JP5035788B2 - Rare earth metal extractant and extraction method - Google Patents
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- JP5035788B2 JP5035788B2 JP2006157842A JP2006157842A JP5035788B2 JP 5035788 B2 JP5035788 B2 JP 5035788B2 JP 2006157842 A JP2006157842 A JP 2006157842A JP 2006157842 A JP2006157842 A JP 2006157842A JP 5035788 B2 JP5035788 B2 JP 5035788B2
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- 229910052761 rare earth metal Inorganic materials 0.000 title claims description 52
- 150000002910 rare earth metals Chemical class 0.000 title claims description 51
- 238000000605 extraction Methods 0.000 title description 47
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical group CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims description 69
- 239000000243 solution Substances 0.000 claims description 21
- 125000000217 alkyl group Chemical group 0.000 claims description 18
- 239000002253 acid Substances 0.000 claims description 17
- 239000007864 aqueous solution Substances 0.000 claims description 13
- 125000004432 carbon atom Chemical group C* 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 11
- 239000003960 organic solvent Substances 0.000 claims description 10
- 150000001335 aliphatic alkanes Chemical class 0.000 claims description 9
- CNDWHJQEGZZDTQ-UHFFFAOYSA-N 2-(2-amino-2-oxoethoxy)acetamide Chemical compound NC(=O)COCC(N)=O CNDWHJQEGZZDTQ-UHFFFAOYSA-N 0.000 claims description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 22
- GHVNFZFCNZKVNT-UHFFFAOYSA-N decanoic acid Chemical compound CCCCCCCCCC(O)=O GHVNFZFCNZKVNT-UHFFFAOYSA-N 0.000 description 21
- 238000002474 experimental method Methods 0.000 description 20
- 239000008346 aqueous phase Substances 0.000 description 19
- 238000000926 separation method Methods 0.000 description 16
- 150000001875 compounds Chemical class 0.000 description 14
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 12
- 230000002378 acidificating effect Effects 0.000 description 11
- 239000012074 organic phase Substances 0.000 description 11
- 229910052693 Europium Inorganic materials 0.000 description 10
- OGPBJKLSAFTDLK-UHFFFAOYSA-N europium atom Chemical compound [Eu] OGPBJKLSAFTDLK-UHFFFAOYSA-N 0.000 description 10
- 229910052757 nitrogen Inorganic materials 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 9
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 8
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 8
- 229910017604 nitric acid Inorganic materials 0.000 description 8
- 229910052698 phosphorus Inorganic materials 0.000 description 8
- 239000011574 phosphorus Substances 0.000 description 8
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 7
- -1 lanthanoid metals Chemical class 0.000 description 6
- VRZYWIAVUGQHKB-UHFFFAOYSA-N 2-[2-(dioctylamino)-2-oxoethoxy]-n,n-dioctylacetamide Chemical compound CCCCCCCCN(CCCCCCCC)C(=O)COCC(=O)N(CCCCCCCC)CCCCCCCC VRZYWIAVUGQHKB-UHFFFAOYSA-N 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 239000003446 ligand Substances 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 239000012071 phase Substances 0.000 description 5
- 239000002904 solvent Substances 0.000 description 5
- PIYNUZCGMLCXKJ-UHFFFAOYSA-N 1,4-dioxane-2,6-dione Chemical compound O=C1COCC(=O)O1 PIYNUZCGMLCXKJ-UHFFFAOYSA-N 0.000 description 4
- KBPLFHHGFOOTCA-UHFFFAOYSA-N 1-Octanol Chemical compound CCCCCCCCO KBPLFHHGFOOTCA-UHFFFAOYSA-N 0.000 description 4
- GPRLSGONYQIRFK-UHFFFAOYSA-N hydron Chemical compound [H+] GPRLSGONYQIRFK-UHFFFAOYSA-N 0.000 description 4
- 229910052747 lanthanoid Inorganic materials 0.000 description 4
- 238000003786 synthesis reaction Methods 0.000 description 4
- KTCIQOVSDDBEIG-UHFFFAOYSA-N 2-ethyl-2-methylheptanoic acid Chemical compound CCCCCC(C)(CC)C(O)=O KTCIQOVSDDBEIG-UHFFFAOYSA-N 0.000 description 3
- YPIFGDQKSSMYHQ-UHFFFAOYSA-N 7,7-dimethyloctanoic acid Chemical compound CC(C)(C)CCCCCC(O)=O YPIFGDQKSSMYHQ-UHFFFAOYSA-N 0.000 description 3
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 150000001732 carboxylic acid derivatives Chemical class 0.000 description 3
- 238000004090 dissolution Methods 0.000 description 3
- 150000002602 lanthanoids Chemical class 0.000 description 3
- 229910052746 lanthanum Inorganic materials 0.000 description 3
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 3
- 230000007935 neutral effect Effects 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- ZJOLSKRAHJDLNZ-UHFFFAOYSA-N 2-(9-carbamoylheptadecan-9-yloxy)-2-octyldecanamide Chemical compound CCCCCCCCC(CCCCCCCC)(C(N)=O)OC(CCCCCCCC)(CCCCCCCC)C(N)=O ZJOLSKRAHJDLNZ-UHFFFAOYSA-N 0.000 description 2
- DUENOCOQRLXLKT-UHFFFAOYSA-N 5,8-diethyldodecan-6-ylphosphonic acid Chemical compound CCCCC(CC)CC(P(O)(O)=O)C(CC)CCCC DUENOCOQRLXLKT-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- QEVGZEDELICMKH-UHFFFAOYSA-N Diglycolic acid Chemical compound OC(=O)COCC(O)=O QEVGZEDELICMKH-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 238000005481 NMR spectroscopy Methods 0.000 description 2
- 238000002835 absorbance Methods 0.000 description 2
- 150000008065 acid anhydrides Chemical class 0.000 description 2
- 150000001412 amines Chemical class 0.000 description 2
- 150000007942 carboxylates Chemical class 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 239000012024 dehydrating agents Substances 0.000 description 2
- 238000007865 diluting Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 125000004433 nitrogen atom Chemical group N* 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 150000003018 phosphorus compounds Chemical class 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 230000002285 radioactive effect Effects 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- VJLDTOPHCSPHKF-UHFFFAOYSA-N 2-(2-amino-2-oxoethoxy)-2-octyldecanoic acid Chemical compound CCCCCCCCC(C(O)=O)(OCC(N)=O)CCCCCCCC VJLDTOPHCSPHKF-UHFFFAOYSA-N 0.000 description 1
- WBZVQGYKIVWFGQ-UHFFFAOYSA-N 2-(2-amino-2-oxoethoxy)acetic acid Chemical compound NC(=O)COCC(O)=O WBZVQGYKIVWFGQ-UHFFFAOYSA-N 0.000 description 1
- MGFUUKQPXCYIJZ-UHFFFAOYSA-N C(CCCCCCC)C(C(=O)N)(OCC(=O)O)CCCCCCCC Chemical compound C(CCCCCCC)C(C(=O)N)(OCC(=O)O)CCCCCCCC MGFUUKQPXCYIJZ-UHFFFAOYSA-N 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- ABLZXFCXXLZCGV-UHFFFAOYSA-N Phosphorous acid Chemical class OP(O)=O ABLZXFCXXLZCGV-UHFFFAOYSA-N 0.000 description 1
- 229910052773 Promethium Inorganic materials 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- 239000007983 Tris buffer Substances 0.000 description 1
- 150000003973 alkyl amines Chemical group 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- UMTJFKXZVNTLFZ-UHFFFAOYSA-N bis(2-ethylhexyl) hydrogen phosphate Chemical compound C(C)C(COP(OCC(CCCC)CC)(O)=O)CCCC.C(C)C(COP(OCC(CCCC)CC)(O)=O)CCCC UMTJFKXZVNTLFZ-UHFFFAOYSA-N 0.000 description 1
- 125000003917 carbamoyl group Chemical group [H]N([H])C(*)=O 0.000 description 1
- 238000006482 condensation reaction Methods 0.000 description 1
- SEGLCEQVOFDUPX-UHFFFAOYSA-N di-(2-ethylhexyl)phosphoric acid Chemical compound CCCCC(CC)COP(O)(=O)OCC(CC)CCCC SEGLCEQVOFDUPX-UHFFFAOYSA-N 0.000 description 1
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 description 1
- LAWOZCWGWDVVSG-UHFFFAOYSA-N dioctylamine Chemical compound CCCCCCCCNCCCCCCCC LAWOZCWGWDVVSG-UHFFFAOYSA-N 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000000921 elemental analysis Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009616 inductively coupled plasma Methods 0.000 description 1
- 150000002634 lipophilic molecules Chemical class 0.000 description 1
- 239000010808 liquid waste Substances 0.000 description 1
- 238000000622 liquid--liquid extraction Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000012454 non-polar solvent Substances 0.000 description 1
- 125000002347 octyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 238000005192 partition Methods 0.000 description 1
- 235000021317 phosphate Nutrition 0.000 description 1
- 150000003008 phosphonic acid esters Chemical class 0.000 description 1
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- VQMWBBYLQSCNPO-UHFFFAOYSA-N promethium atom Chemical compound [Pm] VQMWBBYLQSCNPO-UHFFFAOYSA-N 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 238000000638 solvent extraction Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 239000008096 xylene Substances 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Manufacture And Refinement Of Metals (AREA)
Description
本願発明は、環境への負荷を最小限に抑え、希土類金属を効果的に抽出・分離することができる新規抽出剤とこれを用いた抽出方法に関するものである。 The present invention relates to a novel extractant capable of effectively extracting and separating rare earth metals while minimizing the burden on the environment, and an extraction method using the same.
希土類金属と呼ばれる元素群(ランタノイド系列)は、物理的、化学的性質が互いに似通っていることから相互分離が困難で、また、高価な金属であり、とくにわが国は希土類金属の資源に乏しいことから、その回収・再利用が求められている。 Elemental groups called lanthanoid metals (lanthanoid series) are difficult to separate from each other because their physical and chemical properties are similar to each other, and are expensive metals, especially because Japan has scarce resources for rare earth metals. The collection and reuse are required.
工業的な希土類金属の抽出・分離には、従来、主に溶媒抽出法(液−液分配法)が用いられてきている。その際の抽出剤としては、従来よりさまざまなものが用いられており、現在では、希土類金属の抽出剤として主にリン系の化合物が利用されている。例えば、ホスホン酸エステルである 2−エチルヘキシル−2−エチルヘキシル−ホスホン酸 [2-ethylhexyl-2-ethylhexyl-phosphonic acid] やその類似体であるビス(2−エチルヘキシル)リン酸 [bis(2-ethylhexyl)phosphoric acid] が最も効果的な抽出剤としてよく知られている。これらの抽出剤は、希土類金属に対する抽出能、選択的分離能が非常に優れている。しかし、その反面、抽出剤自身の水への溶解が少なくないこと、劣化した抽出剤を完全焼却できず腐食性残渣を残してしまうことなどの問題点がある。 Conventionally, a solvent extraction method (liquid-liquid distribution method) has been mainly used for industrial extraction and separation of rare earth metals. Various extractants have been used in the past, and currently phosphorus-based compounds are mainly used as rare earth metal extractants. For example, phosphonic acid ester 2-ethylhexyl-2-ethylhexyl-phosphonic acid and its analog bis (2-ethylhexyl) phosphoric acid [bis (2-ethylhexyl) Phosphoric acid] is well known as the most effective extractant. These extractants are very excellent in extraction ability and selective separation ability for rare earth metals. On the other hand, however, there are problems such as the fact that the extractant itself is not dissolved in water, and that the deteriorated extractant cannot be completely incinerated, leaving a corrosive residue.
一方、リン系以外の抽出剤としては、カルボン酸系の抽出剤が注目されている。例えば、2−メチル−2−エチル−1−ヘプタン酸:ネオデカン酸 [2-methyl-2-ethyl-1-heptanoic acid:neodecanoic acid] が実用化されている。このものは、ホスホン酸エステルやリン酸エステルといったリン系抽出剤と比較すれば水への溶解度が低く、かつ炭素、水素、酸素のみから構成される化合物なので、残渣を残すことなく完全焼却処分が可能である。しかし一方で、中性以上の高pH条件下でしか抽出が起こらず、リン系抽出剤と比べれば抽出能が著しく劣る。また、選択的分離能もリン系抽出剤には到底及ばない。 On the other hand, carboxylic acid-based extractants have attracted attention as non-phosphorus-based extractants. For example, 2-methyl-2-ethyl-1-heptanoic acid: neodecanoic acid has been put into practical use. Compared with phosphorus-based extractants such as phosphonates and phosphates, this is a compound composed of only carbon, hydrogen, and oxygen, so it can be completely incinerated without leaving a residue. Is possible. However, on the other hand, extraction occurs only under high pH conditions that are neutral or higher, and the extraction ability is remarkably inferior to that of phosphorus-based extractants. Further, the selective separation ability is not as good as that of the phosphorus-based extractant.
また、高硝酸濃度の高レベル放射性廃液中からの超ウラン元素の抽出を目的として、ジグリコールアミド(以下 DGA と省略する)の骨格(>N−CO−CH2−O−CH2−CO−N<)を有する抽出剤である N,N,N',N'−テトラオクチル−3−オキサペンタン−1,5−ジアミド:テトラオクチルジグリコールアミド [N,N,N',N'-tetraoctyl-3-oxapentane-1,5-diamde:tetraoctyldiglycolamide] (以下 TODGA と省略する)が開発されている(非特許文献1記載)。この TODGA は、強酸性条件(pH=0以下)において、超ウラン元素に限らず希土類金属も抽出できることが確認されている。ただ、この TODGA の場合には、抽出のために pH=0以下の強酸性条件を必要とするため、このための設備、プロセスとその管理の負担が大きく、実際的ではないという問題点がある。
本願発明は、以上のとおりの背景から、pH が 1 〜 3 程度の適度な酸性条件下において、希土類金属を効率的に抽出・分離することができ、抽出剤自身の水への溶解度が低く、完全に焼却処分が可能であって、実用化されているリン系化合物に匹敵する、希土類金属に対する優れた抽出能と選択的分離能を有し、しかもその製造が低コストである、環境負荷低減型の新規抽出剤と、この抽出剤を用いた抽出方法を提供することを課題としている。 From the background as described above, the present invention can efficiently extract and separate rare earth metals under moderate acidic conditions with a pH of 1 to 3, and the extractant itself has low solubility in water. Environmental impact reduction that can be completely incinerated, has excellent extraction ability and selective separation ability for rare earth metals, comparable to commercially available phosphorus compounds, and is inexpensive to manufacture. It is an object to provide a novel extractant of a type and an extraction method using the extractant.
本願発明者は、前記課題を解決すべく鋭意研究を重ねた結果、カルボキシル基(−COOH)を含むジグリコールアミド酸(以下 DGAA と省略する)の骨格(>N−CO−CH2−O−CH2−COOH)が多座配位子として強く希土類金属に結合することを見出している。 As a result of intensive studies to solve the above problems, the inventor of the present application has found that a skeleton of diglycolamide acid (hereinafter abbreviated as DGAA) containing a carboxyl group (—COOH) (> N—CO—CH 2 —O—). CH 2 -COOH) are found to bind to rare earth metal strongly as multidentate ligands.
そして、DGA型抽出剤のカルバモイル基(−CO−N<)の替わりに酸性官能基であるカルボキシル基(−COOH)を有する DGAA型抽出剤は、酸濃度が低いほど、より大きな抽出能を発揮し、酸濃度が高いほどより大きな抽出能を示す DGA型抽出剤 TODGA とは、まったく逆であることも見出している。すなわち、DGAA型抽出剤の場合、低酸性条件下ではカルボキシル基の一部がカルボキシレート(−COO-)となって希土類金属イオンに配位し、逆に高酸性条件下では、酸解離が抑えられることによって配位子としての働きが消失する。また、DGAA型抽出剤は、DGA型抽出剤のような電気的に中性な配位子(分子性配位子)とは異なり、陰イオンであるカルボキシレートが配位子(イオン性配位子)として働くことから、配位結合的な相互作用に加えて静電結合的な相互作用が生じる。よって、カルボキシレートが作用する条件下においては、TODGA のような DGA型抽出剤よりも強い抽出能を発揮すると考えられる。 And DGAA type extractant that has a carboxyl group (-COOH) that is an acidic functional group instead of carbamoyl group (-CO-N <) of DGA type extractant shows a larger extractability as the acid concentration is lower. However, it has also been found that it is exactly the opposite of the DGA-type extractant TODGA, which has a higher extractability as the acid concentration is higher. That is, in the case of DGAA type extractant, a portion of the carboxyl groups at low acidic conditions carboxylate (-COO -) becomes coordinated to the rare earth metal ions, in highly acidic conditions Conversely, the acid dissociation suppressed As a result, the function as a ligand disappears. In addition, unlike DGAA type extractants, which are electrically neutral ligands (molecular ligands) like DGA type extractants, an anion carboxylate is a ligand (ionic coordination). Since it acts as a (child), an electrostatic coupling interaction occurs in addition to a coordination coupling interaction. Therefore, under conditions where carboxylate acts, it is considered that the extractability is stronger than DGA-type extractants such as TODGA.
本願発明は以上のような新しい知見に基づいて完成されたものである。 The present invention has been completed based on the above new findings.
本願発明では、第一に、pH1〜3の範囲の条件下において希土類金属を抽出する抽出剤であって、無極性アルカン系有機溶媒にDGAAの骨格を有する次式: In the present invention, first, an extractant for extracting a rare earth metal under a pH range of 1 to 3, which has a DGAA skeleton in a nonpolar alkane organic solvent:
(R1およびR2は、各々、同一または別異のアルキル基を示し、少なくともいずれか一方は炭素数6以上のアルキル基であることを示す。なお、アルキル基は直鎖でも分鎖でも良い。)
で表されるDGAAが溶解している溶液であることを特徴とする希土類金属の抽出剤を提供し、第二に、無極性アルカン系有機溶媒がヘキサンである前記の希土類金属の抽出剤を提供する。DGAA骨格にアルキル鎖を導入して、親油性を付与した化合物を無極性アルカン系有機溶媒に溶解した溶液を抽出剤として希土類金属の抽出に活用することができ、しかも、DGAA骨格にアルキル鎖を導入した化合物は、1段階の合成反応によって、容易かつ高収率で合成することができ、低コストでの生産が可能な抽出剤となる。また、本願発明は、抽出すべき希土類金属を含む水溶液を、上記の抽出剤と適度な酸性条件下、すなわち従来のDGA骨格の化合物を用いる場合に比べてより低い酸濃度であるpHが1〜3程度、望ましくはpH4までの範囲の酸性条件下で接触させることで有機相である抽出剤に希土類金属を抽出し、分液した有機相を、前記水溶液よりも酸の濃度を高くした別の水溶液と接触させることで別の水溶液に希土類金属を逆抽出することを特徴とする希土類金属の抽出方法を提供する。
(R 1 and R 2 each represent the same or different alkyl group, and at least one of them represents an alkyl group having 6 or more carbon atoms. The alkyl group may be linear or branched. .)
A rare earth metal extractant characterized in that it is a solution in which DGAA is dissolved is provided. Second, the rare earth metal extractant in which the nonpolar alkane organic solvent is hexane is provided. To do. A solution in which an alkyl chain is introduced into the DGAA skeleton and a lipophilic compound is dissolved in a non-polar alkane organic solvent can be used for extraction of rare earth metals as an extractant, and the alkyl chain is added to the DGAA skeleton. The introduced compound can be synthesized easily and in high yield by a one-step synthesis reaction, and becomes an extractant that can be produced at low cost. Further, the present invention is an aqueous solution containing a rare earth metal to give extract, moderate acidic conditions and the extraction agent, i.e., pH is lower acid concentration than the case of using a compound of conventional DGA backbone 1 Rare earth metals are extracted into an extractant that is an organic phase by contacting under acidic conditions in the range of about 3, preferably up to pH 4, and the separated organic phase is separated from the aqueous solution with a higher acid concentration. There is provided a method for extracting a rare earth metal, characterized in that the rare earth metal is back-extracted into another aqueous solution by contacting with the aqueous solution.
上記のとおりの本願発明によれば、適度な酸性条件(pH=1〜3程度)で、希土類金属の効率的な抽出溶媒相への抽出・分離を達成でき、高酸性条件(pH=0以下)では、逆に抽出溶媒相から効率的に希土類金属を回収(逆抽出)することが可能となる。 According to the present invention as described above, the extraction / separation of the rare earth metal into the extraction solvent phase can be efficiently achieved under moderate acidic conditions (pH = 1 to 3), and high acidic conditions (pH = 0 or less) ), On the contrary, it is possible to efficiently recover (reverse extraction) the rare earth metal from the extraction solvent phase.
これによって、抽出剤自身の水への溶解度が低く、完全に焼却処分が可能な環境負荷低減型の抽出剤をもってして、従来より実用化されているリン系抽出剤に匹敵する、希土類金属に対する優れた抽出能と選択的分離能が実現されることになる。 As a result, the extractant itself has low solubility in water and has an environmental load-reducing extractant that can be completely incinerated. Excellent extraction ability and selective separation ability will be realized.
本願発明は上記のとおりの特徴をもつものであるが、以下にその実施の形態について説明する。 The present invention has the features as described above, and an embodiment thereof will be described below.
DGAAの骨格を有し、その窒素原子に二つの同一もしくは別異のアルキル基を導入した化合物(以下、これらを総じてRDGAAと省略する)を合成する際は、アミンとジグリコール酸の縮合反応を用い、活性化した酸成分として酸無水物の無水ジグリコール酸を用いる。また、対称酸無水物を用いれば、酸の半分はアミンと反応しない利点もある。つまり、次式: When synthesizing a compound having a DGAA skeleton and introducing two identical or different alkyl groups into the nitrogen atom (hereinafter collectively referred to as RDGAA), a condensation reaction of amine and diglycolic acid is performed. An acid anhydride diglycolic acid anhydride is used as the activated acid component. In addition, if a symmetric acid anhydride is used, there is an advantage that half of the acid does not react with the amine. That is, the following formula:
に従って、以下の手順で合成を行う。
The synthesis is performed according to the following procedure.
無水ジグリコール酸をジクロロメタン中に懸濁させ、無水ジグリコールに対して等molよりも若干少ない量の第二級アルキルアミンをジクロロメタン中に溶解させて、両者を 0〜30℃で混合する。無水ジグリコール酸が反応すると溶液が透明になり、そこで反応を終了する。純水洗浄、脱水剤で水を除去、濾過、溶媒除去、再結晶による精製を経て、目的の生成物が得られる。 Diglycolic anhydride is suspended in dichloromethane, and an amount of secondary alkylamine slightly less than equimol with respect to anhydrous diglycol is dissolved in dichloromethane, and both are mixed at 0-30 ° C. When the diglycolic anhydride is reacted, the solution becomes transparent and the reaction is terminated there. The target product is obtained through pure water washing, removal of water with a dehydrating agent, filtration, solvent removal, and purification by recrystallization.
本願発明の抽出剤に含まれる前記の一般式で表されるジグリコールアミド酸においては、R1およびR2のアルキル基の少なくともいずれか一方は炭素数6以上のアルキル基であるが、一般的には炭素数は6〜18、より好ましくは7〜12が考慮される。炭素数が6未満の場合には親油性が十分でなく、水相への溶解が無視できなくなる。また、炭素数が過剰に大きい場合にはその製造がコスト高になるとともに抽出能そのものの向上には寄与しないことになる。なお、R1およびR2については親油性が確保される限り、一方が炭素数6以上であれば他方は6未満であってもよいが、製造上、そして安全性の観点からは、いずれも炭素数 6以上のもので、さらには同数であることが好適に考慮される。 In diglycol amic acid represented by the general formula that is part of the extracting agent of the present invention, although at least one of the alkyl groups R 1 and R 2 are alkyl group having 6 or more carbon atoms, generally Specifically, 6 to 18 carbon atoms, more preferably 7 to 12 carbon atoms are considered. When the number of carbon atoms is less than 6, the lipophilicity is not sufficient and dissolution in the aqueous phase cannot be ignored. Further, when the carbon number is excessively large, the production becomes expensive and does not contribute to the improvement of the extraction ability itself. As long as one of R 1 and R 2 is lipophilic, as long as one has 6 or more carbon atoms, the other may be less than 6, but from the viewpoint of production and safety, both It is preferably considered that the number of carbon atoms is 6 or more, and the same number.
例えば、より好適なものとして、2つのオクチル基(−C8H17)を導入した化合物、N,N−ジオクチル−3−オキサペンタン−1,5−アミド酸:ジオクチルジグリコールアミド酸[N,N-dioctyl-3-oxapentane-1,5-amic acid:dioctyldiglycol amic acid](以下 DODGAA と省略する)が例示される。 For example, a compound having two octyl groups (—C 8 H 17 ) introduced therein, N, N-dioctyl-3-oxapentane-1,5-amidic acid: dioctyl diglycolamidic acid [N, N-dioctyl-3-oxapentane-1,5-amic acid: dioctyldiglycol amic acid] (hereinafter abbreviated as DODGAA).
上記の合成法で得られた RDGAA を用いての、希土類金属の抽出・分離操作は以下の手順で行う。 The extraction and separation of rare earth metals using RDGAA obtained by the above synthesis method is performed according to the following procedure.
抽出したい目的の希土類金属を含む、適度な酸性条件、より望ましくは pH を 1〜3 の間に調整した水溶液と、それと同体積の、 RDGAA を含む有機溶媒を混合し、常温で 10〜20分間振とうし、さらに 5分間遠心分離し、両相を分取すれば、目的の希土類金属が抽出された有機相を得る。その後、測定等の目的で水相に回収(逆抽出)する場合は、上記の場合よりも酸濃度を高くした、たとえば pHを 0以下にした水溶液で同様の操作を行うことで、目的の希土類金属が逆抽出された水相を得る。 Mix an aqueous solution containing the desired rare earth metal to be extracted in moderately acidic conditions, more preferably pH adjusted to between 1 and 3, and an organic solvent containing RDGAA in the same volume, and at room temperature for 10 to 20 minutes. Shake, centrifuge for 5 minutes, and separate both phases to obtain the organic phase from which the target rare earth metal has been extracted. After that, when recovering (back-extracting) into the aqueous phase for the purpose of measurement or the like, the target rare earth can be obtained by performing the same operation with an aqueous solution having a higher acid concentration than the above case, for example, having a pH of 0 or less An aqueous phase from which the metal has been back extracted is obtained.
用いる有機溶媒は、希土類金属に配位しないように電子対供与性(ドナー性)が小さく、抽出剤の効果を減じないために電子対受容性(アクセプター性)も小さい無極性溶媒が好ましく、上記抽出剤を溶解することができれば特に制限はない。例えば、四塩化炭素、ベンゼン、トルエン、キシレン、ヘキサン等が挙げられるが、取り扱いが容易で安全性が高い等の理由から、ヘキサンのような無極性アルカン系溶媒が好ましい。 The organic solvent to be used is preferably a nonpolar solvent having a small electron pair donating property (donor property) so as not to coordinate with the rare earth metal, and a small electron pair accepting property (acceptor property) so as not to reduce the effect of the extractant. There is no particular limitation as long as the extractant can be dissolved. For example, carbon tetrachloride, benzene, toluene, xylene, hexane and the like can be mentioned, but a nonpolar alkane solvent such as hexane is preferable because it is easy to handle and has high safety.
本願発明の抽出剤は、希土類金属を含む水相の pH が高いほど、抽出能は向上するが、希土類金属は中性〜アルカリ性では水酸化物の沈殿を生ずるので注意が必要であり、好ましくは、pH=1〜3 で調整する。 The extractant of the present invention has a higher extractability as the pH of the aqueous phase containing the rare earth metal is higher. However, since the rare earth metal is neutral to alkaline, caution must be exercised. Adjust at pH = 1-3.
本願発明の抽出剤は、抽出剤の濃度を大きくすると抽出率は向上するが、抽出しようとする希土類金属の量に比して十分ではない場合には抽出率の低下が起こるので、少なくとも希土類金属に対して10倍以上、好ましくは100倍以上の濃度とする。 In the extractant of the present invention, when the concentration of the extractant is increased, the extraction rate is improved. However, if the extractant is not sufficient as compared with the amount of the rare earth metal to be extracted, the extraction rate is lowered. The concentration is 10 times or more, preferably 100 times or more.
本願発明の抽出剤は、有機相へ抽出した後、前記水相よりも pH を低くした(pH=0以下)別の水相と接触させることで水相に希土類金属を逆抽出することができ、例えば、塩酸や硝酸を希釈して調製した溶液が好適に使用される。 The extractant of the present invention can extract the rare earth metal back to the aqueous phase by extracting it to the organic phase and then bringing it into contact with another aqueous phase having a pH lower than that of the aqueous phase (pH = 0 or less). For example, a solution prepared by diluting hydrochloric acid or nitric acid is preferably used.
(実施例)
ジグリコールアミド酸骨格にアルキル基を導入した化合物の合成方法
ヘキサンなどのアルカン系無極性有機溶媒に可溶な化合物を調製するため、ジグリコールアミド酸(DGAA)の骨格(>N−CO−CH2−O−CH2−COOH)の窒素原子に親油性の高いアルキル基を導入する。これまでの研究から、少なくとも一方のアルキルが、炭素原子を6個以上有することによって、抽出剤として十分な親油性を付加できることがわかっている。ここでは、炭素数8のアルキル基を2つ持つジオクチルジグリコールアミド酸(DODGAA)の合成法を例として示す。反応式は以下に示す通りである。
( Example )
Method for synthesizing compounds in which alkyl group is introduced into diglycolamide acid skeleton Diglycolamide acid (DGAA) skeleton (> N-CO-CH) to prepare compounds soluble in alkane nonpolar organic solvents such as hexane 2- O—CH 2 —COOH) introduces a highly lipophilic alkyl group into the nitrogen atom. Previous studies have shown that at least one alkyl can have sufficient lipophilicity as an extractant by having 6 or more carbon atoms. Here, as examples synthesis of two lifting Tsuji octyl diglycol amic acid alkyl group having 8 carbon atoms (DODGAA). The reaction formula is as shown below.
1)無水ジグリコール酸 4.2g を丸底フラスコに取り、ジクロロメタン 40ml を入れて懸濁させた。その後、ジオクチルアミン(純度 98%)7g をジクロロメタン 10ml に溶解させ、滴下漏斗にてゆっくりと加えた。室温で攪拌しながら、無水ジグリコール酸が反応して溶液が透明になることを確認し、反応を終了した。 1) 4.2 g of diglycolic anhydride was placed in a round bottom flask and suspended in 40 ml of dichloromethane. Thereafter, 7 g of dioctylamine (purity 98%) was dissolved in 10 ml of dichloromethane and slowly added with a dropping funnel. While stirring at room temperature, it was confirmed that diglycolic anhydride reacted to make the solution transparent, and the reaction was terminated.
2)上記溶液を水で洗浄し、水溶性不純物を除去した。 2) The above solution was washed with water to remove water-soluble impurities.
3)水洗浄後の溶液に、脱水剤として硫酸ナトリウムを加えた。 3) Sodium sulfate was added as a dehydrating agent to the solution after washing with water.
4)溶液を吸引ろ過した後、エバポレータを用いて溶媒を蒸発させた。 4) The solution was suction filtered, and the solvent was evaporated using an evaporator.
5)ヘキサンを用いて再結晶(3回)した後、真空乾燥した。収量 9.57g 、収率 94.3%であった。 5) Recrystallized using hexane (3 times) and then vacuum dried. The yield was 9.57 g, and the yield was 94.3%.
6)核磁気共鳴法(NMR)及び元素分析により組成を確認し、純度が 99%以上であることがわかった。 6) The composition was confirmed by nuclear magnetic resonance (NMR) and elemental analysis, and it was found that the purity was 99% or more.
このように、DODGAAは1つの化学反応のみで容易に合成でき、精製も容易なので、製造に要するコストが安価である。
DODGAAを用いた希土類金属の抽出・分離
合成したDODGAAを用いて希土類金属の抽出・分離実験を行った。具体的には、DODGAAをヘキサンに溶解して0.03M DODGAAヘキサン溶液を調製し、以下に示すような希土類金属に対する2つの抽出実験を行った。
Thus, DODGAA can be easily synthesized by only one chemical reaction and can be easily purified, so that the cost required for production is low.
Extraction and separation of rare earth metals using DODGAA
Rare earth metal extraction / separation experiments were conducted using synthesized DODGAA . Specifically, 0.03M DODGAA hexane solution was prepared by dissolving DODGAA in hexane, and two extraction experiments for rare earth metals as shown below were conducted.
(抽出実験1)DODGAAヘキサン溶液の抽出能
希土類金属としてユウロピウムを選び、分配比(有機相に抽出された金属の濃度を水相に残った金属の濃度で割った値)の水相中の酸濃度に対する依存を測定した。その要領は以下の通りである。
(Extraction experiment 1) Extraction ability of DODGAA hexane solution Select europium as the rare earth metal, and partition ratio (the concentration of the metal extracted into the organic phase divided by the concentration of the metal remaining in the aqueous phase) in the aqueous phase The dependence on concentration was measured. The procedure is as follows.
1)ユウロピウムを 1×10-4M 含む種々の pH(およそ 1〜2.5 の範囲)の硝酸水溶液と、それと同体積の 0.03M の DODGAA を含むヘキサン溶液を試験管に用意し、25℃に設定した恒温庫内で 15分間振とうした。 1) Prepare nitric acid solutions containing various pH (approximately 1 to 2.5) nitric acid containing 1 × 10 -4 M of europium and hexane solution containing 0.03M DODGAA in the same volume in a test tube and set to 25 ° C. Shake for 15 minutes in the oven.
2)恒温庫内で 5分間、遠心分離した後、両相を分取した。 2) After centrifuging for 5 minutes in a thermostatic chamber, both phases were separated.
3)分取した水相は、硝酸水溶液で希釈し、誘導結合プラズマ質量分析装置(ICP-MS)を用いて、ユウロピウムの濃度を測定した。 3) The collected aqueous phase was diluted with an aqueous nitric acid solution, and the concentration of europium was measured using an inductively coupled plasma mass spectrometer (ICP-MS).
4)分取した有機相は、3M 硝酸水溶液を用いて逆抽出操作を行い、逆抽出相を採取して希釈した後、ICP-MS を用いて、ユウロピウムの濃度を測定した。 4) The extracted organic phase was subjected to back extraction using a 3M nitric acid aqueous solution, and after collecting and diluting the back extracted phase, the concentration of europium was measured using ICP-MS.
5)3)、4)の測定結果から、ユウロピウムの分配比(DEu(III))を求めた。 5) From the measurement results of 3) and 4), the distribution ratio of europium (D Eu (III) ) was determined.
図1に、0.03M DODGAA を用いて得られた実験結果を、0.03M の 2−メチル−2−エチル−1−ヘプタン酸:ネオデカン酸 [2-methyl-2-ethyl-1-heptanoic acid:neodecanoic acid](シェル化学社製 商品名「Versatic 10」)(以下 Versatic 10 と省略する)を用いて種々のpH(およそ 5〜7 の範囲)で行った実験結果(比較例1)と比較して示す。なお、Versatic 10 の実験では、HEPES−TRIS 緩衝溶液を使用して pH をおよそ 5〜7 の間で調整、また、DODGAA の実験では、硝酸によって pH をおよそ 1〜2.5 の間で調整した。なお、DODGAA の実験では、有機相への溶解を促進するため、ヘキサンにオクタノール(5%)を添加した。
Fig. 1 shows the experimental results obtained using 0.03M DODGAA, with 0.03M 2-methyl-2-ethyl-1-heptanoic acid: neodecanoic acid [2-methyl-2-ethyl-1-heptanoic acid: neodecanoic acid] (trade name “
この結果から、DODGAA と Versatic 10 では、ユウロピウムに対する抽出能に格段の差があることがわかる。また、いずれの抽出剤の場合も、水素イオン濃度の減少(pH の増加)に従って、その 3乗に比例して、分配比が大きくなることがわかる。
From this result, it can be seen that DODGAA and
図2に、0.03M DODGAA での結果を、0.03M の 2−エチルヘキシル−2−エチルヘキシル−ホスホン酸 [2-ethylhexyl-2-ethylhexyl-phosphonic acid] (大八化学工業社製 商品名「PC88A」)(以下 PC88A と省略する)、及び 0.03M のビス(2−エチルヘキシル)リン酸 [bis(2-ethylhexyl)phosphoric acid](以下 D2EHPAと省略する)(大八化学工業社製)を用いて、同様な条件(pH がおよそ 1〜2.5 の範囲)で行った実験結果と比較して示す(比較例2を参照)。水相の pH は、いずれの抽出剤の場合も硝酸を用いておよそ 1〜2.5 の間で調整した。なお、DODGAA の実験では、有機相への溶解を促進するため、ヘキサンに 1−オクタノール(5%)を添加した。 Fig. 2 shows the results for 0.03M DODGAA, and 0.03M 2-ethylhexyl-2-ethylhexyl-phosphonic acid (trade name “PC88A” manufactured by Daihachi Chemical Industry Co., Ltd.) (Hereinafter abbreviated as PC88A) and 0.03M bis (2-ethylhexyl) phosphoric acid (hereinafter abbreviated as D2EHPA) (manufactured by Daihachi Chemical Industry Co., Ltd.). The results are shown in comparison with the results of experiments conducted under various conditions (pH is in the range of about 1 to 2.5) (see Comparative Example 2). The pH of the aqueous phase was adjusted between about 1 and 2.5 with nitric acid for all extractants. In DODGAA experiments, 1-octanol (5%) was added to hexane to promote dissolution in the organic phase.
この結果から、DODGAA と PC88A 及び D2EHPA とでは、ユウロピウムに対する抽出能がほぼ同等であることがわかる。正確には、DODGAA のユウロピウムに対する抽出能はPC88A よりも大きく、D2EHPA よりもやや小さい。また、いずれの抽出剤の場合も、水素イオン濃度の減少(pH の増加)に従って、その 3乗に比例して、分配比が大きくなることがわかる。 From this result, it can be seen that DODGAA, PC88A and D2EHPA have almost the same extraction ability for europium. To be precise, the extraction ability of DODGAA for europium is larger than PC88A and slightly smaller than D2EHPA. It can also be seen that for any extractant, the distribution ratio increases in proportion to the third power as the hydrogen ion concentration decreases (increases in pH).
(抽出実験2)DODGAAヘキサン溶液の選択的分離能
14種の希土類金属(放射性のプロメチウムを除くすべての希土類金属)について、水相中の酸濃度を一定(pH=1.5)にして、(抽出実験1)と同じ0.03MのDODGAAを含む有機相を用いて抽出操作を行い、同様の要領でそれぞれの希土類金属の分配比を測定した。なお、選択的分離能を比較するため、一例として、軽ランタノイドからの分離という観点でランタンを代表として選び、ランタンからの分離係数(対象とする希土類金属(ランタノイド:Ln)の分配比(DLn(III))をランタンの分配比(DLa(III))で割った値)として結果をまとめた。
(Extraction experiment 2) Selective resolution of DODGAA hexane solution
For the 14 rare earth metals (all rare earth metals except radioactive promethium), the organic phase containing 0.03M DODGAA is the same as (Extraction Experiment 1) with the acid concentration in the aqueous phase kept constant (pH = 1.5). The extraction operation was performed, and the distribution ratio of each rare earth metal was measured in the same manner. In order to compare the selective resolution, as an example, lanthanum was selected as a representative from the viewpoint of separation from light lanthanoids, and the separation factor from lanthanum (target rare earth metal (lanthanoid: Ln) distribution ratio (D Ln The results are summarized as (III) ) divided by the lanthanum distribution ratio (D La (III) ).
図3に、0.03M DODGAA を用いて得られた実験結果を、0.03M Versatic 10 を用いて pH=6.9 で得られた実験結果と比較して示す(比較例1を参照)。DODGAA では pH=1.5 において得られた結果、Versatic 10 では pH=6.9 において得られた結果を示す。Versatic 10 は pH=1.5 ではまったく抽出が起こらないため、十分な抽出が起こる pH=6.9 を選んだ。
FIG. 3 shows the experimental results obtained using 0.03M DODGAA in comparison with the experimental results obtained at pH = 6.9 using 0.03M Versatic 10 (see Comparative Example 1). Results obtained at pH = 1.5 for DODGAA and results obtained at pH = 6.9 for
この結果から、DODGAA と Versatic 10 では、選択的分離能にも、格段の差があることがわかる。
From this result, it can be seen that DODGAA and
図4に、0.03M DODGAA での結果を、0.03M PC88A 及び 0.03M D2EHPA を用いて同じ pH 条件(pH=1.5)で行った実験結果と比較して示す(比較例2を参照)。 FIG. 4 shows the results for 0.03M DODGAA compared to the results of experiments using 0.03M PC88A and 0.03M D2EHPA under the same pH conditions (pH = 1.5) (see Comparative Example 2).
この結果から、DODGAAヘキサン溶液の選択的分離能は、軽希土についてはPC88Aヘキサン溶液及びD2EHPAヘキサン溶液に勝り、重希土についてはPC88Aヘキサン溶液及びD2EHPAヘキサン溶液に劣ることがわかる。
DODGAAの水への溶解度の測定
合成したDODGAAの水への溶解度を測定した。過剰量のDODGAAを水(純水)に投入し、30分間振とう、さらに室温で1日以上放置した後、遠心分離を2回行ってから水溶液を分取し、水に溶解したDODGAAの濃度を紫外部の吸光度に基づいて決定した。
From this result, the selective separation capability of DODGAA hexane solution For the light rare earth better than PC88A hexane solution and D2EHPA hexane solution, for the heavy rare earths inferior to PC88A hexane solution and D2EHPA hexane.
Measuring the solubility of DODGAA in water
The solubility of synthesized DODGAA in water was measured. Add an excess amount of DODGAA to water (pure water), shake for 30 minutes, and leave it at room temperature for more than 1 day, then centrifuge twice and separate the aqueous solution. The concentration of DODGAA dissolved in water Was determined based on the absorbance in the ultraviolet region.
表1に、得られた結果を、Versatic 10 、PC88A 、及び D2EHPA の結果とともに示す(比較例3を参照)。
Table 1 shows the results obtained together with the results of
(比較例1)抽出能、選択的分離能のカルボン酸系抽出剤(Versatic 10)との比較
DODGAA を用いての(抽出実験1)及び(抽出実験2)と同様の要領で、カルボン酸系抽出剤である Versatic 10(0.03M)を用いた抽出実験を行った。結果を図1及び図3に示す。ただし、水相の pH の条件は、DODGAA による抽出実験と Versatic 10 による抽出実験とでは大きく異なる。
(比較例2)抽出能、選択的分離能のリン系抽出剤(PC88A 、D2EHPA)との比較
DODGAA を用いての(抽出実験1)及び(抽出実験2)と同様の要領で、リン系抽出剤であるPC88A 及び D2EHPA(いずれも 0.03M)を用いた抽出実験を行った。結果を図2及び図4に示す。水相の pH の条件も、DODGAA による抽出実験の場合と、ほぼ同じである。
(比較例3)水に対する溶解度の Versatic 10 、PC88A 、及び D2EHPA との比較
DODGAA のときと同様に、過剰量の Versatic 10 、PC88A 、もしくは D2EHPA を水(純水)に投入し、30分間振とう、さらに室温で 1日以上放置した後、遠心分離を 2回行ってから水溶液を分取し、水に溶解した抽出剤の濃度を紫外部の吸光度に基づいて決定した。結果を表1に示す。
(Comparative Example 1) Comparison with extractability and selective separation ability of carboxylic acid-based extractant (Versatic 10)
In the same manner as (Extraction Experiment 1) and (Extraction Experiment 2) using DODGAA, an extraction experiment was conducted using Versatic 10 (0.03M), which is a carboxylic acid-based extractant. The results are shown in FIGS. However, the pH condition of the aqueous phase differs greatly between the extraction experiment by DODGAA and the extraction experiment by
(Comparative Example 2) Comparison with extractant and selective extractant of phosphorus extractant (PC88A, D2EHPA)
In the same manner as (Extraction Experiment 1) and (Extraction Experiment 2) using DODGAA, an extraction experiment using PC88A and D2EHPA (both 0.03M), which are phosphorus-based extractants, was conducted. The results are shown in FIGS. The pH conditions of the aqueous phase are almost the same as in the extraction experiment using DODGAA.
(Comparative Example 3) Comparison of water solubility with
As in the case of DODGAA, add
以上の実施例、比較例により、C、H、O、Nのみからなる完全焼却処分が可能である化合物(たとえばDODGAA)を用いて、希土類金属の抽出を行った結果、完全焼却処分が可能な既存のカルボン酸系化合物(Versatic 10)を大きく上回る抽出能・選択的分離能を示すとともに、完全焼却処分はできないが非常に高性能なリン系化合物(PC88A、D2EHPA)にも劣らないことが明らかになった。さらに、水に対する前記化合物の溶解度が、これら既存の化合物(PC88A、D2EHPA、Versatic 10)と比較して著しく小さいため、水環境への前記化合物の負荷を大幅に低減することが可能である。また、水への溶解度が著しく小さいことは、有機相の繰り返し利用に伴う前記化合物の損失も著しく小さくなり、前記化合物を頻繁に補充する必要がなくなるため、経済的である。なお、DODGAAの合成及び精製は非常に容易であるため、製造に要するコストも安価である。また、本願発明で提案する希土類金属の抽出法によって、pH を調節することで容易に有機相への抽出、水相への逆抽出を可能にし、そのpHの領域では、腐食が少なくリサイクル効率に優れた硝酸を用いることが可能であり、抽出工程が安価である。 As a result of extracting rare earth metals using a compound (for example, DODGAA) consisting of only C, H, O, and N according to the above examples and comparative examples, complete incineration is possible. It is clear that the extractability and selective separation ability greatly exceed the existing carboxylic acid compounds (Versatic 10), and it is not inferior to the very high performance phosphorus compounds (PC88A, D2EHPA) although it cannot be completely incinerated. Became. Furthermore, since the solubility of the compound in water is significantly smaller than these existing compounds (PC88A, D2EHPA, Versatic 10), it is possible to greatly reduce the load of the compound on the water environment. In addition, the extremely low solubility in water is economical because the loss of the compound due to repeated use of the organic phase is remarkably reduced, and it is not necessary to replenish the compound frequently. Since synthesis and purification of DODGAA is very easy, the cost required for production is also low. In addition, the rare earth metal extraction method proposed in the present invention allows easy extraction into the organic phase and back extraction into the aqueous phase by adjusting the pH. Excellent nitric acid can be used and the extraction process is inexpensive.
Claims (4)
無極性アルカン系有機溶媒に次式
(R1およびR2は、各々、同一または別異のアルキル基を示し、少なくともいずれか一方は炭素数6以上のアルキル基であることを示す。なお、アルキル基は直鎖でも分鎖でも良い。)
で表されるジグリコールアミド酸が溶解している溶液であることを特徴とする希土類金属の抽出剤。 An extractant for extracting rare earth metals under conditions in the range of pH 1-3,
For nonpolar alkane organic solvents
(R 1 and R 2 each represent the same or different alkyl group, and at least one of them represents an alkyl group having 6 or more carbon atoms. The alkyl group may be linear or branched. .)
A rare earth metal extractant characterized by being a solution in which diglycolamide acid represented by
前記抽出剤は、無極性アルカン系有機溶媒に次式
(R 1 およびR 2 は、各々、同一または別異のアルキル基を示し、少なくともいずれか一方は炭素数6以上のアルキル基であることを示す。なお、アルキル基は直鎖でも分鎖でも良い。)
で表されるジグリコールアミド酸が溶解している溶液であることを特徴とする希土類金属の抽出方法。 After extracting the aqueous solution in contact with the extracted polishes extractant rare earth metals including rare earth metal to be extracted is adjusted to a range of pH 1-3, the extractant was separated, then the aqueous solution separated and extractant by contact with an aqueous solution of high acid concentration than a method of extracting that rare earth metals to back-extracted into an aqueous solution of rare earth metals,
The extractant is a nonpolar alkane organic solvent represented by the following formula:
(R 1 and R 2 each represent the same or different alkyl group, and at least one of them represents an alkyl group having 6 or more carbon atoms. The alkyl group may be linear or branched. .)
A method for extracting a rare earth metal, which is a solution in which diglycolamide acid represented by
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