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Volumn 66, Issue 6, 2011, Pages 803-820

Metal ion binding properties of a copolymer resin: Synthesis, characterization, and its applications

Author keywords

Batch equilibrium; Copolymers; Ion exchangers; Morphology; Resins

Indexed keywords

AVERAGE MOLECULAR WEIGHT; BATCH EQUILIBRIUM; BATCH EQUILIBRIUM METHOD; BINDING CAPACITIES; CHELATING COPOLYMERS; CONDUCTOMETRIC TITRATIONS; COPOLYMER RESINS; DIVALENT METAL ION; ELECTROLYTE CONCENTRATION; ELEMENTAL ANALYSIS; FTIR; H NMR SPECTROSCOPY; INTRINSIC VISCOSITY; METAL-ION BINDING PROPERTIES; NON-AQUEOUS; PHYSICOCHEMICAL PARAMETERS; REACTION MEDIUM; SEM; SEMICRYSTALLINES; SPECTRAL STUDIES; TIME INTERVAL; WIDE PH RANGE;

EID: 79954591369     PISSN: 01700839     EISSN: None     Source Type: Journal    
DOI: 10.1007/s00289-010-0385-8     Document Type: Article
Times cited : (18)

References (50)
  • 1
    • 28044447859 scopus 로고    scopus 로고
    • Selective separation of mercury (II) using a synthetic resin containing amine and mercaptan as chelating groups
    • DOI 10.1016/j.reactfunctpolym.2005.07.001, PII S1381514805001240
    • AA Atia AM Donia KZ Elwakeel 2005 Selective separation of mercury(II) using a synthetic resin containing amine and mercaptan as chelating groups React Funct Polym 65 267 275 10.1016/j.reactfunctpolym.2005.07.001 1:CAS:528:DC%2BD2MXht1Cqu7rO (Pubitemid 41690087)
    • (2005) Reactive and Functional Polymers , vol.65 , Issue.3 , pp. 267-275
    • Atia, A.A.1    Donia, A.M.2    Elwakeel, K.Z.3
  • 2
    • 0037407591 scopus 로고    scopus 로고
    • A new chelating sorbent for metal ion extraction under high saline conditions
    • 10.1016/S0039-9140(03)00030-4 1:CAS:528:DC%2BD3sXivFSjtLo%3D
    • D Prabhakaran MS Subramanian 2003 A new chelating sorbent for metal ion extraction under high saline conditions Talanta 59 1227 1236 10.1016/S0039-9140(03)00030-4 1:CAS:528:DC%2BD3sXivFSjtLo%3D
    • (2003) Talanta , vol.59 , pp. 1227-1236
    • Prabhakaran, D.1    Subramanian, M.S.2
  • 3
    • 30344447679 scopus 로고    scopus 로고
    • Column chromatographic separation of metal ions on 1-(2-pyridylazo)-2- napthol modified Amberlite IR-120 resin
    • DOI 10.1002/jssc.200500170
    • S Nabi A Alim A Islam M Amjad 2005 Column chromatographic of metal ions on 1-(2-pyridylazo)-2-naphthol modified amberlite IR-20 resin J Appl Polym Sci 18 2463 2467 (Pubitemid 43055945)
    • (2005) Journal of Separation Science , vol.28 , Issue.18 , pp. 2463-2467
    • Nabi, S.A.1    Alim, A.2    Islam, A.3    Amjad, M.4
  • 4
    • 0032027441 scopus 로고    scopus 로고
    • Polymer-supported reagents for the selective complexation of metal ions: An overview
    • PII S1381514898000169
    • RA Beauvais SD Alexandratos 1998 Polymer supported reagents for the selective complexation of metal ions: an overview React Funct Polym 36 113 123 10.1016/S1381-5148(98)00016-9 1:CAS:528:DyaK1cXit12qsL8%3D (Pubitemid 128393895)
    • (1998) Reactive and Functional Polymers , vol.36 , Issue.2 , pp. 113-123
    • Beauvais, R.A.1    Alexandratos, S.D.2
  • 5
    • 11244303448 scopus 로고    scopus 로고
    • Synthesis, characterization and ion-exchange properties of acrylic copolymers derived from 8-quinolinyl methacrylate
    • SA Patel BS Shah RM Patel PM Patel 2004 Synthesis, characterization and ion-exchange properties of acrylic copolymers derived from 8-quinolinyl methacrylate Iran Polym J 13 445 453 1:CAS:528:DC%2BD2MXhtFGgurw%3D (Pubitemid 40056356)
    • (2004) Iranian Polymer Journal (English Edition) , vol.13 , Issue.6 , pp. 445-453
    • Patel, S.A.1    Shah, B.S.2    Patel, R.M.3    Patel, P.M.4
  • 6
    • 49549108702 scopus 로고    scopus 로고
    • Chelation properties of poly(2-hydroxy-4-acryloyloxybenzophenone) resins toward some divalent metal ions
    • 10.1002/app.28264 1:CAS:528:DC%2BD1cXosFWlur4%3D
    • RM Zalloum SM Mubarak 2008 Chelation properties of poly(2-hydroxy-4- acryloyloxybenzophenone) resins toward some divalent metal ions J Appl Polym Sci 109 3180 3184 10.1002/app.28264 1:CAS:528:DC%2BD1cXosFWlur4%3D
    • (2008) J Appl Polym Sci , vol.109 , pp. 3180-3184
    • Zalloum, R.M.1    Mubarak, S.M.2
  • 7
    • 7044224920 scopus 로고    scopus 로고
    • Synthesis and analytical application of a chelating resin based on a crosslinked styrene/maleic acid copolymer for the extraction of trace-metal ions
    • DOI 10.1002/app.21109
    • PK Roy AS Rawat Choudhary PK Rai 2004 Synthesis and analytical application of a chelating resin based on a crosslinked styrene/maleic acid copolymer for the extraction of trace metal ions J Appl Polym Sci 94 1771 1779 10.1002/app.21109 1:CAS:528:DC%2BD2cXotl2iu7Y%3D (Pubitemid 39417907)
    • (2004) Journal of Applied Polymer Science , vol.94 , Issue.4 , pp. 1771-1779
    • Roy, P.K.1    Rawat, A.S.2    Choudhary, V.3    Rai, P.K.4
  • 8
    • 0036825604 scopus 로고    scopus 로고
    • Water-soluble acidic polyelectrolytes with metal-removing ability
    • BL Rivas ED Pereira P Gallegos KE Geckeler 2002 Water soluble acidic polyelectrolytes with metal-removing ability Polym Adv Technol 13 1000 1005 10.1002/pat.247 1:CAS:528:DC%2BD3sXpvFWlug%3D%3D (Pubitemid 36230253)
    • (2002) Polymers for Advanced Technologies , vol.13 , Issue.10-12 , pp. 1000-1005
    • Rivas, B.L.1    Pereira, E.D.2    Gallegos, P.3    Geckeler, K.E.4
  • 9
    • 0036151202 scopus 로고    scopus 로고
    • Ion-exchange properties of a salicylic acid-melamine-formaldehyde terpolymer resin
    • DOI 10.1016/S1381-5148(01)00072-4, PII S1381514801000724
    • WB Gurnule HD Juneja LJ Paliwal 2002 Ion-exchange properties of salicylic acid-melamine-formaldehyde terpolymer resin React Funct Polym 50 95 100 10.1016/S1381-5148(01)00072-4 1:CAS:528:DC%2BD38Xht1Oju7Y%3D (Pubitemid 34086312)
    • (2002) Reactive and Functional Polymers , vol.50 , Issue.2 , pp. 95-100
    • Gurnule, W.B.1    Juneja, H.D.2    Paliwal, L.J.3
  • 10
  • 11
    • 77956384036 scopus 로고    scopus 로고
    • Synthesis and characterization of anthranilic acid-thiourea- paraformaldehyde copolymer
    • 1:CAS:528:DC%2BD3sXkslCis78%3D
    • M Karunakaran A Burkanudeen 2003 Synthesis and characterization of anthranilic acid-thiourea-paraformaldehyde copolymer Orient J Chem 19 225 228 1:CAS:528:DC%2BD3sXkslCis78%3D
    • (2003) Orient J Chem , vol.19 , pp. 225-228
    • Karunakaran, M.1    Burkanudeen, A.2
  • 12
    • 34250189109 scopus 로고    scopus 로고
    • Chelation ion-exchange properties of ortho-nitrophenol-thiourea- paraformaldehyde terpolymer
    • A Burkanudeen M Karunakaran 2002 Chelation ion-exchange properties of ortho-nitrophenol-thiourea-paraformaldehyde terpolymer Orient J Chem 18 65 68
    • (2002) Orient J Chem , vol.18 , pp. 65-68
    • Burkanudeen, A.1    Karunakaran, M.2
  • 13
    • 34250217119 scopus 로고    scopus 로고
    • Studies of chelation ion-exchange properties of copolymer resin derived from salicylic acid and its application
    • BA Shah AV Shah PM Shah 2006 Studies of chelation ion-exchange properties of copolymer resin derived from salicylic acid and its application Iran Polym J 16 173 184
    • (2006) Iran Polym J , vol.16 , pp. 173-184
    • Shah, B.A.1    Shah, A.V.2    Shah, P.M.3
  • 14
    • 46649096398 scopus 로고    scopus 로고
    • Synthesis, characterization and chelation ion-exchange studies of a copolymer resin derived from 8-hydroxyquinoline-formaldehyde-catechol
    • 1:CAS:528:DC%2BD1cXnvFOlsro%3D
    • BA Shah AV Shah BN Bhandari RR Bhatt 2008 Synthesis, characterization and chelation ion-exchange studies of a copolymer resin derived from 8-hydroxyquinoline-formaldehyde-catechol J Iran Chem Soc 5 252 261 1:CAS:528:DC%2BD1cXnvFOlsro%3D
    • (2008) J Iran Chem Soc , vol.5 , pp. 252-261
    • Shah, B.A.1    Shah, A.V.2    Bhandari, B.N.3    Bhatt, R.R.4
  • 15
    • 0033740494 scopus 로고    scopus 로고
    • Chelating resin IV: Chelating resins of formaldehyde condensed phenolic schiff bases derived from 4,4-diaminodiphenyl ether with hydroxybenzaldehyde: Synthesis, characterization and metal ion adsorption studies
    • 10.1002/1097-4628(20000801)77:5<967::AID-APP3>3.0.CO;2-5 1:CAS:528:DC%2BD3cXjvFWgt7c%3D
    • S Samal RR Das RK Dey S Acharya 2000 Chelating resin IV: chelating resins of formaldehyde condensed phenolic schiff bases derived from 4,4-diaminodiphenyl ether with hydroxybenzaldehyde: synthesis, characterization and metal ion adsorption studies J Appl Polym Sci 77 967 981 10.1002/1097-4628(20000801)77:5<967::AID-APP3>3.0.CO;2-5 1:CAS:528:DC%2BD3cXjvFWgt7c%3D
    • (2000) J Appl Polym Sci , vol.77 , pp. 967-981
    • Samal, S.1    Das, R.R.2    Dey, R.K.3    Acharya, S.4
  • 16
    • 70350148698 scopus 로고    scopus 로고
    • An eco-friendly synthesis of a terpolymer resin: Characterization and chelation ion-exchange property
    • 1:CAS:528:DC%2BD1MXhsVGnurzN
    • RS Azarudeen MA Riswan Ahamed D Jeyakumar Burkanudeen 2009 An eco-friendly synthesis of a terpolymer resin: characterization and chelation ion-exchange property Iran Polym J 18 821 832 1:CAS:528:DC%2BD1MXhsVGnurzN
    • (2009) Iran Polym J , vol.18 , pp. 821-832
    • Azarudeen, R.S.1    Riswan Ahamed, M.A.2    Jeyakumar, D.3    Burkanudeen4
  • 17
    • 77954887621 scopus 로고    scopus 로고
    • Thermogravimetric study of 8-hydroxyquinoline 5-sulphonic acid-melamine-formaldehyde terpolymer resins-II
    • 10.1007/s10973-010-0672-5 1:CAS:528:DC%2BC3cXmsVGmtbc%3D
    • RN Singru WB Gurnule 2010 Thermogravimetric study of 8-hydroxyquinoline 5-sulphonic acid-melamine-formaldehyde terpolymer resins-II J Therm Anal Colorim 100 1027 1036 10.1007/s10973-010-0672-5 1:CAS:528:DC%2BC3cXmsVGmtbc%3D
    • (2010) J Therm Anal Colorim , vol.100 , pp. 1027-1036
    • Singru, R.N.1    Gurnule, W.B.2
  • 18
    • 0000480534 scopus 로고
    • Chelation ion-exchange properties of salicylic acid-thiourea-trioxane terpolymer
    • Manavalan R, Patel MM (1983) Chelation ion-exchange properties of salicylic acid-thiourea-trioxane terpolymer. Micromol Chem 184:717-723
    • (1983) Micromol Chem , vol.184 , pp. 717-723
    • Manavalan, R.1    Patel, M.M.2
  • 19
    • 79952450258 scopus 로고    scopus 로고
    • Eco-friendly application of p-cresol-melamine-formaldehyde polymer resin as ion-exchanger and its electrical and thermal study
    • Singru RN, Gurnule WB, Khati VA, Zade AB, Dontulwar RA (2010) Eco-friendly application of p-cresol-melamine-formaldehyde polymer resin as ion-exchanger and its electrical and thermal study. Desalination 263:200-210
    • (2010) Desalination , vol.263 , pp. 200-210
    • Singru, R.N.1    Gurnule, W.B.2    Khati, V.A.3    Zade, A.B.4    Dontulwar, R.A.5
  • 20
    • 77949389609 scopus 로고    scopus 로고
    • Chelation ion-exchange properties of copolymer resins derived from p-cresol, oxamide and formaldehyde
    • 1:CAS:528:DC%2BC3cXltF2msbs%3D
    • RN Singru WB Gurnule 2010 Chelation ion-exchange properties of copolymer resins derived from p-cresol, oxamide and formaldehyde Iran Polym J 19 169 189 1:CAS:528:DC%2BC3cXltF2msbs%3D
    • (2010) Iran Polym J , vol.19 , pp. 169-189
    • Singru, R.N.1    Gurnule, W.B.2
  • 21
    • 67449106115 scopus 로고    scopus 로고
    • Terpolymer resin VIII: Chelation ion exchanger properties of 2,4-dihydroxybenzophenone-oxamide-formaldehyde terpolymer resins
    • 10.1002/app.29769
    • WB Gurnule SS Butoliya AB Zade 2009 Terpolymer resin VIII: chelation ion exchanger properties of 2,4-dihydroxybenzophenone-oxamide-formaldehyde terpolymer resins J Appl Poly Sci 113 1 9 10.1002/app.29769
    • (2009) J Appl Poly Sci , vol.113 , pp. 1-9
    • Gurnule, W.B.1    Butoliya, S.S.2    Zade, A.B.3
  • 22
    • 0000250435 scopus 로고
    • Ion-exchange properties of a 2-hydroxy 4-methoxyacetophenone-thiourea- trioxane tercopolymer resins
    • 10.1088/0954-0083/3/4/006 1:CAS:528:DyaK3sXhtVegt78%3D
    • HB Pancholi MM Patel 1991 Ion-exchange properties of a 2-hydroxy 4-methoxyacetophenone-thiourea-trioxane tercopolymer resins High Perform Polym J 3 257 262 10.1088/0954-0083/3/4/006 1:CAS:528:DyaK3sXhtVegt78%3D
    • (1991) High Perform Polym J , vol.3 , pp. 257-262
    • Pancholi, H.B.1    Patel, M.M.2
  • 23
    • 36448975254 scopus 로고    scopus 로고
    • Synthesis, characterization and thermal degradation of 8-hydroxyquinoline-guanidine-formaldehyde terpolymer
    • DOI 10.1016/j.eurpolymj.2007.09.006, PII S0014305707004922
    • PEP Machael JM Barbe HD Juneja LJ Paliwal 2007 Synthesis, characterization and thermal degradation of 8-hydroxyquinoline-guanidine- formaldehyde terpolymer Euro Polym J 43 4995 5000 10.1016/j.eurpolymj.2007.09. 006 (Pubitemid 350166339)
    • (2007) European Polymer Journal , vol.43 , Issue.12 , pp. 4995-5000
    • Michael, P.E.P.1    Barbe, J.M.2    Juneja, H.D.3    Paliwal, L.J.4
  • 24
    • 39549099523 scopus 로고    scopus 로고
    • A benign approach of microwave assisted synthesis of copolymeric resin with improved thermal, spectral and ion-exchange properties
    • BA Shah AV Shah NB Patel 2008 A benign approach of microwave assisted synthesis of copolymeric resin with improved thermal, spectral and ion-exchange properties Iran Polym J 17 3 17 1:CAS:528:DC%2BD1cXjsl2iurw%3D (Pubitemid 351281206)
    • (2008) Iranian Polymer Journal (English Edition) , vol.17 , Issue.1 , pp. 3-17
    • Shah, B.A.1    Shah, A.V.2    Patel, N.B.3
  • 26
    • 0342845312 scopus 로고    scopus 로고
    • Preparation and characterization of poly(amidoxime) chelating resin from polyacrylonitrile grafted sago starch
    • Lutfor MR, Silong S, Wan Md Zin, Ab Rahman MZ, Ahmad M, Haron J (2000) Preparation and characterization of poly(amidoxime) chelating resin from polyacrylonitrile grafted sago starch. Eur Polym J 36:2105-2113
    • (2000) Eur Polym J , vol.36 , pp. 2105-2113
    • Lutfor, M.R.1    Silong, S.2    Md Zin, W.3    Ab Rahman, M.Z.4    Ahmad, M.5    Haron, J.6
  • 27
    • 6944240012 scopus 로고    scopus 로고
    • Antimicrobial activity on the copolymers of 2, 4-dicholophenyl methacrylate with methyl methacrylate: Synthesis and characterization
    • 10.1002/pola.20348 1:CAS:528:DC%2BD2cXotlGrsLc%3D
    • MV Patel A Patel Samir Arbinda Roy RM Patel 2004 Antimicrobial activity on the copolymers of 2, 4-dicholophenyl methacrylate with methyl methacrylate: Synthesis and characterization J Appl Polym Sci Part A Polym Chem 42 5227 5234 10.1002/pola.20348 1:CAS:528:DC%2BD2cXotlGrsLc%3D
    • (2004) J Appl Polym Sci Part A Polym Chem , vol.42 , pp. 5227-5234
    • Patel, M.V.1    Patel Samir, A.2    Roy, A.3    Patel, R.M.4
  • 30
    • 0027112813 scopus 로고    scopus 로고
    • Chelation ion exchange properties of resins derived from semicarbazone of 2-hydroxy acetophenone-substituted benzoic acid-formaldehyde
    • Bastia TK, Lenka S, Nayak (2003) Chelation ion exchange properties of resins derived from semicarbazone of 2-hydroxy acetophenone-substituted benzoic acid-formaldehyde. J Appl Polym Sci 46:739-744
    • (2003) J Appl Polym Sci , vol.46 , pp. 739-744
    • Bastia, T.K.1    Lenka, S.2    Nayak3
  • 33
    • 0043065472 scopus 로고    scopus 로고
    • Chelation ion-exchange properties of copolymer resins derived from 8-hydroxyquinoline, melamine and formaldehyde
    • 1:CAS:528:DC%2BD38XhsFKku7c%3D
    • WB Gurnule HD Juneja LJ Paliwal 2001 Chelation ion-exchange properties of copolymer resins derived from 8-hydroxyquinoline, melamine and formaldehyde Ultra Sci 13 3 333 339 1:CAS:528:DC%2BD38XhsFKku7c%3D
    • (2001) Ultra Sci , vol.13 , Issue.3 , pp. 333-339
    • Gurnule, W.B.1    Juneja, H.D.2    Paliwal, L.J.3
  • 37
    • 84864835186 scopus 로고    scopus 로고
    • High resolution scanning electron microscopy of immunogold labeled cells by the use of thin plasma coating osmium
    • E Suzuki 2002 High resolution scanning electron microscopy of immunogold labeled cells by the use of thin plasma coating osmium J Microsc 153 208
    • (2002) J Microsc , vol.153 , pp. 208
    • Suzuki, E.1
  • 38
    • 58149201123 scopus 로고    scopus 로고
    • Metal ion uptake bychelating resin derived from o-substituted benzoic acid and its synthesis, characterization and properties
    • 10.1002/masy.200851412 1:CAS:528:DC%2BD1MXhvVWltLo%3D
    • BA Shah AV Shah BA Shab 2008 Metal ion uptake bychelating resin derived from o-substituted benzoic acid and its synthesis, characterization and properties Macromol Symp 274 81 90 10.1002/masy.200851412 1:CAS:528: DC%2BD1MXhvVWltLo%3D
    • (2008) Macromol Symp , vol.274 , pp. 81-90
    • Shah, B.A.1    Shah, A.V.2    Shab, B.A.3
  • 40
    • 85066256921 scopus 로고
    • Raw water treatment by ion exchange
    • K. Dorfner (eds). Walter de Gruyter Berlin, New York
    • Arden TV (1991) Raw water treatment by ion exchange. In: Dorfner K (ed) Ion exchangers. Walter de Gruyter, Berlin, New York, p 717
    • (1991) Ion Exchangers , pp. 717
    • Arden, T.V.1
  • 43
    • 0027077417 scopus 로고    scopus 로고
    • Synthetic resins: XV Chelation ion-exchange properties of 2,4-dinitrophenylhydrazone of resacetophenone-formaldehyde resin
    • Lenka S, Parija A, Nayak PL (2007), Synthetic resins: XV Chelation ion-exchange properties of 2,4-dinitrophenylhydrazone of resacetophenone- formaldehyde resin. Polym Int 29:103-106
    • (2007) Polym Int , vol.29 , pp. 103-106
    • Lenka, S.1    Parija, A.2    Nayak, P.L.3
  • 44
    • 84985582621 scopus 로고
    • Salicylic acid-biuret-trioxane tercopolymer resins
    • 10.1002/apmc.1989.051730105 1:CAS:528:DyaK3cXhvF2ltbw%3D
    • TK Pal RB Kharat 1989 Salicylic acid-biuret-trioxane tercopolymer resins Die Angewandte Macromol Chem 173 55 68 10.1002/apmc.1989.051730105 1:CAS:528:DyaK3cXhvF2ltbw%3D
    • (1989) Die Angewandte Macromol Chem , vol.173 , pp. 55-68
    • Pal, T.K.1    Kharat, R.B.2
  • 47
    • 67651109089 scopus 로고    scopus 로고
    • Synthesis and chelation ion-exchange properties of 2,4- dihydroxyacetophenone-biuret-formaldehdye terpolymer resin
    • 1:CAS:528:DC%2BD1MXotFKhs7o%3D
    • SS Rahangdale AB Zade WB Gurnule 2009 Synthesis and chelation ion-exchange properties of 2,4-dihydroxyacetophenone-biuret-formaldehdye terpolymer resin Indian J Chem 48A 531 535 1:CAS:528:DC%2BD1MXotFKhs7o%3D
    • (2009) Indian J Chem , vol.48 , pp. 531-535
    • Rahangdale, S.S.1    Zade, A.B.2    Gurnule, W.B.3
  • 49
    • 47949096191 scopus 로고    scopus 로고
    • Synthesis, characterization and thermal degradation studies of terpolymer resins derived from p-cresol, melamine and formaldehyde
    • 10.1002/app.28197 1:CAS:528:DC%2BD1cXmvFWhurg%3D
    • RN Singru AB Zade WB Gurnule 2008 Synthesis, characterization and thermal degradation studies of terpolymer resins derived from p-cresol, melamine and formaldehyde J Appl Polym Sci 109 859 868 10.1002/app.28197 1:CAS:528: DC%2BD1cXmvFWhurg%3D
    • (2008) J Appl Polym Sci , vol.109 , pp. 859-868
    • Singru, R.N.1    Zade, A.B.2    Gurnule, W.B.3
  • 50
    • 62749203696 scopus 로고    scopus 로고
    • Copolymer resin VII: 8-hydroxyquinoline-5-sulphonuic acid-thiourea- formaldehyde copolymer resins and their ion exchange properties
    • 10.1002/app.29369 1:CAS:528:DC%2BD1MXht12lt7g%3D
    • VD Mane NJ Wahane WB Gurnule 2009 Copolymer resin VII: 8-hydroxyquinoline-5-sulphonuic acid-thiourea-formaldehyde copolymer resins and their ion exchange properties J Appl Polym Sci 111 3039 3049 10.1002/app.29369 1:CAS:528:DC%2BD1MXht12lt7g%3D
    • (2009) J Appl Polym Sci , vol.111 , pp. 3039-3049
    • Mane, V.D.1    Wahane, N.J.2    Gurnule, W.B.3


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