MÉMOIRE
SCIENCES
1990
ISSN 0302-2684
GËOLOGIOUES
Proceedings of the 9
thInternational Clay Conference Strasbourg, 1989
Volume l
CLAY-ORGANIC INTERACTIONS CLAY MINERALS IN SOILS
Editors in chief
v.c. FARMER and Y. TARDY
Associate Editors : R.A. EGGLETON, B. FRITZ, R. GIESE, K. KODAMA, H. PAQUET, J.A.RAUSSEL-COLOM and R.J. WILSON
Editing coordination: J. DUPLAY
Publié avec le concours de l'Université Louis Pasteur et du Centre National de la Recherche Scientifique
COMITÉ D'ÉDITION Directeur de la publication et Rédacteur en chef:
Rédactrices en chef adjointes:
Secrétaire de rédaction:
Respon~ablede l'impression:
Responsable de la gestion financière:
Responsable scientifique de la publicité:
Bertrand FRITZ Hélène PAQUET et Anne-Marie KARPOFF Danièle AUNIS François GAUTHIER-LAFAYE Bertrand FRITZ Monique SCHULER
COMITÉ DE DIRECTION
Président: Georges MILLOT, de l'Académie des Sciences
Pierre CHEVALLIER Jacques LUCAS
Jean DERCOURT Daniel NAHON
Bertrand FRITZ Michel STEINBERG
Hubert de La ROCHE Francis WEBER
Echanges:
Ventes et abonnements:
Editeur:
Bibliothèque de l'Institut de Géologie, Betty KIEFFER, Bibliothécaire Marguerite WOLF, Régisseur
Institut de Géologie, Université Louis Pasteur de Strasbourg et Centre de Géochimie de la Surface, CNRS 1, rue Blessig, F-67084 STRASBOURG Cedex (France)
Proceedings of the
9 th International Clay Conference 1989
Strasbourg, France, August 28 to September 2, 1989
ORGANIZED BY
Groupe français des Argiles (GFA) Université Louis Pasteur (ULP)
Centre National de la Recherche Scientifique (CNRS)
Institut Français de Recherche Scientifique pour le Développement en Coopération (ORSTOM) Institut National de la Recherche Agronomique (INRA)
UNDER THE AUSPICES OF
Association Internationale pour l'Etude des Argiles (AIPEA)
Volume l
CLAY-ORGANIC INTERACTIONS CLAY MINERALS IN SOILS
Editors in chief
v.c. FARMER and Y. TARDY
Associate Editors :
R.A. EGGLETON, B. FRITZ, R. GIESE, K. KODAMA, H. PAQUET, J.A. RAUSSEL-COLOM and R.J. WILSON
Editing coordination:
J. DUPLAY
3
CONFERENCE ORGANIZING COMMITTEE
Prof. Yves TARDY, General Chairman Dr. Hélène PAQUET, Secretary General Dr. Liliane PRÉVÔT, Treasurer
Dr. Norbert CLAUER, Poster Session Chairman Dr. Joëlle DUPLAY, Mrs Danièle AUNIS, Publications Dr. Jean-Luc PROBST, Technical arrangements
Profs Jean-Pierre EBERHART, Michel HOFFERT, José HONNOREZ and Jacques LUCAS, Drs Ronan LE DRED, Charles-Henri PONS, Hélène SUQUET and Francis WEBER, Advisory members
Mrs Helga EBERHART and Dr. Melba HONNOREZ, Accompanying members Program Mrs Marie-Thérèse STEHLÉ, Secretary office
Mrs Jeanine RINCKENBERGER and Mrs TANGY, Agence Tourmaline
EDITORIAL BOARD
Editors in chief: V.C. FARMER and Y. TARDY
Associate Editors : R.A. EGGLETON, B. FRITZ, R. GIESE, H. KODAMA, H. PAQUET, J.A. RAUSSEL- COLOM, R.J. WILSON
Editing coordination: J. DUPLAY
COUNCIL OF AIPEA IN 1989
President: Prof. J. KONTA (Czechoslovakia)
Vice-President: Prof. U. SCHWERTMANN (F.R. Germany) Past President: Prof. HELLER-KALLAI (Israel)
Secretary General: Prof. A.J. HERBILLON (Belgium), Prof. R.A. SCHOONHEYDT (Belgium) Treasurer : Dr. C.R. De KIMPE (Canada)
Councillors : Dr. J.B. HAYES (U.S.A.), Prof. K. NAGASAWA (Japan), Prof. De SOUZA SANTOS (Bra- zil) (second term) ; Dr. V.C. FARMER (UK), Prof. E. GALAN HUERTOS (Spain), Prof. J.P. QUIRK (Australia) (new members),
HONORARYSPONSORS
OF THE 9
thINTERNATIONAL CLAY CONFERENCE
GROUPE FRANCAIS DES ARGILES - President-Treasurer : Prof. B. SIFFERT i Vice-president- Secretary: Dr. M. THIRYiCouncillors: N. CLAUER, P. DEBRABANT, A. DECARREAU, L. GATINEAU, G. GEIRNAERT, S. BÉNIN,
J.
MAMY, C. MARTY, A. MEUNIER, B. PAQUET, G. PÉDRO, H. PÉ- ZERAT, R. PROST, M. RAUTUREAU, M. ROBERT, B. SIEFFERT, M. STEINBERG, H. SUQUET, Y. TARDY, M. TERCE, M. THIRY, N. TRAUTH, M. VOUILLEMETSOCIÉTÉ FRANCAISE DE MINÉRALOGIE - Président: J. FABRIÈS SOCIÉTÉ GÉOLOGIQUE DE FRANCE - Président: J. DIDIER
COMITÉ NATIONAL FRANCAIS DE GÉOLOGIE (CNFG) - Président: H. RADIER
ASSOCIATION FRANCAISE POUR L'ÉTUDE DES SOLS (AFES) - Président:
J.
BOULAINE ASSOCIATION FRANCAISE DE CÉRAMIQUE - Vice-Président: F. LEBOUCHARDRÉSEAU EUROPÉEN POUR L'ÉTUDE DES LATÉRITES (EUROLAT) - Président: Y. TARDY
TECHNICAL REFEREES
The editors are deeply indebted to the following individuals who gave of their time and talent as technical referees of manuscripts subrnitted for publicationinthis volume.
Aaggaard P.
Adams J.M.
Ajmone-Marsan F.
Anderson D.
April R.
Arduino E.
Bailey S.
Bain D.
Barberis E.
Bardossy G.
Behra P.
Bergaya F.
Bini C.
Bish D.L.
Bleam W.
Borggaard O.
Bottero J.Y.
Bottino G.
Brime C.
Bühmann D.
Cases J.
Cathelineau M.
Chagnon A.
ChamleyH.
Chapman N.
Chermak J.
Clauer N.
Colten-Bradley V.
Coyne L.
Crovisier J.L.
De Kimpe C.
De La Calle C.
Decarreau A.
Deconinck J.F Desjardin M.
Dixon J.B.
Douglas L.A.
Eberl D.
Eggleton T.
Ewing R.C.
Ferrell R.
Formoso M.
Freyssinet P.
Fripiat J.
Gatineau L.
Gilkes R.J.
Gomes Celso de S.F.
Granbow B.
Grattan-Bellew P.E.
Guggenheim S.
Hall P.
Hauff P.
Heckroodt R.O.
Heller-Kallai1.
Hern J.D.
Herbillon A.
Honnorez J.
Huang P.M.
HuffW.
Huggett J.
Hughes R.E.
lldefonse P.
Jahren J.
Johns W.D.
Kevan L.
Kharaka Y.K.
Koch C.
Kolmer H.
Konta J.
Kostic N.
Kotlyar 1.
Kühnel R.
Lagaly G.
Lasaga A.C.
Latouche C.
Le Dred R.
Linares J.
Lipsicas M.
Longstaffe F.
Loughnan F .C.
Mack A.R.
Mackenzie R.
Made B.
Manceau A.
Margulies L.
May H.
Mendelovici E.
Meunier A.
Minato H.
Minichelli D.
Mitchell D.
Moberg J.P.
Moore D.M.
Morgan D.J.
Mortland M.
Muller Von Moos M..
Murad E.
Murray H.
Nagasawa K.
Odom I.E.
OIson C.
Parfitt R.L.
Pedro G.
Petit J.C.
Pevear D.
Pinnavaia T.
Poirier J .E.
Pollastro R.
Poppi L.
Post J.L.
Primmer T.J.
Prost R.
Proust D.
Prudencio M.I.
Purvis K.
Push R.
Ransom B.
Rautureau M.
Righi D.
Robert M.
Rodas M.
Ross G.J.
Sawhney B.
Schoonheydt R.
Schulze D.
Schwertmann U.
Scott A.D.
Sebastian Pardo E.
Sequeira-Braga M.A.
Serratosa J.M.
Shaw H.F.
Shayan A.
Shimoyama A.
Siddiqui M.K.
Sieffermann R.
Stone W.
Starr M.
Stucki J.
Sugahara Y.
Suquet H.
Tahoun S.
Tarnocai C.
Tazaki K.
Tessier D.
Thiry M.
Thorez J.
Tomadin 1.
Torrent J.
Utada M.
Van Damme H.
Van Olphen H.
Van Oort F.
Van Reeuwijk L.P.
Velde B.
Veniale F.
Siffert B.
Simonot-Grange M.H.
Sindelar J.
Singer A.
Spears A.
Sposito G.
Srodon J.
Stahr K.
Steinberg M.
Stoch 1.
Viani B.
Vieillard P.
Violante P.
Wada K.
Wagner J.F.
Warren E.
Weiss A.
Wells N.
White J.L.
Xyla A.
Yoshinaga N.
Yuretich R.
Yvon J.
Zalba P.
Zanchetta J.V.
5
PREFACE
Upon the request of Prof. Jiri KONTA, the Chairman, and the recommendations of the Council of AIPEA, we have extended the number of papers published, from 60 initially envisaged, to about 90 which represents 900 printed pages. They are distributed among 10 chapters and 5 volumes: memoirs nO 85 to 89 of the journalSciences Géologiquesedited by the" Institut de Géologie de Strasbourg ".
Reviews were mostly the work of the Associate Editors : R.A. EGGLETON from Australia, R. GIESE from USA, K. KODAMA from Canada, J.A. RAUSSEL-COLOM from Spain, R.J. WILSON from UK, B. FRITZ and H. PAQUET from France,assisted by about 180 referees.
The editing coordination was assumed by J. DUPLAY, while the final decision and responsability of printing (or rejecting) was taken conjointly by V.C. FARMER from Scotland and myself.
The 10 chapters are of unequallength and may appear to certain people to be of unequal value. How- ever, AIPEA, the Association Internationale Pour l'Etude des Argiles is a multidisciplinary group and an international association. AlI disciplines and aIl countries were - l hope - equally treated, even if results are unequal.
Concerning the topics of the conference, sorne efforts have been made in two directions which - 1 think - are complementary. Together with \V.D. JOHNS we tried to develop the topic "Clay mineraIs and origin of life" which is now include-d in the chapter clay-organic interactions. This subject has to be encouraged in the future because it can inject new spirit in the clay mineraI community. On the other hand, together with F. KARLSSON and R. PUSCH from Sweden we try to encourage a group involved in waste disposaI which is a preoccupation of the modern societies. Modestly it appears that this enterprise was successful.
The organization of the conference was mostly based on poster sessions, remarkably coordinated by N. CLAUER and J. HONNOREZ. Most ofthe people consulted after the conference havejudged this initia- tive as positive. The fact that 150 papers were submitted and amongt them 90 were selected for publication confirrns that poster sessions contributed to the promotion of a large number of written contributions of high quality.
Ifa clay mineraI was 3.8 billion years ago, the secret nest of the creation of life, we hope - together with H. PAQUET the Secretary General of the 9th International Clay Conference - that these 5 books will be for the next 3 billion years a record of what we are today : AIPEA, the Association Internationale Pour l'Etude des Argiles a long life organization.
Yves TARDY GeneraI Chairman
Co-editor in chief
7
TABLE OF CONTENTS
Volume l, Mémoire 85
Organizing Committee Preface, by Prof. Y. TARDY Table of contents
CLAY-ORGANIC INTERACTIONS
3 5 7
1
J. CENENS and R.A. SCHOONHEYDT - Quantitative absorption spectroscopy of 15 cationic dyes on c1ays
A. JULG - Asymmetrical adsorption on kaolinite and origin of the L-homochirality of the 25 amino acids in the proteins of living organisms
K. TAZAKI, F.G. FERRIS, R.G. WIESE and W.S. FYFE - Bacteriallepidocrocite 35 and hematite in chert
B.L. SAWHNEY and M.P.N. GENT - Reactions ofneutral, nonpolar organic contam- 45 inants with clay mineraIs
B.S.J. PRAKASH - Reaction of methyl phenyl ether with metal ion-exchanged montmo- 51 rillonites
R. NAVARRO.GONZALEZ, A. NEGRON.MENDOZA, S. RAMOS and 55 C. PONNAMPERUMA - Radiolysis of aqueous solutions of acetic acid in the presence of Na-montmorillonite
CLAY MINERALS IN SOILS
K. WADA - MineraIs and mineraI formation in soils derived from volcanic ash in the 69 Tropics
J. KONTA - MineraIs in clay fraction of soils, rivers and recent detrital sediments: unity 79 of relations
R. APRIL and D. KELLER - Interactions between mineraIs ,and roots in forest soi!s 89 M.A. SEQUEIRA BRAGA-, J.E. LOPES NUNES, H. PAQUET and G. MIL- 99 LOT - Climatic zonality of coarse granitic saprolites (" arenes") in atlantic Europe from Scandinavia to Portugal
G. SIEFFERMANN and S. TJOJUDO - Evidence of mobility and input of Al, Fe, Ti 109 and trace elements in altered volcanic rocks from Kalimantan, Indonesia
A. SHAYAN, A. SINGER and C.J. LANCUCKI - Nature of baked clayey layer 119 intercalated between two basalt flows
S. OKUMURA - Geochemistry ofplagioc1ase weathering in Nabari gabbroic body, South- 129 west Japan, and a kinetic model of neoformation mechanism in open system
O.K. BORGGAARD - Kinetics and mechanisms of soil iron oxide dissolution in EDTA, 139 oxalate and dithioniate
V.C. FARMER and A.R. MILNES - Podzol to laterite : a possible genetic sequence 149 N. KOSTIC - An investigation on clay mineraI formation in brown soi! profiles in Central 155 Serbia, Yugoslavia
M.L.L. FORMOSO, N. DANI, A. NOVIKOFF and 1. VALETON - Mineralogical 165 evolution of supergenic alteration in alkaline rocks of Lages, southern Brazil
A.M. INIGUEZ, P.B. ZALBA and R.R. AND REIS - Mineralogy and chemistry of 175 Cambrian (?) paleosols, Tandilia system, Buenos Aires Province, Argentina
M.S. AKHTAR and J.B. DIXON - Clay mineralogy and K/Ca+Mg quantity/intensity 185 relationships in selected alluvial soils of Pakistan
G.S.R. KRISHNAMURTI and P.M. HUANG - Kinetics of Fe(II) oxygenation and 195 the nature of hydolytic products as influenced by ligands
F. VAN OORT and A.M. JAUNET - Origin, mineralogical behaviour and spatial dis- 205 tribution of 2/1 clay minerals in a ferrallitic soil cover on volcanic parent rock of Guadeloupe
Index of authors 215
Volume II, Mémoire 86
Organizing Committee Preface, by Prof. Y. TARDY Table of contents
SURFACE CHEMISTRY
3 5 7
J. FRIPIAT - High resolution solid state nuclear magnetic resonance applied to clay surface 15 studies
F. FIGUERAS, Z. KLAPYTA, A. AUROUX and C. GUEGUEN - Influence of 25 the structure of the original clayon the properties of pillared clay materials
R.F. GIESE, C.J. VAN OSS, J. NORRIS and P.M. COSTANZO- Surface energies 33 of sorne smectite clay minerais
H. TATEYAMA, K. TSUNEMATSU, H. HIROSUE, K. KIMURA, T. FURU- 43 SAWA and Y. ISHIDA - Synthesis of the expandable fluorine mica from talc and its colloidal properties
D.P. VLIERS, B. VAN DE VLIET, R.A. SCHOONHEYDT and F.C. DE 51 SCHRYVER - Luminescence quenching ofRu(BiPy)~+on clays with CuH andFe(CN)~- P. MALLA and S. KOMARNENI - Effect of crystal chemistry on pore structure and 59 hydrophilicity of alumina-pillared smectites : water sorption study
S.S. SINGH and H. KODAMA - Structural evolution of a polynuclear 69 hydroxyaluminum-montmorillonite complex with an 18.8
A
pillared structure on agingS. HATIPOGLU,
c.
EYLEM, H. GOKTÜRK and H.N. ERTEN - Sorption of 79 strontium and barium on clays and soil fractionsSTRUCTURE AND MIXED LAYERING OF CLAYS
S.W. BAILEY - Halloysite - A critical assessment 89
S.GUGGENHEIM - The dynamics of thermal decomposition in aluminous dioctahedral 99 2:1 layer silicates : a crystal chemical mode]
W.E.E. STONE - Structural iron in kaolinite. A study by proton magnetic resonance 109 R. STOESSER, R. LUECK, D. GYEPESOVA, H. SLOSIARIKOVA, 115 A. RERICHA and B. CICEL - On the intercalation and GPa pressure treatment of clay minerais. An EPR study
A.C. OLIS and L.A. DOUGLAS - The classification of high charge expanding clays 2:1 127 phyllosilicates
9
G. LOU and P.M. HUANG - Impact of structural perturbation of allophanic materials 137 by citric acid on their surface aIteration
E. NARlTA and T. YAMAGISHI - Adsorption of carboxylate ions by magnesium- 147 aluminium oxide : formation of layered hydrotaIcite-like compounds
D. SAEHR, R. LE DRED and J. BARON - Ion exchanges K+ ;=Né and availability 157 of two groups of exchange sites ina vermiculite. 1. Providing evidence for two site groups
Index of authors 167
Volume III, Mémoire 87
Organizing Committee Preface, by Prof. Y. TARDY Table of contents
GEOCHEMISTRY OF CLAYS
3 5 7
J .P. BELLAT and M.H. SIMONOT-GRANGE - Adsorption-desorption of water by 15 sepiolite. Characterization of zeolitic water
M.H. SIMONOT-GRANGE - Thermodynamic properties of adsorbed water in zeolites 25 and comparison with clay minerais
A. ELM'CHAOURl and M.H. SIMONOT-GRANGE - Hydration thermodynamic 35 functions of hectorite and nontronite from experimental isotherms and the Polanyi-Dubinin theory
ZHENG ZILI, TI XI and LI ZHIGUO - The clay mineraI geochemistry of one paly- 45 gorskite clay deposit in east China
M.A. CASTRO, J. POYATO, M.M. TOBIAS and J.M. TRlLLO - Sorption of 55 water by La-montmorillonite as a mechanism for La retention at 3000
NUCLEAR WASTE DISPOSAL
F. KARLSSON - Utilization of certain chemical and physicaI properties of smectite for 65 isolation of radioactive waste in Sweden
J .P. RAFFENSPERGER and R.E. FERRELL Jr. - Permeant-induced changes in the 75 permeability, microtexture, and pore structure of unconsolidated water-sensitive sediments D.G. BROOKINS - Clay mineraIs in sandstone uranium deposits : radwaste applications 85 C. CANTALE, S. CASTELLI, A. DONATO and G. GUIDI - Behaviour of the 97 Italian Bel 15 borosilicate glass incorporating MTR HLW with reference to the disposai in clay formations
H. ISHIKAWA, K. AMEMIYA, Y. YUSA and N. SASAKI - Comparison offun- 107 damental properties of japanese bentonites as buffer material for waste disposai
L. BORGESSON - Laboratory testing and computor simulation of clay barrier behaviour 117 R. PUSCH, H. HOKMARK and O. KARNLAND - MicrostructuraI impact on the 127 conductivity of smectite buffer clays
R. PUSCH and O. KARNLAND - Geological evidence ofsmectite longevity 139 J.F. WAGNER and K.A. CZURDA - Sorption ofradionuclides by Tertiary clays 149
Index of authors 159
Volume IV, Mémoire 88
Organizing Committee Preface, by Prof. Y. TARDY Table of contents
CLAYS IN SEDIMENTS
3 5 7
J.F. DECONINCK and H. AC CARIE - Palygorskite and eustatism during Mid- 15 Cretaceousinthe Maiella Mountain (Abruzzi, Central Italy)
R. CHESTER - The atmospheric transport of clay mineralS to the world ocean 23 W.D. HUFF and D.J. MORGAN - Stratigraphy, mineralogy and tectonic setting of 33 Silurian K-bentonites in southern England and Wales
M. RODAS, M.G. GARZON, F.L. LUQUE and R. MAS - Correlation between 43 the Paleogene detritic facies inthe margins of the Tajo and Duero basins (Central Spain) : mineralogical, sedimentological and geomorphological characteristics
B. WEINGARTEN, R. YURETICH, R. BRADLEY and M.L. SALGADO- 53 LABOURIAU - Environmentally controlled variations in clay mineraI assemblages from lake sediments in the Venezuelan Andes
A.G. TÜRKMENOGLU and S. AKER - Origin of sedimentary bentonite deposits of 63 Çankiri basin, Turkey
C. LATOUCHE, N. MAILLET and G. AUFFRET - Mineralogical study oftwo sites 73 in the abyssal plains of Madeira and Nares (North Atlantic Ocean) ESOPE cruise
A. SANCHEZ BELLON, E. SEBASTIAN PARDO and G. BARRAGAN 83 BAZAN - An analysis of the clay mineraIs from the Miocene-Pliocene boundary in the southern sector of the Vera Basin (S.E. Spain) and its palaeogeographical implications
DIAGENESIS AND HYDROTHERMALISM
M.E. STRICKLER and R.E. FERRELL Jr. - Provenance: the dominant factor in 95 clay mineralogy of the upper Wilcox Formation
WANG XINGXIN - Characteristics of clay mineraIs and their efi'ects on production 105 capacity of the Cretaceous sandstone reservoirs of Songliao Basin, China
D.A. SPEARS - Kaolinite in coal measures sediments from the Pennine Basin, England: 115 a reVlew
K. PURVIS - The clay mineralogy of the Upper Triassic Skagerrak Formation, Central 125 North Sea
A. MEXIAS, M. FORMOSO, A. MEUNIER and D. BEAUFORT - Composition 135 and crystallization of corrensite in volcanic and pyroclastic rocks of Hilario Formation (RS) Brazil
R.W. TANK - Clay mineraIs of the Conasauga Group (middle to late Cambrian) in 145 northeast Tennessee
N.M.M. GONCALVES, P. DUDOIGNON and A. MEUNIER-The hydrothermal 153 alteration of continental basaltic flows in northern Parana Basin (Ribeirao Preto, Sao Paulo State, Brazil)
J. EVANS - The importance of detrital clay mineralogy in controlling geochemical fluxes 163 during shale diagenesis
A. SINGER and A. BANIN - Characteristics and mode ofpalagonite - A review 173
Index of authors 183
11
Volume V, Mémoire 89
Organizing Committee Preface, by Prof. Y. TARDY Table of contents
INDUSTRIAL APPLICATIONS OF CLAYS
3 5 7
F.J. ECKHARDT, H. RÔSCH and V. STEIN - Brick-clays !rom Lower-Saxony 15 (FRG) - Technical and environmental problems
YU XIANZHEN and ZHOU CHUYI - Purification of sepiolite and preparation of 25 silica
J. YVON, L. MICHOT and J.M. CASES - Clays and derived products in polyphased 33 materials
F.A. KRUSE and P.L. HAUFF - Remote sensing clay mineraI investigations for geologic 43 applications using visible/in!rared imaging spectroscopy
T. FUJITA, H. SUGIYAMA, M. ADACHI and H. NAKAZAWA - Strengthening 53 of clay aerogel by use of additives
S. TOMURA, R. MIYAWAKI, M. MAEDA, Y. SHIBASAKI, S. SAMEJIMA 63 and Y. YAMASHITA - Synthesis of kaolinite : effects of seeding
P. SENNETT - Changes in the physical properties of kaolin on exposure to elevated 71 temperature
F. VENIALE - Uses and applications of clays and clay mineraIs. State-of-the-art and 81 perspectives
M. SUGIURA, M. HORII, H. HAYASHI, T. SUZUKI, O. KAMIGAITO, S. NO- 91 GAWA and S. OISHI - Deodorizing paper using ,B-sepiolite
J. BAUDRACCO - Variations in permeability and migrations offine particles in uncon- 101 solidated sandstone submitted to percolation of saline solutions
L. STOCH - Chemical reactions of clay mineraIs and their utilization 111
ANALYTICAL TECHNIQUES TEACHING OF CLAY MINERALOGY
A.F. KOSTER van GROOS - High-pressure DTA method for clay analysis 123 J.S. JAHREN and A. OLSEN - Transmission electron microscopy of authigenic layer- 133 silicates from offshoreNorway
A.J. BLOODWORTH, A. HURST and D.J. MORGAN - Detection and estimation 143 of low levels of kaolinite by evolved water vapour analysis
R. SZYMANSKI, L. LOEBER and C. DURAND - Local composition of reference 149 clays as studied statistically by analytic scanning transmission electron microscopy
S.P. ALTANER, R.J. KIRKPATRICK and C.A. WEISS Jr. -Magic-anglespinning 161 nuclear magnetic resonance investigation of phyllosilicates
H. KODAMA - Use of color-coded transparencies for vizualizing layer silicate structures 171 D.C. GOLDEN, H. SITTERTZ-BHATKAR and J.B. DIXON - Structural changes 179 during the transformation of birnessite to buserite and todorokite
Index of authors 187
CLAY-ORGANIC INTERACTIONS
Proceedings of the 9th InternationalClay Conference, Strasbourg, 1989,V.C. FARMER and Y. TARDY (Eds) Sei. GéoJ., Mém., 85,p. 15 - 23,Strasbourg, 1990
QUANTITATIVE ABSORPTION SPECTROSCOPY OF CATIONIC DYES ON CLAYS Jos CENENS* and Robert A. SCHOONHEYDT*
ABSTRACT - The dimerization and trimerization reactions of proflavine and methYle~e blue on barasym SSM-100, laponite and hectorite in their Na+- and Ca +-forms in aqueous suspension can be quantitatively studied with theoretical equations derived for equilibrium reactions in solution.
The dime:fization constant for methylene blue on hectorite is ~266- 153 mole- dm • The trimerization constant on barasym is 772 mole- dm . Th~
dimerization constant for p~oflavine on hectorite is 266 - 294 mole- 1dm and on barasym 197 mole- 1dm • This successful treatment implies that for hectorite both the external surface and the interlamellar surface are freely available for diffusion and aggregation of the dye molecules. On barasym the reactions occur exclusively on the external surface of the aggregates. On laponite the treatment was unsuccessful, because the dimerization reaction was sterically hindered in the interlamellar space of the aggregates.
INTRODUCTION
The absorption spectra of proflavine (PF) and methylene blue (MS) on hectorite (H), laponite (L) and barasym ~SM-100 (BS) are significantly different from those of the 2.5 * 10- molar aqueous solutions of monomers, in which the ion exchange is performed (CENENS et al., 1987;
CENENS and SCHOONHEYDT, 1988).
At the surface, the monomer band of the dyes rapidly decreases with increasing loadings and at shorter wavelengths dimer and even trimer bands gain intensity. This process is called metachromasy (MICHAELIS and GRANICK, 1945; SCHUBERT and LEVINE, 1955). The monomer of proflavine (PFH+) absorbs at 458 nm, the dimer «PF)2) at 430 nm and these are the only species found at the surface in suitable pH conditions irrespective of the type of clay (CENENS et al., 1987). The monomers of methylene blue (MBH+) on edges and on the planar surfaces absorb at 673 nm and at 653 nm respectively. The dimer is formed on aIl the clays and absorbs around 600 nm, while trimers, which absorb at 570 nm, are only formed on those clays which have a large external or N2-BET surface, Land BS (CENENS and
SCHOONHEYDT, 1988).
Laboratorium voor Oppervlaktechemie, K.U.Leuven, K. Mercierlaan, 92, 3030 Leuven, Belgium.
of the clay-dye dispersions and the elsewhere (CENENS et al., 1987; CENENS points important in the present context It is the purpose of this paper to show that the di- and trimerization reactions on the surface can be treated quantitatively as in solution. Qualitative insight into the organization of the clay particles in aqueous suspensions is then obtained.
l - EXPERIMENTAL The clays, the preparation
spectroscopy have been described and SCHOONHEYDT, 1988). Only the are given below.
Different loadings were obtained by mixing 30 cm3 aqueous clay suspensions with 10 cm3 of a 10-5 molar dye solution. The final dye concentration of the suspensions was then constant and equal to 2.5
*
10-6 mole. The amount of clay was varied so as to obtain the desired loadings. For BS the suspensions were at pH
=
9. After equilibration overnight in the dark the absorbance of the suspensions at the wavelenghts of the monomer maxima was followed as a function of the loading. These maxima are 458 nm for PFH+, 673 nm for MBH+ on BS and 653 nm for MBH+ on the other clays.II - THEORY
For the reaction n M (M)n with equilibrium constant
the relation between the extinction coefficient f at a given wavelength and the aggregation number n and aggregation constant Kn is
(MATAGA, 1957):
n
K
n ELOG (Co
(1 -
EEm)) = LOG [---,,...---.:-] + n LOG (Co
(:m -
n"Em) ) (1)
(1 _
~_)n-l n
Em
with Co' the total dye concentration on the surface fm, the extinction coefficient of the monomer and f n , the extinction coeff~cient of the nth aggregate.
Plotting log ( Co ( 1 - f/f m)) vs. log ( Co ( f/f m - fn/f )) yields a straight line. From the slope and the intercept on the vei'tical axis n and Kn can be calculated.
For n
=
2 Le. pure dimerization, equation (1) becomes (HIDA and SANUI<I, 1970):(fm-f)!
1 C 2 =
, 0
17
((2)
Plotting ( (m -
d
vs.«( -
()/Co)1/2 yields a straight line. From the slope and the interce~s on the abscissa and ordinate the dimerization constant K2 and ( (m - (2/2) are obtained.The application of equations (1) and (2) requires the knowledge of (, (m' ( /n and CO. These are obtained as follows.
(~) ( is the absorbance value at the chosen wavelength divided by the dye concentration of 2.5
*
10-6 mole.(2) The (m values were determined in previous studies (CENENS and SCHOONHEYDT, 1988; CENENS, 1988). The numbers are 116 000 dm3 mole-1 cm-1 for MBH+ at 673 nm; 100 000 dm~ mol-1 cm-1 for MBH+ at 653 nm and 60000 dm3 mole-1 cm-1 for PFH+ at 458 nm.
(3) (n/n is estimated from the spectra at high loadings, where only dimers are seen in the absorption spectra. The value found was 12 000 dm3 I!'0le- 1 . cm-.1 for (MB) 2' (MB) 3 and (PF) 2 at the chosen wavelengths of
~nvest~gat~on.
(4) For the surface concentration of the .dyes a surface volume is defined in which the dyes reside. This volume is the surface area multiplied by a layer thickness of 1 nm. This thickness corresponds to three molecules with their molecular planes parallel to each other. With a unit cell volume of 0.4605 nm3 and a mean particle diameter of 300 nm for H and 30 nm for L surface areas of 775 m2/g and 819 m2/g are obtained respectively. This corresponds to surface volumes of 7.75
*
10-7 m3/g for H and 8.19*
10-7 m3/g for L. For the mica - type BS the surface volume is obtained in the same way by using the N2-BET surface area of 133 m2 /g( VAN OLPHEN and FRIPIAT, 1979). Its value ~s 1.33
*
10-7 m3/g.Examples of plots of equations (1) and (2) are shown in figure l . When the calculated parameters indicated that only dimerization occurred on the surface, K2 and (2/2 were used in equation (3), due to Spencer and Sutter (1979):
= ---~--- (3)
4 K2 Co
Theoretical (-values were obtained, plotted and compared with the experimental values in figures 2 - 5.
III - RESULTS
At the chosen wavelengths the monomer absorption is predominant. The absorbance decreases with loading for aIl the samples, but the details of the decrease are dependent on the type of clay and on the dye. This is shown in figures 2 - 7.
LOG(CO(i-_SL )) Em n E"m
-3.2 -3.0 -2.8 -2.6 -2:4J -2·~1.6
• e
M
l /e
-2.0 r-b
3_ . " , /e
8
~)(
! J ...
/~ ---n--
0~ ...-:;--
-~
~E 2 -3.~311\111\1- e ' " •
•
20 26 32 38-3.6
Em-E" )( 10-3
Figure 1: Application experimental Ca2 +-H (the samples) .
of equations (1) (e) and (2) ( . ) ta the absorbance values of PF (at 458 nm) on Na+- and data points are average values over the two
•
21.
30:10 0.11r
1
w w
() 008 ()
2 Z
<t <t
CC co
c:: c::
0 0
III III
CC CO 0.07
Cl <t
• •
0.04
•
0.03 0.05
0 4 8 12 16 20 24 28 0 4 8 12 16 20 24
f.1
MOL .G-1f.1
MOL .G-1Figure 2: Variation of the PFH+ absorbance at 458 nm with loading on Na+- 135: (e) experimental datai ( - ) calculated with equation (3) and K2
=
197 mole-1 dm3 .Figure 3: Variation of the PFH+ absorbance at 458 nm with loading on Na+- and Ca2 +-H: (e) experimental datai ( _ ) calculated with equation (3) and K2
=
294 mole-1 dm3 .OD5 0':."--2O::':---40'=--6::'-:o:-""':'a'::-0-1-':-0-=-0--
•
/-lMOL .G-1
• •
•
003'----'---L_-'---"-_'---...L.---L...J
o
20 40 60ao
100 120 140 /-lMOL .G-119
4 0.24 5
0.0
020
w 006 w
u u
z
Z<1: <1:
tri 0.05 tri
Cl::
~
0l/l
•
l/ltri CIl
<1:
0.04 <1:
Figure 4: Variation of the PFH+ absorbance at 458 nm with loading on Na+- and Ca 2+-L: (e) experimental data; ( - ) calculated with equation (3) and K2
=
2600 mole-1dm3Figure 5: Variation of the MBH+ absorbance at 653 nm with loading on Na+- H: (e) experimental data; (_) calculated with equation (3) and K2
=
153 mole-1dm3 .•
7
• •
•• •
0.04 0.20
i :::r. '
~
o.oa!-
tri<1:
6
3
o1...o4... . - ...-1I~....o.-I...I
o 2
% of CEC
01.--...-...J..--'----'---1--L.--
o
20 40 60ao
100 120 ,llMOL .G-1Figure 6: Variation of the MBH+ absorbance with loading on B5 at pH
=
9.Figure 7: Variation of the MBH+ absorbance at 653 nm with loading on Na+- L (0) and ca2+-L (e).
A - DIMERIZATION
The absorbance values of PFH+ on Na+-BS, Na+- and Ca 2+-L, and Na+- and Ca2+-H vary with the loading in the same way (figs. 2-4). The data points presented in figures 2, 3 and 4 are mean values of the data foints obtained from different experiments (3 with Na+-L and 1 with Ca 2 -L, 2 with Na+-H, 1 with Ca2+-H and 2 with Na+-BS). The mean deviation is 0.005 absorbance units. The decrease of the absorbance with loading is very fast: at 20 ~mol g-l (i.e. less than 5% of the exchange capacity), the absorbance has almost reached a constant small value. On L this low level is reached at smaller loadings than on H. MB+ on Na+-H shows the same picture (fig. 5).
The aggregation number and the aggregation constant are determined from the data of figures 2 to 5 with equation (1). The results are sununarized in Table 1. They show that the aggregation number is very close to 2, suggesting that only dimerization has taken place on the surface. This is confirmed by the successful application of equation (2), of which the results are also given in Table 1. Finally, the data points of Figures 2 to 5 were fitted with equation (3) and the K values of Table 1. The fit is given as a continuous line through the
~ata
points.The excellent agreement between the data points and the calculated line shows that dimerization is the only reaction at the surface of these clays.
B - TRIMERIZATION
Figure 6 shows the data for MB+ on Na+-BS. The decrease of the absorbance with the loading is fitted with equation (1), and an aggregation number of 2.82 is found. This indicates that the surface aggregation is close to a trimerization reaction. It is confirmed by the intensity gain of the typical trimer band at 575 nm (CENENS and SCHOONHEYDT, 1988).
C - SYSTEMS WITH MORE THAN ONE TYPE OF REACTION.
For MB on Na+ - and Ca2+ - L the decrease of the monomer absorbance with loading does not follow the simple patterns of dimerization or trimerization (fig. 7). The equations (1) (3) do not give reliable parameters. For PF good fits can be obtained with equations (1) and (2) (Tab. 1). However the reaction on the surface is not a pure dimerization reaction, because the aggregation number obtained from equation (1) is only 1.72. When pure dimerization was assumed by application of equation (2), an unusually large K2 was obtained. These data suggest that besides aggregation reactions other phenomena come into play.
IV - DISCUSSION
A - DIMERIZATION AND TRIMERIZATION
The most important result is that solution equations can be applied successfully to dye aggregation reactions on the surface. The implication of that result will be discussed in the next paragraphs.
In equation (1) the extinction coefficients of the monomer and dimer are fixed and the aggregation number and aggregation constant are determined. With equation (2) the aggregation number (= 2) is fixed and the dimerization constant and (! - ! /2) are determined. Both equations
21
give exactly the,same aggregation constant only if one obtains n= 2 with equation (1) and Em and E2/2 are the same in both equations. This situation is almost attained for MB+ on Na+-H and PFH+ on Na+- and Ca2+-H (Tab. 1). The dimerization constants for these cases are the most reliable. The K2 values for the dimerization reaction of PFH+ in aqueous solution range rrom 395 to 2700 mol- l .dm3 (TURNER et al., 1972; MATAGA, 1957) and from 2000 to 5900 mol-1dm3 for MBH+ (SPENCER and SUTTER, 1979;
BERGMANN and O'KONSKI, 1963). Our values are lower, meaning that dimerization is ~ore favoured in water than on the surface. This is not unreasonable as the clay surface - water environment is less polar than water (MAES et al., 1980). However, a word of caution is appropriate here, because the aggregation constants depend on the choice of the surface volume. A somewhat larger volume or, at constant surface area, a somewhat larger surface thickness will lead to the same aggregation constants as in aqueous solutions.
PFH+ on Na+- and Ca 2+-L gives statistically reliable dimerization parameters (Tab. 1), but the numbers fall outside the expected range to be phyically meaningful. The application of equation (1) gives n
=
1.72,which indicates that the reaction is not a pure dimerization. The hypothesis of a dimerization leads to a too high K2 value of 2600 mole-1 dm3 . When i t is assumed that the dimerization only occurs on the external surface (N2-BET is 360 m2.g-1 ) at the loadings under investigation, then a K~ value of 1147 mol-1.dm3 is obtained. This value is closer to that of PFH on H. This would indicate that only the external surface is important or only part of it. That is Na+- and Ca 2+-L occur as aggregates in aqueous suspension.
Table 1: Aggregation parameters of methylene b1ue and proflavine on c1ays
equation (1)
n Kn
r*
equation (2)Em-E2/2 K2
r*
MB on
Na+-H 1.94 126 0.97 104538 153 0.95
Na+-BS 2.82 772 0.98 not determined (0.60)
PF on
Na+-L 1.72 861 0.95 47930 2600 0.98
Ca2+-L
Na+-H 1. 95 266 0.99 49222 294 0.96
Ca2+-H
Na+-BS not determined (0.80) 48617 197 0.93
* ,
r=
linear regression coefficientFor MB+ on Na+-Bs the application of equation (1) leads to n
=
2.82,which is evidence for an almost pure trimerization reaction. Indeed, the absorption spectra show a trimer band at 570 nm (CENENS and SCHOONHEYDT, 1988). According to Braswell (1968) the trimerization constant of methylene blue in solution is comparable to the dimerization constant.
The value of 772 mole-2 dm6 on the surface is smaller and the same discussion can be repeated as given above for the dimerization constants.
B - ORGANIZATION OF CLAY PARTICLES IN AQUEOUS SUSPENSION
The surface concentrations have been calculated with surface volumes, which extend over the total surface areas of H and Land over the N2-BET
surface area of BS. In aIl cases excellent agreement between calculated 'and experimental data have been obtained except for MS on Na+- and Ca 2+- L. This means that the total surface area (interlamellar + external) is available for dimerization reactions in the case of PF on H and Land MB on H. This result can be interpreted in two ways: (1) these clays occur as randomly oriented, individual clay platelets; (2) they occur as aggregates, but then the distance between the individual clay sheets in the aggregate must be large enough to allow free diffusion and dimerization of the d~es in the interlamellar space.
In the case of Na - and Ca 2+-L aggregates do exist, but the fact that no physically acceptable dimerization constants could be derived, is indicative that the interlamellar surface is not freely available for MBH+, at least at the loadings investigated.
The thickness of the plane of MS is 0.325 nm, a dimer measures 0.65 nm (HANG and BRINDLEY, 1970); for PFH+ the same values can be used. Thus, free diffusion and dimerization in the interlamellar space means that the interlamellar distance in the aggregate is at least 0.65 nm and probably close to 1 nm.
Trimerization of MB only occurs on those clays that have a small particle size and occur as aggregates in suspension. The reaction occurs only on the external surface of the aggregates in the suspension. This is the case for BS. It is remarkable that the N2-BET surface area can be used to calculate a trimerization constant. It means that the size of the aggregates in suspension is the same as in the powder. For MB+ on Na+- and Ca2+-L dimerization and trimerization reactions occur almost consecutively. Dimerization occurs on the total surface and trimerization only on the external surface (CENENS and SCHOONHEYDT, 1988). The absence of trimerization on the interlamellar surface is probably due to the fact that the clay platelets collapse when a certain amount of dimers is formed on the interlamellar space, thus preventing trimer formation. The difference in behavior of MS on Na+- and Ca 2+-L as shown in Figure 7 sugqests that the Ca 2+-L is a slightly more open system than Na+-L i.e.
Ca 2+-L is closer to Na+- and Ca 2+-H than Na+-L.
CONCLUSIONS
Aggregation of dyes on the surface of clays in aqueous suspension can be treated quantitatively as in solution. The clay surface is therefore a solvent. It is less polar than water, because the aggregation constants are smaller than in water. The molecules move in the surface volume as in solution. There is therefore no specific dye - surface interaction, large enough to induce deviations from solution-like behavior. Deviations however do occur, but they are due to incomplete swelling, thus imposing a sterical hindrance to diffusion and aggregation in the interlamellar space.
ACKNOWLEDGMENT - J.C. acknowledges a PH. D. grant from the 1.W.
o.
N. L.(Belgium). This work was supported by the National Fund for Scientific Research of Belgium.
23
REFERENCES
BERGMAN K. and O'KONSKI C.T. (1963) - A spectroscopie study of methylene blue monomer, dimer and complexes with montmorillonite. J. Phys.
Chem., 67, p. 2169 - 2177.
BRASWELL E. (1968) Evidence for the trimerization in aqueous solutions of methylene blue. J. Phys. Chem., 72, p. 2477 - 2483.
CENENS J. (1988) - Spectroscopy of dye molecules at clay surfaces. Ph.D.
Thesis N°164, Faculty of Agronomy, K.U.Leuven, p. 158.
CENENS J. and SCHOONHEYDT R.A. (1988) - Visible spectroscopy of methylene blue on hectorite, laponite Band barasym in aqueous suspension.
Clays ans Clay Min. 36, p. 214 - 224.
CENENS J., VLIERS D.P., SCHOONHEYDT R.A. and DE SCHRYVER F.C. (1987) - Spectroscopie study of the surface chemistry of proflavine on clay mineraIs: Proc. Internat. Clay Conf. Denver, 1985; Schutz, L.G., Van Olphen, H. and Mumpton, F.A., (Eds), Clay MineraIs Soc., Bloomington, Indiana, p. 352 - 358.
HANG P.T. and BRINDLEY G.W. (1970) - Methylene blue adsorption by clay mineraIs. Determination of surface areas and cation exchange capacities (clay-organic studies XVIII). Clays and Clay Min., 18, p.
203 - 212.
HIDA M. and SANUKI T. (1970) - Studies of the aggregation of dyes. The scope of the maximum slope method. Bull. Chem. Soc. Japan, 43, p.
2291 - 2296.
MAES A., SCHOONHEYDT R.A., CREMERS A. and UYTTERHOEVEN J .B. (1980) Spectroscopy of cu(en)22+ on clay surfaces Surface and charge density effects. J. Phys. Chem., 84, p. 2795 - 2799.
MATAGA N. (1957) - Note on the polymerization of dyes in solution. Bull.
Chem. Soc. Japan, 30, p. 375 - 379.
MICHAELIS L. and GRANICK S. (1945) - Metachromasy of basic dyestuffs. J.
Am. Chem. Soc., 67, p. 1212 ~ 1219.
SCHUBERT W. and LEVINE A. (1955) - A qualitative theory of metachrornasy in solution. J. Amer. Chem. Soc., 77, P. 197 - 4201.
SPENCER W. and SUTTER J.R. (1979) - Kinetic study of the monomer - dirner equilibriurn of methylene blue in aqueous solution. J. Phys. Chem., 83, p. 1573 - 1576.
TURNER D.H., FLYNN G.W., LUNDBERG S.K., FALLER L.D. and SUTIN N. (1972) - Dimerization of proflavine by the laser Raman temperature-jurnp method. Nature, 239, p. 215 - 217.
VAN OLPHEN H. and FRIPIAT J.J. (1979) - Data handbook for clay mineraIs and other non-metallic mineraIs. Pergamon, New York, 346 p.
Proceedingsofthe91h International Ciay Conference, Strasbourg, 1989,V.C. FARMER and Y. TARDY (Eds) Sei. Géoi., Mém., 85,p. 25 - 34,Strasbourg, 1990
ASYMMETRICAL ADSORPTION ON KAOLINITE AND ORIGIN OF THE L-HOMOCHIRALITY Of THE AMINO ACIOS IN THE PROTEINS Of
LIVING ORGANISMS
André JULG*
ABSTRACT - Geolog1cal and astrophyslcal data allow us to consider that the a<X1ltlon ofCN- to nltrlles in~jdlc
medium is the most probablew~for the synthesls of the flrst amino acids 3.5x 109 yearscq;l. Moreover. kaolinite was obundont ot this epœh. This minerol exhibits two enontiomeric forms occording os the
(ô.
'li,ë) trihedron of the unit œil is direct or indirect (form Aand~resp.). Owing to the weak nuclear interactions, the form A is very slighl.ly more abundant than the form ~. Theoretlcal calculations show that, on the form A, the formation of L-alan1ne and the adsorption of the corresponding positive ion necessary for ils polycondensation into peptides. are favored with respect to the O-iSûmer. The L-homochirality of proteins would be explained by autœatalytic processes from the dissymmetry inducedbythe population dtfference of the two forms of kaolinite.1NTRODUCTI ON
The fa ct that all the proteins of the living organisms are bUllt up on amino aclds belonging to the L-series (fig. 1), Is certainly one of the most important questions in Biochemistry because it is strongly connected with the problem of the appearance of Life. The rare natural D-forms whlch exlst, belong, Indeed, to non-protelnlc molecules, as luclferln, octopln, echinomycine, or occur in the walls of certain bacteria (CORRIGAN,
1969),
1t is only after the death of the organism that the amlno acids of proteins racemize progressively. The case of the amino acids of the bone collagen is typical in this regard. The D/L ratio of the various amlno aclds ln the fossll bones lncreases as the age of the sample lncreases (BADA and PROTSCH,1973 ;
ARMSTRONG et a1.,1983 ;
JULG et a1.,1987),
showing clearly that the L- homochirality of amine acids is a very old phenomenon. Given the continuity ln the evolution of the living organlsms, we must thlnk that thls hOmochlrallty has been reached practlcally at the very time of the appearance of Life on Earth, i.e. ca. 3.5x109
years ago, and that it has been held by means of replicatlon processes from asymmetric molecules ln the living ce11s.* Laboratoire de Chimie ThéoriQue, UniverSité de Provence,
13331
Marseille Cedex3,
France and CRI'1C2, Campus de Lumlny, Case913, 13288
Marseille Cedex9,
France,L _
form1 1 1 1 1
1
1 1 1 1 1 1 1 1 1
1
D _
formFigure 1: L- andD- conformations of amlno aclds.
N.B. : wltlJ few exceptions, L-forms are dextro-rotatory, andD-forms levo-rotatoryAmong all the numerous physical causes which have been envisaged in order to account for this L-homochirality (MASON,
1983),only the energy difference 6E between two enantiomeric forms arising from the weak nuclear interactions (WEINBERG,
1967 ;SALAM,
1968)seems to have been accepted. For small molecules
~Eis extremely weak : ca. 10-
17kcal/mol for alanine, val ine, serine, aspartic acid (MASON and TRANTER,
1983 ;TRANTER,
1985), the L-form's being more stable than the D-forms.
Nevertheless, according to these authors, these differences would be able to explain the L-homochlrallty. Mathematlcal models uslng the bifurcation theory have, Indeed, been constructed to show that a very small initial L/D dissymmetry can be amplified to lead to the complete dominance of one enantiomeric form (KONDEPUDI and NELSON,
1983,1985).
Nevertheless, such an explanation exhlbits the dlsadvantage of not taking the physical conditions in which the first amlno acids were syntheslzed and polycondensated Into account.
The aim of thls paper is precisely to show the predominant role which kaolinite was able to play at the preblot1c level ln the acqu1sltion of the L-homochlrality of the living prote1ns.
1 -
PHYSICO-CHEMICAL CONDITIONS IN WHICH L1FE APPEARED ON EARTHLtfe appeared on Earth under phys1co-chemlcal conditions very dlfferent from those we
know at the present time. Geological studies of soils dating from this epoch, indeed, show a
thlck sedimentation which lnvolves a drastic eroslon of granitic basements under the effect
of abundant atmospheric precipitations. Moreover, these sediments are grey owlng to the
presence of Fe
2+Ions. This lndicates that the atmosphere and the ocean medium were
reduclng. Oxygen was absent. Subsequently, when oxygen appeared, freed from the
atmospheric C02 by the photosynthesls carried out by the first vegetal organisms
27
(cyanobacteria), sediments become reddish (LABEYRIE,
1985).The importantquantity of Oz in the present atmosphere indlcates that C02 was very abundant ln the primitive atmosphere.
Moreover, temperature was certalnly hlgh (ca. 80·0 This temperature and the presence or CO
2explaln that, under the eHect or the heavy preclpltatlons, feldspar or granltes has been decomposed Into clays, essentially lnto kaollnlte owlng to these drastlc conditions, whlch deposited in shallow waters around the continents or in lakes and lagoons.
Recent astrophysical studies, performed in situ in the solar system, allow us to make the composition of the early terrestrial atmosphere precise. One thinks, indeed, that the big planets (Jupiter, Saturn, Uranus, Neptun) and their satellites, whose temperatures have remained very low owing to their distance with respect to Sun, have been practically not modified since their formation,
4.5x 109years ago. In particular, Titan, the biggest satellite of Saturn -its diameter is roughly eQual to the half of that of Earth- exhibits an atmosphere essentlally constltuted by Nz
(95 %)saturated and unsaturated hydrocarbOns, HCN and nitrlles, CO, COz and Hz. Oxygen is absent. Water, If lt exists, ls solld owlng to the low temperature of the surface
(94K), and confined under the ocean of CzHs which covers the satellite CENCRENAZ and BIBING,
1987 ;GAUTIER,
1985).All these features aJ10w us to imagine the chemical composition of the environment in which Life appeared on Earth. Waters were richin COz and contained HCN, nitriles and unsaturated hydrocarbons, i.e. particularly reactive molecules.
Il - THE MILLER REACTION
Among all the numerous mecMnisms which have been suggested for the synthesis of the first amino acids (CAIRNS-SMITH,
1982),that proposed by MILLER as far back as
1957,seems to be the mechanism which best agrees with our present knowledge about the early physico- chemical conditions. Under the effect of the reducing medium, nitriles RCN which were present in the early atmosphere are transformed into the corresponding imines which give iminium ions by addition of CW (Miller's reaction) :
(1)
which affords the amino acids RCH(COz)-NHz on hydrolysis. Nevertheless, in the absence of an asymmetrical cause, such a reaction, performed from achiral molecules, leads necessarily to a racemic
(D+L)mixture.
Glven that numerous experlmentsshOw that on clays (kaollnlte and montmorlllonlte)
amlno aclds form from sultable reduclng mixtures (e.g. CO, Hz, NH3) and condense Into
pOlypeptides of high molecular mass
(> 104)<THENG,
1974),the role of clays cannot be
19nored in the general process proposed by MILLER. Before making the role played by the clays,
and more especlally by kaol1nlte, precise, lt Is necessary to glve some detalls about thelr
structure.
III - STRUCTURE Of KAOLINITE AND MONTMORILLONITE
Kaolinite, Si
4AI
40,o<OH)e, occurs as minute hexagonal plates, constituted by layers stacked in a triclinic arrangement with only translatlonal symmetry. The characteristics of the unit cell are the following ŒRINDLEY and ROBINSON, 1946):
a = 5.14 ;
b= 8.93 ; c = 7.37
Àex = 91.8· ; f3 = 104.5· ;
~= 90·
Each layer is constituted by a sheet of regular tetrahedra about 51 atoms, topped with octahedra about .8.l atoms <fig. 2).
Q- -- - -- -0- ---- --0- -
---0- --- - ...<;)
· .
·
,·
,· .
Face
TI
u
o
OX>1l€nFace
l
b~ 8.93À
.OH DAI • Si
Figure 2: Structure of kaollnlte: projection on aplane perpendlcular to tne
~-axlsThis mineraI possesses two enantiomeric forms according as the trihedron <a,D,ë> is direct or indirect. We will denote these two forms A and a respectively.
By analogy wlth the results obtained for small molecules, we can conclude that, owing to the weak nuclear interactions, the energies of the two enantiomeric forms A and a are
sllghtly different. Unfortunately, the dlfflculty of the calculatlon of âE precluded us from
obtainlng a quantitative result, but we were able algebralcally to predlct the slgn or this
latter <JULG, 1988). ThIS Is sufflclent to conclude that the rorm A Is more stable than the
form li, and, consequently, that the form A is more abundant than the form Il. However,
29
although the value
ofâE for a crystal has to be larger than those obtalned for small molecuJes, the populatIon ratio
AIB 15certalnly too close to
1for any experlmental verlflcatlon of thts theoretlcal forecast to be allowed.
The basic layers and, conseQuently, the crystals themselves, exhibit two faces of a dlfferent nature (fig.
2).The one
15constituted by oxygen atoms belonging to the 5i0
4tetrahedra (Face 1>, the other by OH groups llnked to aluminum atoms (Face ID.
On the other hand, from the values theoretically obtained for various crystals (JULG,
1978),we can estimate the net charges carried by the various atoms of kaolinite :
.sJ. : +3.0 ; Al: +2.1 ;
Q:-1.4 ; Q.ti: -0.8 .
A priori, these values favor adsorption of positive ions on face
1.This will be confirmed by our calculation
(~.illli.a).Montmor1l10nlte crystals are constituted by layers whose two faces are ldentical wlth face
1of kaolinlte. This explalns that both kaolinite and montmorl11onlte are working for the synthesis and for the polycondensation of amino acids. But in montmorillonite, the stacklng
ofthe layers
15monocllnic, so that thls mineraI does not ex1st ln two Inverse forms and, conseQuently, it has not been able to play a role in the natural
LlOdiscrimination.
IV -
ROLE PLAVEO SV KAOLINITE IN THE MILLER REACTIONThe chirality of kaolinite can induce an asymmetry in the MILLER reaction. From what we have seen, indeed, it is logical to think that RÇH=NH
2+ion adsorbs on face
1of kaolinite.
According to whether this ion is adsorbed as figure 3 lndicates or on lts other face, the' nucleophilic addition of CN- (reaction
1)affords the L- or O-precursor of the corresponding amino acid. We will cali these two types of reaction, L- and O-adsorption respectively.
C-
NN C
'4t
H +
-...c ===NH /
jc<
2~ . ' ,C~
H • '1 "" CH:J NH'2
Figure 3: Tlle n(Jcleopllilic addition of a cyanide ion to an etllylimini(Jm cation to form
L-«-4mlno-proprlonltrlle
Consequently, on a given structure (6 or a) of kaolinite, a certain type of adsorption (L or D) Is favored wlth respect to the other, and an optlcally active mixture of the two corresponding amino acids is obtained on hydrolysis.
ln the absence of experimental data, we have theoretically calculated the adsorption energy of the ethyliminium ion (CH
3CH=NH
2)+ on various sites of kaolinite (JULG, 1987 ; JULG and OZIAS, 1988). The method is summarized ln the appendix. The results are the following.
On the structure 6 -Ca,D,C) direct- adsorption preferentially occurs on face 1so that the L-precursor (L-adsorption) is obtained. Figure 4 indicates the optimal L-adsite. For the . optimal D-adslte, the adsorption energy is weaker than that of the optimal L-site by 0.4 kcallmol. This value Is much larger than the activation energy difference arising from the weak interactions (ca. 10- 17 kcallmol, TRANTER, 1986). The adsorption energies for all the other sites are slgnlficantly weaker (by 2 kcallmol at leaso.
o o
o
o o o o
o
o
o o o
o
Figure 4:
Preferentia/ adsite of t/Je positive ion ofalanine on t/Je face 1 ofkao/inite. T/Je CIrc/es represent oxygen atoms and t/Je arrows t/Jemo/ecu/es. T/Je sign~ indicates t/Je position of t/Je NH]~group.
Consequently, the asymmetric adsorption of ethyllmlnlum Ion on kaollnite leads to a
difference between the populations of the L- and D-forms
ofalanine, owing to the fact that
the form A of kaolinite is slightly more abundant than the form a. More precisely, according
to our results, If the ratio of the number of 6 crystals over that of a crystals Is equal to 1+x
(O<x« 1), the"asymmetry ratio r = (L
-D)/(L+D) would be equal to xii 0 at 80'C for alanine (the
slze of the crystals Is assumed to be the same for all of them). Consequently, even if x Is
31
very small, say weaker than 10-3 or 10-4, r remains incomparably larger than the ratio arising from the weak interactions, rWI - 10- 17.
v -
ASYMMETRIC ADSORPTION Of THE AMINO ACIOS ON KAOLINITEThe precursor being a neutral molecule Is weakly llnked wlth the substrate, so that
1tIs easily liberated in the aqueous ambient medium where, on hydrolysis, it affords the corresponding amino acid without modifying the configuration of the asymmetric carbon.
But these acids can, in their turn, be adsorbed on kaolinlte. In fact, given the high concentration in COz, the medium is acidic and the adsorbed species Is the positive ion.
Consequently, adsorption happens on face 1of kaolinite. The calculation (JULG, 1986) shows that on the structure
A,L-Ala+ ions are adsorbed on face 1preferentlally to D-Ala+ ions. The difference between the energles correspondlng to the optimal L- and D-adsorptions (ca. 0.03 kcallmol) is weaker than that obta'ined for the adsorption of the ethyliminium ion. In any case, the L-:.forms are here agaln favored wlth respect to the D-forms.
Moreover, Ala+ Ions adsorb sa that the polycondensation Into a syntactlc peptide, i.e.
whOse unities belong to the same serles, Is possible (fig. 4).
Nevertheless, a point has to be emphaslzed. In the living organisms, indeed, the synthesis of proteins is realized by RNA molecules which are themselves synthesized by DNA with the assistance of an enzyme, i.e. a protein, so that the question is to know which structure, protein or nucleic acid, is older. In fact, given that in the atmosphere of Titan adenine, which is a pentamer of HCN, has been detected ŒNCRENAZ and BIBING, 1987), we can guess that the fundamental bases of the nucleic acids were present on Earth at prebiotlc tlmes, so that the flrst nuclelc actds and the flrst protelns would have Independently appeared before the definitive process of synthesis was adopted in the living cells.
CONCLUSION
The most Important poInt which emerges from our calculatlons Is that the flrst amine aclds may have been syntheslzed on kaollnlte wlth a very weak domInance of the form L.
Subsequently, these aclds would be condensed on kaollnite. Although the dlfference between the L- and D-populations of the free amino acids was extremely weak,the homochlrality was able to be reached in an open flow-reaction system by autocatalytic processes with mutual annihilation in the formation of the two enantiomers, provided that the initial concentrations ln L- and D-amino acids are malntained at a flxed level (KONDEPUDI and NELSON, 1983,1985). In our model, this latter condition would be ensured by the saturation in L- and D-'amino acids on the faces 1 of kaollnite. It results from the calculations performed by KONDEPUDI and NELSON (1985) that homochlrallty can be attalned very qulckly.
For instance, ln a lake of volume 4x 109 lIters
(lkm xl km x 4 m), with concentratIons ln
amino acids of 10-3 M, a relative difference in concentrations between the L- and 0-
populations of 10-17(1.e. corresponding to the
~Earising from the weak nuclear interactions) leads to L-homochirality after only 104 years. In a greater volume, the necessary time would be much greater. Other things being equal, in our model where the initial difference between the L- and D-populations is incomparably larger than that which arises from the weak interactions, the tlme necessary to reach the hOmochlral ity must be considerably reduced wlth respect to that obtained by the weak interaction mode1. Although we do not know the exact conditions (concentration, volume) in which the polycondensation
ofthe first amino acids happened, we can think that the concentration was locally sufficient (on kaolinite) for homochirality to be very quiCkly reached, geologically speaking.
Nevertheless, it is important to emphasize that, even if the asymmetric adsorption on kaolinite has been the working cause of the L-homochirality of amino acids, the first cause remains the weak nuclear lnteractions, but at the mineraI level and not at the molecular level as certain authors claim (MASON and TRANTER, 1983).
APPENDIX
