ㄽᩥࡢせ᪨

DFT Study Aiming to Reveal the Mechanism of Minor Actinides/Lanthanides Separation by
Solvent Extraction㸦⁐፹ᢳฟ࡟ࡼࡿ࣐࢖ࢼ࣮࢔ࢡࢳࣀ࢖ࢻ/ࣛࣥࢱࣀ࢖ࢻศ㞳ᶵᵓࡢゎ᫂ࡢࡓࡵࡢ DFT ィ⟬࡟ࡼࡿ◊✲㸧         ῝ ⃝ ඃ ே1㸬◊✲⫼ᬒ ཎᏊຊⓎ㟁࡟ࡼࡾ⏕ࡌࡿ౑⏝῭ࡳ᰾⇞ᩱࡢ෌ฎ⌮ᚋࡢᗫᾮࡣ㧗ࣞ࣋ࣝᨺᑕᛶᗫᾮ(HLLW)࡜࿧ࡤࢀ
ࡿࠋHLLW ࡟ࡣᵝࠎ࡞✀㢮ࡢඖ⣲ࡀྵࡲࢀ࡚࠸ࡿࡀࠊࡑࡢ୰࡛࣐࢖ࢼ࣮࢔ࢡࢳࣀ࢖ࢻ(MA; Np, Am,Cm )࡜࿧ࡤࢀࡿඖ⣲⩌ࡣࠊ㠀ᖖ࡟㛗࠸༙ῶᮇࢆᣢࡘࡇ࡜࡛▱ࡽࢀ࡚࠸ࡿࠋࡑࡇ࡛ࠊMA ࡟ᑐࡋ࡚୰ᛶᏊ⥺ࢆ↷ᑕࡋ࡚࡯࠿ࡢ᰾✀࡟ኚ᥮ࡋࠊ༙ῶᮇࢆ▷⦰ࡉࡏࡿ᪉ἲࡀ᳨ウࡉࢀ࡚࠸ࡿࡀࠊᗫᾮ୰࡟ྠ᫬࡟
Ꮡᅾࡍࡿࣛࣥࢱࣀ࢖ࢻ(Ln)ࡣ MA ࡟ᑐࡍࡿᏑᅾẚࡢ኱ࡁࡉࡸ୰ᛶᏊ࡜ࡢ཯ᛂ᩿㠃✚ࡢ኱ࡁࡉ࠿ࡽࠊMA࡟ᑐࡍࡿ୰ᛶᏊ⥺↷ᑕࢆ㜼ᐖࡍࡿᛶ㉁ࡀ࠶ࡿࠋࡋࡓࡀࡗ࡚ࠊMA ࡜ Ln ࡣ᰾ኚ᥮๓࡟ศ㞳ࡋ࡚࠾ࡃᚲせࡀ࠶ࡿࠋ1)ศ㞳ࡢ᪉ἲ࡜ࡋ࡚᭷ຊどࡉࢀ࡚࠸ࡿࡶࡢࡢ୍ࡘࡀࠊ⁐፹ᢳฟἲ࡛࠶ࡿࠋ㐣ཤࡢ◊✲࡛ࡣࠊ᪤ሗࡢ MA 㑅ᢥᛶࢆ♧ࡍ❅⣲㓄఩Ꮚ࡜◲㯤㓄఩Ꮚࠊ࠾ࡼࡧ Ln 㑅ᢥᛶࢆ♧ࡍ㓟⣲㓄఩Ꮚ࡟ࡘ࠸࡚㔞Ꮚ໬Ꮫィ⟬ࢆ⏝࠸ࡓ◊✲ࡀ࡞ࡉࢀࠊᢳฟ๣ࡢ㑅ᢥᛶࡣ㓄఩ཎᏊ࡜㔠ᒓࡢ㛫ࡢ㌶㐨ࡀ⤖ྜⓗ࡛࠶ࡿ࠿࡝࠺࠿࡟౫ࡿࠊ࡜࠸࠺ࡇ࡜ࡀ♧ࡉࢀࡓࠋ2)ࡋ࠿ࡋ࡞ࡀࡽࠊ㓄఩ᙧែࡀࡑࢀࡒࢀࡢ㓄఩Ꮚ࡛᏶඲࡟ྠࡌ࡛ࡣ࡞࠸ࡇ࡜࡟␲ၥࢆᣢࡗࡓࠋࡲࡓࠊࡼࡾ㑅ᢥᛶࢆྥୖࡍࡿ᪉ἲࡢ᥈⣴ࢆ㔜せどࡋࡓࠋ2㸬ࢡ࢚࣮ࣛ࢘ࣥࢸࣝᆺ㓄఩Ꮚࡢ Am/Eu 㑅ᢥᛶ࡟ࡘ࠸࡚ࡢ DFT ◊✲ 3)㓄఩ᙧែࡢ㐪࠸ࢆᴟຊᢚ࠼ࡿࡓࡵ࡟ࠊศᏊ㦵᱁ࡣྠ୍ࡔࡀ␗࡞ࡿ㓄఩ཎᏊࢆᣢࡘ㓄఩Ꮚ࡜ࡋ࡚ࢡ࢚࣮ࣛ࢘ࣥࢸࣝࢆ᥇⏝ࡋࠊ◊✲ࡣ஧ẁ㝵࡟ศࡅ࡚⾜࠺ࡇ࡜࡜ࡋࡓࠋࡲࡎึࡵ࡟ 12-ࢡࣛ࢘ࣥ-4(12C4)ࠊ15-ࢡࣛ࢘ࣥ-5(15C5)ࠊ
18-ࢡࣛ࢘ࣥ-6(18C6)ࡢ 3 ࡘࡢ㓟⣲ࢡ࢚࣮ࣛ࢘ࣥࢸࣝࡀ Ln ࡢ௦⾲࡛࠶ࡿࣘ࢘ࣟࣆ࣒࢘(Eu)࡜ᡂࡍ㘒య࡟ࡘ࠸࡚㔞Ꮚ໬Ꮫィ⟬ࢆ⏝࠸ࡓゎᯒࢆ⾜࠸ࠊ᭱㐺࡞⎔ࢧ࢖ࢬࡢỴᐃࢆヨࡳࡓࠋゎᯒ⤖ᯝ࠿ࡽྛ㘒యࡀ⏕ᡂࡍࡿሙྜࡢ
Gibbs ࢚ࢿࣝࢠ࣮ΔG ࢆ⟬ฟࡍࡿ࡜ࠊ࠸ࡎࢀࡢ㔠ᒓ࡛ࡶ 18C6 ࡢሙྜ࡟᭱ࡶᏳᐃ࡞㘒యࢆᡂࡍࡇ࡜ࡀࢃ࠿ࡗࡓࠋ⥆࠸࡚ࠊ18C6 ࡢ㓟⣲ཎᏊࢆ❅⣲ཎᏊᅗ 1 X618C6 ࡢ୍⯡ᵓ(N618C6)ࡲࡓࡣ◲㯤ཎᏊ(S618C6)࡟⨨ࡁ᥮࠼ࡓሙྜ㸦ᅗ 1㸧࡟ࡘ࠸࡚ Eu

㐀((X = O, S, NH)ࡲࡓࡣ MA ࡢ௦⾲࡛࠶ࡿ࢔࣓ࣜࢩ࣒࢘(Am)࡜ᡂࡍ㘒యࡢゎᯒࢆ⾜ࡗࡓࠋ㘒⏕ᡂ Gibbs ࢚ࢿࣝࢠ࣮ゎᯒࡢ⤖ᯝࠊN618C6 ࡜ S618C6 ࡣ࠸ࡎࢀࡶ⨨᥮๓ࡢ 18C6 ࡼࡾࡶ㧗࠸ Am 㑅ᢥᛶࢆᣢࡘࡇ࡜ࢆ♧၀ࡋࡓࠋ⤖ྜ㠡Ⅼ(Bond Critical Point)ゎᯒࡢ⤖ᯝ࠿ࡽࡣࠊAm ࡜㓄఩ཎᏊࡢ㛫ࡢ⤖ྜࡣ Eu ࡜ẚ࡭࡚㒊ศⓗ࡟ඹ᭷⤖ྜⓗ࡛࠶ࡾࠊࡑࡢഴྥࡣ 18C6 ࡼࡾࡶ N618C6ࠊS618C6 ࡢ࡜ࡁ࡟኱ࡁࡃ࡞ࡿࡇ࡜ࡀ♧ࡉࢀࡓࠋࡲࡓࠊ≧ែᐦᗘ(Density of State)ゎᯒࢆ⾜࠺࡜ࠊAm ࡢ f ㌶㐨࡜◲㯤ࡲࡓࡣ❅⣲ཎᏊࡢ㛫ࡢ཯⤖ྜⓗ࡞ᐤ୚ࡀ Am-f ㌶㐨࡜㓟⣲ཎᏊ࡜ࡢ㛫ࡢࡶࡢࡼࡾࡶᑠࡉࡃ࡞ࡾࠊAm ࡜❅⣲࣭◲㯤㓄఩ཎᏊࡢ㛫࡟ࡣࡼࡾ㧗࠸ඹ᭷ᛶࡀ࠶ࡿࡇ࡜ࡀ♧၀ࡉࢀࡓࠋࡇࡢࡇ࡜ࡣࠊN618C6 ࡸ S618C6 ࡀ 18C6 ࡼࡾࡶ㧗࠸Am 㑅ᢥᛶࢆ♧ࡋࡓࡢࡣࠊAm ࡢ f ㌶㐨ࡢඹ᭷⤖ྜ࡟ᑐࡍࡿᐤ୚ࡢ኱ࡁࡉࡀ㛵ࢃࡗ࡚࠸ࡿࡇ࡜ࢆព࿡ࡋࠊ
Am/Eu 㑅ᢥᛶࡣ Am ࡢ f ㌶㐨࡜㓄఩ཎᏊࡢ㛫ࡢ⤖ྜࡢඹ᭷ᛶ࡟ᨭ㓄ࡉࢀ࡚࠸ࡿ࡜࡜ࡶ࡟ࠊ᪤ሗࡢ㓟⣲㓄఩Ꮚ࡟ Eu 㑅ᢥᛶࢆ♧ࡍࡶࡢࡀ࠶ࡿࡇ࡜࠿ࡽࠊ㓄఩ᵓ㐀ࡶ Am/Eu 㑅ᢥᛶ࡟ᐤ୚ࡍࡿࡇ࡜ࡀ♧၀ࡉࢀࡓࠋ
3㸬BTPhen ᆺ㓄఩Ꮚ࡟࠾ࡅࡿ⨨᥮ᇶᑟධຠᯝ࡟ࡘ࠸࡚ࡢ DFT ◊✲ 4)
 2,9-Bis(1,2,4-triazine-3-yl)-1,10-Phenanthroline (BTPhen)ࢆᇶ
ᮏ㦵᱁࡜ࡍࡿ㓄఩Ꮚࡣ Am 㑅ᢥᛶࢆ♧ࡋࠊ㧗࠸㓟࣭ᨺᑕ⥺⪏ᛶࢆᣢࡘࡇ࡜࡛▱ࡽࢀ࡚࠸ࡿࠋࡇࡢ BTPhen ࡢࣇ࢙ࢼࣥࢺࣟࣜࣥ⎔ 5,6 ఩ࡢỈ⣲ࢆ⮯⣲࡟⨨᥮ࡋࡓᢳฟ๣ࡣࠊEu ࡢศ㓄ẚࡀ∦᪉ࡢࡳ⨨᥮ࡋࡓሙྜࡲࡓࡣ࠸ࡎࢀࡶ⨨᥮ࡋ࡞࠿ࡗࡓሙྜ࡟ẚ࡭࡚ 10 ศࡢ 1 ࡟పῶࡋࠊ⤖ᯝ࡜ࡋ࡚ Am/Eu ศ㓄ࡀ኱ᖜ࡟ྥୖࡍࡿࡇ࡜ࡀุ᫂ࡋࡓࠋ5)ࡋ࠿ࡋ
࡞ࡀࡽࠊࡑࡢヲ⣽ࡣ᫂ࡽ࠿࡛࡞࠸ࡢ࡛ࠊDFT ィ⟬ࢆ⏝࠸ࡓ◊✲࡟ྲྀࡾ⤌ࢇࡔࠋ◊✲ࡣ 2 ẁ㝵࡟ศࡅ࡚⾜ࡗࡓࠋ1 ࡘ┠ࡣ BTPhen ᆺ㓄఩Ꮚࡢ⮯⣲⨨᥮ᩘࢆኚ໬ࡉࡏࡿࡇ࡜࡟ࡼࡾ⏕ࡌࡿ㘒⏕ᡂ Gibbs ࢚ࢿࣝࢠ࣮ࡸ⤖ྜ࡟㛵ࡍࡿࣃ࣓࣮ࣛࢱࡢኚ໬ࢆㄪᰝ࣭ゎᯒࡋࡓࠋ㘒⏕ᡂ

ᅗ 2 X2BTPhen ࡢ୍⯡ᵓ㐀
(X = H, F, Cl, Br, I, CH3, NH2,CN)

Gibbs ࢚ࢿࣝࢠ࣮ゎᯒ࡛ࡣࠊᐇ㝿ࡢᐇ㦂࡜ྠᵝ࡟⨨᥮ᩘࡀከ࠸࡯࡝㧗࠸ Am 㑅ᢥᛶࢆⓎ᥹ࡍࡿࡇ࡜ࡀ
♧ࡉࢀࡓࠋࡲࡓ≧ែᐦᗘゎᯒࡢ⤖ᯝࠊ⮯⣲⨨᥮ᩘࡀቑຍࡍࡿ࡯࡝㔠ᒓ d ㌶㐨ࡢ⤖ྜ࡬ࡢᐤ୚ࡀῶᑡࡋࠊf ㌶㐨ࡢᐤ୚ࡀ┦ᑐⓗ࡟㔜せࡉࢆቑࡍࡇ࡜ࡀ♧၀ࡉࢀࡓࠋ2 ࡘ┠ࡢ◊✲࡛ࡣ BTPhen ᆺ㓄఩Ꮚࡢࣇ࢙
ࢼࣥࢺࣟࣜࣥ⎔ 5㸪6 ఩ࡢ୧᪉ࢆྛ✀ࣁࣟࢤࣥ(ࣇࢵ⣲࣭ሷ⣲࣭⮯⣲࣭ࡼ࠺⣲)࡛⨨᥮ࡋࡓሙྜ࡟ࡘ࠸࡚
ྠᵝ࡟ゎᯒࡋࠊ⨨᥮ࡍࡿࣁࣟࢤࣥࡢ㐪࠸࡟ࡼࡿᙳ㡪ࢆẚ㍑ㄪᰝࡋࡓࠋ㘒⏕ᡂ Gibbs ࢚ࢿࣝࢠ࣮ゎᯒࡢ⤖ᯝࠊ⨨᥮ࡍࡿࣁࣟࢤࣥࡢ㟁Ẽ㝜ᛶᗘࡀ㧗࠸࡯࡝ ΔG ್ࡣṇࡢ᪉ྥ࡟ᐤࡾࠊ⏕ᡂࡍࡿ㘒యࡀ୙Ᏻᐃ໬
ࡍࡿ୍᪉࡛ࠊAm 㑅ᢥᛶࡣྥୖࡍࡿഴྥࡀ♧ࡉࢀࡓࠋࡇࡢ⤖ᯝࡣࠊ㟁Ꮚ྾ᘬⓗ࡞ࣁࣟࢤࣥ⨨᥮ᇶࢆᑟධࡍࡿࡇ࡜࡟ࡼࡾ㓄఩Ꮚࡢ㘒ᙧᡂ⬟ࡀపୗࡍࡿ୍᪉࡛ࠊ㔠ᒓ࠿ࡽࡢ㟁Ꮚࡢ㏫౪୚ࡀቑຍࡋࡓࡓࡵ࡟ほࡉࢀࡓ࡜⪃࠼ࡽࢀࡿࠋࡲࡓࠊ≧ែᐦᗘゎᯒࡣࠊ⨨᥮ࡋࡓࣁࣟࢤࣥࡢ㟁Ẽ㝜ᛶᗘࡀ኱ࡁ࠸࡯࡝㔠ᒓ d㌶㐨ࡢ⤖ྜ࡬ࡢᐤ୚ࡀῶᑡࡋࠊf ㌶㐨ࡢᐤ୚ࡀ┦ᑐⓗ࡟㔜せ࡜࡞ࡗ࡚࠸ࡿࡇ࡜ࢆ♧၀ࡋࡓࠋࡇࢀࡽࡢ⤖ᯝ࠿ࡽࠊᢳฟ๣ࡢ㟁Ꮚⓗ࡞⎔ቃࢆኚ໬ࡉࡏࡿࡇ࡜ࡣ Am/Eu 㑅ᢥᛶ࡟ᐤ୚ࢆࡶࡓࡽࡍࡇ࡜ࡀ♧ࡉࢀࡓࠋࡲࡓ f ㌶㐨ࡢᐤ୚ࡣࠊEu ࡢሙྜࡣ཯⤖ྜⓗ࡞ᐤ୚ࡀቑຍࡍࡿ୍᪉࡛ࠊAm ࡢሙྜࡣ⤖ྜⓗ࡞ᐤ୚࡜཯
⤖ྜⓗ࡞ᐤ୚ࡢ୧᪉ࡀቑ኱ࡍࡿࡇ࡜ࡀ♧ࡉࢀࡓࠋ4㸬ࡲ࡜ࡵ ᮏ◊✲࡛ࡣࠊAm ࡜ Eu ࡢ㑅ᢥⓗศ㞳࡟࠾ࡅࡿ⁐፹ᢳฟᶵᵓࢆゎ᫂ࡍࡿࡓࡵ㓄఩㦵᱁ࢆྠࡌ࡟ࡋ࡚◊✲ࡋࡓࠋࡲࡓࠊ⨨᥮ᇶࢆᑟධࡋ࡚㑅ᢥᛶࢆྥୖࡉࡏࡿ◊✲ࢆ⾜ࡗࡓࠋ⌧ᅾࠊ࢔࣑ࣀᇶ࡞࡝ࡶᑟධࡋ࡚㑅ᢥᛶྥୖࡢࡉࡽ࡞ࡿ᳨ウࡶ㐍ࡵ࡚࠸ࡿࠋᮏ◊✲ࡢᡂᯝࢆ฼⏝ࡋࠊᢳฟᶵᵓ࡟㛵ࡍࡿ㆟ㄽࡢ῝໬ࡸ᪂ࡓ࡞㧗ຠ⋡࣭㧗ᛶ⬟࡞ᢳฟ๣ࡢ㛤Ⓨࡀᮇᚅࡉࢀࡿࠋ
5㸬ཧ⪃ᩥ⊩
1) K. L. Nash, Solvent Extr. Ion Exch., 1993, 11, 729-768.
2) M. Kaneko, S. Miyashita, S. Nakashima, Inorg. Chem., 2015, 54, 7103-7109.
3) Y. Fukasawa, M. Kaneko, S. Nakashima, J. Radioanal. Nucl. Chem., 2021, 329, 77-84.
4) Y. Fukasawa, S. Nakashima, RSC Advances, 2023, 13, 2476-2482.
5) A. Afsar, D. M. Laventine, L. M. Harwood, M. J. Hudson, A. Geist, Chem. Commn., 2013, 49, 8534-8536.