Surface Complexation Modeling

This book provides a description of the generalized two layer surface complexation model, data treatment procedures, and thermodynamic constants for sorption of metal cations and anions on gibbsite, the most common form of aluminum oxide found in nature and one of the most abundant minerals in soils, sediments, and natural waters. The book provides a synopsis of aluminum oxide forms and a clearly defined nomenclature. Compilations of available data for sorption of metal cations and anions on gibbsite are presented, and the results of surface complexation model fitting of these data are given. The consistency of the thermodynamic surface complexation constants extracted from the data is examined through development of linear free energy relationships which are also used to predict thermodynamic constants for ions for which insufficient data are available to extract constants. The book concludes with a comparison of constants extracted from data for sorption on gibbsite with those determined previously for hydrous ferric oxide (HFO), hydrous manganese oxide (HMO), and goethite. The overall objective of this book is the development and presentation of an internally consistent thermodynamic database for sorption of inorganic cations and anions on gibbsite, an abundant and reactive mineral in soils, sediments, and aquatic systems. Its surface has a high affinity for sorption of metal cations and anions, including radionuclides. The gibbsite database will enable simulation and prediction of the influence of sorption on the fate of these chemical species in natural systems and treatment processes in which aluminum oxides are abundant. It thus will help to advance the practical application of surface complexation modeling.

This book provides a description of the generalized two layersurface complexation model, data treatment procedures, andthermodynamic constants for sorption of metal cations and anions ongibbsite, the most common form of aluminum oxide found in natureand one of the most abundant minerals in soils, sediments, andnatural waters. The book provides a synopsis of aluminum oxideforms and a clearly defined nomenclature. Compilations of availabledata for sorption of metal cations and anions on gibbsite arepresented, and the results of surface complexation model fitting ofthese data are given. The consistency of the thermodynamic surfacecomplexation constants extracted from the data is examined throughdevelopment of linear free energy relationships which are also usedto predict thermodynamic constants for ions for which insufficientdata are available to extract constants. The book concludes with acomparison of constants extracted from data for sorption ongibbsite with those determined previously for hydrous ferric oxide(HFO), hydrous manganese oxide (HMO), and goethite.The overall objective of this book is the development andpresentation of an internally consistent thermodynamic database forsorption of inorganic cations and anions on gibbsite, an abundantand reactive mineral in soils, sediments, and aquatic systems. Itssurface has a high affinity for sorption of metal cations andanions, including radionuclides. The gibbsite database will enablesimulation and prediction of the influence of sorption on the fateof these chemical species in natural systems and treatmentprocesses in which aluminum oxides are abundant. It thus will helpto advance the practical application of surface complexationmodeling.

FOREWORD.PREFACE.CHAPTER 1 - Aluminum Oxides and Hydroxides underEnvironmental Conditions.1. INTRODUCTION.1.1 Occurrence of Aluminum Oxides and Hydroxides in theSubsurface.1.2 Occurrence of Aluminum Oxides and Hydroxides in SurfaceWater.1.3 Use of Aluminum Hydroxide in Water Treatment.1.4 Summary.CHAPTER - Formation and Properties of Gibbsite andclosely-related minerals.2. Formation and properties of Gibbsite and closely-relatedminerals.2.1 Al Polymerization Models.2.2 Formation of Gibbsite and Other Al-Hydroxides andOxyhydroxides.2.3 Aluminum Hydroxide Polymorphs: Structure andNomenclature.2.4 Gibbsite.2.5 Bayerite.2.6 Nordstrandite.2.7 Doyleite.2.8 Other forms of aluminum oxides and oxyhydroxides.2.9 Other forms that manufactured under high temperature andpressure.CHAPTER 3 - Types of Available Data.3.1 Gibbsite Structure Verification.3.2 Physical-Chemical Properties.3.3 Acid-Base Titration Data.3.4 Cation and Anion Sorption Data.3.5 Spectroscopic Data for Sorption on Gibbsite.3.6 Proton Release/Uptake Data.3.7 Electrokinetic Data.3.8 Summary.CHAPTER 4 - Data Compilation and Treatment Methods.4.1 Collection of data.4.2 Assessment of Data Quality.4.3 Compilation of Surface Properties.4.4 Extraction of Equilibrium Sorption Constants.4.5 Optimal Fit Simulations.4.6 Presentation of Results.CHAPTER 5 - Surface Properties of Gibbsite.5.1 Surface Area.5.2 Site Density.5.3 Point of Zero Charge.5.4 Surface Acid-Base Chemistry.5.5 Effects of Dissolution on Gibbsite Surface Acid-BaseChemistry.5.6 Summary.CHAPTER 6 - Cation Sorption on Gibbsite.6.1 Modeling Methodology and Reactions.6.2 Available Spectroscopic Data and Use in Modeling.6.3 Copper.6.4 Lead.6.5 Cobalt.6.6 Cadmium.6.7 Manganese.6.8 Iron.6.9 Calcium.6.10 Zinc.6.11 Mercury.6.12 Uranium.6.13 Thorium.CHAPTER 7 - Anion Sorption on Gibbsite.7.1 Modeling Methodology and Reactions.7.2 Available Spectroscopic Data and Use in Modeling.7.3 Phosphate.7.4 Arsenate.7.5 Arsenite.7.6 Molybdate.7.7 Selenate.7.8 Chromate.7.9 Borate.7.10 Sulfate.7.11 Fluoride.7.12 Silicate.CHAPTER 8 - Coherence and Extrapolation of Results.8.1 Cation Sorption on Gibbsite.8.2 Anion Sorption on Gibbsite.8.3 Comparison of Gibbsite surface complexation constants withthose of Goethite, Hydrous Ferric Oxide and Hydrous ManganeseOxide.8.4 Summary.REFERENCES.APPENDIX A. Summary of Experimental Details.