Method for producing scandium compound

Abstract

Provided is a technology for more effectively adsorbing scandium by suppressing the amount of chromium adsorbed onto a chelate resin in an ion exchange treatment of an acidic solution containing scandium and impurities including chromium using the chelate resin.　The present invention comprises an ion exchange treatment step for passing an acidic solution containing scandium and impurities including chromium through a column filled with an iminodiacetic acid-type chelate resin to adsorb the scandium onto the chelate resin, wherein, in the ion exchange treatment step, the acidic solution is passed in the range of 40-70ºC, and when the amount of the scandium adsorbed onto the chelate resin is qSc and the maximum amount of the scandium adsorbed onto the chelate resin is qmax,Sc, the passed liquid amount BV in which qSc / qmax,Sc is 0.5 is defined as a lower limit value and the value of the passed liquid amount BV in which the apparent separation factor αapp,Cr(III) Sc(III), defined by the relationship between the scandium and the chromium contained in the acidic solution, is 1 is defined as an upper limit value, and the passed liquid amount BV of the acidic solution is set in the range of the lower limit value to the upper limit value.

Description

Method for producing scandium compounds

[0001] The present invention relates to a method for producing a scandium compound by subjecting an acidic solution containing scandium and impurities containing chromium to an ion exchange treatment using a chelating resin.

[0002] Scandium is extremely useful as an additive for high-strength aluminum alloys and as an electrode material for fuel cells, but its use has been limited due to its low production volume and high cost.

[0003] Nickel oxide ores, such as laterite and limonite, are known to contain trace amounts of scandium. However, because nickel oxide ores have a low nickel content, there has been a problem in that recovering nickel is costly. For this reason, nickel oxide ores have only been used for purposes other than pyrometallurgy, where they are melted at high temperatures in a furnace to obtain ferronickel, an alloy of iron and nickel, which is used as a raw material for stainless steel.

[0004] However, when nickel oxide ore is processed using pyrometallurgy, scandium is separated from nickel, but is distributed together with many impurities into the slag, which is a chemically stable form, making it technically difficult to recover scandium at a high purity. For this reason, there has been little research into industrial methods for recovering scandium contained in nickel oxide ore.

[0005] However, in recent years, a high-pressure acid leaching (HPAL) process has been put into industrial use, in which nickel oxide ore is charged into a pressurized vessel together with a sulfuric acid solution and heated to a high temperature of about 240°C to 260°C to perform solid-liquid separation into a nickel-containing leachate and a leach residue (see, for example, Patent Document 1).

[0006] In the HPAL process, a neutralizing agent is added to the leachate obtained by leaching to separate impurities, and then a sulfiding agent is added to recover nickel as nickel sulfide. The recovered nickel sulfide can then be processed in an existing nickel refining process to obtain nickel salt compounds such as electrolytic nickel and nickel sulfate.

[0007] When such an HPAL process is used, scandium contained in nickel oxide ore is contained in the leachate together with nickel. Then, a neutralizing agent is added to the obtained leachate to separate impurities, and then a sulfiding agent is added to perform sulfiding treatment. Nickel is recovered as nickel sulfide, while scandium remains in the acidic solution after the addition of the sulfiding agent. Therefore, by using the HPAL process, nickel and scandium can be effectively separated.

[0008] However, the scandium separated by the HPAL process is dilute and contains a variety of impurities. Therefore, further purification is required to separate the scandium from the impurities and concentrate and recover it. For example, Patent Document 2 discloses a method using a chelating resin.

[0009] Specifically, the method disclosed in Patent Document 2 involves first selectively leaching nickel and scandium from nickel oxide ore in an acidic solution under high temperature and pressure in an oxidizing atmosphere to obtain a leachate, then adjusting the pH of the leachate to 2 to 4 and using a sulfiding agent to selectively precipitate and recover nickel as a sulfide. Next, the resulting sulfided solution from which nickel has been recovered is brought into contact with a chelating resin to adsorb scandium, the chelating resin is washed with a dilute acid, and then the chelating resin is brought into contact with a strong acid after washing to elute the scandium.

[0010] Nickel oxide ore is known to contain impurities such as iron, aluminum, chromium, manganese, and magnesium, although the types and amounts of these impurities vary depending on the region where it is produced.

[0011] In particular, chromium contained in nickel oxide ore behaves similarly to scandium and is easily adsorbed by chelating resin, but is difficult to elute unless a sulfuric acid solution with a higher concentration is used than when eluting scandium.

[0012] Therefore, Patent Document 3 discloses a method of eluting chromium from a chelating resin using a sulfuric acid solution having a higher concentration than the sulfuric acid solution used to elute scandium.

[0013] Specifically, Patent Document 3 discloses a scandium recovery method including an ion exchange step in which a post-sulfurization solution obtained by hydrometallurgy using a nickel oxide ore containing scandium, aluminum, and chromium is subjected to an ion exchange treatment using a chelating resin. The ion exchange step includes an adsorption step in which the post-sulfurization solution is brought into contact with the chelating resin to adsorb scandium onto the chelating resin, a scandium elution step in which a sulfuric acid solution of 0.3 N or more but less than 3 N is brought into contact with the chelating resin to obtain a scandium eluate, and a chromium removal step in which a sulfuric acid solution of 3 N or more is brought into contact with the chelating resin that has been subjected to the scandium elution step to remove the chromium adsorbed onto the chelating resin.

[0014] That is, the method disclosed in Patent Document 3 involves adsorbing the impurity chromium together with scandium onto a chelating resin, and then utilizing the difference in concentration of the sulfuric acid solution used for elution to elute only scandium from the chelating resin while the chromium remains adsorbed onto the chelating resin, thereby separating it from chromium. However, this method is premised on the adsorption of the impurity chromium onto the chelating resin as described above, and therefore the amount of adsorbed impurities, including chromium, may increase, which may increase the processing load in the elution step.

[0015] In response to this, Patent Document 4 proposes a method for increasing the recovery amount of scandium by contacting an acidic solution containing scandium and chromium with a chelating resin at a predetermined temperature to reduce the amount of chromium adsorbed. This method is useful because it can prevent an increase in the processing load in the elution step by suppressing the amount of impurities containing chromium adsorbed to the chelating resin.

[0016] In this way, by performing an ion exchange treatment using a chelating resin on an acidic solution containing scandium and impurities including chromium, a purified acidic solution can be obtained by removing chromium. Then, by converting scandium from the acidic solution into the desired compound, a scandium compound with a low impurity content can be produced.

[0017] However, there is still room for improvement in ion exchange treatment using chelating resins, and there is a need for a technology that more effectively suppresses adsorption of chromium-containing impurities onto chelating resins in treatment of acidic solutions containing scandium and chromium-containing impurities.

[0018] Japanese Patent Application Laid-Open No. 3-173725 Japanese Patent Application Laid-Open No. 9-194211 Japanese Patent Application Laid-Open No. 2014-218719 Japanese Patent Application Laid-Open No. 2021-050378

[0019] Therefore, an object of the present invention is to provide a method for more effectively adsorbing scandium by suppressing the amount of chromium adsorbed onto a chelating resin in an ion exchange treatment using a chelating resin for an acidic solution containing at least scandium and chromium.

[0020] The present inventors focused on the amount of solution passed through a chelating resin packed in a column in an ion exchange treatment, and discovered that there is an optimal range of the amount of solution passed through in relation to the amount of scandium adsorbed onto the chelating resin, depending on the temperature range of the acidic solution passed through, and thus completed the present invention.

[0021] (1) A first aspect of the present invention is a method for producing a scandium compound from an acidic solution containing at least scandium (Sc) and chromium (Cr), comprising: an ion exchange treatment step of passing the acidic solution through a column packed with an iminodiacetic acid type chelating resin to adsorb the scandium contained in the acidic solution onto the chelating resin; and a compound production step of producing a scandium compound from a scandium eluate obtained by eluting the scandium adsorbed onto the chelating resin. In the ion exchange treatment step, the acidic solution is adjusted to a temperature range of 40° C. to 70° C. and passed through the column, and the amount of scandium adsorbed onto the chelating resin is measured by q Ｓｃ The maximum adsorption amount of scandium on the chelating resin is q ｍａｘ,Ｓｃ When this is the case, q Ｓｃ / q ｍａｘ,Ｓｃ The apparent separation factor αapp,Cr(III) defined as follows in relation to scandium and chromium contained in the acidic solution is set to the lower limit value of the flow rate BV of the acidic solution at which the separation factor αapp,Cr(III) is 0.5: Ｓｃ(III) The method for producing a scandium compound is characterized in that the upper limit of the flow rate BV of the acidic solution is set to a value at which the apparent separation factor αapp,Cr(III) Ｓｃ(III) are the apparent distribution ratios D of scandium and chromium, respectively. ａｐｐ,ｉ αapp,Cr(III) Ｓｃ(III) =D ａｐｐ，Ｓｃ(III) / D ａｐｐ，Ｃｒ(III) and the apparent distribution rate D ａｐｐ,ｉ is the amount of adsorption to the chelating resin q ｉ and the concentration C in the solution after passing the acidic solution through the chelating resin. ｅｆ,ｉ Therefore, D ａｐｐ,ｉ =q ｉ / C ｅｆ,ｉ (expressed as

[0022] (2) A second aspect of the present invention is a method for producing a scandium compound according to the first aspect, wherein the leakage rate, expressed as the ratio of the metal concentration in the acidic solution after passing through the chelating resin to the metal concentration in the acidic solution before passing through the chelating resin, is smaller than the leakage rate of chromium.

[0023] (3) A third aspect of the present invention is a method for producing a scandium compound according to the first or second aspect, wherein the acidic solution is a solution obtained by subjecting nickel oxide ore to leaching with a sulfuric acid solution, and adding a sulfiding agent to the obtained leachate to separate nickel sulfide.

[0024] (4) A fourth aspect of the present invention is the method for producing a scandium compound according to the first or second aspect, wherein the concentration of scandium contained in the acidic solution is 10 mg / L or more.

[0025] (5) A fifth aspect of the present invention is a method for producing a scandium compound according to the first or second aspect of the present invention, wherein the compound production step comprises producing a precipitate containing scandium from the scandium eluate and roasting the precipitate to produce scandium oxide.

[0026] According to the present invention, in an ion exchange treatment using a chelating resin for an acidic solution containing scandium and chromium, the amount of impurities containing chromium adsorbed to the chelating resin can be reduced, and scandium can be more effectively adsorbed.

[0027] This makes it possible to produce a scandium compound with a low impurity content from the scandium eluate obtained through the ion exchange treatment.

[0028] 3A is a graph showing the relationship between the metal ion concentration in the eluate recovered from the column after passing an acidic solution through a chelating resin, and the amount of metal ion adsorption on the chelating resin, based on the results of an ion exchange treatment test. Similar to FIG. 1 , this graph shows the relationship between the metal ion concentration in the eluate and the amount of metal ion adsorption on the chelating resin, and is a graph showing the relationship between the temperature condition of 60°C and the amount of acidic solution passed through BV of 15, 35, and 50. In the ion exchange treatment test, this graph shows the measurement results of the scandium leakage rate under the treatment condition of a pass rate BV of 35, and a breakthrough curve based on the measurement results of the scandium leakage rate under the treatment condition of a pass rate BV of 50. Similar to FIG. 3A , this graph shows the breakthrough curve based on the measurement results of the scandium leakage rate under the treatment conditions of a pass rate BV of 35 and 50. In the ion exchange treatment test, this graph shows the relationship between the apparent separation factor between scandium and chromium and the scandium adsorption efficiency, versus the amount of acidic solution passed through BV. 1 is a graph showing the relationship between the apparent separation coefficient in the relationship between scandium and impurity metals and the adsorption efficiency of scandium versus the amount of acid solution passed through BV in an ion exchange treatment test. 2 is a graph showing a breakthrough curve shown by the relationship between the leakage rates of scandium and chromium versus the amount of acid solution passed through BV when the temperature of the acid solution when passed through the chelating resin was 23° C. in an ion exchange treatment test. 3 is a graph showing a breakthrough curve shown by the relationship between the leakage rates of scandium and chromium versus the amount of acid solution passed through BV when the temperature of the acid solution when passed through the chelating resin was 60° C. in an ion exchange treatment test.

[0029] Specific embodiments of the present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be implemented with various modifications within the scope of the present invention. In this specification, the expression "X to Y" (X and Y are arbitrary numerical values) means "at least X and at most Y."

[0030] 1. Overview of the Method for Producing Scandium Compounds The method for producing a scandium compound according to this embodiment is a method for producing a scandium compound from an acidic solution containing at least scandium and chromium. For example, the acidic solution may be a solution obtained by subjecting nickel oxide ore to a leaching treatment with a sulfuric acid solution, and then adding a sulfurizing agent to the resulting leachate to separate nickel sulfide.

[0031] This production method includes an ion exchange treatment step in which the acidic solution is passed through a column packed with an iminodiacetic acid type chelating resin, thereby causing the scandium contained in the acidic solution to be adsorbed onto the chelating resin, and a compound production step in which a scandium compound is produced from the scandium eluate obtained by eluting the scandium adsorbed onto the chelating resin.

[0032] The ion exchange treatment step is characterized in that the acidic solution is adjusted to a temperature range of 40°C to 70°C and passed through a column packed with a chelating resin, and the range of the amount of acidic solution passed through the chelating resin, BV, is set as follows, to allow scandium to be adsorbed onto the chelating resin.

[0033] That is, the amount of scandium (Sc) adsorbed on the chelating resin is q Ｓｃ , the maximum adsorption amount of scandium on the chelating resin is q ｍａｘ, Ｓｃ When this is the case, q Ｓｃ / q ｍａｘ, Ｓｃ The apparent separation factor αapp,Cr(III) defined in terms of the relationship between scandium and chromium contained in the acidic solution is calculated by taking the value of the flow rate BV of the acidic solution at which the separation factor αapp,Cr(III) is 0.5 as the lower limit. Ｓｃ(III) The value of the flow rate BV of the acidic solution at which the value of β becomes 1 is set as the upper limit, and the flow rate BV of the acidic solution to the chelating resin packed in the column is set in the range from the lower limit to the upper limit.

[0034] The volume of the acidic solution passed through the chelating resin (BV) is a unit that expresses the volume of the acidic solution passed through the chelating resin as a multiple of the volume of the chelating resin in the column. For example, if the volume of the acidic solution passed through the chelating resin is 450 mL and the volume of the chelating resin in the column is 15 mL, then BV = 450 mL / 15 mL = 30.

[0035] Also, "apparent separation factor αapp,Cr(III) Ｓｃ(III) " is the apparent distribution ratio D of scandium and chromium ａｐｐ, ｉ By "αapp, Cr(III) Ｓｃ(III) =D ａｐｐ，Ｓｃ(III) / D ａｐｐ，Ｃｒ(III) " Also, "apparent distribution rate D ａｐｐ,ｉ " is the amount of adsorption q ｉ and the concentration C in the solution after passing the acidic solution through the chelating resin. ｅｆ,ｉ Therefore, "D ａｐｐ,ｉ =q ｉ / C ｅｆ,ｉ " is defined as follows.

[0036] As described above, in the method for producing a scandium compound according to the present embodiment, in the ion exchange treatment step, the temperature of the acidic solution passed through the chelating resin is adjusted to a temperature range of 40° C. or higher and 70° C. or lower, and the flow rate BV of the acidic solution is set to a range from a specific lower limit to an upper limit based on the scandium adsorption amount and the apparent separation factor between scandium and the impurity chromium. This effectively prevents chromium, an impurity contained in the acidic solution, from being adsorbed onto the chelating resin, thereby reducing the impurity content in the resulting scandium eluate and increasing the scandium content.

[0037] Then, in the compound production process, a scandium compound of the desired form is produced from the obtained scandium eluate, whereby a scandium compound with a low impurity content and an improved scandium content can be obtained.

[0038] 2. Acidic Solution Containing Impurities Including Scandium and Chromium Prior to a more detailed description of the ion exchange treatment step in the method for producing a scandium compound according to this embodiment, the acidic solution to be treated will be described. The acidic solution to be treated is a solution containing scandium that is recovered by adsorption onto a chelating resin in the ion exchange treatment step. The acidic solution also contains at least chromium as an impurity.

[0039] The acidic solution to be treated is not particularly limited, but preferably has a scandium concentration of 10 mg / L or more. If the acidic solution has a scandium concentration of 10 mg / L or more, the treatment in the ion exchange treatment step described below can be suitably applied. Furthermore, the concentration of chromium, which is an impurity, in the acidic solution is not particularly limited, but preferably has a concentration of 0.1 mg / L or more and 500 mg / L or less.

[0040] For example, the acidic solution is not particularly limited, but may be a solution obtained by subjecting nickel oxide ore to leaching with a sulfuric acid solution, and then adding a sulfurizing agent to the resulting leachate to separate nickel sulfide. Nickel oxide ore contains scandium, as well as elements such as chromium, iron, aluminum, manganese, and magnesium. Therefore, the solution obtained by subjecting nickel oxide ore to a hydrometallurgical process is a sulfuric acidic solution containing impurities including scandium and chromium.

[0041] The hydrometallurgical process for nickel oxide ore can be carried out by a known method, but will be briefly described below. The hydrometallurgical process includes a leaching step in which nickel oxide ore is leached with a sulfuric acid solution under high temperature and pressure to obtain a leachate, a neutralization step in which a neutralizing agent is added to the leachate to obtain a neutralized precipitate containing impurities and a neutralized solution, and a sulfurization step in which a sulfurizing agent is added to the neutralized solution to obtain nickel sulfide and a sulfurized solution. The sulfurized solution recovered from the sulfurization step is a sulfuric acid solution containing impurities including scandium and chromium.

[0042] (Leaching step) The leaching step is a step in which a sulfuric acid solution is added to a slurry of nickel oxide ore using, for example, a high-temperature pressurized vessel (autoclave), and the mixture is stirred under high temperature and high pressure to produce a leached slurry consisting of a leachate and a leach residue. In the leaching step, the obtained leach slurry consisting of the leachate and the leach residue is washed and subjected to solid-liquid separation into a leachate containing nickel, cobalt, scandium, etc. and a leach residue mainly containing hematite.

[0043] Nickel oxide ores include mainly so-called laterite ores such as limonite ore and saprolite ore, which contain scandium.

[0044] (Neutralization step) The neutralization step is a step in which a neutralizing agent is added to the obtained leachate to adjust the pH, thereby obtaining a neutralized precipitate containing impurities and a neutralized solution. As a result of the neutralization treatment in the neutralization step, valuable metals such as nickel, cobalt, and scandium are contained in the neutralized solution, and most of the impurities, including iron and aluminum, become the neutralized precipitate. As the neutralizing agent, a conventionally known agent can be used, and examples thereof include calcium carbonate, slaked lime, and sodium hydroxide.

[0045] (Sulfurization step) The sulfurization step is a step of adding a sulfurizing agent to the neutralized solution obtained from the neutralization step to obtain nickel sulfide and a sulfurized solution. By the sulfurization treatment in the sulfurization step, nickel, cobalt, zinc, etc. become sulfides, and scandium is contained in the sulfurized solution.

[0046] Specifically, in the sulfurization step, a sulfiding agent such as hydrogen sulfide gas, sodium sulfide, or sodium hydrosulfide is added to the obtained neutralized liquid to produce sulfides containing nickel and cobalt with few impurities and a post-sulfurization liquid containing scandium with a stabilized nickel concentration at a low level. In the sulfurization treatment in the sulfurization step, the slurry containing nickel sulfide is subjected to a sedimentation separation treatment using a thickener or the like to separate and recover the nickel sulfide, while the post-sulfurization liquid containing scandium is allowed to overflow and recover.

[0047] In the manufacturing method according to the present embodiment, the post-sulfurization liquid obtained through the hydrometallurgical process of nickel oxide ore as described above can be used as an acidic solution containing impurities including scandium and chromium.

[0048] 3. Ion Exchange Treatment Step The production method according to the present embodiment includes an ion exchange treatment step of passing an acidic solution containing scandium and impurities including chromium through a column packed with an iminodiacetic acid type chelating resin, thereby causing the scandium contained in the acidic solution to be adsorbed onto the chelating resin.

[0049] Specifically, the ion exchange treatment process includes at least an adsorption process in which scandium in an acidic solution is adsorbed onto the chelating resin by passing the acidic solution through a column packed with the chelating resin, and an elution process in which scandium is eluted from the chelating resin to obtain a scandium eluate. Each process will be described below.

[0050] <3-1. Adsorption Step> The adsorption step is a step in which an acidic solution is passed through a column packed with a chelating resin to bring the acidic solution into contact with the chelating resin, thereby adsorbing scandium in the acidic solution onto the chelating resin.

[0051] The chelating resin used is an iminodiacetic acid type chelating resin having iminodiacetic acid as a functional group. The iminodiacetic acid type chelating resin has higher selectivity as the metal ion to be adsorbed becomes a multivalent ion. Therefore, the iminodiacetic acid type chelating resin can adsorb trivalent scandium ions (Sc ３＋ ) can be adsorbed with high selectivity.

[0052] However, iminodiacetic acid type chelating resins have a problem in that they are unable to absorb impurities, particularly trivalent chromium ions (Cr ３＋ The selectivity of chromium in the form of chromium is also relatively high. Therefore, chromium may be adsorbed to the adsorption sites before scandium, resulting in a decrease in the amount of scandium adsorbed. Also, scandium adsorbed on the chelating resin may begin to be replaced by chromium during treatment.

[0053] As a result of investigations by the present inventors, focusing on the flow rate BV of the chelating resin, which has conventionally been determined empirically, it has been found that there is an optimal range of the flow rate BV in relation to the amount of scandium adsorbed onto the chelating resin, depending on the temperature range of the acidic solution passed through. Therefore, in the production method of this embodiment, as will be described in detail later, in the ion exchange treatment step, the temperature of the acidic solution passed through the chelating resin is adjusted to a range of 40°C to 70°C, and lower and upper limits of the flow rate BV are set, so that the flow rate BV of the acidic solution passed through the chelating resin falls within the range from the lower limit to the upper limit.

[0054] Specifically, when scandium is adsorbed onto the chelating resin in a temperature range of 40° C. to 70° C., the lower limit of the amount of liquid passed through the chelating resin BV is set to q Ｓｃ , the maximum adsorption amount of scandium on the chelating resin is q ｍａｘ,Ｓｃ When this is the case, q Ｓｃ / q ｍａｘ,Ｓｃ The upper limit of the amount of solution BV passed through the chelating resin is determined by the apparent separation factor αapp,Cr(III) defined in terms of the relationship between scandium and chromium contained in the acidic solution. Ｓｃ(III) is the value of the flow rate BV of the acidic solution at which the value of

[0055] [Regarding Setting of Lower and Upper Limits of Flow Rate BV] Here, a test will be described in which a solution having the composition shown in Table 1 below was prepared as an acidic solution containing impurities including scandium and chromium, and the acidic solution was passed through an iminodiacetic acid type chelating resin to perform ion exchange treatment.

[0056] As test conditions, the iminodiacetic acid type chelating resin used was Diaion CR11 (trade name) manufactured by Mitsubishi Chemical Corporation, and 15 mL of the chelating resin was packed into the column. The pH of the acidic solution was set to 2.0, and SV = 4 h －１The flow rate BV was set to BV = 15 to 50. The temperature of the acidic solution when passing through the chelating resin was set to two conditions: 23°C and 60°C, and tests were conducted under these conditions. SV is a unit that expresses the amount of acidic solution passed through per hour as a multiple of the volume of the chelating resin in the column.

[0057] 1 is a graph showing the relationship between the metal ion concentration in the eluate recovered from the column after passing an acidic solution through the chelating resin at a flow rate BV of 50 and the amount of metal ions adsorbed onto the chelating resin, based on the results of an ion exchange treatment test. ａｐｐ，ｉ " is defined as the "apparent distribution coefficient" of the metal ion (i), and the metal ion concentration in the eluate is expressed as C ｅｆ，ｉ The amount of metal ions adsorbed on the chelating resin is q ｉ When "D ａｐｐ，ｉ =q ｉ / C ｅｆ，ｉ The eluate is a solution that comes out of the column after the acidic solution has been passed through the chelating resin, and is also called the post-passage solution.

[0058] In the graph of FIG. 1, the metal ions located on the upper left side have an apparent distribution ratio D ａｐｐ，ｉ The test results shown in the graph of Figure 1 indicate that scandium (Sc) has the highest selectivity to chelating resins at a temperature of 23°C, and chromium (Cr) has the highest selectivity to chelating resins at a temperature of 60°C.

[0059] From these results, the "apparent separation factor (α)" between scandium (Sc), which is the target of adsorption to the chelating resin, and other metal ions (i) such as chromium, is calculated as follows: ａｐｐ,ｉ Ｓｃ(III) That is, the apparent separation factor can be calculated by the above-mentioned apparent distribution ratio using the formula "α ａｐｐ,ｉ Ｓｃ(III) =D ａｐｐ, Ｓｃ(III) / D ａｐｐ,ｉWhen this apparent separation factor is greater than 1, it means that the selectivity of scandium is higher than that of other metal ions such as chromium.

[0060] Similar to the graph in FIG. 1 , FIG. 2 is a graph showing the relationship between the metal ion concentration in the recovered eluate and the amount of metal ions adsorbed onto the chelating resin. The graph shows the results when the temperature of the acidic solution when passed through the chelating resin was set to 60° C. and the flow rate BV of the acidic solution was set to BV = 15, 35, and 50.

[0061] As shown in the graph of FIG. 2, under the temperature condition of 60° C., when the flow rate BV of the acidic solution through the chelating resin is BV=15, 35, the apparent separation factor (αapp,Cr(III)) between scandium and chromium is 0.05. Ｓｃ(III) ) is greater than 1. In other words, scandium has a higher selectivity for the chelating resin than chromium, and therefore it is possible to increase the amount of scandium adsorbed while effectively suppressing the adsorption of chromium.

[0062] In addition, in the ion exchange treatment, the scandium leakage rate from the chelating resin can be measured from the scandium concentration in the acidic solution before adsorption of scandium onto the chelating resin and the scandium concentration in the eluate after adsorption of scandium onto the chelating resin. That is, the scandium leakage rate can be expressed as "leakage rate (%) = scandium concentration in eluate after adsorption / scandium concentration in acidic solution before adsorption × 100," and refers to the proportion of scandium that migrates into the eluate without being adsorbed onto the chelating resin.

[0063] Based on this leakage rate, the amount of scandium adsorbed to the chelating resin can be determined from a breakthrough curve that shows the relationship between the leakage rate at that time and the amount of acid solution passed through BV in the ion exchange treatment.

[0064] 3A is a graph obtained from the above-mentioned ion exchange treatment test, and is a graph of a breakthrough curve based on the measurement results of the scandium leakage rate under the treatment condition of a liquid flow rate BV of 35 and the measurement results of the scandium leakage rate under the treatment condition of a liquid flow rate BV of 50. As shown in the graph of FIG. 3A, when the liquid flow rate BV is 50, the leakage rate is 100%, and the shaded area in the graph is the maximum amount of scandium adsorbed to the chelating resin. The maximum amount of adsorption is referred to as "q ｍａｘ,Ｓｃ " is expressed as ".

[0065] Similarly to FIG. 3A, FIG. 3B is a graph of the breakthrough curve based on the measurement results of the scandium leakage rate under each treatment condition where the flow rate BV is 35 and 50. The shaded area in the graph indicates the amount of adsorption up to the flow rate BV of 35. The amount of adsorption of scandium up to the flow rate BV of 35 is referred to as "q Ｓｃ (35)".

[0066] As shown in the graphs of Figures 3A and 3B, the amount of scandium adsorbed onto the chelating resin depends on the amount of acidic solution passed through BV. From this, it is possible to determine the adsorption efficiency of scandium onto the chelating resin under treatment conditions with a predetermined amount of solution passed through BV. In other words, the maximum amount of scandium adsorbed (q ｍａｘ,Ｓｃ ) to the scandium adsorption amount (q Ｓｃ The adsorption efficiency of scandium onto the chelating resin can be determined from the ratio of q Ｓｃ / q ｍａｘ,Ｓｃ The higher the ratio, the higher the scandium adsorption efficiency.

[0067] In the ion exchange process in which scandium is adsorbed onto a chelating resin, the maximum adsorption amount of scandium (q ｍａｘ,Ｓｃ ) to the scandium adsorption amount (q Ｓｃ It is preferable to set the flow rate BV so that the ratio of (a) to (b) is 0.5 or more.

[0068] Therefore, in the manufacturing method according to the present embodiment, in the ion exchange treatment step, qＳｃ / q ｍａｘ,Ｓｃ The value of the amount of acidic solution BV at which the adsorption efficiency of scandium is increased is set as the lower limit, and the amount of solution BV at which the adsorption efficiency of scandium is increased is set as the lower limit.

[0069] FIG. 4 is a graph obtained from the above-mentioned ion exchange treatment test, showing the apparent separation coefficient (αapp,Cr(III)) between scandium and chromium versus the flow rate (BV) of the acidic solution. Ｓｃ(III) ) and scandium adsorption efficiency (q Ｓｃ / q ｍａｘ,Ｓｃ 4 is a graph showing the relationship between the apparent separation factor and the scandium adsorption efficiency.

[0070] As mentioned above, the apparent separation factor (αapp,Cr(III) Ｓｃ(III) ) is greater than 1, this means that scandium has a higher selectivity for the chelating resin than chromium, suppressing the adsorption of chromium and increasing the amount of scandium adsorbed. On the other hand, in a region where the apparent separation factor is smaller than 1, the selectivity for chromium for the chelating resin is higher than that for scandium, resulting in preferential adsorption of chromium. As shown in the graph of Figure 4, it can be seen that the apparent separation factor depends on the flow rate BV of the acidic solution, and in a region where the flow rate BV is greater than 35, the apparent separation factor becomes smaller than 1. In other words, the selectivity for chromium for the chelating resin is higher than that for scandium.

[0071] Therefore, in the production method according to the present embodiment, in the ion exchange treatment step, the apparent separation factor (αapp,Cr(III)) defined in terms of the relationship between scandium and chromium contained in the acidic solution is Ｓｃ(III) The upper limit value is the amount of solution BV passed through the acid solution at which the ratio (%) of scandium to chromium is 1. This allows the treatment to be carried out while maintaining a state in which the chelating resin has higher selectivity for scandium than for the impurity chromium, and effectively suppresses adsorption of chromium.

[0072] FIG. 5 is a graph similar to FIG. 4, showing the apparent separation coefficient (α) between scandium and impurities other than chromium versus the flow rate BV of the acidic solution. ａｐｐ，ｉ Ｓｃ(III) ) is shown. Here, data on iron (Fe), aluminum (Al), and nickel (Ni) contained in the acidic solution whose composition is shown in Table 1 above are shown as other impurities. The apparent separation factor (α ａｐｐ，ｉ Ｓｃ(III) The upper limit of the acid solution flow rate BV is the value at which the ratio of scandium to chromium (αapp,Cr(III)) becomes 1, and the flow rate BV is set to be up to that upper limit. This allows the treatment to be carried out while maintaining a state in which the selectivity of the chelating resin for scandium is higher than that of the impurity, and adsorption of the impurity can be effectively suppressed. As shown in the graph of Figure 5, the apparent separation factor (αapp,Cr(III)) between scandium and chromium is Ｓｃ(III) By setting the upper limit of the amount of acidic solution passed (BV) at which the ratio (%) of scandium to other impurities is 1, a higher selectivity for scandium can be maintained in relation to other impurities.

[0073] 6A is a graph of a breakthrough curve showing the relationship between the leakage rates of scandium and chromium and the amount of acid solution passed through BV when the temperature of the acid solution when passed through the chelating resin was 23° C. in the above-mentioned ion exchange treatment test. Similarly, FIG. 6B is a graph of a breakthrough curve when the temperature of the acid solution when passed through the chelating resin was 60° C.

[0074] As shown in the graph in Figure 6A, under the temperature condition of 23°C, the leakage rate of scandium is small and the amount of adsorption to the chelating resin is large regardless of the flow rate BV. On the other hand, the leakage rate of chromium is large and the amount of adsorption to the chelating resin is small. Therefore, under the temperature condition of 23°C, under any flow rate BV, scandium is preferentially adsorbed to the chelating resin over the impurity chromium.

[0075] In contrast, as shown in the graph of Figure 6B, under the temperature condition of 60°C, in the region where the flow rate BV is low, the leakage rate of scandium is low and the amount of chromium adsorbed to the chelating resin is high, but compared to the temperature condition of 23°C, the leakage rate of chromium is low and the amount of chromium adsorbed to the chelating resin is high. Furthermore, the graph of Figure 6B shows that when the flow rate BV of the acidic solution is around BV = 35, the leakage rates of scandium and chromium are reversed, and chromium is preferentially adsorbed to the chelating resin. In this case, it is necessary to terminate the flow of the acidic solution when the flow rate BV is around BV = 35.

[0076] Thus, in the ion exchange treatment, the amount of adsorption of impurities, including scandium and chromium, onto the chelating resin at a given flow rate BV varies depending on the temperature conditions of the acidic solution during flow. From this perspective, it is preferable to set the temperature conditions of the acidic solution during flow and to set the upper limit of the flow rate BV of the acidic solution according to the temperature conditions. Specifically, it is preferable to set the flow rate BV so that the leakage rate of scandium is smaller than the leakage rate of chromium.

[0077] As shown in the graph of Fig. 6B, the temperature condition during liquid passage under which the leakage rates of scandium and chromium are reversed depending on the condition of the liquid flow rate BV is in the range of 40°C to 70°C, or in the range of 45°C to 70°C.

[0078] When the temperature condition of the acidic solution during the passage is in the range of 40° C. or higher and 70° C. or lower, the upper limit of the amount of the acidic solution passed through the chelating resin (BV) is, as described above, the apparent separation factor (αapp,Cr(III)) defined in relation to the relationship between scandium and chromium contained in the acidic solution. Ｓｃ(III) ) can be set to the value of the flow rate BV of the acidic solution at which the value of the flow rate BV becomes 1.

[0079] <3-2. Elution step> The elution step is a step of eluting scandium adsorbed on the chelating resin to obtain a scandium eluate. Specifically, in the elution step, scandium is eluted by bringing a sulfuric acid solution into contact with the chelating resin on which scandium has been adsorbed, thereby obtaining a scandium eluate.

[0080] When preparing a scandium eluent, the normality of the sulfuric acid solution used to elute scandium is preferably in the range of 0.3 N to 3.0 N, more preferably in the range of 0.5 N to 2.0 N. By setting the normality to 3.0 N or less, the elution of impurities adsorbed to the chelating resin can be suppressed. On the other hand, by setting the normality to 0.3 N or more, scandium can be efficiently eluted from the chelating resin.

[0081] In addition, when eluting scandium from the chelating resin, the scandium eluate obtained from the elution step may be used and the scandium eluate may be brought into contact with the chelating resin to elute scandium, thereby increasing the concentration of scandium contained in the scandium eluate.

[0082] 4. Compound Production Process for Producing a Scandium Compound The compound production process is a process for producing a scandium compound from the scandium eluate obtained through the ion exchange treatment process. For example, the scandium contained in the scandium eluate can be converted into the form of scandium oxide.

[0083] In the compound production process, a scandium compound can be produced by a known method using a scandium eluent. For example, a scandium hydroxide precipitate can be produced by adding an alkali to the scandium eluent to perform a neutralization treatment. Alternatively, a scandium oxalate precipitate can be produced by performing an oxalation treatment on the scandium eluent. Among these, the method using the oxalation treatment more effectively separates impurities and produces a scandium compound containing scandium at a high purity.

[0084] Specifically, in the oxalation process, oxalic acid is added to a scandium eluent to form a precipitate of scandium oxalate, or the oxalation process may involve adding the scandium eluent to a reaction vessel containing an oxalic acid solution to form a precipitate of scandium oxalate.

[0085] When producing scandium oxide as a scandium compound, the scandium hydroxide or scandium oxalate obtained as described above is subjected to a roasting treatment. Specifically, the roasting treatment is a process in which the scandium oxalate precipitate obtained by the oxalation treatment is washed with water, dried, and then roasted. By undergoing such a roasting treatment, scandium can be converted into scandium oxide of extremely high purity. The roasting conditions are not particularly limited, but for example, the scandium is placed in a tubular furnace and heated at approximately 900°C for approximately two hours.

[0086] Prior to the compound production process for producing a scandium compound, the scandium eluate obtained through the ion exchange process may be subjected to a purification process such as a solvent extraction process or a neutralization process. For example, by performing the solvent extraction process as a purification process, impurities contained in the scandium eluate can be selectively extracted into an organic solvent containing an extractant, thereby purifying the scandium eluate and obtaining a solution in which scandium is concentrated.

[0087] The present invention will be explained in more detail below by showing examples, but the present invention is not limited to the following examples in any way.

[0088] <Ion Exchange Treatment> In order to produce a scandium compound from an acidic solution containing scandium (Sc) and impurities including chromium (Cr), the acidic solution was subjected to an ion exchange treatment using a chelating resin. Specifically, a solution having the composition shown in Table 2 below was prepared as an acidic solution containing scandium and impurities including chromium, and the acidic solution was passed through an iminodiacetic acid type chelating resin to perform the ion exchange treatment.

[0089]

[0090] An acidic solution was passed through a column packed with a chelating resin, and an adsorption treatment was performed to adsorb scandium contained in the acidic solution onto the chelating resin. Regarding the treatment conditions, the iminodiacetic acid type chelating resin used was Diaion CR11 manufactured by Mitsubishi Chemical Corporation, and 15 mL of the chelating resin was packed into the column. The pH of the acidic solution was set to 2.0, and the SV was set to 4 h. －１ It was decided.

[0091] As shown in Table 3 below, in Examples 1 to 4 and Comparative Examples 1 to 4, the temperature of the acidic solution when passed through the chelating resin was adjusted to a range of 40° C. to 70° C. In Comparative Example 5, the temperature of the acidic solution was adjusted to 75° C.

[0092] Here, the upper and lower limits of the flow rate BV of the acidic solution through the chelating resin were set as follows: The amount of scandium adsorbed onto the chelating resin described below was determined from a breakthrough curve, which shows the relationship between the flow rate BV of the acidic solution through the chelating resin and the leakage rate at that time, as shown in Figures 3A and 3B , as an example, based on the scandium leakage rate through the chelating resin. The scandium leakage rate is expressed as "Leakage rate (%) = scandium concentration in the eluate after adsorption / scandium concentration in the acidic solution before adsorption × 100."

[0093] That is, for the lower limit of the flow rate BV, the amount of scandium adsorbed to the chelating resin is q Ｓｃ The maximum amount of scandium adsorbed onto the chelating resin is q ｍａｘ,Ｓｃ When this is the case, q Ｓｃ / q ｍａｘ,Ｓｃ Specifically, as shown in Table 3 below, when the temperature of the acidic solution during the liquid passage was 45°C, 60°C, and 70°C, the q Ｓｃ / q ｍａｘ,Ｓｃ The flow rates BV of the acidic solutions for which the pore size is 0.5 are BV=26, BV=17, and BV=12.5, respectively.

[0094] In addition, the upper limit of the flow rate BV is determined by the apparent separation coefficient αapp,Cr(III) Ｓｃ(III) The apparent separation factor αapp,Cr(III) was defined as the amount of acidic solution passed through BV at which the value of αapp,Cr(III) was 1.Ｓｃ(III) are the apparent distribution ratios D of scandium and chromium, respectively. ａｐｐ, ｉ αapp,Cr(III) Ｓｃ(III) =D ａｐｐ，Ｓｃ(III) / D ａｐｐ，Ｃｒ(III) Also, the apparent distribution rate D ａｐｐ,ｉ is the amount of adsorption onto the chelating resin, q ｉ and the concentration C in the eluate after passing the acidic solution ｅｆ, ｉ Therefore, D ａｐｐ,ｉ =q ｉ / C ｅｆ,ｉ Specifically, as shown in Table 3 below, when the temperature of the acidic solution during the liquid passage is set to 45°C, 60°C, and 70°C, the apparent separation factor αapp,Cr(III) Ｓｃ(III) The flow rates BV of the acidic solutions at which the ratio of the saturation voltage to the saturation voltage is 1 are BV=65, BV=37, and BV=13, respectively.

[0095] In the examples (Examples 1 to 4), the amount of acidic solution passed through the chelating resin (BV) was set within the range from the lower limit to the upper limit based on the lower and upper limits of the amount of solution passed through (BV) set in this way. On the other hand, in the comparative examples (Comparative Examples 1 to 4), the amount of solution passed through (BV) was set outside the range from the lower limit to the upper limit. The amount of solution passed through (BV) of the acidic solution in each test example is as shown in Table 3 below.

[0096] The following Table 3 shows the measurement results of the adsorption rates of scandium (Sc) and chromium (Cr) along with the above-mentioned test conditions. Note that the scandium leakage rate can be calculated as described above by the formula "Leakage rate (%) = scandium concentration in eluate after adsorption / scandium concentration in acidic solution before adsorption × 100", and the chromium leakage rate can be calculated in the same way.

[0097]

[0098] As shown in the results in Table 3, in Examples 1 to 4, the adsorption of chromium to the chelating resin was suppressed, and scandium was efficiently adsorbed. This is because the temperature of the acidic solution passed through the chelating resin was adjusted to the range of 40 to 70°C, and the q Ｓｃ / q ｍａｘ, ＳｃThe apparent separation coefficient αapp,Cr(III) is calculated by taking the value of the flow rate BV at which αapp,Cr(III) is 0.5 as the lower limit. Ｓｃ(III) This is thought to be because the value of the liquid flow rate BV at which the value of 1 is set as the upper limit, and the liquid flow rate BV is set within the range from the lower limit to the upper limit.

[0099] On the other hand, in Comparative Examples 1 and 3, although chromium adsorption was suppressed and scandium was effectively adsorbed, the scandium adsorption sites remained on the chelating resin due to the small liquid flow rate BV, resulting in poor yield. Furthermore, in Comparative Examples 2 and 4, the liquid flow rate BV was excessive, so the scandium adsorption sites became saturated and scandium was not sufficiently adsorbed, resulting in a high scandium leakage rate at that liquid flow rate BV. Furthermore, in Comparative Example 5, the scandium leakage rate was high, which is thought to have led to substitution adsorption of chromium, resulting in a high chromium adsorption rate and failure to effectively adsorb scandium.

Claims

1. A method for producing a scandium compound from an acidic solution containing at least scandium (Sc) and chromium (Cr), comprising: an ion exchange treatment step of passing the acidic solution through a column packed with an iminodiacetic acid type chelating resin, thereby adsorbing the scandium contained in the acidic solution onto the chelating resin; and a compound production step of producing a scandium compound from a scandium eluate obtained by eluting the scandium adsorbed onto the chelating resin, wherein in the ion exchange treatment step, the acidic solution is adjusted to a temperature in the range of 40°C to 70°C and passed through the column, and the amount of scandium adsorbed onto the chelating resin is measured by q Ｓｃ The maximum adsorption amount of scandium on the chelating resin is q ｍａｘ,Ｓｃ When this is the case, q Ｓｃ / q ｍａｘ,Ｓｃ The apparent separation factor αapp,Cr(III) in the relationship between scandium and chromium contained in the acidic solution is defined as follows: Ｓｃ(III) a value of the flow rate BV of the acidic solution at which the apparent separation factor αapp,Cr(III) is 1 is set as an upper limit value, and the flow rate BV of the acidic solution is set in a range from the lower limit value to the upper limit value. Ｓｃ(III) are the apparent distribution ratios D of scandium and chromium, respectively. ａｐｐ,ｉ αapp,Cr(III) Ｓｃ(III) =D ａｐｐ，Ｓｃ(III) / D ａｐｐ，Ｃｒ(III) The apparent distribution ratio D ａｐｐ,ｉ is the amount of adsorption to the chelating resin q ｉ and the concentration C in the solution after passing the acidic solution through the chelating resin. ｅｆ,ｉ Therefore, D ａｐｐ,ｉ =q ｉ / C ｅｆ,ｉ It is expressed as 2. The method for producing a scandium compound according to claim 1, wherein the leakage rate is expressed as the ratio of the metal concentration in the acidic solution after passing through the chelating resin to the metal concentration in the acidic solution before passing through the chelating resin, and the leakage rate of scandium is smaller than the leakage rate of chromium.

3. The method for producing a scandium compound according to claim 1 or 2, wherein the acidic solution is a solution obtained by subjecting nickel oxide ore to leaching with a sulfuric acid solution, and then adding a sulfiding agent to the resulting leachate to separate nickel sulfide.

4. The method for producing a scandium compound according to claim 1 or 2, wherein the concentration of scandium contained in the acidic solution is 10 mg / L or more.

5. The method for producing a scandium compound according to claim 1 or 2, wherein the compound production step comprises producing a precipitate containing scandium from the scandium eluate and roasting the precipitate to produce scandium oxide.

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