JP6455782B2 - Scandium separation - Google Patents

Description

  The present invention relates to a method for selectively separating scandium (Sc) by a separation and concentration method based on a solvent extraction method and recovering a scandium raw material from a zirconium (Zr) waste solution.

A stable supply of energy is an essential requirement to form a sustainable and sustainable society. Since the Fukushima nuclear accident, ensuring energy stability has become more urgent than ever. Wind power and solar power generation are very attractive in terms of using renewable energy, but stable power generation cannot be expected. Thermal power generation using shale gas or natural gas is cleaner than oil and coal, but CO ₂ emissions are inevitable. On the other hand, since power generation by fuel cells only discharges water, it is envied as a power generation method that greatly contributes to the promotion of global warming countermeasures. Recently, a solid oxide fuel cell using a new electrode has been developed, and it is attracting attention as a next-generation energy system because of its high power generation efficiency. The demand for scandium as an electrode material is rapidly expanding, and even under such circumstances, even scan reagent, scandium oxide (Sc ₂ O ₃ ), is difficult to obtain.

  Although the abundance of Sc is large (Clark number: 22 ppm), since there is no ore produced together, it is currently produced by separating and recovering from refining residues such as U, Ti, W, Al, and Ni. However, Sc is classified into the same hard acid as Ti, Zr, and the like, and since it has similar chemical properties, it is technically difficult to separate from these concentrated main components. According to the present invention, if a scandium resource regeneration technology can be established and a resource recycling system is established, a stable and sustainable supply of scandium that does not pollute and destroy the global environment is not only ensured. As a result, the development of high-efficiency solid oxide fuel cells will be promoted and the price will be greatly reduced, so that the power-saving home “Smart House”, regional power generation, and distributed power sources for smart grids will spread all at once. This will bring about a revolutionary change in the social structure. In addition, the development of a new infrastructure is encouraged, resulting in the early realization of a low-carbon society and, consequently, the construction of a vibrant and sustainable society.

In Patent Document 1, an organic solvent is added to an aqueous phase-containing Sc solution containing at least one of Fe, Al, Ca, Y, Mn, Cr, and Mg in addition to Sc, and the Sc component is contained in the organic solvent. Then, in order to separate the trace component extracted together with Sc in the organic solvent, scrubbing by adding an aqueous hydrochloric acid solution, removing the trace component, adding an aqueous NaOH solution in the organic solvent, the Sc remaining in the solvent to prepare a slurry containing Sc (OH) _3, which was dissolved Sc (OH) ₃ obtained by filtration with hydrochloric acid, to give the chloride scandium solution, which was added with oxalic acid oxalic acid There is a description of a rare earth metal recovery method characterized in that a scandium precipitate is filtered, the precipitate is filtered, trace impurities are separated in the filtrate, and then calcined to obtain high-purity scandium oxide. Unlike the BOHTP (thiophosphoric acid O, O-bis (2-ethylhexyl)) used in the present invention, the extraction material of Patent Document 1 uses PC-88A. PC-88A has low selectivity and is not suitable for separation from zirconium (Note: PC-88A is a trade name of an industrial extraction reagent used for extraction of metal ions).

  Patent Document 2 provides a method for efficiently recovering nickel and scandium from an oxide ore containing nickel and scandium. A leaching step of leaching an oxide ore containing nickel and scandium with an acid under high temperature and high pressure to obtain a leachate containing nickel and scandium; a step of adding a neutralizing agent to the leachate and removing iron and aluminum as precipitates; Further, a method is described in which a neutralizing agent is added to the remaining liquid sequentially to recover scandium and nickel as precipitates. However, it is not suitable for the separation of scandium from zirconium, which has similar chemical properties.

  Patent Document 3 provides a scandium adsorbent that can achieve high capacity and high efficiency, replacing the conventional adsorbent with a low processing speed and a low throughput. An adsorbent for collecting and recovering scandium dissolved in a solution, by generating a reactive site on a polymer substrate, and then forming a graft chain by reactive monomer alone or co-graft polymerization It is characterized by introducing a metal ion collecting group. The base material is manufactured from a woven fabric, a nonwoven fabric, a film, a hollow fiber membrane or a thread made of polyolefin fibers such as polyethylene and polypropylene, and the reactive monomer is a vinyl monomer having a phosphate group. In other words, scandium is proposed to be collected using an olefin fiber in which a phosphate group is chemically bonded. Although collection efficiency has been examined in detail, desorption efficiency and selectivity for other ions have not been studied. By analogy with the extraction performance of organophosphorus compound-based chelating reagents, there appears to be a problem in desorption efficiency and selectivity. Furthermore, since the separation properties of scandium from coexisting ions have not been evaluated, the selectivity is unknown.

  Although extraction of scandium has been attempted in this way, there is also a problem that back extraction into the aqueous phase is incomplete in any extraction system.

JP H09-291320 A JP 2000-313928 A JP 2005-152756 A

  In the techniques disclosed in Patent Documents 1 to 3 as described above, it is difficult to separate scandium and zirconium having similar chemical properties, and the cost is high, and the recovery of the extracted scandium is incomplete. have.

  The present invention has been made in view of the above, and an object of the present invention is to provide a method capable of obtaining a scandium recovery material by a production process simpler than the conventional method and recovering scandium with high efficiency.

  The inventors of the present invention have made extensive studies to achieve the above object. As a result, we discovered that scandium could be extracted almost quantitatively by using a toluene solution of Phoslex DT-8 (registered trademark; manufactured by SC Organic Chemical Co., Ltd.) that was accidentally air-oxidized (air-oxidized). The resulting compound is BOHTP (thiophosphate O, O-bis (2-ethylhexyl)). By developing this, it has been found that the basis for creating a system having excellent separation and concentration characteristics not found in other reagents can be created, and that the above object can be achieved, and the present invention has been completed.

That is, the present invention has the following features.
(1) a first step of performing a pretreatment for supporting thiophosphate O, O-bis (2-ethylhexyl) as an extractant on a carrier;
A second step in which the carrier pre-treated in the first step is loaded into a solvent in which the extractant is dispersed to support the extractant;
A third step of filling the column with the support obtained in the second step, passing a metal-containing solution containing zirconium and scandium through the column, and adsorbing scandium to the support;
And a fourth step of recovering scandium by washing the carrier on which scandium is adsorbed in the third step with an acid, and separating scandium.
(2) separation of scandium described responsible body is characterized in that the vitreous (1).

  According to the scandium separation method of the present invention, zirconium and scandium can be separated more easily than the conventional method, and a separation system can be manufactured easily and at a reduced cost. Since scale-up of manufacturing equipment and the like can be easily performed, capital investment can be greatly suppressed and it can be suitably used in this field.

It is the schematic diagram which showed that Phoslex DT-8 (trademark) oxidizes and becomes BOHTP. The SEM observation result of the surface modification state of the glass bead by time change is shown. The concentration (behavior) of scandium and zirconium in the sample solution, cleaning solution, and back extraction of Example 1 is shown. Effect of pH on metal ion collection by solid phase extraction using BOHTP-supported glass beads of Example 3 (trend confirmation test (1) results; contained elements (Sc, Zr, Y, Ti) Effect of pH on metal ion collection by solid phase extraction using BOHTP-supported glass beads of Example 3 (trend confirmation test (2) results; contained elements (Ti, Al) Effect of pH on metal ion collection by solid phase extraction using BOHTP-supported glass beads of Example 3 (trend confirmation test (3) results; contained elements (Fe, Al)

The present invention proposes a method for selectively separating Sc (III) by a separation and concentration method based on a solvent extraction method to obtain a Sc raw material from a Zr waste liquid. Although extraction of Sc (III) has been attempted in the past, there is a problem that back extraction into an aqueous phase is incomplete although extraction is easily performed in any extraction system. The inventors have been able to perform almost quantitative extraction of Sc (III) and reverse extraction by using a toluene solution of Phoslex DT-8 (registered trademark) that has been accidentally air-oxidized (FIG. 1) (Hydrometallurgy, 133, 33). -36 (2013).) As a result of structural analysis by ³¹ P-NMR and LC-MS in the 2011 research, the compound which is the main component of Sc (III) extraction in the oxidized DT-8 extraction system was thiophosphate O, O-bis (2-ethylhexyl). ) (O, O-bis (2-ethylhexyl) hydrogen thiophosphate)) (Solvent Extr. Res. Dev., Jpn., 21, 65-70 (2014).). In 2012, a pure substance of BOHTP was synthesized separately, and Sc (III) / ZrO (II) was extracted and separated using this. As a result, it was possible to separate well, and Sc (III) was 3 mol / dm. It was confirmed that the organic phase could be back-extracted quantitatively with the ³ hydrochloric acid solution.

  Although it is possible to apply this extraction system as it is to a mixer settler of an industrial solvent extraction apparatus and start operation at a plant scale, the present invention uses BOHTP as a porous material in terms of capital investment, environmental compatibility, and production capacity. A functional adsorbent supported on a carrier was newly prepared and packed in a column, and a zirconium waste liquid (main component: ZrO (II): 20000 ppm, Ti (IV): 2000 ppm, Y (III): 1500 ppm, (Sc (III): 200 ppm) by passing water through and allowing scandium to be separated and recovered at a recovery rate of about 90% or more, under a preferable condition at a recovery rate of about 93% or higher, and under a more preferable condition at a recovery rate of about 95% or higher. It is in having established. Further details are described below.

As the carrier, an inorganic material carrier is preferably used. In addition to glass, silica, silica gel, activated carbon, alumina, apatite and the like are used as the inorganic material carrier. Material preferably used is a glass. These are not only available for general-purpose products at a low price, but also have the feature of being easy to collect target substances by precipitating in water due to their large specific gravity .

  Although there is no restriction | limiting in particular in the magnitude | size of a support | carrier, Use of the bead type (diameter about 0.01 mm-about 0.3 mm) generally marketed for columns is preferable.

(Step 1: Carrier surface modification)
First, the carrier is surface-modified. Here, the alkali treatment by the hydrothermal synthesis method when glass is used as the material will be specifically described. Even for other carriers, the processing conditions may be changed depending on the material.

Prior to hydrothermal synthesis, glass beads are placed in a container such as a flask as necessary and washed with acid. The acid is preferably hydrochloric acid that can be easily removed with water. The hydrochloric acid concentration may be about 0.3 to 2 mol / dm ³ . Although there is no restriction | limiting in washing | cleaning time, What is necessary is just to aim at 10 minutes-60 minutes. After acid cleaning, remove the acid with pure water. As a reference for removing the acid, for example, the pH of the filtrate filtered by suction may be 5 or more.

  The surface of the glass beads is made porous using an alkali treatment by a hydrothermal synthesis method. The equipment used for hydrothermal synthesis may be a commercially available device such as an autoclave, a combination of a pressure-resistant jacket and a thermostat, and a heating reflux apparatus.

Acid-washed glass beads and sodium hydroxide are placed in a container that is not corroded by alkali, such as a PTFE crucible. Sodium hydroxide may be about 0.1 to 10 (quantity ratio). The sodium hydroxide concentration may be about 0.5 to 7 mol / dm ³ .

  An example of hydrothermal synthesis conditions is shown. As an example, the hydrothermal synthesis temperature range is 100 to 200 ° C, preferably 130 to 170 ° C. At 100 ° C. or lower, the modification does not proceed sufficiently, and at 200 ° C. or higher, it becomes difficult to keep the modification only on the surface.

  FIG. 2 shows the result of observing the surface modification (porosification) state of the glass beads by SEM while changing the hydrothermal synthesis time to 2 hours, 4 hours, and 8 hours. The state of surface modification can be easily grasped by SEM observation. From these SEM photographs, it can be seen that the surface area of the glass beads is greatly increased by performing hydrothermal synthesis for 8 hours or more. As a result, in the next step, the extraction material can be efficiently supported on the glass beads as the carrier. The hydrothermal synthesis time may be in the range of 1 to 48 hours, preferably 8 to 30 hours, and more preferably 15 to 25 hours.

As another example, the target surface-modified glass beads can also be obtained by heating and stirring at 90 ° C. or more for 72 hours or more while refluxing using a 5 mol / dm ³ sodium hydroxide solution.

  During hydrothermal synthesis, surface modification may be promoted by stirring as necessary. After hydrothermal synthesis, the glass beads are removed from the instrument and washed with hydrochloric acid and pure water as described above. After washing, if necessary, the glass beads are dried with a thermostat and stored in a glass bottle or the like.

  Note that this step is not necessarily required when a material having a large surface area such as silica gel is used as the carrier.

(Step 2: Pretreatment of carrier)
Next, pretreatment for efficiently loading the extractant on the carrier is performed. When beads are used as the carrier, the surface of the carrier is phenylated. Silane treatment is preferably used for phenylation. The phenylation will be described more specifically. As a surface modification for supporting the extractant described later on the glass bead that has been subjected to the alkali treatment, a phenyl group is chemically bonded to the glass bead by a silane coupling agent treatment. The alkali-treated glass beads and anhydrous toluene are put into a glass container or the like, and a silane treating agent is added while heating at 100 to 200 ° C. under reflux. As the silane treating agent, commercially available phenyltrichlorosilane or diphenyldichlorosilane can be used. The amount of anhydrous toluene may be in the range of about 3 to 10 times the glass bead capacity. The reflux time may be about 2 to 5 hours. After natural cooling, the toluene is washed with methanol and then vacuum dried.

(Step 3: Loading of extraction material)
Next, the loading of the extraction material will be described. The extractant functions as a chelating agent. As the extractant, it is preferable to use a monothiophosphate compound, particularly thiophosphate O, O-bis (2-ethylhexyl) (BOHTP).

  Here, the carrying of the extraction material with respect to the extraction material will be specifically described by taking as an example the case where glass beads are used as the carrier and BOHTP is used as the extraction material. First, 5 to 20%, preferably 10 to 15%, of BOHTP with respect to the weight of the glass beads subjected to phenylation treatment is dissolved in an organic solvent 5 to 20 times the amount of BOHTP and shaken using a shaker. The organic solvent may be ethanol, isopropyl alcohol, toluene, hexane or the like, but hexane handling is good. There is no limitation on the number of times and time of shaking, but 20 to 50 times / minute and 10 to 100 minutes may be used as a guide. After shaking, the glass beads are transferred to an eggplant flask, and the organic solvent is distilled off under reduced pressure using a device such as a rotary evaporator. Here, in order to further improve the efficiency of loading BOHTP, the shaker is used, but the shake is not necessarily performed. Similarly, vacuum distillation was performed to further improve the efficiency of loading BOHTP, but BOHTP may be supported by simply immersing glass beads in an organic solvent without performing vacuum distillation.

The required glass bead amount and scandium recoverable amount can be calculated. The loading rate of BOHTP on the glass beads may be changed as necessary. As a calculation example, since the molecular weight of BOHTP is 338.486, the amount of scandium adsorbed on the assumption that 1.0180 g of BOHTP is supported at a loading rate of 100% is calculated as a calculation example. Assuming that 3 g of glass beads were used, the calculation process is shown in the following equation.
In this case, the scandium load can be set to 10 mg or the like.

(Step 4: Step of adsorbing scandium on the carrier)
Next, a process of passing a metal-containing solution containing scandium through the column and adsorbing scandium to the carrier will be described. In the present specification, the metal-containing solution refers to a solution containing scandium ions. Specifically, a solution containing at least one of titanium ions and zirconium ions in addition to scandium ions is assumed. The metal-containing solution is particularly preferably a zirconium waste liquid containing zirconium as a main component.

Here, the case where glass beads are used as a carrier will be specifically described as an example. The column is filled with glass beads supporting BOHTP. The order of flowing the solution is a sample solution, a washing solution, and a back extraction solution. The concentration of the sample solution is adjusted as necessary. The metal ion concentration of the sample solution is not particularly limited, but may be about 0.05 to 10 mmol / dm ³ . As a masking agent for preventing interference by zirconium, a mixed solution of 0.05 to 0.3 mol / dm ³ tripotassium citrate may be prepared with hydrochloric acid and sodium hydroxide at a pH of around 1 to 6, preferably at a pH of 2 to 5. . As the masking agent, ammonium citrate salt or sodium citrate salt can also be used. Since the relationship between pH and extraction rate changes to coexisting elements, it is preferable to conduct a prior tendency test depending on the coexisting elements. The adsorption tendency test by the batch method of the product of the present invention will be described later .

(Step 5: Step of collecting scandium)
Next, the scandium is recovered by washing the carrier adsorbed with scandium with a back extract. It is preferable to use an acid for the back extract. And dilute hydrochloric acid is suitable among acids, but no particular concentration limits, well at about 0.1 to 10 mol / dm ^3, preferably from 3 mol / dm ^3.

  The features of the present invention are repetitive, but (1) high extraction characteristics that can perform both quantitative and reverse extraction of scandium, and (2) high scandium selectivity that can be almost completely separated from zirconium in one batch operation. It is in.

  Details are described in the following examples to further clarify the invention.

  The present invention will be specifically described by the following examples, but the present invention is not limited to the examples.

  For the concentration measurement of the sample solution, ICP-OES (VISTA Pro type manufactured by VARIAN) was used. When measuring the back extraction solution, the concentration was adjusted as appropriate.

  Hereinafter, ion-exchanged water is used as water, and is referred to as “pure water”. Sample solution preparation reagents, hydrochloric acid, sodium hydroxide, toluene, hexane, and methanol were manufactured by Kanto Chemical Co., Inc. The product made by Tokyo Chemical Industry Co., Ltd. was used for the phenyl trichlorosilane used for phenylation. The calculation of the recovery rate was scandium elution amount / load amount × 100 (%).

In preparation of the sample solution, the concentration of scandium and zirconium was 0.1 mmol / dm ³ , a mixed solution of 0.1 mol / dm ³ tripotassium citrate was added as a masking agent, 3 mol / dm ³ hydrochloric acid, 3 mol / dm ^A 200 ml portion was prepared with 3 sodium hydroxide at around pH 3.

As the glass beads, Flusin GU 80 / 100MESH (diameter 150 μm) manufactured by GL Sciences Inc. was used. Before hydrothermal synthesis, about 40 g of glass beads were placed in an Erlenmeyer flask and acid washed with 1 mol / dm ³ hydrochloric acid for 1 hour. Thereafter, the acid was removed with pure water. Moreover, it was set as the time when pH of the filtrate which carried out suction filtration became 5 or more as a reference | standard which removed the acid. 10 g of acid-washed glass beads and 30 ml of 2 mol / dm ³ sodium hydroxide were placed in a PTFE crucible and placed in a thermostat set at 150 ° C. Stirring was performed every 30 minutes until 2 hours from the start, and stirring was performed every 1 hour from 2 hours to 8 hours. Thereafter, stirring was not performed until 24 hours after the start of hydrothermal synthesis. 24 hours after the start of hydrothermal synthesis, the synthesis tool was taken out of the thermostat, washed with 1 mol / dm ³ hydrochloric acid, and washed with pure water in the same manner as described above. Thereafter, the glass beads were dried with a thermostat for 1 hour and stored in a glass bottle.

  As a surface modification for supporting BOHTP as an extractant on glass beads that had been subjected to alkali treatment, phenyl groups were chemically bonded to the glass beads by silane coupling agent treatment. Under the phenylation treatment conditions, 25 ml of alkali-treated glass beads and 150 ml of anhydrous toluene were placed in a three-necked flask, and 25 ml of phenyltrichlorosilane was added dropwise little by little while stirring at 250 rpm under reflux heating at 150 ° C. After refluxing for 4 hours, the heating was stopped, and when the temperature reached 70 ° C. or less, 110 ml of methanol was added and stirred for 50 minutes to stop the reaction. Then, it filtered with the suction filtration apparatus, wash | cleaned the residual toluene with 200 ml of methanol, and vacuum-dried it for 1 day or more with the vacuum desiccator.

  10 ml of phenyl-treated glass beads and 100 ml of BOHTP (trade name: MSP-8, manufactured by Daihachi Chemical Industry Co., Ltd.) with a mass of 10% of the weight of the glass beads were put in a shaker. And shaken at 40 rpm for 1 hour. BOHTP was used without purification. After shaking, the glass beads were transferred to an eggplant flask and hexane was removed by distillation under reduced pressure using a rotary evaporator, followed by vacuum drying for 2 hours or more.

A column was filled with 1.0034 g of BOHTP-supported glass beads, and a sample solution, a washing solution, and a back extraction solution were passed therethrough. Washing solution 0.01 mol / dm ³ hydrochloric acid 100 ml, as the stripping solution, a 3 mol / dm ³ HCl was 50ml passed through. The passed solution was divided and collected in a test tube.

  The test conditions of Example 1 are shown in Table 1, and the test results are shown in FIG. 1 and Table 2.

Test conditions of Example 1

Test result of Example 1

  As a result, the adsorption rate was 90% or higher, and the recovery rate was also 95% or higher.

  3.3540 g of BOHTP-supported glass beads prepared in Example 1 were used. Other conditions were scaled up and processed based on Example 1. Table 3 shows the test conditions and Table 4 shows the test results.

Test conditions of Example 2

Test result of Example 2

  In this example, the adsorption rate was 90%, and the recovery rate was 90% or more.

Batch method adsorption tendency test results (adsorbent performance evaluation)
0.1 g of BOHTP-supported glass beads prepared in Example 1 and 10 ml of a sample solution having various metal ion concentrations of 0.1 to 1.0 mmol / dm ³ were shaken at 40 rpm for 24 hours. Adsorption tendency of Sc and other impurity elements was confirmed. The pH of the sample solution was adjusted using ³ mol / dm ³ hydrochloric acid and aqueous sodium hydroxide. The adsorption tendency test was carried out under the following three conditions. 4 to 6 show the influence of pH on each metal ion collection.
Adsorption tendency test No. The test conditions are as follows.
Test (1): Contained elements: Sc, Zr, Y, Ti (1.0 mmol / dm ³ )
Test (2): containing ^{elements: Ti, Al (0.1mmol / dm} 3, 1.0mmol / dm 3)
Test (3): Contained elements: Fe, Al (1.0 mmol / dm ³ )

From these results, it was confirmed that Sc can be separated from each impurity element with high purity .

  According to the scandium separation method of the present invention, zirconium and scandium can be separated more easily than the conventional method, and a separation system can be manufactured easily and at a reduced cost. Since it is easy to scale up manufacturing equipment, etc., capital investment can be greatly reduced. The resource recycling system is the foundation of construction, and as a result, the development of high-efficiency solid oxide fuel cells is promoted and its price is greatly reduced, resulting in the early realization of a low-carbon society, and vigorous and sustainable development. It will lead to the construction of a possible society.

Claims (2)

A first step of performing a pretreatment for supporting thiophosphate O, O-bis (2-ethylhexyl) as an extractant on a carrier;
A second step in which the carrier pretreated in the first step is loaded into a solvent in which the extractant is dispersed to support the extractant;
A third step of packing the carrier obtained in the second step, passing a metal-containing solution containing zirconium and scandium through the column, and adsorbing scandium to the carrier;
And a fourth step of washing the support on which scandium is adsorbed in the third step with an acid to recover the scandium. Separation of scandium as claimed in claim 1, wherein the carrier is a glassy.