JP2015118010A - Decontamination method for soil contaminated with radioactive materials, and decontamination device - Google Patents
Decontamination method for soil contaminated with radioactive materials, and decontamination device Download PDFInfo
- Publication number
- JP2015118010A JP2015118010A JP2013261750A JP2013261750A JP2015118010A JP 2015118010 A JP2015118010 A JP 2015118010A JP 2013261750 A JP2013261750 A JP 2013261750A JP 2013261750 A JP2013261750 A JP 2013261750A JP 2015118010 A JP2015118010 A JP 2015118010A
- Authority
- JP
- Japan
- Prior art keywords
- soil
- decontamination
- cesium
- treatment liquid
- radioactive cesium
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000002689 soil Substances 0.000 title claims abstract description 131
- 238000005202 decontamination Methods 0.000 title claims abstract description 95
- 230000003588 decontaminative effect Effects 0.000 title claims abstract description 62
- 239000012857 radioactive material Substances 0.000 title description 6
- 229910052792 caesium Inorganic materials 0.000 claims abstract description 128
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 claims abstract description 127
- 230000002285 radioactive effect Effects 0.000 claims abstract description 69
- 239000007788 liquid Substances 0.000 claims abstract description 59
- 229910019142 PO4 Inorganic materials 0.000 claims abstract description 27
- 238000003756 stirring Methods 0.000 claims abstract description 23
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims abstract description 17
- 239000010452 phosphate Substances 0.000 claims abstract description 17
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims abstract description 16
- 238000005406 washing Methods 0.000 claims abstract description 16
- 238000010438 heat treatment Methods 0.000 claims abstract description 10
- 239000003463 adsorbent Substances 0.000 claims description 46
- DCYOBGZUOMKFPA-UHFFFAOYSA-N iron(2+);iron(3+);octadecacyanide Chemical class [Fe+2].[Fe+2].[Fe+2].[Fe+3].[Fe+3].[Fe+3].[Fe+3].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-] DCYOBGZUOMKFPA-UHFFFAOYSA-N 0.000 claims description 40
- 239000000835 fiber Substances 0.000 claims description 38
- 238000000034 method Methods 0.000 claims description 35
- 238000000605 extraction Methods 0.000 claims description 29
- 238000001179 sorption measurement Methods 0.000 claims description 29
- 235000021317 phosphate Nutrition 0.000 claims description 26
- 229960003351 prussian blue Drugs 0.000 claims description 17
- 239000013225 prussian blue Substances 0.000 claims description 17
- 239000007864 aqueous solution Substances 0.000 claims description 15
- 239000000758 substrate Substances 0.000 claims description 14
- 239000000463 material Substances 0.000 claims description 13
- 150000003467 sulfuric acid derivatives Chemical class 0.000 claims description 12
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 10
- 239000004927 clay Substances 0.000 claims description 10
- 229910017604 nitric acid Inorganic materials 0.000 claims description 10
- 150000003013 phosphoric acid derivatives Chemical class 0.000 claims description 10
- 239000000243 solution Substances 0.000 claims description 9
- 239000002585 base Substances 0.000 claims description 8
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 6
- 229910052783 alkali metal Inorganic materials 0.000 claims description 5
- 229920002678 cellulose Polymers 0.000 claims description 5
- 239000001913 cellulose Substances 0.000 claims description 5
- 239000004745 nonwoven fabric Substances 0.000 claims description 5
- 150000001340 alkali metals Chemical class 0.000 claims description 4
- 238000013019 agitation Methods 0.000 claims description 3
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims description 3
- 150000001342 alkaline earth metals Chemical class 0.000 claims description 3
- 229910021529 ammonia Inorganic materials 0.000 claims description 3
- 239000002253 acid Substances 0.000 abstract description 36
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 13
- 229910001868 water Inorganic materials 0.000 abstract description 13
- 239000000470 constituent Substances 0.000 abstract 1
- 229910021653 sulphate ion Inorganic materials 0.000 abstract 1
- 238000003795 desorption Methods 0.000 description 23
- 229910052723 transition metal Inorganic materials 0.000 description 20
- -1 transition metal salt Chemical class 0.000 description 17
- 238000002474 experimental method Methods 0.000 description 15
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 13
- LWIHDJKSTIGBAC-UHFFFAOYSA-K potassium phosphate Substances [K+].[K+].[K+].[O-]P([O-])([O-])=O LWIHDJKSTIGBAC-UHFFFAOYSA-K 0.000 description 13
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 12
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 11
- UETZVSHORCDDTH-UHFFFAOYSA-N iron(2+);hexacyanide Chemical compound [Fe+2].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-] UETZVSHORCDDTH-UHFFFAOYSA-N 0.000 description 11
- 150000003839 salts Chemical class 0.000 description 11
- 229910010272 inorganic material Inorganic materials 0.000 description 10
- 150000002484 inorganic compounds Chemical class 0.000 description 9
- 229910017053 inorganic salt Inorganic materials 0.000 description 9
- 229910000402 monopotassium phosphate Inorganic materials 0.000 description 9
- 235000019796 monopotassium phosphate Nutrition 0.000 description 9
- 239000006228 supernatant Substances 0.000 description 9
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 8
- 238000006243 chemical reaction Methods 0.000 description 8
- 239000010949 copper Substances 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- GNSKLFRGEWLPPA-UHFFFAOYSA-M potassium dihydrogen phosphate Chemical compound [K+].OP(O)([O-])=O GNSKLFRGEWLPPA-UHFFFAOYSA-M 0.000 description 8
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 7
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 6
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 6
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 6
- 235000011130 ammonium sulphate Nutrition 0.000 description 6
- 239000011651 chromium Substances 0.000 description 6
- 239000011572 manganese Substances 0.000 description 6
- 150000007522 mineralic acids Chemical class 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- 239000003513 alkali Substances 0.000 description 5
- 229910017052 cobalt Inorganic materials 0.000 description 5
- 239000010941 cobalt Substances 0.000 description 5
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 5
- 239000003337 fertilizer Substances 0.000 description 5
- 239000000047 product Substances 0.000 description 5
- 239000002901 radioactive waste Substances 0.000 description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 4
- NIPNSKYNPDTRPC-UHFFFAOYSA-N N-[2-oxo-2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 NIPNSKYNPDTRPC-UHFFFAOYSA-N 0.000 description 4
- 229910052802 copper Inorganic materials 0.000 description 4
- 239000010419 fine particle Substances 0.000 description 4
- 150000004677 hydrates Chemical class 0.000 description 4
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 4
- 229910052759 nickel Inorganic materials 0.000 description 4
- 239000000049 pigment Substances 0.000 description 4
- 239000000941 radioactive substance Substances 0.000 description 4
- 235000011121 sodium hydroxide Nutrition 0.000 description 4
- 239000001488 sodium phosphate Substances 0.000 description 4
- JBQYATWDVHIOAR-UHFFFAOYSA-N tellanylidenegermanium Chemical compound [Te]=[Ge] JBQYATWDVHIOAR-UHFFFAOYSA-N 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 239000010936 titanium Substances 0.000 description 4
- VZSRBBMJRBPUNF-UHFFFAOYSA-N 2-(2,3-dihydro-1H-inden-2-ylamino)-N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]pyrimidine-5-carboxamide Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C(=O)NCCC(N1CC2=C(CC1)NN=N2)=O VZSRBBMJRBPUNF-UHFFFAOYSA-N 0.000 description 3
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 3
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 3
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 229910001413 alkali metal ion Inorganic materials 0.000 description 3
- TVFDJXOCXUVLDH-RNFDNDRNSA-N cesium-137 Chemical compound [137Cs] TVFDJXOCXUVLDH-RNFDNDRNSA-N 0.000 description 3
- 229910052804 chromium Inorganic materials 0.000 description 3
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 3
- 229910052748 manganese Inorganic materials 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 229910021645 metal ion Inorganic materials 0.000 description 3
- 150000007524 organic acids Chemical class 0.000 description 3
- VLTRZXGMWDSKGL-UHFFFAOYSA-N perchloric acid Chemical class OCl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-N 0.000 description 3
- 230000005855 radiation Effects 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 239000013049 sediment Substances 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 150000003624 transition metals Chemical class 0.000 description 3
- 229920000742 Cotton Polymers 0.000 description 2
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 2
- 229910021578 Iron(III) chloride Inorganic materials 0.000 description 2
- 229920000433 Lyocell Polymers 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 229920000297 Rayon Polymers 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 2
- TVFDJXOCXUVLDH-OUBTZVSYSA-N cesium-134 Chemical compound [134Cs] TVFDJXOCXUVLDH-OUBTZVSYSA-N 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- MHJAJDCZWVHCPF-UHFFFAOYSA-L dimagnesium phosphate Chemical compound [Mg+2].OP([O-])([O-])=O MHJAJDCZWVHCPF-UHFFFAOYSA-L 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000004043 dyeing Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
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- 150000004820 halides Chemical class 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 2
- 239000004137 magnesium phosphate Substances 0.000 description 2
- 229910000403 monosodium phosphate Inorganic materials 0.000 description 2
- 235000019799 monosodium phosphate Nutrition 0.000 description 2
- 150000002823 nitrates Chemical class 0.000 description 2
- PJNZPQUBCPKICU-UHFFFAOYSA-N phosphoric acid;potassium Chemical compound [K].OP(O)(O)=O PJNZPQUBCPKICU-UHFFFAOYSA-N 0.000 description 2
- XAEFZNCEHLXOMS-UHFFFAOYSA-M potassium benzoate Chemical compound [K+].[O-]C(=O)C1=CC=CC=C1 XAEFZNCEHLXOMS-UHFFFAOYSA-M 0.000 description 2
- FGIUAXJPYTZDNR-UHFFFAOYSA-N potassium nitrate Chemical compound [K+].[O-][N+]([O-])=O FGIUAXJPYTZDNR-UHFFFAOYSA-N 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000002964 rayon Substances 0.000 description 2
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- 229910052706 scandium Inorganic materials 0.000 description 2
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 description 2
- AJPJDKMHJJGVTQ-UHFFFAOYSA-M sodium dihydrogen phosphate Chemical compound [Na+].OP(O)([O-])=O AJPJDKMHJJGVTQ-UHFFFAOYSA-M 0.000 description 2
- 159000000000 sodium salts Chemical class 0.000 description 2
- 229920002994 synthetic fiber Polymers 0.000 description 2
- 239000012209 synthetic fiber Substances 0.000 description 2
- AWDBHOZBRXWRKS-UHFFFAOYSA-N tetrapotassium;iron(6+);hexacyanide Chemical compound [K+].[K+].[K+].[K+].[Fe+6].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-] AWDBHOZBRXWRKS-UHFFFAOYSA-N 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- PNDPGZBMCMUPRI-HVTJNCQCSA-N 10043-66-0 Chemical compound [131I][131I] PNDPGZBMCMUPRI-HVTJNCQCSA-N 0.000 description 1
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- 244000025254 Cannabis sativa Species 0.000 description 1
- 235000012766 Cannabis sativa ssp. sativa var. sativa Nutrition 0.000 description 1
- 235000012765 Cannabis sativa ssp. sativa var. spontanea Nutrition 0.000 description 1
- 239000005696 Diammonium phosphate Substances 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 229920001407 Modal (textile) Polymers 0.000 description 1
- HCMVSLMENOCDCK-UHFFFAOYSA-N N#C[Fe](C#N)(C#N)(C#N)(C#N)C#N Chemical compound N#C[Fe](C#N)(C#N)(C#N)(C#N)C#N HCMVSLMENOCDCK-UHFFFAOYSA-N 0.000 description 1
- MKYBYDHXWVHEJW-UHFFFAOYSA-N N-[1-oxo-1-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propan-2-yl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(C(C)NC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 MKYBYDHXWVHEJW-UHFFFAOYSA-N 0.000 description 1
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 1
- 229910021586 Nickel(II) chloride Inorganic materials 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- 229920001328 Polyvinylidene chloride Polymers 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
- 238000010306 acid treatment Methods 0.000 description 1
- 229910000272 alkali metal oxide Inorganic materials 0.000 description 1
- 229910001860 alkaline earth metal hydroxide Inorganic materials 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 description 1
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000010426 asphalt Substances 0.000 description 1
- YYRMJZQKEFZXMX-UHFFFAOYSA-L calcium bis(dihydrogenphosphate) Chemical compound [Ca+2].OP(O)([O-])=O.OP(O)([O-])=O YYRMJZQKEFZXMX-UHFFFAOYSA-L 0.000 description 1
- FUFJGUQYACFECW-UHFFFAOYSA-L calcium hydrogenphosphate Chemical compound [Ca+2].OP([O-])([O-])=O FUFJGUQYACFECW-UHFFFAOYSA-L 0.000 description 1
- 239000001506 calcium phosphate Substances 0.000 description 1
- 235000011132 calcium sulphate Nutrition 0.000 description 1
- 235000009120 camo Nutrition 0.000 description 1
- 235000005607 chanvre indien Nutrition 0.000 description 1
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- GVPFVAHMJGGAJG-UHFFFAOYSA-L cobalt dichloride Chemical compound [Cl-].[Cl-].[Co+2] GVPFVAHMJGGAJG-UHFFFAOYSA-L 0.000 description 1
- UFMZWBIQTDUYBN-UHFFFAOYSA-N cobalt dinitrate Chemical compound [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O UFMZWBIQTDUYBN-UHFFFAOYSA-N 0.000 description 1
- 229910001981 cobalt nitrate Inorganic materials 0.000 description 1
- KTVIXTQDYHMGHF-UHFFFAOYSA-L cobalt(2+) sulfate Chemical compound [Co+2].[O-]S([O-])(=O)=O KTVIXTQDYHMGHF-UHFFFAOYSA-L 0.000 description 1
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- 150000004696 coordination complex Chemical class 0.000 description 1
- 125000004093 cyano group Chemical group *C#N 0.000 description 1
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 description 1
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- 235000019791 dimagnesium phosphate Nutrition 0.000 description 1
- ZPWVASYFFYYZEW-UHFFFAOYSA-L dipotassium hydrogen phosphate Chemical compound [K+].[K+].OP([O-])([O-])=O ZPWVASYFFYYZEW-UHFFFAOYSA-L 0.000 description 1
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- 238000012432 intermediate storage Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- NJWYTAHMQKIIQQ-UHFFFAOYSA-N iron(3+);hydrate Chemical compound O.[Fe+3] NJWYTAHMQKIIQQ-UHFFFAOYSA-N 0.000 description 1
- LHOWRPZTCLUDOI-UHFFFAOYSA-K iron(3+);triperchlorate Chemical compound [Fe+3].[O-]Cl(=O)(=O)=O.[O-]Cl(=O)(=O)=O.[O-]Cl(=O)(=O)=O LHOWRPZTCLUDOI-UHFFFAOYSA-K 0.000 description 1
- YHGPYBQVSJBGHH-UHFFFAOYSA-H iron(3+);trisulfate;pentahydrate Chemical compound O.O.O.O.O.[Fe+3].[Fe+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O YHGPYBQVSJBGHH-UHFFFAOYSA-H 0.000 description 1
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- 244000144972 livestock Species 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
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- 239000006012 monoammonium phosphate Substances 0.000 description 1
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- 229910000401 monomagnesium phosphate Inorganic materials 0.000 description 1
- 235000019785 monomagnesium phosphate Nutrition 0.000 description 1
- QMMRZOWCJAIUJA-UHFFFAOYSA-L nickel dichloride Chemical compound Cl[Ni]Cl QMMRZOWCJAIUJA-UHFFFAOYSA-L 0.000 description 1
- KBJMLQFLOWQJNF-UHFFFAOYSA-N nickel(ii) nitrate Chemical compound [Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O KBJMLQFLOWQJNF-UHFFFAOYSA-N 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
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- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
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Landscapes
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
Abstract
Description
本発明は、放射性物質、特に放射性セシウムで汚染された土壌の除染方法及び除染装置に関する。 The present invention relates to a decontamination method and a decontamination apparatus for soil contaminated with radioactive substances, particularly radioactive cesium.
２０１１年３月１１日に発生した東日本大震災による福島第一原子力発電所における未曾有の事故は、今もなお、農業、水産業、畜産業はもとより、周辺住民の生活に深刻な影響を及ぼしている。原発事故そのものの収束はもちろんのこと、事故により環境中に放出されたヨウ素（131Ｉ）、セシウム（134Ｃｓ、137Ｃｓ）、ストロンチウム（90Ｓｒ）等の放射性物質の除去は、現在、我が国の喫緊の課題となっている。特に主要な放射性物質であって、約３０年という長い半減期を有するセシウム１３７（137Ｃｓ）の環境中、特に、土壌からの除染については、現在、各種機関により様々なアプローチが検討されている。 The unprecedented accident at the Fukushima Daiichi NPS due to the Great East Japan Earthquake that occurred on March 11, 2011 still has a serious impact on the lives of local residents as well as agriculture, fisheries and livestock industries. . The removal of radioactive materials such as iodine ( 131 I), cesium ( 134 Cs, 137 Cs), and strontium ( 90 Sr) released into the environment by the accident as well as the convergence of the nuclear accident itself is currently It is an urgent issue. Especially a major radioactive material, environment 137Cs with a long half-life of about 30 years (137 Cs), in particular, for the decontamination of soil, currently, a variety of approaches by various engine is considered Yes.
現況、土壌の除染方法は、放射性物質の濃度が高い表層の土壌を剥ぎ取って、仮置き場や中間貯蔵設備に移動させ保管することである。この方法の最大の問題点は、膨大な量の汚染土壌の保管場所の確保が困難なことであり、このことが、土壌除染が加速されない最大の要因である。そこで、汚染土壌から放射性物質だけを分離回収する技術がいくつか提案されている。例えば、有機酸や無機酸等を用いて汚染土壌から放射性物質を抽出する方法や、高温高圧水や亜臨界水を用いて抽出する方法が提案されている。 At present, the soil decontamination method is to peel off the surface soil with a high concentration of radioactive material and move it to a temporary storage site or intermediate storage facility for storage. The biggest problem of this method is that it is difficult to secure a storage place for a huge amount of contaminated soil, and this is the biggest factor that soil decontamination is not accelerated. Therefore, several techniques for separating and recovering only radioactive substances from contaminated soil have been proposed. For example, a method of extracting a radioactive substance from contaminated soil using an organic acid, an inorganic acid, or the like, or a method of extracting using high-temperature high-pressure water or subcritical water has been proposed.
しかし、チェルノブイリ原発事故により放出された放射性物質の土壌での分布状態や存在形態についての継続調査結果では、セシウム１３７の大部分（７０−９９％）は表層５ｃｍに残っているものの、その大部分（７９−９９％）は、土壌に固定化された形態（例えば、土壌中鉱物と結合しているもの、ホットパーティクル内に存在しているもの）で存在していることが報告されている（例えば、非特許文献１参照）。このような固定化が、土壌からセシウムを効率よく抽出することを困難にしており、例えば、通常の水、酸、アルカリ洗浄では、土壌からのセシウム除去率は１０〜３０％程度に留まるとの報告もなされている。そこで、放射性セシウム汚染土壌を、フッ素イオンを含む処理液と接触させ、固定化されたセシウムの抽出効率を向上させた除染方法等も提案されている（例えば、特許文献１参照）。 However, according to the results of continuous surveys on the distribution and presence of radioactive materials released in the Chernobyl nuclear accident in the soil, most of cesium 137 (70-99%) remains in the surface layer of 5 cm, but most of it. (79-99%) are reported to exist in a form immobilized on the soil (for example, those bonded to minerals in the soil, existing in hot particles) ( For example, refer nonpatent literature 1). Such immobilization makes it difficult to efficiently extract cesium from the soil. For example, with normal water, acid, and alkali cleaning, the cesium removal rate from the soil remains at about 10 to 30%. Reports have also been made. Then, the decontamination method etc. which made radioactive cesium contaminated soil contact the process liquid containing a fluorine ion and improved the extraction efficiency of the fixed cesium are proposed (for example, refer to patent documents 1).
このように、現在一般的に行われている土壌の除染方法（表層土壌剥ぎ取り法）では、大量の汚染土壌を移動、集積、保管する必要があり、その場所の確保が困難であり；また、放射性物質を土壌から除去する既存の除染方法でも、人体や生態系への影響が懸念される化学物質が使用され、その結果として除染した土壌でも環境中に戻せないといった課題がある。さらに、放射性物質の土壌からの抽出に高濃度の酸を使用する場合は、除染装置に特殊な材料を必要とするため、除染装置が高価となること；高濃度の酸の取り扱いが困難であること；専門的な知識や技術を要し、専門家でなければ従事できない場合があるといった課題もある。 In this way, the soil decontamination method (surface soil stripping method) that is generally used at present requires moving, accumulating and storing a large amount of contaminated soil, and it is difficult to secure the location; In addition, existing decontamination methods that remove radioactive materials from the soil use chemical substances that may be harmful to the human body and ecosystem, and as a result, there is a problem that even decontaminated soil cannot be returned to the environment. . In addition, when high-concentration acid is used for extraction of radioactive substances from soil, decontamination equipment is expensive because it requires special materials; handling of high-concentration acid is difficult There are also issues that require specialized knowledge and skills, and may only be possible by professionals.
したがって、現行の除染事業だけではなく、汚染土壌を集積せず、且つ低コストで専門家の立ち会い不要な小規模分散型土壌除染システムの構築が求められている。 Therefore, not only the current decontamination business but also the construction of a small-scale distributed soil decontamination system that does not accumulate contaminated soil and that is low cost and does not require the presence of experts.
本発明者らは、これまでに、「プルシアンブルー類縁体を担持した親水性繊維基材からなるセシウム吸着材」に係る発明を完成させた（国際公開第２０１３／０２７６５２号パンフレット）。かかるセシウム吸着材は、プルシアンブルー類縁体を、親水性繊維基材に固定化したものであり、安全かつ取扱いが容易である。また安価で入手が容易な材料から、簡便な製造方法により得ることが出来るため、経済的な側面からも、広範囲に亘る環境浄化への適用に優れたものである。さらには、除染の対象に応じて、セシウム吸着材を最適な態様へと容易に加工することができる点、また環境中の放射性セシウムを吸着させた後、（セシウムが吸着した）プルシアンブルー類縁体の遷移金属塩を環境中に取り残すことなく、吸着材のみを容易に回収することができるため、表土を取り除くような物理的な除染方法と比較して、放射性廃棄物の量を抑制することもできる点で有利である。 The present inventors have so far completed the invention relating to “cesium adsorbent comprising a hydrophilic fiber substrate carrying Prussian blue analogue” (International Publication No. 2013/027652 pamphlet). Such a cesium adsorbent is obtained by immobilizing Prussian blue analogue on a hydrophilic fiber substrate, and is safe and easy to handle. In addition, since it can be obtained from an inexpensive and easily available material by a simple manufacturing method, it is excellent in application to environmental purification over a wide range from an economical aspect. Furthermore, depending on the object of decontamination, the cesium adsorbent can be easily processed into an optimal mode, and after adsorbing radioactive cesium in the environment, Prussian blue related (adsorbed by cesium) Reduces the amount of radioactive waste compared to physical decontamination methods that remove topsoil because only the adsorbent can be easily recovered without leaving the body transition metal salt in the environment. It is advantageous in that it can also be performed.
本発明者らは、上記課題を解決するために鋭意検討した結果、人体や生態系への影響が少なく、農地に還元しても差し支えない成分として、農地等で使われている肥料の成分に着目し、該成分を含む処理液による、放射性セシウムの汚染土壌からの効率的な抽出方法を確立した。さらにかかる抽出方法と、本発明者らが開発した前記セシウム吸着材とを組合せ、低コストで専門家の立ち会い不要な小規模分散型土壌除染システムを構築し、本発明を完成させた。 As a result of diligent studies to solve the above problems, the present inventors have little influence on the human body and ecosystem, and as a component that can be returned to farmland, the fertilizer component used in farmland etc. Attention was paid to the establishment of an efficient method for extracting radioactive cesium from contaminated soil using a treatment solution containing the component. Further, by combining the extraction method and the cesium adsorbent developed by the present inventors, a small-scale distributed soil decontamination system that is low cost and does not require the presence of an expert is constructed to complete the present invention.
本発明は、以下のとおりである：
［１］放射性セシウムで汚染された土壌を、リン酸塩及び硫酸塩からなる群より選択される少なくとも一種の成分を含み、且つｐＨが４以下である処理液と接触させ、土壌から放射性セシウムを抽出する工程を含む、放射性セシウムで汚染された土壌の除染方法。
［２］抽出工程後の処理液を、プルシアンブルー類縁体を担持した親水性繊維基材からなるセシウム吸着材と接触させ、放射性セシウムをセシウム吸着材へ吸着させる工程を含む、前記［１］に記載の除染方法。
［３］リン酸塩及び硫酸塩が、アルカリ金属、アルカリ土類金属及びアンモニアのリン酸塩及び硫酸塩である、前記［１］又は［２］に記載の除染方法。
［４］処理液が、リン酸塩及び硫酸塩からなる群より選択される少なくとも一種の成分と、硝酸とを含む水溶液である、前記［１］〜［３］のいずれかに記載の除染方法。
［５］抽出工程前の処理として、放射性セシウムで汚染された土壌から粘土分を除去する工程を含む、前記［１］〜［４］のいずれかに記載の除染方法。
［６］処理液が、吸着工程後に回収した処理液である、前記［２］〜［５］のいずれかに記載の除染方法。
［７］放射性セシウムで汚染された土壌からセシウムを除去する除染装置であって、
前記土壌及び処理液を受け入れる中空の容器；
前記容器の外壁若しくは前記容器内に配設され、前記容器内に受け入れた前記土壌及び処理液を加熱するための加熱手段；及び
前記容器内に受け入れた前記土壌及び処理液を撹拌するための撹拌手段
を備える撹拌洗浄槽を含み、
前記処理液が、リン酸塩及び硫酸塩からなる群より選択される少なくとも一種の成分を含み、且つｐＨが４以下である、除染装置。
［８］前記撹拌洗浄槽から排出される放射性セシウムを含む処理液及びプルシアンブルー類縁体を担持した親水性繊維基材からなるセシウム吸着材を受け入れる中空の容器
を備える吸着槽を含む、前記［７］に記載の除染装置。
［９］前記セシウム吸着材が、プルシアンブルーを担持したセルロース系長繊維不織布である、前記［８］に記載の除染装置。
The present invention is as follows:
[1] The soil contaminated with radioactive cesium is brought into contact with a treatment solution containing at least one component selected from the group consisting of phosphate and sulfate and having a pH of 4 or less, and radioactive cesium is removed from the soil. A method for decontamination of soil contaminated with radioactive cesium, comprising a step of extracting.
[2] The method according to [1], including a step of bringing the treatment liquid after the extraction step into contact with a cesium adsorbent composed of a hydrophilic fiber base supporting a Prussian blue analog, and adsorbing radioactive cesium onto the cesium adsorbent. Decontamination method as described.
[3] The decontamination method according to the above [1] or [2], wherein the phosphate and sulfate are phosphates and sulfates of alkali metal, alkaline earth metal and ammonia.
[4] Decontamination according to any one of [1] to [3], wherein the treatment liquid is an aqueous solution containing at least one component selected from the group consisting of phosphates and sulfates and nitric acid. Method.
[5] The decontamination method according to any one of [1] to [4], including a step of removing clay from soil contaminated with radioactive cesium as the treatment before the extraction step.
[6] The decontamination method according to any one of [2] to [5], wherein the treatment liquid is a treatment liquid collected after the adsorption step.
[7] A decontamination apparatus for removing cesium from soil contaminated with radioactive cesium,
A hollow container for receiving the soil and the treatment liquid;
A heating means for heating the soil and the treatment liquid disposed in the outer wall of the container or in the container and received in the container; and agitation for stirring the soil and the treatment liquid received in the container A stirred washing tank comprising means,
The decontamination apparatus, wherein the treatment liquid contains at least one component selected from the group consisting of phosphates and sulfates, and has a pH of 4 or less.
[8] The above-mentioned [7], further comprising an adsorption tank comprising a hollow container for receiving a cesium adsorbent comprising a treatment liquid containing radioactive cesium discharged from the stirring and washing tank and a hydrophilic fiber base material supporting a Prussian blue analog. ] Decontamination apparatus.
[9] The decontamination apparatus according to [8], wherein the cesium adsorbent is a cellulose-based long fiber nonwoven fabric supporting Prussian blue.
本発明の放射性セシウムで汚染された土壌の除染方法により、汚染土壌から固定化された放射性セシウムを効率よく抽出することができる。また本発明の除染方法で使用する試薬は、いずれも既に農地等で使われている肥料の成分であり、人体や生態系への影響の懸念がなく、除染された土壌を環境中に戻すことができる。したがって、従前の表層土壌剥ぎ取り法のように、汚染土壌の移動、集積、保管は不要である。さらに本発明の除染装置は、特別な材料を必要としないので低コストであり、また専門家による操作を必要としないので、地域住民やボランティア等による自らの手による土壌除染が可能となる。本発明の除染方法及び除染装置により、汚染土壌の除染の加速が期待できる。 By the decontamination method for soil contaminated with radioactive cesium of the present invention, radioactive cesium immobilized from the contaminated soil can be efficiently extracted. In addition, the reagents used in the decontamination method of the present invention are all components of fertilizers already used in farmland, etc., and there is no concern about the impact on the human body and ecosystem, and the decontaminated soil is put into the environment. Can be returned. Therefore, it is not necessary to move, accumulate, or store contaminated soil as in the conventional method of stripping the surface soil. Furthermore, since the decontamination apparatus of the present invention does not require a special material, it is low cost and does not require operation by an expert, so that soil decontamination can be performed by local residents, volunteers, etc. by their own hands. . By the decontamination method and decontamination apparatus of the present invention, acceleration of decontamination of contaminated soil can be expected.
［放射性セシウムで汚染された土壌の除染方法］
＜抽出工程＞
本発明は、放射性セシウムで汚染された土壌を、リン酸塩及び硫酸塩からなる群より選択される少なくとも一種の成分を含み、且つｐＨが４以下である処理液と接触させ、土壌から放射性セシウムを抽出する工程を含む、放射性セシウムで汚染された土壌の除染方法に関する。
[Decontamination method of soil contaminated with radioactive cesium]
<Extraction process>
In the present invention, soil contaminated with radioactive cesium is brought into contact with a treatment solution containing at least one component selected from the group consisting of phosphate and sulfate and having a pH of 4 or less. The present invention relates to a method for decontaminating soil contaminated with radioactive cesium, which includes a step of extracting.
本発明において、「放射性セシウムで汚染された土壌」は、放射性セシウム（134Ｃｓ、137Ｃｓ）を含む土壌を指す。特には、放射性セシウム濃度が８０００Ｂｑ／ｋｇ超のものを指す。８０００Ｂｑ／ｋｇは、廃棄物を安全に処分するために法律で定められた目安であり、例えば、放射性セシウム濃度が８０００Ｂｑ／ｋｇ以下であれば、一般廃棄物と同様の埋め立て処分等ができる。また「土壌」は、居住地、農地等から採取したもののみならず、汚泥、焼却灰、又は河川や湖沼等の堆積物等であってもよい。 In the present invention, “soil contaminated with radioactive cesium” refers to soil containing radioactive cesium ( 134 Cs, 137 Cs). In particular, it refers to a radioactive cesium concentration of more than 8000 Bq / kg. 8000 Bq / kg is a standard established by law for safely disposing of waste. For example, if the radioactive cesium concentration is 8000 Bq / kg or less, landfill disposal similar to general waste can be performed. The “soil” is not limited to those collected from residential areas, farmland, etc., but may be sludge, incinerated ash, or sediments such as rivers and lakes.
本発明に係る処理液は、リン酸塩及び硫酸塩からなる群より選択される少なくとも一種の成分を含み、且つｐＨが４以下の水溶液である。ここで、リン酸塩及び硫酸塩としては、アルカリ金属、アルカリ土類金属及びアンモニアのリン酸塩及び硫酸塩を挙げることができる。リン酸塩の例としては、リン酸一ナトリウム、リン酸二ナトリウム、リン酸三ナトリウム、リン酸一カリウム、リン酸二カリウム、リン酸三カリウム、リン酸一カルシウム、リン酸一水素カルシウム、リン酸二カルシウム、リン酸一マグネシウム、リン酸二マグネシウム、リン酸一アンモニウム、リン酸二アンモニウム等を挙げることができる。好ましくは、リン酸一ナトリウム及びリン酸一カリウムであり、より好ましくはリン酸一カリウムである。硫酸塩の例としては、硫酸ナトリウム、硫酸カリウム、硫酸カルシウム、硫酸アンモニウム（硫安）等を挙げることができる。好ましくは、硫酸アンモニウムである。 The treatment liquid according to the present invention is an aqueous solution containing at least one component selected from the group consisting of phosphates and sulfates and having a pH of 4 or less. Here, examples of the phosphate and sulfate include phosphates and sulfates of alkali metals, alkaline earth metals, and ammonia. Examples of phosphates include monosodium phosphate, disodium phosphate, trisodium phosphate, monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, monocalcium phosphate, calcium monohydrogen phosphate, phosphorus Examples thereof include dicalcium acid, monomagnesium phosphate, dimagnesium phosphate, monoammonium phosphate, and diammonium phosphate. Preferred are monosodium phosphate and monopotassium phosphate, and more preferred is monopotassium phosphate. Examples of sulfates include sodium sulfate, potassium sulfate, calcium sulfate, ammonium sulfate (ammonium sulfate) and the like. Preferably, it is ammonium sulfate.
本発明に係る「リン酸塩及び硫酸塩からなる群より選択される少なくとも一種の成分」は、１種又は２種以上のリン酸塩、１種又は２種以上の硫酸塩、あるいは１種のリン酸塩及び１種の硫酸塩の組み合わせであってよく、好ましくは、１種のリン酸塩であるか、１種のリン酸塩及び１種の硫酸塩の組み合わせであり、より好ましくリン酸一カリウムであるか、リン酸一カリウム及び硫酸アンモニウムの組み合わせである。処理液におけるリン酸塩及び硫酸塩の濃度（合計）は、セシウムの除去率の点から、好ましくは０．５０Ｍ〜５．０Ｍであり、より好ましくは０．６０Ｍ〜２．５Ｍであり、特に好ましくは０．９０Ｍ〜２．２Ｍである。 The “at least one component selected from the group consisting of phosphates and sulfates” according to the present invention is one or more phosphates, one or more sulfates, or one type It may be a combination of phosphate and one sulfate, preferably one phosphate, or a combination of one phosphate and one sulfate, more preferably phosphoric acid Monopotassium or a combination of monopotassium phosphate and ammonium sulfate. The concentration (total) of phosphate and sulfate in the treatment liquid is preferably 0.50M to 5.0M, more preferably 0.60M to 2.5M, particularly from the viewpoint of the removal rate of cesium. Preferably it is 0.90M-2.2M.
本発明に係る処理液は、水にリン酸塩及び硫酸塩からなる群より選択される少なくとも一種の成分を所望の濃度となるよう添加した後、ｐＨが４以下となるよう酸成分を添加することにより調整される。ｐＨは、セシウムの除去率の点から、好ましくは１〜３であり、より好ましくは１．５〜２．５であり、特に好ましくは約２である。酸成分は、有機酸又は無機酸のいずれであってもよい。有機酸の例としては、酢酸、クエン酸、シュウ酸等を挙げることができ、無機酸の例としては、塩酸、硫酸、硝酸等を挙げることができる。環境負荷の点から、酸成分は、好ましくは無機酸であり、セシウムの除去率の点から、より好ましくは硝酸である。なお硝酸は、ステンレスの腐食作用が比較的小さいことから、除染装置への負荷が小さくて済む点、さらには、反応後に塩基を投入することで硝酸カリウム等の肥料成分に変化させ、無害化することが可能である点からも好ましい。 In the treatment liquid according to the present invention, at least one component selected from the group consisting of phosphate and sulfate is added to water so as to have a desired concentration, and then an acid component is added so that the pH becomes 4 or less. It is adjusted by. The pH is preferably 1 to 3, more preferably 1.5 to 2.5, and particularly preferably about 2 in terms of the removal rate of cesium. The acid component may be either an organic acid or an inorganic acid. Examples of the organic acid include acetic acid, citric acid, oxalic acid, and the like, and examples of the inorganic acid include hydrochloric acid, sulfuric acid, nitric acid, and the like. From the viewpoint of environmental load, the acid component is preferably an inorganic acid, and more preferably nitric acid from the viewpoint of the removal rate of cesium. Since nitric acid has a relatively small corrosive effect on stainless steel, the load on the decontamination equipment can be reduced. Furthermore, by adding a base after the reaction, it is changed to fertilizer components such as potassium nitrate and rendered harmless. It is also preferable because it is possible.
本発明の除染方法は、汚染土壌を、処理液と接触させ、土壌から放射性セシウムを抽出する工程を含む。汚染土壌と処理液とを接触させる手段は特に限定されないが、典型的には、汚染土壌を処理液中で撹拌・懸濁させる。これにより、汚染土壌から、固定化された放射性セシウムが処理液に抽出される。汚染土壌と処理液の比（固液比（質量基準））は、汚染土壌の量、その放射能濃度等に応じて適宜設定されるが、２：１〜1：１００、好ましくは１：２〜５０、より好ましくは１：５〜２０である。撹拌条件もまた、汚染土壌の量、その放射能濃度等に応じて適宜設定されるが、例えばセシウム除去率の点から、周囲温度〜１００℃の温度、好ましくは５０℃〜１００℃の温度、より好ましくは８０℃〜１００℃の温度で、０．５時間から１０時間、好ましくは１〜５時間、より好ましくは１〜３時間行う。 The decontamination method of the present invention includes a step of bringing contaminated soil into contact with a treatment liquid and extracting radioactive cesium from the soil. The means for bringing the contaminated soil into contact with the treatment liquid is not particularly limited, but typically, the contaminated soil is stirred and suspended in the treatment liquid. Thereby, the immobilized radioactive cesium is extracted from the contaminated soil into the treatment liquid. The ratio of the contaminated soil to the treatment liquid (solid-liquid ratio (mass basis)) is appropriately set according to the amount of contaminated soil, its radioactivity concentration, etc., but 2: 1 to 1: 100, preferably 1: 2. ~ 50, more preferably 1: 5-20. The stirring conditions are also appropriately set according to the amount of contaminated soil, the radioactivity concentration, etc., for example, from the point of cesium removal rate, ambient temperature to 100 ° C, preferably 50 ° C to 100 ° C, More preferably, it is performed at a temperature of 80 ° C. to 100 ° C. for 0.5 hours to 10 hours, preferably 1 to 5 hours, more preferably 1 to 3 hours.
本発明の除染方法は、汚染土壌を、処理液と接触させ、土壌から放射性セシウムを抽出する工程の前に、放射性セシウムで汚染された土壌から粘土分（ここで「粘土分」とは、直径２μｍ未満の微粒子を指す）を除去する工程を含んでもよい。かかる除去工程は特に限定されないが、簡便には、汚染土壌を水中で撹拌・懸濁させ、静置させた後、粘土分を含む上澄みを除去することにより実施される。汚染土壌と水の比（固液比（質量基準））は、汚染土壌の量、その放射能濃度等に応じて適宜設定されるが、例えば１：１〜１００、好ましくは１：２〜５０、より好ましくは１：５〜２０である。撹拌条件もまた、汚染土壌の量、その放射能濃度等に応じて適宜設定されるが、例えば周囲温度〜１００℃の温度、好ましくは周囲温度〜５０℃の温度、より好ましくは周囲温度で、３０秒から１時間、好ましくは１〜２０分、より好ましくは１〜５分行う。なお、既往の研究では、土壌中の粘土分を回収することで放射能濃度を大幅に低減した報告も存在するが、本発明者らの検討では、最大で４５％程度の放射能濃度の低減が見られたが、粘土分を除去する工程単独では、十分な除染効果は得られなかった。 In the decontamination method of the present invention, before the step of bringing contaminated soil into contact with the treatment liquid and extracting radioactive cesium from the soil, the clay content from the soil contaminated with radioactive cesium (herein, “clay content” A step of removing fine particles having a diameter of less than 2 μm) may be included. Such a removal step is not particularly limited, but is simply carried out by stirring and suspending the contaminated soil in water and allowing it to stand, and then removing the supernatant containing clay. The ratio of the contaminated soil to water (solid-liquid ratio (mass basis)) is appropriately set according to the amount of contaminated soil, its radioactivity concentration, etc., for example, 1: 1 to 100, preferably 1: 2 to 50. More preferably, it is 1: 5-20. The stirring conditions are also set as appropriate according to the amount of contaminated soil, the radioactivity concentration, etc., for example, ambient temperature to 100 ° C, preferably ambient temperature to 50 ° C, more preferably ambient temperature, 30 seconds to 1 hour, preferably 1 to 20 minutes, more preferably 1 to 5 minutes. In the past studies, there are reports that the radioactivity concentration has been significantly reduced by collecting clay in the soil, but in the study by the present inventors, the radioactivity concentration has been reduced by about 45% at the maximum. However, a sufficient decontamination effect was not obtained by the process of removing the clay alone.
＜吸着工程＞
本発明の除染方法は、前述の抽出工程に加え、抽出工程後の処理液を、プルシアンブルー類縁体を担持した親水性繊維基材からなるセシウム吸着材と接触させ、放射性セシウムをセシウム吸着材へ吸着させる工程を含んでもよい。本発明に係る「プルシアンブルー類縁体を担持した親水性繊維基材からなるセシウム吸着材」は、繊維の内部にプルシアンブルー類縁体が固定化していることを特徴とするものである。
<Adsorption process>
In the decontamination method of the present invention, in addition to the extraction step described above, the treatment liquid after the extraction step is brought into contact with a cesium adsorbent comprising a hydrophilic fiber substrate carrying a Prussian blue analog, and radioactive cesium is brought into contact with the cesium adsorbent A step of adsorbing to the substrate may be included. The “cesium adsorbent comprising a hydrophilic fiber substrate carrying a Prussian blue analogue” according to the present invention is characterized in that the Prussian blue analogue is immobilized inside the fiber.
本発明に係る、プルシアンブルー類縁体とは、ヘキサシアノ金属酸イオンを構築素子としたシアノ架橋型金属錯体の一種であり、一般式：ＭＡ ｍ［ＭＢ（ＣＮ）６］ｎ・ｈＨ２Ｏで示される化合物であり、この金属イオン（ＭＡ、ＭＢ）がシアノ基で交互に架橋した面心立方構造をしていると解される。ここで、ＭＡは、第一遷移金属である。したがって、本発明に係るプルシアンブルー類縁体は、ヘキサシアノ金属酸の遷移金属塩であると言い換えてもよい。第一遷移金属としては、スカンジウム（Ｓｃ）、チタン（Ｔｉ）、バナジウム（Ｖ）、クロム（Ｃｒ）、マンガン（Ｍｎ）、鉄（Ｆｅ）、コバルト（Ｃｏ）、ニッケル（Ｎｉ）、銅（Ｃｕ）及び亜鉛（Ｚｎ）が挙げられる。好ましくは、鉄（Ｆｅ）、コバルト（Ｃｏ）、ニッケル（Ｎｉ）、銅（Ｃｕ）及び亜鉛（Ｚｎ）、より好ましくは、鉄（Ｆｅ）、特に第二鉄（Ｆｅ（III））が挙げられる。 The Prussian blue analog according to the present invention is a kind of cyano-bridged metal complex having hexacyanometalate ion as a building element, and has a general formula: M A m [M B (CN) 6 ] n · hH 2 O in a compound represented, the metal ions (M a, M B) is understood is a crosslinked face-centered cubic structure alternately with a cyano group. Here, M A is the first transition metal. Therefore, the Prussian blue analog according to the present invention may be rephrased as a transition metal salt of hexacyano metal acid. As the first transition metal, scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu ) And zinc (Zn). Preferably, iron (Fe), cobalt (Co), nickel (Ni), copper (Cu) and zinc (Zn), more preferably iron (Fe), particularly ferric iron (Fe (III)). .
前記一般式において、ＭＢは、八面体６配位構造をとりうる金属種であればよく、好ましくは、クロム（Ｃｒ）、マンガン（Ｍｎ）、鉄（Ｆｅ）、コバルト（Ｃｏ）であり、より好ましくは、鉄（Ｆｅ）、特に第一鉄（Ｆｅ（II））である。なお前記一般式において、ｍ、ｎ及びｈの値は、ＭＡおよびＭＢの酸化数に応じて定まる。 In the general formula, M B may be any metal species capable of forming a octahedral six-coordinate structure, preferably, a chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), More preferred is iron (Fe), especially ferrous iron (Fe (II)). Note in the general formula, m, the values of n and h is determined according to the oxidation number of M A and M B.
本発明に係るプルシアンブルー類縁体（すなわち、ヘキサシアノ金属酸の遷移金属塩）は、ヘキサシアノ金属酸の無機塩と、遷移金属元素を含む無機化合物との反応により得られる生成物であって、前記一般式で表されるものを含むものであればよい。なお、本発明に係るプルシアンブルー類縁体は、そのヘキサシアノ金属酸の遷移金属塩の一部の金属イオンが、原料由来のアルカリ金属イオン等で置換されているものを含んでいてもよい。 The Prussian blue analog according to the present invention (that is, a transition metal salt of hexacyano metal acid) is a product obtained by the reaction of an inorganic salt of hexacyano metal acid and an inorganic compound containing a transition metal element, Anything may be used as long as it includes what is represented by the formula. The Prussian blue analog according to the present invention may include those in which some of the metal ions of the transition metal salt of hexacyano metal acid are substituted with alkali metal ions derived from the raw material.
例えば、本発明に係るプルシアンブルー類縁体の一態様である、ヘキサシアノ鉄（II）酸の遷移金属塩としては、そのスカンジウム（Ｓｃ）塩、チタン（Ｔｉ）塩、バナジウム（Ｖ）塩、クロム（Ｃｒ）塩、マンガン（Ｍｎ）塩、鉄（Ｆｅ）塩、コバルト（Ｃｏ）塩、ニッケル（Ｎｉ）塩、銅（Ｃｕ）塩及び亜鉛（Ｚｎ）塩が挙げられる。好ましくは、ヘキサシアノ鉄（II）酸の鉄（Ｆｅ）塩、コバルト（Ｃｏ）塩、ニッケル（Ｎｉ）塩、銅（Ｃｕ）塩及び亜鉛（Ｚｎ）塩が挙げられ、より好ましくは、鉄（Ｆｅ）塩、特に第二鉄（Ｆｅ（III））塩が挙げられる。なお、本発明に係るヘキサシアノ鉄（II）酸の遷移金属塩は、ヘキサシアノ鉄（II）酸の無機塩と、遷移金属元素を含む無機化合物との反応により得られる生成物であって、前記一般式（但し、ＭＢが、特に第一鉄（Ｆｅ（II））である）で表されるものを含むものであればよいが、その一部の金属イオンが、原料由来のアルカリ金属イオン等で置換されているものを含んでいてもよい。 For example, as a transition metal salt of hexacyanoferrate (II) which is an embodiment of the Prussian blue analog according to the present invention, its scandium (Sc) salt, titanium (Ti) salt, vanadium (V) salt, chromium ( Examples include Cr) salts, manganese (Mn) salts, iron (Fe) salts, cobalt (Co) salts, nickel (Ni) salts, copper (Cu) salts, and zinc (Zn) salts. Preferably, iron (Fe) salt, cobalt (Co) salt, nickel (Ni) salt, copper (Cu) salt and zinc (Zn) salt of hexacyanoferrate (II) acid may be mentioned, and iron (Fe) is more preferable. ) Salts, in particular ferric (Fe (III)) salts. The transition metal salt of hexacyanoferrate (II) acid according to the present invention is a product obtained by the reaction of an inorganic salt of hexacyanoferrate (II) acid and an inorganic compound containing a transition metal element, formula (However, the M B, particularly ferrous (Fe (II)) is a) may be any, including those represented by, but part of the metal ions, alkali metal ions such as derived from the raw material May be substituted with.
本発明に係るプルシアンブルー類縁体の最も好適な例である、ヘキサシアノ鉄（II）酸の第二鉄（Ｆｅ（III））塩は、プルシアンブルー又は紺青等とも称され、古くから顔料として用いられている。その理想的な化学組成はＦｅ（III）４［Ｆｅ（II）（ＣＮ）６］３・ｘＨ２Ｏ（ｘ＝１４〜１６）（すなわち「ヘキサシアノ鉄（II）酸鉄（III）水和物」）であるが、その製法等に応じて一部の鉄イオンが置換されていることもある。本発明に係るプルシアンブルーは、ヘキサシアノ鉄（II）酸の無機塩と、第二鉄（III）を含む無機化合物との反応により得られるものであって、前記化学組成を有するものを含むものであればよいが、一部の鉄イオンが、原料由来のアルカリ金属イオン等で置換されているものを含んでいてもよい。 A ferric (Fe (III)) salt of hexacyanoferrate (II), which is the most preferred example of the Prussian blue analog according to the present invention, is also called Prussian blue or bitumen and has been used as a pigment for a long time. ing. Its ideal chemical composition is Fe (III) 4 [Fe (II) (CN) 6 ] 3 × H 2 O (x = 14-16) (ie, “hexacyanoferrate (II) iron (III) hydrate” )), But some iron ions may be substituted depending on the production method. Prussian blue according to the present invention is obtained by a reaction between an inorganic salt of hexacyanoferrate (II) and an inorganic compound containing ferric iron (III), and includes those having the above chemical composition. What is necessary is that some iron ions may be substituted with raw material-derived alkali metal ions or the like.
ヘキサシアノ金属酸の無機塩は、水溶性であって、かつ遷移金属元素を含む無機化合物との反応により、本発明に係るプルシアンブルー類縁体（すなわち、ヘキサシアノ金属酸の遷移金属塩）を形成しうるものであれば特に限定はない。例としては、ヘキサシアノ金属酸のアルカリ金属塩（ナトリウム塩、カリウム塩等）またはその水和物が挙げられる。具体的には、ヘキサシアノクロム（III）酸、ヘキサシアノマンガン（II）酸、ヘキサシアノ鉄（II）酸若しくはヘキサシアノコバルト（III）酸のアルカリ金属塩（ナトリウム塩、カリウム塩等）、又はそれらの水和物が挙げられる。 The inorganic salt of hexacyano metal acid is water-soluble and can form the Prussian blue analog according to the present invention (that is, a transition metal salt of hexacyano metal acid) by reaction with an inorganic compound containing a transition metal element. If it is a thing, there will be no limitation in particular. Examples include alkali metal salts (sodium salt, potassium salt, etc.) of hexacyano metal acid or hydrates thereof. Specifically, hexacyanochromium (III) acid, hexacyanomanganese (II) acid, hexacyanoiron (II) acid or hexacyanocobalt (III) acid alkali metal salt (sodium salt, potassium salt, etc.), or hydration thereof Things.
例えば、ヘキサシアノ金属酸が、ヘキサシアノ鉄（II）酸である場合、ヘキサシアノ鉄（II）酸の無機塩は、水溶性であって、かつ遷移金属元素を含む無機化合物との反応によりヘキサシアノ鉄（II）酸の遷移金属塩を形成しうるものであれば特に限定はない。具体例としては、ヘキサシアノ鉄（II）酸カリウム、ヘキサシアノ鉄（II）酸ナトリウム又はそれらの水和物が挙げられる。ヘキサシアノ鉄（II）酸カリウム又はその水和物の使用が好ましい。 For example, when the hexacyanometallic acid is hexacyanoiron (II) acid, the inorganic salt of hexacyanoiron (II) acid is water-soluble and reacts with an inorganic compound containing a transition metal element to form hexacyanoiron (II There is no particular limitation as long as it can form a transition metal salt of an acid. Specific examples include potassium hexacyanoferrate (II), sodium hexacyanoferrate (II) or hydrates thereof. The use of potassium hexacyanoferrate (II) or a hydrate thereof is preferred.
遷移金属元素を含む無機化合物は、水溶性であって、かつヘキサシアノ金属酸の無機塩との反応により、本発明のプルシアンブルー類縁体（すなわち、ヘキサシアノ金属酸の遷移金属塩）を形成しうるものであれば特に限定はない。そのような遷移金属元素を含む無機化合物としては、前記第一遷移金属のハロゲン化物、硝酸塩、硫酸塩、過塩素酸塩又はそれらの水和物等が挙げられる。例えば、塩化第二鉄（III）、塩化コバルト（II）、塩化ニッケル（II）等のハロゲン化物；硝酸第二鉄（III）、硝酸コバルト（II）、硝酸ニッケル（II）等の硝酸塩；硫酸第二鉄（III）、硫酸コバルト（II）等の硫酸塩；過塩素酸第二鉄（III）等の過塩素酸塩；又はそれらの水和物が挙げられる。 An inorganic compound containing a transition metal element is water-soluble and can form the Prussian blue analog of the present invention (that is, a transition metal salt of hexacyanometal acid) by reaction with an inorganic salt of hexacyanometal acid. If there is no particular limitation. Examples of the inorganic compound containing such a transition metal element include halides, nitrates, sulfates, perchlorates or hydrates of the first transition metal. For example, halides such as ferric chloride (III), cobalt chloride (II), nickel chloride (II); nitrates such as ferric nitrate (III), cobalt nitrate (II), nickel nitrate (II); sulfuric acid Examples thereof include sulfates such as ferric (III) and cobalt (II) sulfate; perchlorates such as ferric (III) perchlorate; and hydrates thereof.
例えば、第二鉄（III）を含む無機化合物は、水溶性であって、かつヘキサシアノ鉄（II）酸の無機塩との反応によりプルシアンブルーを形成しうるものであれば特に限定はない。例えば、塩化第二鉄（III）、硝酸第二鉄（III）、硫酸第二鉄（III）、過塩素酸第二鉄（III）又はそれらの水和物が挙げられる。 For example, the inorganic compound containing ferric iron (III) is not particularly limited as long as it is water-soluble and can form Prussian blue by reaction with an inorganic salt of hexacyanoferrate (II) acid. For example, ferric chloride (III), ferric nitrate (III), ferric sulfate (III), ferric perchlorate (III) or a hydrate thereof may be mentioned.
本発明に係るセシウム吸着材の基材としては、親水性繊維基材が使用される。本発明に係る親水性繊維は、吸水性繊維と言い換えてもよい。親水性繊維は、一般に水分子を取り込みやすい繊維の総称であり、例としては、羊毛、綿、絹、麻、パルプなどの天然繊維、レーヨン、ポリノジック、キュプラ（ベンベルグ（登録商標））、リヨセル（テンセル（登録商標））等のセルロース系再生繊維が挙げられる。またアセテート、トリアセテートなどの半合成繊維、あるいはポリアミド系、ポリビニルアルコール系、ポリ塩化ビニリデン系、ポリ塩化ビニル系、ポリエステル系、ポリアクリロニトリル系、ポリオレフィン系またはポリウレタン系繊維等の合成繊維を公知の方法で改質し、親水性を付与したものであってもよい。価格や入手の容易さから、親水性繊維としては天然繊維又はセルロース系再生繊維、特に綿、レーヨン又はキュプラが好ましい。 As the base material for the cesium adsorbent according to the present invention, a hydrophilic fiber base material is used. The hydrophilic fiber according to the present invention may be rephrased as a water-absorbing fiber. Hydrophilic fibers are a general term for fibers that generally easily absorb water molecules. Examples of such fibers include natural fibers such as wool, cotton, silk, hemp, and pulp, rayon, polynosic, cupra (Bemberg (registered trademark)), lyocell ( Cellulose regenerated fibers such as Tencel (registered trademark). In addition, semi-synthetic fibers such as acetate and triacetate, or synthetic fibers such as polyamide, polyvinyl alcohol, polyvinylidene chloride, polyvinyl chloride, polyester, polyacrylonitrile, polyolefin or polyurethane fibers by a known method. It may be modified and imparted with hydrophilicity. From the viewpoint of price and availability, natural fibers or cellulosic regenerated fibers, particularly cotton, rayon, or cupra are preferred as hydrophilic fibers.
また親水性繊維基材は、上述のような親水性繊維よりなる織物、編物若しくは不織布製品または紙製品であってよい。その形状は、目的とする用途、すなわち除染の対象に応じて適宜選択し、加工すればよい。例えば、水の除染を目的とする場合には、ペレット状、フィルタ状、シート状等であってよく、土壌の除染を目的とする場合は、広範囲をカバーすることができるシート状等であってよい。そのような基材の加工は、基材へのプルシアンブルー類縁体の担持前に行うことができるが、以下に述べるように、本発明のセシウム吸着材は、プルシアンブルー類縁体が繊維の内部および表面に安定的に固定化しているので、担持後に行うこともできる。 The hydrophilic fiber substrate may be a woven fabric, a knitted fabric, a nonwoven fabric product or a paper product made of the hydrophilic fiber as described above. The shape may be appropriately selected and processed according to the intended use, that is, the object of decontamination. For example, in the case of decontamination of water, it may be in the form of pellets, filters, sheets, etc. In the case of decontamination of soil, in the form of sheets that can cover a wide range. It may be. Such a base material can be processed before the Prussian blue analog is supported on the base material. However, as described below, the cesium adsorbent of the present invention has a Prussian blue analog in the fiber and Since it is stably immobilized on the surface, it can also be carried out after loading.
本発明に係るセシウム吸着材は、プルシアンブルー類縁体、特に好ましくはプルシアンブルーを担持した親水性繊維基材からなるものであって、繊維の表面のみならず内部にプルシアンブルー類縁体が固定していることを特徴とするものである。特に、プルシアンブルーのような「顔料」は、水や有機溶媒などの媒質に不溶で、基質に対して染着性がない。したがって、顔料により繊維基材を染色（捺染）する場合、通常、バインダー樹脂などで後処理し、顔料を繊維の表面に付着した形で固定化することを要する。一方、本発明のセシウム吸着材では、プルシアンブルー類縁体は、ヘキサシアノ金属酸の無機塩と遷移金属元素を含む無機化合物との反応によりin situで形成され、繊維の表面および内部に微粒子として存在するため、バインダー樹脂などによらず安定的に繊維に固定している。 The cesium adsorbent according to the present invention is composed of a Prussian blue analogue, particularly preferably a hydrophilic fiber substrate carrying Prussian blue, and the Prussian blue analogue is fixed not only on the surface of the fiber but also inside. It is characterized by being. In particular, a “pigment” such as Prussian blue is insoluble in a medium such as water or an organic solvent, and has no dyeing property to a substrate. Therefore, when a fiber substrate is dyed (printed) with a pigment, it is usually necessary to post-treat with a binder resin or the like and fix the pigment attached to the fiber surface. On the other hand, in the cesium adsorbent of the present invention, the Prussian blue analog is formed in situ by the reaction between an inorganic salt of hexacyanometal acid and an inorganic compound containing a transition metal element, and exists as fine particles on the surface and inside of the fiber. Therefore, it is stably fixed to the fiber regardless of the binder resin.
本発明に係るセシウム吸着材は、国際公開第２０１３／０２７６５２号パンフレットに記載の方法に従い製造することができる。典型的には、（ａ）親水性繊維よりなる基材をヘキサシアノ金属酸の無機塩の水溶液で処理する工程；及び（ｂ）工程（ａ）で処理した基材を、遷移金属元素を含む無機化合物の水溶液で処理する工程を含む製造方法により作製される。また、本発明に係るセシウム吸着材は、例えば小津産業(株)から放射性セシウム除染布（商品名：五大力ＰＢ；プルシアンブルーを担持したセルロース系長繊維不織布）として入手することができる。 The cesium adsorbent according to the present invention can be produced according to the method described in International Publication No. 2013/027652. Typically, (a) a step of treating a substrate composed of hydrophilic fibers with an aqueous solution of an inorganic salt of hexacyanometal acid; and (b) an inorganic material containing a transition metal element, the substrate treated in step (a). It is produced by a production method including a step of treating with an aqueous solution of a compound. The cesium adsorbent according to the present invention can be obtained, for example, from Ozu Sangyo Co., Ltd. as a radioactive cesium decontamination cloth (trade name: Five Great Strength PB; a cellulose-based long fiber nonwoven fabric carrying Prussian blue).
抽出工程後の処理液とセシウム吸着材とを接触させる手段は特に限定されないが、例えば、抽出工程後の処理液中に、ペレット状又はシート状のセシウム吸着材を浸漬させる。これにより、処理液中の放射性セシウムが、セシウム吸着材に吸着される。浸漬条件は、処理液の量、その放射能濃度等に応じて適宜設定されるが、例えば周囲温度〜１００℃の温度、好ましくは周囲温度〜５０℃の温度、より好ましくは周囲温度で、０．５時間から１０時間、好ましくは１〜５時間、より好ましくは１〜３時間行う。 The means for bringing the treatment liquid after the extraction step into contact with the cesium adsorbent is not particularly limited. For example, the pellet-like or sheet-like cesium adsorbent is immersed in the treatment liquid after the extraction step. Thereby, the radioactive cesium in a process liquid is adsorb | sucked by a cesium adsorption material. The immersion conditions are appropriately set according to the amount of the treatment liquid, the radioactivity concentration, etc., for example, ambient temperature to 100 ° C., preferably ambient temperature to 50 ° C., more preferably ambient temperature, 0 .5 hours to 10 hours, preferably 1 to 5 hours, more preferably 1 to 3 hours.
セシウム吸着剤による吸着工程に付した後の処理液は、回収して、土壌から放射性セシウムを抽出する工程に再利用することができる。すなわち、回収した処理液を、汚染土壌の２回目以降の抽出工程で用いてもよく、また新たな汚染土壌の１回目の抽出工程で用いてもよい。再利用の際、リン酸塩及び硫酸塩の添加や、ｐＨの調整を、必要に応じて適宜行うことができる。抽出のための処理液を回収、再利用することにより、最終的に生じる放射性廃棄物の総量を減容することができる。 The treatment liquid after being subjected to the adsorption step with the cesium adsorbent can be collected and reused for the step of extracting radioactive cesium from the soil. That is, the collected treatment liquid may be used in the second and subsequent extraction steps of contaminated soil, or may be used in the first extraction step of new contaminated soil. At the time of reuse, addition of phosphate and sulfate and adjustment of pH can be appropriately performed as necessary. By collecting and reusing the processing solution for extraction, the total amount of radioactive waste that is finally generated can be reduced.
＜脱着工程＞
また、本発明の除染方法は、吸着工程で使用し、放射性セシウムが吸着したセシウム吸着剤から放射性セシウムを脱着及び濃縮する工程を含んでもよい。脱着及び濃縮工程は、酸処理により吸着剤から放射性セシウムを脱着することにより、あるいはアルカリ処理によりセシウム吸着剤から担持されたプルシアンブルー類縁体自体と共に放射性セシウムを脱離することにより実施することができる。これらは、放射性セシウムが吸着したセシウム吸着剤を、それぞれ酸又はアルカリ水溶液に浸漬することにより、実施することができる。脱着液（酸又はアルカリ水溶液）を繰り返し使用することにより、最終的に生じる放射性廃棄物の総量を減容することができる。一方、放射性セシウムが脱着した親水性繊維基材は、非放射性廃棄物として焼却処理することが可能である。この点からも、最終的に生じる放射性廃棄物の総量を大幅に減容することができる。
<Desorption process>
Moreover, the decontamination method of the present invention may include a step of desorbing and concentrating radioactive cesium from a cesium adsorbent adsorbed by radioactive cesium used in the adsorption step. The desorption and concentration steps can be carried out by desorbing radioactive cesium from the adsorbent by acid treatment or by desorbing radioactive cesium together with Prussian blue analog itself carried from the cesium adsorbent by alkali treatment. . These can be carried out by immersing a cesium adsorbent adsorbed with radioactive cesium in an acid or alkaline aqueous solution, respectively. By repeatedly using the desorption liquid (acid or alkaline aqueous solution), the total amount of the radioactive waste finally generated can be reduced. On the other hand, the hydrophilic fiber substrate from which radioactive cesium has been desorbed can be incinerated as non-radioactive waste. Also from this point, the total amount of the radioactive waste finally generated can be greatly reduced.
脱着工程で使用される酸又はアルカリは、特に限定されないが、好ましくは無機酸又は無機アルカリであり、無機酸の例としては、塩酸、硫酸、リン酸等が挙げられ、無機アルカリの例としては、アルカリ金属又はアルカリ土類金属の水酸化物、特には水酸化ナトリウム、水酸化カリウム等が挙げられる。脱着及び濃縮条件は、セシウム吸着剤の容量等に応じて適宜設定されるが、例えば周囲温度〜１００℃の温度、好ましくは周囲温度〜５０℃の温度、より好ましくは周囲温度で、０．５時間から１０時間、好ましくは１〜５時間、より好ましくは１〜３時間行う。 The acid or alkali used in the desorption step is not particularly limited, but is preferably an inorganic acid or an inorganic alkali. Examples of the inorganic acid include hydrochloric acid, sulfuric acid, phosphoric acid, and the like. Examples of the inorganic alkali include , Alkali metal or alkaline earth metal hydroxides, particularly sodium hydroxide and potassium hydroxide. The desorption and concentration conditions are appropriately set according to the capacity of the cesium adsorbent, etc., for example, ambient temperature to 100 ° C., preferably ambient temperature to 50 ° C., more preferably ambient temperature, 0.5 The time is 10 hours, preferably 1 to 5 hours, more preferably 1 to 3 hours.
［放射性セシウムで汚染された土壌からセシウムを除去する除染装置］
本発明はまた、放射性セシウムで汚染された土壌からセシウムを除去する除染装置に関する。本発明の除染装置は、
− 放射性セシウムで汚染された土壌及び処理液を受け入れる中空の容器；
− 前記容器の外壁若しくは前記容器内に配設され、前記容器内に受け入れた前記土壌及び処理液を加熱するための加熱手段；及び
− 前記容器内に受け入れた前記土壌及び処理液を撹拌するための撹拌手段
を備える撹拌洗浄槽を含むものであって、且つ前記処理液が、リン酸塩及び硫酸塩からなる群より選択される少なくとも一種の成分を含み、且つｐＨが４以下であるものである。
[Decontamination equipment for removing cesium from soil contaminated with radioactive cesium]
The present invention also relates to a decontamination apparatus that removes cesium from soil contaminated with radioactive cesium. The decontamination apparatus of the present invention is
-A hollow container for receiving radioactive cesium contaminated soil and treatment liquid;
-Heating means disposed on the outer wall of the container or in the container for heating the soil and the treatment liquid received in the container; and-for stirring the soil and the treatment liquid received in the container And a treatment tank containing at least one component selected from the group consisting of phosphate and sulfate, and having a pH of 4 or less. is there.
本発明の除染装置は、前記撹拌洗浄槽に加えて、吸着槽を備えることもできる。すなわち、本発明の除染装置は、
− 前記撹拌洗浄槽から排出される放射性セシウムを含む処理液及びプルシアンブルー類縁体を担持した親水性繊維基材からなるセシウム吸着材を受け入れる中空の容器
を備える吸着槽を含んでもよい。
The decontamination apparatus of the present invention can also include an adsorption tank in addition to the stirring and washing tank. That is, the decontamination apparatus of the present invention is
-You may include an adsorption tank provided with the hollow container which receives the processing liquid containing the radioactive cesium discharged | emitted from the said stirring washing tank, and the cesium adsorption material which consists of a hydrophilic fiber base material which carry | supported the Prussian blue analog.
本発明の除染装置において、好ましくは、前記セシウム吸着材はプルシアンブルーを担持したセルロース系長繊維不織布である。 In the decontamination apparatus of the present invention, preferably, the cesium adsorbent is a cellulose-based long fiber nonwoven fabric supporting Prussian blue.
図１は、本発明の除染装置の１つの構成例を示した概略図である。以下、図１を参照しながら、本発明の除染装置を用いた、本発明の除染方法について概説する。この実施形態では、除染装置は、撹拌洗浄槽及び吸着槽から構成されている。前述の本発明の汚染土壌の除染方法において、抽出工程は、撹拌洗浄槽で実施され、吸着工程は、吸着槽で実施される。 FIG. 1 is a schematic view showing one configuration example of the decontamination apparatus of the present invention. Hereinafter, the decontamination method of the present invention using the decontamination apparatus of the present invention will be outlined with reference to FIG. In this embodiment, the decontamination apparatus is comprised from the stirring washing tank and the adsorption tank. In the above-described decontamination method for contaminated soil of the present invention, the extraction step is carried out in a stirring washing tank, and the adsorption step is carried out in an adsorption tank.
例えば抽出工程では、撹拌洗浄槽の容器１で、水と、リン酸塩及び硫酸塩からなる群より選択される少なくとも一種の成分とにより処理液を調製し、そこに放射性セシウムで汚染された土壌を加え、撹拌手段２により両者を接触させる。ここで、放射性セシウムで汚染された土壌は、予め粘土分を除去したものであってもよい。続いて、そこに酸を加え、ｐＨ４以下に調整する。加熱手段３により所定の温度に加熱し、所定の時間、撹拌手段２により両者を接触させ、土壌から放射性セシウムを抽出する。冷却手段４により周囲温度まで冷却後、撹拌手段２を停止し、土壌が十分に沈殿するまで静置し、次いで処理液循環ライン５により上澄み部（抽出液）を吸着槽の容器６に移す。 For example, in the extraction process, in the container 1 of the stirred washing tank, a treatment liquid is prepared with water and at least one component selected from the group consisting of phosphate and sulfate, and soil contaminated with radioactive cesium is prepared there. And both are brought into contact with each other by the stirring means 2. Here, the soil contaminated with radioactive cesium may be obtained by removing clay in advance. Then, an acid is added there and it adjusts to pH 4 or less. The mixture is heated to a predetermined temperature by the heating means 3, and both are brought into contact by the stirring means 2 for a predetermined time to extract radioactive cesium from the soil. After cooling to the ambient temperature by the cooling means 4, the stirring means 2 is stopped and allowed to stand until the soil is sufficiently settled, and then the supernatant (extract) is transferred to the container 6 of the adsorption tank by the treatment liquid circulation line 5.
吸着工程では、吸着槽の容器６に移された放射性セシウムを含む処理液（抽出液）中に、プルシアンブルー類縁体を担持した親水性繊維基材からなるセシウム吸着材７を導入／回収手段８を用いて導入し、所定の時間、両者を接触させ、放射性セシウムをセシウム吸着材７へ吸着させる。吸着工程に付した処理液は、処理液循環ライン５により回収され、吸着槽の容器６から撹拌洗浄槽の容器１に移され、汚染土壌の２回目以降の抽出工程に、あるいは新たな汚染土壌の１回目の抽出工程に再利用することができる。 In the adsorption process, a cesium adsorbent 7 made of a hydrophilic fiber substrate carrying a Prussian blue analog is introduced into / collected in the treatment liquid (extract) containing radioactive cesium transferred to the container 6 of the adsorption tank. The two are brought into contact with each other for a predetermined time to adsorb radioactive cesium to the cesium adsorbent 7. The treatment liquid subjected to the adsorption process is recovered by the treatment liquid circulation line 5 and transferred from the adsorption tank container 6 to the stirring washing tank container 1 for the second and subsequent extraction processes of contaminated soil or newly contaminated soil. Can be reused in the first extraction step.
以下、本発明の具体的態様を実施例として示すが、これらは例示であって、本発明を限定することを意図するものではない。 Specific embodiments of the present invention will be described below as examples, but these are exemplifications and are not intended to limit the present invention.
［放射能濃度測定］
実施例における放射能濃度の測定は、γ線測定器であるＮａＩ（Ｔｌ）検出器（ＡＴＯＭＴＥＸ，ＲＫＧ−ＡＴ１３２０Ａ）を用い、ソフトウェア（ＡＴＯＭＴＥＸ, ＡＴＭＡ）で解析を行った。
[Radioactivity concentration measurement]
In the Examples, the radioactivity concentration was measured using a NaI (Tl) detector (ATOMTEX, RKG-AT1320A), which is a γ-ray measuring device, and analyzed with software (ATOMTEX, ATMA).
［土壌試料］
実施例における土壌試料は、地権者の了承を得て福島県相馬郡飯舘村の水田にて、深さ５ｃｍまでを許容深度として表層の土壌を採取し、環境試料採取法（文部科学省，１９８３）に基づき１０５℃に設定した乾燥器内で乾燥させたものである。
[Soil sample]
The soil samples in the examples were collected from the soil in the surface of the paddy field in Iitate-mura, Soma-gun, Fukushima Prefecture with the consent of the landowner. ) And dried in a dryer set at 105 ° C.
実施例１−１：抽出工程
［実験手順］
（i）土壌試料６０g（乾燥時の放射能濃度：２７,４４０Ｂｑ／ｋｇ）に水１０００ｍＬを加え、周囲温度で１分撹拌し、次いで２分静置した後、上澄み液を回収し、上澄み液と共に土壌中の粘土分（微粒子）を除去した。
（ii）撹拌洗浄槽で、リン酸１カリウムの１Ｍ水溶液６００ｍＬを調製し、（i）の粘度分を除去した土壌を加えて撹拌した（固液比１：１０）。
（iii）次いで（ii）に硝酸（１３Ｎ）を滴下してｐＨ２ に調整した。
（iv）約１００℃に加熱し、撹拌しながら２時間保温した。
（v）土壌が十分に沈殿するまで静置して、上澄み部（抽出液）を回収した。
（vi）沈殿部（処理土壌）を洗浄後、一部を採取・乾燥して放射能濃度を測定した。
［実験結果］
得られた土壌の放射能濃度は４,４７０Ｂｑ／ｋｇであり、除染率は８４％であった。なお、セシウムの除染率は以下の式で定義し、その結果を図２に示す。
Example 1-1: Extraction Step [Experimental Procedure]
(I) Water (1000 mL) was added to a soil sample (60 g, radioactivity concentration at drying: 27,440 Bq / kg), stirred at ambient temperature for 1 minute, and then allowed to stand for 2 minutes. Then, the supernatant was recovered and the supernatant was collected. At the same time, clay (fine particles) in the soil was removed.
(Ii) In a stirring washing tank, 600 mL of a 1M aqueous solution of monopotassium phosphate was prepared, and the soil from which the viscosity of (i) was removed was added and stirred (solid-liquid ratio 1:10).
(Iii) Nitric acid (13N) was then added dropwise to (ii) to adjust to pH2.
(Iv) Heated to about 100 ° C. and kept warm for 2 hours with stirring.
(V) The mixture was allowed to stand until the soil sufficiently settled, and the supernatant (extract) was collected.
(Vi) After washing the sediment (treated soil), a part was collected and dried, and the radioactivity concentration was measured.
[Experimental result]
The radioactivity concentration of the obtained soil was 4,470 Bq / kg, and the decontamination rate was 84%. The decontamination rate of cesium is defined by the following formula, and the result is shown in FIG.
実施例１−２：抽出工程
手順（ii）のリン酸１カリウムの１Ｍ水溶液を、硫酸アンモニウム１Ｍ水溶液に換えた以外は、実施例１−１と同様の実験手順を実施した。得られた土壌の放射能濃度は１３,９５０Ｂｑ／ｋｇであり、除染率は４９％であった。結果を図２に示す。
Example 1-2: The same experimental procedure as in Example 1-1 was carried out except that the 1M aqueous solution of monopotassium phosphate in the extraction step procedure (ii) was replaced with a 1M aqueous solution of ammonium sulfate. The radioactivity concentration of the obtained soil was 13,950 Bq / kg, and the decontamination rate was 49%. The results are shown in FIG.
実施例１−３：抽出工程
手順（ii）のリン酸１カリウムの１Ｍ水溶液を、硫酸アンモニウム１Ｍ及びリン酸１カリウム１Ｍの水溶液に換えた以外は、実施例１−１と同様の実験手順を実施した。得られた土壌の放射能濃度は６,７６０Ｂｑ／ｋｇであり、除染率は７５％であった。結果を図２、３に示す。
Example 1-3: The same experimental procedure as in Example 1-1 was performed, except that the 1M aqueous solution of monopotassium phosphate in the extraction step procedure (ii) was replaced with an aqueous solution of 1M ammonium sulfate and 1M potassium phosphate. did. The radioactivity concentration of the obtained soil was 6,760 Bq / kg, and the decontamination rate was 75%. The results are shown in FIGS.
実施例１−４：抽出工程
手順（iii）の硝酸（１３Ｎ）を、塩酸（１２Ｎ）に換えた以外は、実施例１−３と同様の実験手順を実施した。得られた土壌の放射能濃度は１０,１５０Ｂｑ／ｋｇであり、除染率は６３％であった。結果を図３に示す。
Example 1-4: The same experimental procedure as in Example 1-3 was carried out except that nitric acid (13N) in the extraction step procedure (iii) was replaced with hydrochloric acid (12N). The radioactivity concentration of the obtained soil was 10,150 Bq / kg, and the decontamination rate was 63%. The results are shown in FIG.
実施例１−５：抽出工程
手順（iii）の硝酸（１３Ｎ）を、硫酸（３６Ｎ）に換えた以外は、実施例１−３と同様の実験手順を実施した。得られた土壌の放射能濃度は１１,５２０Ｂｑ／ｋｇであり、除染率は５８％であった。結果を図３に示す。
Example 1-5: The same experimental procedure as in Example 1-3 was carried out except that nitric acid (13N) in the extraction step procedure (iii) was replaced with sulfuric acid (36N). The radioactivity concentration of the obtained soil was 11,520 Bq / kg, and the decontamination rate was 58%. The results are shown in FIG.
比較例１：抽出工程
手順（iii）を除いた以外は、実施例１−３と同様の実験手順を実施した。得られた土壌の放射能濃度は２２,２３０Ｂｑ／ｋｇであり、除染率は１９％であった。結果を図３に示す。
Comparative Example 1: The same experimental procedure as in Example 1-3 was performed except that the extraction step procedure (iii) was omitted. The radioactivity concentration of the obtained soil was 22,230 Bq / kg, and the decontamination rate was 19%. The results are shown in FIG.
実施例２：吸着工程
（１）土壌からのセシウム抽出液の作成
土壌試料５４０ｇ（乾燥時の放射能濃度：５７，６００Ｂｑ／ｋｇ）にリン酸二水素カリウム１Ｍの水溶液５．４ｋｇを加え、さらにこれに硝酸を加えてｐＨ２ になるよう調整した。この後、１００℃付近で２時間攪拌し、冷却した。その後、一晩静置し土壌が完全に沈降させることによって上澄み５．３Ｌ（セシウム１３７の濃度：４７１Ｂｑ／ｋｇ、セシウム１３４ の濃度：２６２Ｂｑ／ｋｇ）を得てこれを吸着実験に供した。
Example 2: Adsorption process
(1) Preparation of cesium extract from soil Add 5.4 kg of 1M aqueous solution of potassium dihydrogen phosphate to 540 g of soil sample (radioactivity concentration at drying: 57,600 Bq / kg), and add nitric acid to this. The pH was adjusted to 2. Thereafter, the mixture was stirred at around 100 ° C. for 2 hours and cooled. Thereafter, the mixture was allowed to stand overnight, and the soil was completely settled to obtain 5.3 L of supernatant (concentration of cesium 137: 471 Bq / kg, concentration of cesium 134: 262 Bq / kg), which was subjected to an adsorption experiment.
（２）吸着実験
抽出液５．３ｋｇ（セシウム１３７の濃度：４７１Ｂｑ／ｋｇ、セシウム１３４ の濃度：２６２Ｂｑ／ｋｇ）に１７７．６ｇ のプルシアンブルーが担持された繊維状のセシウム吸着剤（小津産業(株)製、五大力ＰＢ）を１５時間接触させることによって放射性セシウムを吸着させた後、これを５０℃のオーブンで乾燥させた。吸着実験終了後の抽出液とプルシアンブルー担持繊維の放射線量を、ＡＴ１３２０Ａ（ＡＴＯＭＴＥＸ 社）で測定し、抽出液からの放射性セシウムの除去率の評価を行った。なお、セシウムの除去率は以下の式で定義した。
(2) Adsorption experiment The fibrous cesium adsorbent (Ozu Sangyo Co., Ltd.) with 177.6 g of Prussian blue supported on 5.3 kg (concentration of cesium 137: 471 Bq / kg, concentration of cesium 134: 262 Bq / kg) After making radioactive cesium adsorb | suck by making it contact for 15 hours, the product made from Co., Ltd., it was dried in 50 degreeC oven. The radiation dose of the extract and Prussian blue-supported fiber after the adsorption experiment was measured with AT1320A (ATOMTEX), and the removal rate of radioactive cesium from the extract was evaluated. The cesium removal rate was defined by the following equation.
表１に吸着実験前の測定値、表２に吸着実験後の測定値を示す。抽出液中の放射性セシウム量を９７％以上除去できたことがわかる。吸着後の抽出液に残留した放射性セシウムの総量は１９Ｂｑ／ｋｇ であり、飲料水の基準値である１０Ｂｑ／Ｌ（≒ｋｇ）以下までにはならなかったが、近い値にはなったことから、精密にセシウム吸着剤の量を制御すれば、上記基準値はクリアできるものと考えられる。 Table 1 shows the measured values before the adsorption experiment, and Table 2 shows the measured values after the adsorption experiment. It can be seen that 97% or more of the radioactive cesium content in the extract was removed. The total amount of radioactive cesium remaining in the extract after adsorption was 19 Bq / kg, and it did not fall below 10 Bq / L (≈kg), which is the standard value for drinking water. If the amount of cesium adsorbent is precisely controlled, it is considered that the reference value can be cleared.
実施例３：脱着工程
実施例２で得られた、放射性セシウムを吸着させたプルシアンブルーが担持された繊維状のセシウム吸着剤のうちの４６．２ｇ（乾重量）を１．１Ｎ の水酸化ナトリウム水溶液（脱着液）に２０分接触させて放射性セシウムを脱着させた。更に脱着液の繰り返し利用の可能性を検討するため、上記で一度使用した脱着液に、別の放射性セシウムを吸着させたプルシアンブルーが担持された繊維状のセシウム吸着材４３．１ｇ（乾重量）を２０分接触させて放射性セシウムを脱着させた。１回目及び２回目の脱着後の脱着液とセシウム吸着材の放射線量を、ＡＴ１３２０Ａ（ＡＴＯＭＴＥＸ 社）で測定し、吸着材からの放射性セシウムの脱着率と、脱着後に吸着材に残留する放射性セシウム量を評価した。なお、脱着率は以下のように定義した。
Example 3: Desorption process 46.2 g (dry weight) of the fibrous cesium adsorbent carrying Prussian blue adsorbed with radioactive cesium obtained in Example 2 was added to 1.1N sodium hydroxide. Radiocesium was desorbed by contact with an aqueous solution (desorption solution) for 20 minutes. Furthermore, in order to examine the possibility of repeated use of the desorption liquid, 43.1 g (dry weight) of a fibrous cesium adsorbent carrying Prussian blue adsorbed with another radioactive cesium in the desorption liquid once used above. Was contacted for 20 minutes to desorb radioactive cesium. The radiation amount of the desorption liquid and the cesium adsorbent after the first and second desorption is measured with AT1320A (ATOMTEX), the desorption rate of radioactive cesium from the adsorbent, and the amount of radioactive cesium remaining on the adsorbent after desorption Evaluated. The desorption rate was defined as follows.
表３に、１回目及び２回目脱着後の脱着液中の放射線量を示す。また表４に脱着実験前の測定値、表５に２回目脱着実験後の測定値を示す。繰り返し脱着を行うことによって脱着液中の放射性セシウムを濃縮できることがわかった。なお、２回目脱着実験後の脱着液を滴定することにより、使用された水酸化ナトリウム量を算出したところ、９０g−ＮａＯＨ／ｋｇ−セシウム吸着材であることがわかった。また、セシウム吸着材からのプルシアンブルーの脱着率として９７％を得ることができた。 Table 3 shows the radiation dose in the desorption liquid after the first and second desorption. Table 4 shows measured values before the desorption experiment, and Table 5 shows measured values after the second desorption experiment. It was found that radioactive cesium in the desorption solution can be concentrated by repeated desorption. When the amount of sodium hydroxide used was calculated by titrating the desorption solution after the second desorption experiment, it was found to be 90 g-NaOH / kg-cesium adsorbent. Moreover, 97% was obtained as the desorption rate of Prussian blue from the cesium adsorbent.
実施例４：実用化スケールでの除染試験
本発明の除染方法の実用化に向けたスケールに設計されたプロトタイプの除染装置（図１）を用い、以下の手順に従い、除染試験を実施した。
［実験手順］
（i）土壌試料５６ｋｇ（dry：放射能濃度：４３，０００Ｂｑ／ｋｇ）に水１００Ｌを加え、周囲温度で２分撹拌し、次いで５分静置した後、上澄み液を回収し、上澄み液と共に土壌中の粘土分（微粒子）を除去した。
（ii）撹拌洗浄槽で、リン酸１カリウムの１Ｍ水溶液５６０Ｌを調製し、（i）の粘度分を除去した土壌を加えて撹拌した（固液比１：１０）。
（iii）次いで（ii）に硝酸（１３Ｎ）を滴下してｐＨ２ に調整した。
（iv）約１００℃に加熱し、撹拌しながら２時間保温した。
（v）土壌が十分に沈殿するまで一晩静置して、上澄み部（抽出液）を吸着槽に移動させると共に、一部を採取して放射能濃度を測定した。
（vi）沈殿部（処理土壌）を洗浄後、一部を採取・乾燥して放射能濃度を測定した。
（vii）次いで（v）で得られた抽出液にプルシアンブルーが担持された繊維状のセシウム吸着剤（小津産業(株)製、五大力ＰＢ）を約２ｋｇ投入し、４時間浸漬させた。抽出液の一部を採取して放射能濃度を測定した。
Example 4: Decontamination test on a practical scale Using a prototype decontamination apparatus (Fig. 1) designed on a scale for practical use of the decontamination method of the present invention, a decontamination test was performed according to the following procedure. Carried out.
[Experimental procedure]
(I) Add 100 L of water to 56 kg of soil sample (dry: radioactivity concentration: 43,000 Bq / kg), stir for 2 minutes at ambient temperature, and then let stand for 5 minutes. Then, collect the supernatant liquid together with the supernatant liquid. Clay content (fine particles) in the soil was removed.
(Ii) In a stirred washing tank, 560 L of a 1M aqueous solution of monopotassium phosphate was prepared, and the soil from which the viscosity of (i) was removed was added and stirred (solid-liquid ratio 1:10).
(Iii) Nitric acid (13N) was then added dropwise to (ii) to adjust to pH2.
(Iv) Heated to about 100 ° C. and kept warm for 2 hours with stirring.
(V) The soil was allowed to stand overnight until the soil sufficiently settled, the supernatant (extract) was moved to the adsorption tank, and a part was collected to measure the radioactivity concentration.
(Vi) After washing the sediment (treated soil), a part was collected and dried, and the radioactivity concentration was measured.
(Vii) Next, about 2 kg of fibrous cesium adsorbent (made by Ozu Sangyo Co., Ltd., Five Great PB) carrying Prussian blue was added to the extract obtained in (v) and immersed for 4 hours. A part of the extract was collected and the radioactivity concentration was measured.
［実験結果］
上記の手順（i）〜（v）に従い、抽出後に一晩かけて土壌を沈降させたところ、抽出液が分離されることが確認できた。得られた土壌抽出液の放射能濃度は１，２６０Ｂｑ／ｋｇ、体積は約５６０Ｌであった。この濃度は、ビーカーサイズの抽出試験によって得られる抽出液と同等であった。従って、プロトタイプ装置でもビーカーサイズに近い精度でセシウム抽出及び抽出液の回収が可能であることが明らかになった。また、この抽出液を手順（vii）で吸着剤によって除染した結果、１２０Ｂｑ／ｋｇまで放射能濃度を低減できた（除去率：約９０％）。これは、吸着の条件を調製することによって更に低濃度まで下げることができると考えられる。
次に、処理前土壌の放射能濃度は４３０００Ｂｑ／ｋｇであったが、これを手順（i）〜（vi）に従って除染した結果、土壌の放射能濃度は１８０００Ｂｑ／ｋｇまで低減された（除染率：約５８％）。この土壌を更に肥料溶液１５００Ｌで再抽出を行ったところ、回収した土壌の放射能濃度は４８００Ｂｑ／ｋｇまで低減された（除染率：８９％）。除染率５８％はビーカーサイズ試験の除染率に比べて低い結果であったが、これはプロトタイプ装置の土壌撹拌能力や加熱能力に改善の余地があるためと思われる。以上の実験結果から、本発明の除染方法及び装置は、除染困難とされる土壌にも対応可能であり、そのプロセスが５０ｋｇ−土壌の規模にスケールアップした場合でも適用できることを示した。
[Experimental result]
According to said procedure (i)-(v), when the soil was settled overnight after extraction, it has confirmed that an extract was isolate | separated. The radioactivity concentration of the obtained soil extract was 1,260 Bq / kg, and the volume was about 560 L. This concentration was equivalent to the extract obtained by the beaker size extraction test. Therefore, it has been clarified that the cesium extraction and extraction liquid recovery can be performed with accuracy close to the beaker size even in the prototype device. Moreover, as a result of decontaminating this extract with the adsorbent in the procedure (vii), the radioactivity concentration could be reduced to 120 Bq / kg (removal rate: about 90%). It is considered that this can be further reduced to a lower concentration by adjusting the adsorption conditions.
Next, the radioactive concentration of the soil before the treatment was 43000 Bq / kg. As a result of decontamination according to procedures (i) to (vi), the radioactive concentration of the soil was reduced to 18000 Bq / kg (removal). Dyeing rate: about 58%). When this soil was further re-extracted with 1500 L of fertilizer solution, the radioactivity concentration of the recovered soil was reduced to 4800 Bq / kg (decontamination rate: 89%). The decontamination rate of 58% was lower than the decontamination rate of the beaker size test. This seems to be because there is room for improvement in the soil mixing ability and heating ability of the prototype device. From the above experimental results, it was shown that the decontamination method and apparatus of the present invention can be applied to soil that is difficult to decontaminate and can be applied even when the process is scaled up to 50 kg-soil.
本発明の放射性セシウムで汚染された土壌の除染方法により、汚染土壌から固定化された放射性セシウムを効率よく抽出することができる。また本発明の除染方法で使用する試薬は、いずれも既に農地等で使われている肥料の成分であり、人体や生態系への影響の懸念がなく、除染された土壌は環境中に戻すことができる。したがって、従前の表層土壌剥ぎ取り法のように、汚染土壌の移動、集積、保管は不要である。さらに本発明の除染装置は、特別な材料を必要としないので低コストであり、また専門家による操作を必要としないので、地域住民やボランティア等による自らの手による土壌除染が可能となる。本発明の除染方法及び除染装置により、汚染土壌の除染の加速が期待できる。 By the decontamination method for soil contaminated with radioactive cesium of the present invention, radioactive cesium immobilized from the contaminated soil can be efficiently extracted. In addition, the reagents used in the decontamination method of the present invention are all components of fertilizers already used in farmland, etc., and there is no concern about the influence on the human body and ecosystem, and the decontaminated soil is in the environment. Can be returned. Therefore, it is not necessary to move, accumulate, or store contaminated soil as in the conventional method of stripping the surface soil. Furthermore, since the decontamination apparatus of the present invention does not require a special material, it is low cost and does not require operation by an expert, so that soil decontamination can be performed by local residents, volunteers, etc. by their own hands. . By the decontamination method and decontamination apparatus of the present invention, acceleration of decontamination of contaminated soil can be expected.
１ 撹拌洗浄槽の容器
２ 撹拌手段
３ 加熱手段
４ 冷却手段
５ 処理液循環ライン
６ 吸着槽の容器
７ セシウム吸着材
８ セシウム吸着材の導入／回収手段
DESCRIPTION OF SYMBOLS 1 Container of stirring washing tank 2 Agitation means 3 Heating means 4 Cooling means 5 Treatment liquid circulation line 6 Adsorption tank container 7 Cesium adsorbent 8 Cesium adsorbent introduction / recovery means
Claims (9)
前記土壌及び処理液を受け入れる中空の容器；
前記容器の外壁若しくは前記容器内に配設され、前記容器内に受け入れた前記土壌及び処理液を加熱するための加熱手段；及び
前記容器内に受け入れた前記土壌及び処理液を撹拌するための撹拌手段
を備える撹拌洗浄槽を含み、
前記処理液が、リン酸塩及び硫酸塩からなる群より選択される少なくとも一種の成分を含み、且つｐＨが４以下である、除染装置。 A decontamination apparatus for removing cesium from soil contaminated with radioactive cesium,
A hollow container for receiving the soil and the treatment liquid;
A heating means for heating the soil and the treatment liquid disposed in the outer wall of the container or in the container and received in the container; and agitation for stirring the soil and the treatment liquid received in the container A stirred washing tank comprising means,
The decontamination apparatus, wherein the treatment liquid contains at least one component selected from the group consisting of phosphates and sulfates, and has a pH of 4 or less.
を備える吸着槽を含む、請求項７に記載の除染装置。 The treatment tank containing radioactive cesium discharged from the stirring and washing tank and an adsorption tank comprising a hollow container for receiving a cesium adsorbent composed of a hydrophilic fiber base material supporting a Prussian blue analog. Decontamination equipment.
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