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Book Description
LES OBJECTIFS DE CE TRAVAIL SONT DE DETERMINER LES PROPRIETES THERMODYNAMIQUES DE LA KAOLINITE ET DE VERIFIER L'APTITUDE DES LOIS CINETIQUES DEDUITES DE LA THEORIE DE L'ETAT TRANSITOIRE A DECRIRE LA CINETIQUE DE DISSOLUTION/CRISTALLISATION DE CE MINERAL DANS DES CONDITIONS HYDROTHERMALES. UNE KAOLINITE NATURELLE D'ORIGINE HYDROTHERMALE, DE PARFAITE CRISTALLINITE ET DEPOURVUE D'IMPURETES MAJEURES, A ETE CHOISIE POUR CETTE ETUDE. DES MESURES DE SOLUBILITE, REALISEES EN MILIEU FAIBLEMENT BASIQUE ENTRE 60 ET 170C, ONT ABOUTI A LA DETERMINATION DE LA CONSTANTE DE DISSOCIATION DE LA KAOLINITE DANS CET INTERVALLE DE TEMPERATURE. UNE REGRESSION LINEAIRE PAR MOINDRES CARRES DES RESULTATS EXPERIMENTAUX A PERMIS DE PROPOSER UNE VALEUR D'ENERGIE LIBRE DE FORMATION DE LA KAOLINITE (25C, 1 BAR) EGALE A -907,68 KCAL/MOL. CETTE VALEUR EST LA PLUS NEGATIVE DES VALEURS DETERMINEES JUSQU'ICI A PARTIR DE MESURES DE SOLUBILITE. PAR AILLEURS, LES PARAMETRES THERMODYNAMIQUES OBTENUS SONT EN ACCORD AVEC CEUX DEDUITS DE L'ETUDE DE L'EQUILIBRE KAOLINITE-BOEHMITE AU-DELA DE 200C. LES MESURES DES VITESSES DE DISSOLUTION/PRECIPITATION DE LA KAOLINITE ONT ETE EFFECTUEES A 150C EN MILIEU ACIDE ET BASIQUE DANS UN LARGE DOMAINE D'AFFINITE CHIMIQUE ET DANS DES SOLUTIONS D'ATTAQUE DE COMPOSITION VARIEE. IL EST MONTRE QUE LES VITESSES DE DISSOLUTION DE LA KAOLINITE DEPENDENT FORTEMENT DE L'AFFINITE CHIMIQUE DE LA REACTION, MEME LOIN DE L'EQUILIBRE. EN MILIEU ACIDE, CES VITESSES SONT UNE FONCTION UNIQUE DE LA TENEUR EN ALUMINIUM DE LA SOLUTION TANDIS QU'EN MILIEU ALCALIN, SILICE ET ALUMINIUM AFFECTENT CONJOINTEMENT LES VITESSES DE LA REACTION, L'EFFET INHIBITEUR DE L'ALUMINIUM RESTANT TOUTEFOIS PREDOMINANT. LES VITESSES DE CRISTALLISATION MESUREES DEPENDENT PEU DE L'AFFINITE CHIMIQUE. CES INFORMATIONS PERMETTENT DE PRECISER LA NATURE DU COMPLEXE ACTIVE ET D'ETABLIR, DANS LE CADRE DE LA THEORIE DE L'ETAT TRANSITOIRE, DE NOUVELLES LOIS CINETIQUES QUI RENDENT COMPTE AVEC PRECISION DES VITESSES DE DISSOLUTION/PRECIPITATION DE LA KAOLINITE DANS UN LARGE DOMAINE D'AFFINITE CHIMIQUE
Book Description
LES OBJECTIFS DE CE TRAVAIL SONT DE DETERMINER LES PROPRIETES THERMODYNAMIQUES DE LA KAOLINITE ET DE VERIFIER L'APTITUDE DES LOIS CINETIQUES DEDUITES DE LA THEORIE DE L'ETAT TRANSITOIRE A DECRIRE LA CINETIQUE DE DISSOLUTION/CRISTALLISATION DE CE MINERAL DANS DES CONDITIONS HYDROTHERMALES. UNE KAOLINITE NATURELLE D'ORIGINE HYDROTHERMALE, DE PARFAITE CRISTALLINITE ET DEPOURVUE D'IMPURETES MAJEURES, A ETE CHOISIE POUR CETTE ETUDE. DES MESURES DE SOLUBILITE, REALISEES EN MILIEU FAIBLEMENT BASIQUE ENTRE 60 ET 170C, ONT ABOUTI A LA DETERMINATION DE LA CONSTANTE DE DISSOCIATION DE LA KAOLINITE DANS CET INTERVALLE DE TEMPERATURE. UNE REGRESSION LINEAIRE PAR MOINDRES CARRES DES RESULTATS EXPERIMENTAUX A PERMIS DE PROPOSER UNE VALEUR D'ENERGIE LIBRE DE FORMATION DE LA KAOLINITE (25C, 1 BAR) EGALE A -907,68 KCAL/MOL. CETTE VALEUR EST LA PLUS NEGATIVE DES VALEURS DETERMINEES JUSQU'ICI A PARTIR DE MESURES DE SOLUBILITE. PAR AILLEURS, LES PARAMETRES THERMODYNAMIQUES OBTENUS SONT EN ACCORD AVEC CEUX DEDUITS DE L'ETUDE DE L'EQUILIBRE KAOLINITE-BOEHMITE AU-DELA DE 200C. LES MESURES DES VITESSES DE DISSOLUTION/PRECIPITATION DE LA KAOLINITE ONT ETE EFFECTUEES A 150C EN MILIEU ACIDE ET BASIQUE DANS UN LARGE DOMAINE D'AFFINITE CHIMIQUE ET DANS DES SOLUTIONS D'ATTAQUE DE COMPOSITION VARIEE. IL EST MONTRE QUE LES VITESSES DE DISSOLUTION DE LA KAOLINITE DEPENDENT FORTEMENT DE L'AFFINITE CHIMIQUE DE LA REACTION, MEME LOIN DE L'EQUILIBRE. EN MILIEU ACIDE, CES VITESSES SONT UNE FONCTION UNIQUE DE LA TENEUR EN ALUMINIUM DE LA SOLUTION TANDIS QU'EN MILIEU ALCALIN, SILICE ET ALUMINIUM AFFECTENT CONJOINTEMENT LES VITESSES DE LA REACTION, L'EFFET INHIBITEUR DE L'ALUMINIUM RESTANT TOUTEFOIS PREDOMINANT. LES VITESSES DE CRISTALLISATION MESUREES DEPENDENT PEU DE L'AFFINITE CHIMIQUE. CES INFORMATIONS PERMETTENT DE PRECISER LA NATURE DU COMPLEXE ACTIVE ET D'ETABLIR, DANS LE CADRE DE LA THEORIE DE L'ETAT TRANSITOIRE, DE NOUVELLES LOIS CINETIQUES QUI RENDENT COMPTE AVEC PRECISION DES VITESSES DE DISSOLUTION/PRECIPITATION DE LA KAOLINITE DANS UN LARGE DOMAINE D'AFFINITE CHIMIQUE
Author: Peter C. Lichtner Publisher: Walter de Gruyter GmbH & Co KG ISBN: 1501509799 Category : Science Languages : en Pages : 452
Book Description
Volume 34 of Reviews in Mineralogy focuses on methods to describe the extent and consequences of reactive flow and transport in natural subsurface systems. Since the field of reactive transport within the Earth Sciences is a highly multidisciplinary area of research, including geochemistry, geology, physics, chemistry, hydrology, and engineering, this book is an attempt to some extent bridge the gap between these different disciplines. This volume contains the contributions presented at a short course held in Golden, Colorado, October 25-27, 1996 in conjunction with the Mineralogical Society of America's (MSA) Annual Meeting with the Geological Society of America in Denver, Colorado.
Author: B. Jamtveit Publisher: Springer Science & Business Media ISBN: 9401591792 Category : Science Languages : en Pages : 420
Book Description
This book is the proceedings of the 11th Kongsberg seminar, held at the Norwegian Mining Museum in the city of Kongsberg, about 70 km Southwest of Oslo. The Kongs berg district is known for numerous Permian vein deposits, rich in native silver. Mining activity in the area lasted for more than 300 years, finally ceasing in 1957. The first eight Kongsberg seminars, organized by professor Arne Bj0rlykke, now director of the Norwegian Geological Survey, were focused on ore-forming processes. These seminars have always been a meeting point for people with a variety of geological backgrounds. Since 1995, the Kongsberg seminars have focussed on geological processes, rather than on specific geological systems, and the selection of invited speakers has been strongly influenced by their interest in the dynamics of geological systems. In 1995 and 1996, various aspects of fluid flow and transport in rocks, were emphasized. The first "Kongsberg proceedings" (of the 1995 seminar) published by Chapman and Hall (Jamtveit and Yardley, 1997) contained 17 chapters dealing with a wide range of topics from field based studies of the effects of fluid flow in sedimentary and metamorphic rocks to computer simulations of flow in complex porous and fractured media. In 1997, the focus was changed to growth, and dissolution processes in geological systems.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Dissolution and precipitation rates of low defect Georgia kaolinite (KGa-1b) as a function of Gibbs free energy of reaction (or reaction affinity) were measured at 22 C and pH 4 in continuously stirred flow through reactors. Steady state dissolution experiments showed slightly incongruent dissolution, with a Si/Al ratio of about 1.12 that is attributed to the re-adsorption of Al on to the kaolinite surface. No inhibition of the kaolinite dissolution rate was apparent when dissolved aluminum was varied from 0 and 60 [mu]M. The relationship between dissolution rates and the reaction affinity can be described well by a Transition State Theory (TST) rate formulation with a Temkin coefficient of 2 R{sub diss} (mol/m2s) = 1.15 x 10−13 [1-exp( -[Delta]G/2RT)]. Stopping of flow in a close to equilibrium dissolution experiment yielded at solubility constant for kaolinite at 22 C of 10{sup 7.57}. Experiments on the precipitation kinetics of kaolinite showed a more complex behavior. One conducted using kaolinite seed that had previously undergone extensive dissolution under far from equilibrium conditions for 5 months showed a quasi-steady state precipitation rate for 105 hours that was compatible with the TST expression above. After this initial period, however, precipitation rates decreased by an order of magnitude, and like other precipitation experiments conducted at higher supersaturation and without kaolinite seed subjected to extensive prior dissolution, could not be described with the TST law. The initial quasi-steady state rate is interpreted as growth on activated sites created by the dissolution process, but this reversible growth mechanism could not be maintained once these sites were filled. Long-term precipitation rates showed a linear dependence on solution saturation state that is generally consistent with a two dimensional nucleation growth mechanism following the equation R{sub ppt}(mol/m2s) = 3.38 x 10−14 exp[181776/T21n[Omega]]. Further analysis using Synchrotron Scanning Transmission X-ray Microscopy (STXM) in Total Electron Yield (TEY) mode of the material from the precipitation experiments showed spectra for newly precipitated material compatible with kaolinite.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Dissolution and precipitation rates of low defect Georgia kaolinite (KGa-1b) as a function of Gibbs free energy of reaction (or reaction affinity) were measured at 22 C and pH 4 in continuously stirred flowthrough reactors. Steady state dissolution experiments showed slightly incongruent dissolution, with a Si/Al ratio of about 1.12 that is attributed to the re-adsorption of Al on to the kaolinite surface. No inhibition of the kaolinite dissolution rate was apparent when dissolved aluminum was varied from 0 and 60 [mu]M. The relationship between dissolution rates and the reaction affinity can be described well by a Transition State Theory (TST) rate formulation with a Temkin coefficient of 2 R{sub diss} (mol/m2s) = 1.15 x 10−13 [1-exp( -[Delta]G/2RT)]. Stopping of flow in a close to equilibrium dissolution experiment yielded a solubility constant for kaolinite at 22 C of 10{sup 7.57}. Experiments on the precipitation kinetics of kaolinite showed a more complex behavior. One conducted using kaolinite seed that had previously undergone extensive dissolution under far from equilibrium conditions for 5 months showed a quasi-steady state precipitation rate for 105 hours that was compatible with the TST expression above. After this initial period, however, precipitation rates decreased by an order of magnitude, and like other precipitation experiments conducted at higher supersaturation and without kaolinite seed subjected to extensive prior dissolution, could not be described with the TST law. The initial quasi-steady state rate is interpreted as growth on activated sites created by the dissolution process, but this reversible growth mechanism could not be maintained once these sites were filled. Long-term precipitation rates showed a linear dependence on solution saturation state that is generally consistent with a two dimensional nucleation growth mechanism following the equation R{sub ppt}(mol/m2s) = 3.38 x 10−14 exp[- 181776/T2 1n[Omega]]. Further analysis using Synchrotron Scanning Transmission X-ray Microscopy (STXM) in Total Electron Yield (TEY) mode of the material from the precipitation experiments showed spectra for newly precipitated material compatible with kaolinite. An idealized set of reactive transport simulations of the chemical weathering of albite to kaolinite using rate laws from HELLMANN and TISSERAND (2006) and this study respectively indicate that while pore waters are likely to be close to equilibrium with respect to kaolinite at pH 4, significant kaolinite supersaturation may occur at higher pH if its precipitation rate is pH dependent.
Author: Craig M. Bethke Publisher: Cambridge University Press ISBN: 1139468324 Category : Science Languages : en Pages : 564
Book Description
This book provides a comprehensive overview of reaction processes in the Earth's crust and on its surface, both in the laboratory and in the field. A clear exposition of the underlying equations and calculation techniques is balanced by a large number of fully worked examples. The book uses The Geochemist's Workbench® modeling software, developed by the author and already installed at over 1000 universities and research facilities worldwide. Since publication of the first edition, the field of reaction modeling has continued to grow and find increasingly broad application. In particular, the description of microbial activity, surface chemistry, and redox chemistry within reaction models has become broader and more rigorous. These areas are covered in detail in this new edition, which was originally published in 2007. This text is written for graduate students and academic researchers in the fields of geochemistry, environmental engineering, contaminant hydrology, geomicrobiology, and numerical modeling.
Author: Helene Paquet Publisher: Springer Science & Business Media ISBN: 3642605257 Category : Science Languages : en Pages : 523
Book Description
Clays and soils are of great importance in various scientific fields, such as agriculture and environmental science, and in mineral deposits. Students and close collaborators of Georges Millot, the eminent French clay sedimentologist, have put together a book with topics ranging from weathering processes and diagenetic evalution of sediments to sedimentary mineral deposits. The book is of interest to practitioners, advanced students as well as teachers in the above fields.
Author: Arthur F. White Publisher: Walter de Gruyter GmbH & Co KG ISBN: 1501509659 Category : Science Languages : en Pages : 600
Book Description
Volume 31 of Reviews in Mineralogy reviews current thinking on the fundamental processes that control chemical weathering of silicates, including the physical chemistry of reactions at mineral surfaces, the role of experimental design in isolating and quantifying these reactions, and the complex roles that water chemistry, hydrology, biology, and climate play in weathering of natural systems. The chapters in this volume are arranged to parallel this order of development from theoretical considerations to experimental studies to characterization of natural systems. Secondly, the book is meant to serve as a reference from which researchers can readily retrieve quantitative weathering rate data for specific minerals under detailed experimental controls or for natural weathering conditions. Toward this objective, the authors were encouraged to tabulate available weathering rate data for their specific topics. Finally this volume serves as a forum in which suggestions and speculations concerning the direction of future weathering research are discussed.
Author: J.I. Drever Publisher: Springer Science & Business Media ISBN: 9789027719621 Category : Science Languages : en Pages : 348
Book Description
Several important developments in our understanding of the chemistry of weathering have occurred in the last few years: 1. There has been a major breakthrough in our understanding of the mechanisms controlling the kinetics of sil icate dissolution, and there have been major advances in computer modeling of weathering processes. 2. There has been a growing recognition of the importance of organic solutes in the weathering process, and hence of the inter-relationships between mineral weathering and the terrestrial ecosystem. 3. The impact of acid deposition ("acid rain") has been widely recognized. The processes by which acid deposition is neutral ized are closely related to the processes of normal chemical weathering; an understanding of the chemistry of weathering is thus essential for predicting the effects of acid deposition. 4. More high-qual ity data have become available on the chemical dynamics of smal I watersheds and large river systems, which represent the integrated effects of chemical weathering.
Author: Jean-Luc Devidal
Author: Jean-Luc Devidal
Author: Peter C. Lichtner
Author: B. Jamtveit
Author: 
Author: 
Author: Craig M. Bethke
Author: Helene Paquet
Author: Arthur F. White
Author: J.I. Drever
Author: H. W. van der Marel