Coordination chemistry hydrous oxide

Some emphasis is given in the first two chapters to show that complex formation equilibria permit to predict quantitatively the extent of adsorption of H+, OH , of metal ions and ligands as a function of pH, solution variables and of surface characteristics. Although the surface chemistry of hydrous oxides is somewhat similar to that of reversible electrodes the charge development and sorption mechanism for oxides and other mineral surfaces are different. Charge development on hydrous oxides often results from coordinative interactions at the oxide surface. The surface coordinative model describes quantitatively how surface charge develops, and permits to incorporate the central features of the Electric Double Layer theory, above all the Gouy-Chapman diffuse double layer model. 

The Coordination Chemistry of the Hydrous Oxide-Water Interface... 

Sulzberger, B. (1990), "Photoredox Reactions at Hydrous Metal Oxide Surfaces a Surface Coordination Chemistry Approach", in W. Stumm, Ed., Aquatic Chemical Kinetics, Wiley-lnterscience, New York, pp. 401-429. 

Aluminum occurs widely in nature in silicates such as micas and feldspars, complexed with sodium and fluorine as cryolite, and in bauxite rock, which is composed of hydrous aluminum oxides, aluminum hydroxides, and impurities such as free silica (Cotton and Wilkinson 1988). Because of its reactivity, aluminum is not found as a free metal in nature (Bodek et al. 1988). Aluminum exhibits only one oxidation state (+3) in its compounds and its behavior in the environment is strongly influenced by its coordination chemistry. Aluminum partitions between solid and liquid phases by reacting and complexing with water molecules and anions such as chloride, fluoride, sulfate, nitrate, phosphate, and negatively charged functional groups on humic materials and clay. 

See, for example, the reviews by B. Sulzberger, Photoredox reactions at hydrous metal oxide surfaces A surface coordination chemistry approach, Chap. 14 in W. Stumm, op. cit.,3 and T. D. Waite, op. cit.27... 

Cationic Surface Complexes. The first paper of the series (4), in i section entitled Preliminary Approach to the Interfacia] Coordination Chemistry of Hydrous Oxides, addressed the mechanism of cation adsorption v hvdroxylated mineral surfaces. Here the term coordination was reserved -r complex formation between cations and surface functional groups through b inding that can be either electrostatic or covalent, or a mixture of both. The dichotomous qualification is much in the spirit of the classic Stem (11) ricture of strong adsorption. 

As mentioned earlier, complex formation reactions at hydrous metal oxide surfaces can be treated as an extension of classic coordination chemistry metal centers on mineral surfaces participate in inner-sphere and outer-sphere coordination reactions with molecules adsorbed from overlying solution, including H2O, OH , O, and solute molecules (Schindler, 1981 Schindler and Stumm, 1987). A variety of protonation/deprotonation and complex-formation reactions determine the speciation of surface sites. A few... 

PHOTOREDOX REACTIONS AT HYDROUS METAL OXIDE SURFACES A SURFACE COORDINATION CHEMISTRY APPROACH... 

Hydrous oxide surfaces contain surface hydroxyl groups (4-10 OH groups per nm2) which exhibit amphoteric behavior. Oxygen donor groups in the hydrous surface enable metal ions to coordinate with the surface290. Since the surface chemistry of an oxide... 

The initial inspiration to develop this monograph has come from the very beautiful research of Dr. Werner Stumm and his colleagues on the surface chemistry of hydrous oxides. The development of the coordination chemistry approach to adsorption, pioneered by him imd Dr. Paul Schiiuller some... 

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