Solid-water interface

Geckeis H, Klenze R, Kim J1 (1999) Solid-water interface reactions of actinides and homologues sorption onto mineral surfaces. Radiochim Acta 87 13-21... 

Adsorption of (bio)polymers occurs ubiquitously, and among the biopolymers, proteins are most surface active. Wherever and whenever a protein-containing (aqueous) solution is exposed to a (solid) surface, it results in the spontaneous accumulation of protein molecules at the solid-water interface, thereby altering the characteristics of the sorbent surface and, in most cases, of the protein molecules as well (Malmsten 2003). Therefore, the interaction between proteins and interfaces attracts attention from a wide variety of disciplines, ranging from environmental sciences to food processing and medical sciences. 

Stumm, W., 1992, Chemistry of the Solid-Water Interface. Wiley, New York. 

The partitioning of As in the aquifer solid-water interface can best be explained with the distribution coefficient, Kd (a ratio of solute adsorbed in sediment to that of dissolved in groundwater). Due to being simplistic in nature, Kd has long been well appreciated as well as applied by geochemical modelers. 

Avena, M. J. and Koopal, L. K. (1999). Kinetics of humic acid adsorption at solid-water interfaces, Environ. Sci. Technol., 33, 2739-2744. 

W. Stum, Chemistry of the Solid-Water Interface. Processes at the Mineral-water and Particle Water Interface in Natural Systems, Wiley/Interscience Publisher, John Wiley Sons Inc, New York, 1992, p. 87. 

Adsorption, the accumulation of matter at the solid-water interface, is the basis of most surface-chemical processes. 

Table 1.1 Coordination Chemistry of the Solid-Water Interface Concepts and important Applications in natural and technical Systems...

Table 1.1 summarizes some of the concepts of the coordination chemistry of the solid-water interface and illustrates some important applications in natural and technical systems. Some of these applications will be discussed in later chapters. 

Table 4.1 Intermolecular Interactions at the Solid-water Interface (Modified from Westall, 1987)...

At the water-air interface hydrophilic groups are oriented toward the water, hydro-phobic groups are oriented toward air. At solid-water interfaces, the orientation depends on the relative affinities for water and for the solid surface. The hydrophilic groups of amphipathic molecules may - if the hydrophobic tendency is relatively small - interact coordinatively with the functional groups of the solid surface (Ulrich et al., 1988) (see Fig. 4.10). 

The adsorption of humic and fulvic acids on surfaces can be interpreted along the scheme of Fig. 4.9c,d. Because of hydrophobic interaction humic and fulvic acids tend to accumulate at the solid-water interface. At the same time the adsorption is influenced by coordinative interaction, e.g., schematically,... 

Kinetically, the adsorption of humic acids at a solid-water interface is controlled by convection or diffusion to the surface. Even at concentrations as low as 0.1 mg/e near-adsorption equilibrium is attained within 30 minutes. At high surface densities, a relatively slow rearrangement of the adsorbed molecules may cause a slow attainment of an ultimate equilibrium (Ochs, Cosovic and Stumm, in preparation). The humic acids adsorbed to the particles modify the chemical properties of their surfaces, especially their affinities for metal ions (Grauer, 1989). 

A comparison with the reversible interface can be made. The reversible solid electrolyte interface can be used in a similar way to explore the distribution of charge components at solid-water interfaces. As we have seen, the surface charge density, o, (Eqs. (3.1) and (iii) in Example 2.1) can be readily determined experimentally (e.g., from an alkalimetric titration curve). The Lippmann equations can be used as with the polarized electrodes to obtain the differential capacity from... 

As mentioned in the Appendix of Chapter 4, the contact angle 0 increases (cos 8 decreases) with increasing hydrophobic character of the solid surface (ysv < ySL), i.e., extensive adsorption at the air-solid surface and minimum adsorption at the solid water interface is needed. 

Regulation of Trace Elements by the Solid-Water Interface in Surface Waters... 

The solid-water interface, mostly established by the particles in natural waters and soils, plays a commanding role in regulating the concentrations of most dissolved reactive trace elements in soil and natural water systems and in the coupling of various hydrogeochemical cycles (Fig. 1.1). Usually the concentrations of most trace elements (M or mol kg-1) are much larger in solid or surface phases than in the water phase. Thus, the capacity of particles to bind trace elements (ion exchange, adsorption) must be considered in addition to the effect of solute complex formers in influencing the speciation of the trace metals. 

Chemistry of the solid-water interface processes at the mineral-water and particle-water interface in natural systems / Werner Stumm with contributions by Laura Sigg (chapter 11), and Barbara Sulzberger (chapter 10). p. cm. 

The chemical complexity of most natural systems often requires that adsorption reactions be described using semi-empirical, macroscopic models. A common approach is to describe the net transfer of an adsorbate from the solution phase to the solid/water interface with a single stoichiometric expression. Such stoichiometries include a generic relationship between the adsorption of a solute and the release or consumption of protons. 

J. Yang, J. Duan, D. Fomasiero, and J. Ralston, Very small bubble formation at the solid-water interface, J. Phys. Chem. B 107,6139-6147 (2003). 

Stumm, W. Sulzberger, B. (1992) The cyding of iron in natural environments Considerations based on laboratory studies of heterogeneous redox processes. Geochim. Cosmochim. Acta 56 3233—3257 Stumm, W (1992) Chemistry of the solid-water interface. Wiley Sons Inc., New York,... 

Geckeis, H. Rabung, T. 2002. Solid-water interface reactions of polyvalent metal ions at iron oxide-hydroxide surfaces. In Hubbard, A. (ed) Encyclopedia of Surface and Colloid Science. Dekker Inc., 4737-4748. 

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