tailieunhanh - Geochemical and Hydrological Reactivity of Heavy Metals in Soils - Chapter 4

Hiệu lực của Phí Kết cấu Proton hấp phụ bề mặt đất sét sorption tại giao diện nước khoáng là những quá trình quan trọng trong đất, trầm tích, nước mặt và nước ngầm. Bằng cách bắt hoặc giải phóng các ion, bề mặt khoáng sản đóng vai trò quan trọng trong màu mỡ của đất, đất tập hợp, sự biệt hóa chất, thời tiết, | 4 Effect of Structural Charges on Proton Adsorption at Clay Surfaces Marcelo J. Avena and Carlos P De Pauli CONTENTS Introduction Structure of Clays The Surface of a Clay Layer Proton Adsorption The Intrinsic Component of Kf The Bond-Valence Principle The Electrostatic Component of kH Case Study Modeling Proton Adsorption Choosing the Model Application to Montmorillonite Application to Illite Application to a Kaolinitic Soil Differences in Behavior of Clays and Metal Oxides Summary and Concluding Remarks Acknowledgments Appendix Isolated Layer Model References INTRODUCTION Ion adsorption and desorption at the mineral-water interface are important processes in soils sediments surface waters and groundwater. By capturing or releasing ions mineral surfaces play key roles in soil fertility soil aggregation chemical speciation weathering and the transport and fate of nutrients and pollutants in the environment. Proton adsorption is a very specific form of ion adsorption. This area is so important 2003 by CRC Press LLC that it is usually treated separately from other forms. Most minerals have reactive surface groups that are capable of binding or releasing protons. This leads to the development of electrical charges at the surface and the ability to control the attachment of metal complexes ions different from protons organic molecules polymers microorganisms and particles. According to Brady et al. 1 understanding proton adsorption is a necessary first step to unraveling the affinity of mineral surfaces for both inorganic and organic species. The main effects of proton adsorption-desorption on the adsorption of metals in general and heavy metals in particular have been recognized for many decades. Protons can be exchanged by metal ions at exchange sites on the mineral surface desorbing protons can leave negatively charged groups at the surface which act as Lewis bases that coordinate