 1. This result shows that the titanium and zirconium separation step of the present invention is applicable to refining processes using various chelating resins and contributes to improvement in refining efficiency.

[0055] It was confirmed that purity of scandium is further increased by selectively performing the step of causing adsorption of scandium on a chelating resin by contact therewith and then eluting the adsorbed scandium into a water-based solution (elution step), the step of bringing a scandium-containing aqueous suspension, a scandium-containing acidic solution, or any of various scandium-containing water-based solutions, which are produced in the steps described above, into contact with an organic solvent containing an extractant to extract scandium into the organic solvent (organic solvent extraction step), the step of subsequently stripping scandium into a water-based solvent (stripping step), and the step of bringing the scandium-containing acidic solution, any of the various scandium-containing water-based solutions, or the scandium-containing organic solution, which are produced in the steps described above, into contact with a water-based solvent containing a precipitant to precipitate 26 scandium and then separating the solution containing the scandium precipitate into solid and liquid fractions (second scandium precipitation and recovery step).

Industrial Applicability [0056] Scandium recovered by the method of the present invention is concentrated scandium with reduced impurities such as titanium and zirconium. Accordingly, the method of the present invention is preferable to obtain high purity scandium from such a crude scandium solution by using various refining processes. 27

Claims (17)

1. CLAIMS [Claim l] A method for separating scandium, comprising the steps of preparing an aqueous stock solution containing at least scandium, titanium, and zirconium; and mixing an acid or an alkali with said aqueous stock solution to adjust the pH to a range of 1.0 to 2.0 to produce a scandium-containing aqueous suspension containing scandium in a liquid phase and titanium and zirconium in a solid phase. [Claim
2. 2] The method for separating scandium according to claim 1, further comprising the steps of removing titanium and zirconium from said scandium-containing aqueous suspension by solid-liquid separation to produce an acidic solution, and mixing an alkali with said acidic solution to adjust the pH to a range of 3.5 to 7.0 to precipitate scandium; and separating said precipitated scandium by solid-liquid separation. [Claim
3. 3] The method for separating scandium according to claim 2, further comprising the steps of bringing a first water-based solution of said precipitated scandium into contact with a chelating resin to cause adsorption of scandium on said chelating resin; and eluting said scandium adsorbed on said chelating resin into a water-based solvent to produce a second water-based solution. [Claim
4. 4] The method for separating scandium according to claim 1, further comprising the steps of bringing said scandium-containing aqueous suspension or an acidic solution produced by solid-liquid separation of said scandium-containing aqueous suspension into contact with a chelating resin to cause adsorption of scandium on said chelating resin; and eluting said scandium adsorbed on said chelating resin into a water-based solvent to produce a second water-based solution. [Claim
5. 5] The method for separating scandium according to claim 1, further comprising the step of; bringing said scandium-containing aqueous suspension or an acidic solution produced by solid-liquid separation of said scandium-containing aqueous suspension into contact with an organic solvent containing an extractant to extract scandium into said organic solvent to produce a scandium-containing organic solution. [Claim
6. 6] The method for separating scandium according to claim 2, further comprising the step of; bringing a first water-based solution of said precipitated scandium into contact with an organic solvent containing an extractant to extract scandium into said organic solvent to produce a scandium-containing organic solution. [Claim
7. 7] The method for separating scandium according to claim 3 or 4, further comprising the step of bringing said second water-based solution containing said eluted scandium into contact with an organic solvent containing an extractant to extract scandium into said organic solvent to produce a scandium-containing organic solution. [Claim
8. 8] The method for separating scandium according to claim 1, further comprising the steps of bringing said scandium-containing aqueous suspension or an acidic solution produced by solid-liquid separation of said scandium-containing aqueous suspension into contact with an organic solvent containing an extractant to extract scandium into said organic solvent to produce a scandium-containing organic solution; and stripping scandium contained in said scandium-containing organic solution into a water-based solvent to produce a third water-based solution. [Claim
9. 9] The method for separating scandium according to claim 2, further comprising the steps of bringing a first water-based solution of said precipitated scandium into contact with an organic solvent containing an extractant to extract scandium into said organic solvent to produce a scandium-containing organic solution; and stripping scandium contained in said scandium-containing organic solution into a water-based solvent to produce a third water-based solution. [Claim
10. 10] The method for separating scandium according to claim 3 or 4, further comprising the steps of bringing said second water-based solution containing said eluted scandium into contact with an organic solvent containing an extractant to extract scandium into said organic solvent to produce a scandium-containing organic solution; and stripping scandium contained in said scandium-containing organic solution into a water-based solvent to produce a third water-based solution. [Claim
11. 11] The method for separating scandium according to claim l, further comprising the steps of bringing an acidic solution produced by solid-liquid separation of said scandium-containing aqueous suspension into contact with a water-based solvent containing a precipitant to precipitate scandium; and recovering scandium by solid-liquid separation. [Claim
12. 12] The method for separating scandium according to claim 2, further comprising the steps of bringing a first water-based solution of said precipitated scandium into contact with a water-based solvent containing a precipitant to precipitate scandium; and recovering scandium by solid-liquid separation. [Claim
13. 13] The method for separating scandium according to claim 3 or 4, further comprising the steps of bringing said second water-based solution containing said eluted scandium into contact with a water-based solvent containing a precipitant to precipitate scandium; and recovering scandium by solid-liquid separation. [Claim
14. 14] The method for separating scandium according to any one of claims 5 to 7, further comprising the steps of: bringing said scandium-containing organic solution containing said extracted scandium into contact with a water-based solvent containing a precipitant to precipitate scandium; and recovering scandium by solid-liquid separation. [Claim
15. 15] The method for separating scandium according to any one of claims 8 to 10, further comprising the steps of: bringing said third water-based solution containing said stripped scandium into contact with a water-based solvent containing a precipitant to precipitate scandium; and recovering scandium by solid-liquid separation. [Claim
16. 16] The method for separating scandium according to any one of claims 1 to 15, wherein said aqueous stock solution is a water suspension of a residue of chlorinated titanium ore. [Claim
17. 17] The method for separating scandium according to any one of claims 1 to 15, wherein said aqueous stock solution is a water suspension of a residue resulting from leaching titanium ore into an acid.