Oxide/water interface

Effect on Oxide—Water Interfaces. The adsorption (qv) of ions at clay mineral and rock surfaces is an important step in natural and industrial processes. SiUcates are adsorbed on oxides to a far greater extent than would be predicted from their concentrations (66). This adsorption maximum at a given pH value is independent of ionic strength, and maximum adsorption occurs at a pH value near the piC of orthosiUcate. The pH values of maximum adsorption of weak acid anions and the piC values of their conjugate acids are correlated. This indicates that the presence of both the acid and its conjugate base is required for adsorption. The adsorption of sihcate species is far greater at lower pH than simple acid—base equihbria would predict. 

Davis, J.A. and Leckie, J.O., Surface ionization and complexation at the oxide/water interface, II surface properties of amorphous iron oxyhydroxide and adsorption of metal ions, J. Colloid Interface Sci. 67, 90-107, 1978. 

Arai Y, Elzinga EJ, Sparks DL (2001) X-ray absorption spettroscopy investigation of arsenite and arsenate adsorption on the aluminium oxide-water interface J Colloid Interf Sci 235 80-88... 

Arai Y, Sparks DL (2002) Residence time effects on arsenate surface speciation at the aluminum oxide-water interface. Soil Sci 167 303-314... 

Oxide-water interfaces, in silica polymer-metal ion solutions, 22 460—461 Oxidimetric method, 25 145 Oxidization devices, 10 77-96 catalytic oxidization, 10 78—96 thermal oxidation, 20 77-78 Oxidized mercury, 23 181 Oxidized polyacrylonitrile fiber (OPF), 23 384... 

Wastewater treatment facilities, industrial hygiene at, 14 213 Wastewater treatment sludge as biomass, 3 684 Waste zero system, 14 110 Water, 26 1-50. See also Dessicants, Drinking water Hydrolysis Liquid water Oxide-water interfaces Seawater Sodium chloride-water system Wastewater Wastewater entries, Ice... 

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

Brown Jr., G. E. (1990), "Spectroscopic Studies of Chemisorption Reaction Mechanisms at Oxide-Water Interfaces", in M. F. Hochelia Jr. and A. F. White, Eds., Minerai-Water Interface Geochemistry, pp. 309-363. 

In surface precipitation cations (or anions) which adsorb to the surface of a mineral may form at high surface coverage a precipitate of the cation (anion) with the constituent ions of the mineral. Fig. 6.9 shows schematically the surface precipitation of a cation M2+ to hydrous ferric oxide. This model, suggested by Farley et al. (1985), allows for a continuum between surface complex formation and bulk solution precipitation of the sorbing ion, i.e., as the cation is complexed at the surface, a new hydroxide surface is formed. In the model cations at the solid (oxide) water interface are treated as surface species, while those not in contact with the solution phase are treated as solid species forming a solid solution (see Appendix 6.2). The formation of a solid solution implies isomorphic substitution. At low sorbate cation concentrations, surface complexation is the dominant mechanism. As the sorbate concentration increases, the surface complex concentration and the mole fraction of the surface precipitate both increase until the surface sites become saturated. Surface precipitation then becomes the dominant "sorption" (= metal ion incorporation) mechanism. As bulk solution precipitation is approached, the mol fraction of the surface precipitate becomes large. 

Brown Jr., G. E., G. A. Parks, and C. J. Chisholm-Brause (1989), "In-Situ X-Ray Absorption Spectroscopic Studies of Ions at Oxide-Water Interfaces", Chimia43, 248-256. 

Davis, J. A., and J. O. Leckie (1978a), "Surface Ionization and Complexation at the Oxide/Water Interface. II. Surface Properties of Amorphous Iron Oxyhydroxide and Adsorption of Metal Ions," J. Colloid Interface Sci. 67, 90-107. 

Yates, D. E., and T. W. Healy (1975), "Mechanism of Anion Adsorption at the Ferric and Chromic Oxide/ Water Interfaces", J. Colloid Interface Sci. 52, 222-228. 

Chan (Chapter 6) presents a simple graphical method for estimating the free energy of EDL formation at the oxide-water interface with an amphoteric model for the acidity of surface groups. Subject to the assumptions of the EDL model, the graphical method allows a comparison of the magnitudes of the chemical and coulombic components of surface reactions. The analysis also illustrates the relationship between model parameter values and the deviation of surface potential from the Nernst equation. 

The "Agl" model for location of ions in the oxide-water interface is probably the best reasonably simple interpretation. 

To a certain extent a similar statement could be made about research on the chemistry of mineral-water interfaces. Some theoretical models (2,3) developed to date have focused primarily on their ability to fit data collected from one experimental technique, namely potentiometric titration. While these models have done much to improve our understanding of the oxide-water interface, we do not have a complete picture of the interfacial region at present. Although potentiometric titrations can still provide new insights, failure to utilize other techniques may result in the problem mentioned in Forni s statement above. 

Furthermore, although other electrostatic models for the oxide/ water interface may yield different relationships among postulated system components, it appears unlikely that either Xp nor x alone will adequately represent the postulated true adsorbate/proton exchange ratio. 

Electron transfer reactions of metal ion complexes in homogeneous solution are understood in considerable detail, in part because spectroscopic methods and other techniques can be used to monitor reactant, intermediate, and product concentrations. Unfavorable characteristics of oxide/water interfaces often restrict or complicate the application of these techniques as a result, fewer direct measurements have been made at oxide/water interfaces. Available evidence indicates that metal ion complexes and metal oxide surface sites share many chemical characteristics, but differ in several important respects. These similarities and differences are used in the following discussions to construct a molecular description of reductive dissolution reactions. 

R.O. James, T.W. Healy, Adsorption of hydrolyzable metal ions at the oxide — water interface. II. Charge reversal of Si02 and Ti02 colloids by adsorbed Co(II), La(III), and Th(IV) as model systems, J. Colloid Interface Sd. 40 (1972) 53-64. 

Stone AT, Torrents A, Smolen J, Vasudevan D, Hadley J (1993) Adsorption of organic-compounds processing ligand donor groups at the oxide-water interface. Environ Sci Technol 27 895-909... 

In systems containing two or more adsorbates, either competitive or synergistic effects may operate. The commonest synergistic effect is that of ternary adsorption (11.5.4). Competitive behaviour may involve competition for the same surface sites, indirect effects due to the change in the electrostatic properties of the oxide/water interface and in some cases, formation of non sorbing, metal-ligand complexes in solution. 

Au, K.-K. Penisson, A.C. Yang, S. O Melia, C.R. (1999) Natural organic matter at oxide/ water interfaces complexation and conformation. Geochim. Cosmochim. Acta 63 2903-2917... 

Brown, G. (1953) The occurrence of lepidocro-dte in British soils. J. Soil Sd. 4 220—228 Brown, G. (1980) Associated minerals. In Brindley, G.W. Brown, G. (eds.) Crystal structures of clay minerals and their X-ray identification. Min. Soc., London, 361-410 Brown, G.E.Jr. (1990) Spectroscopic studies of chemisorption reaction mechanisms at oxide/water interfaces. In Hochella, M.F.Jr. 

C. J. (1989) In situ X-ray absorption spectroscopic studies of ions at oxide-water interfaces. Chimia 43 248-256... 

Charlet, L. Manceau, A.A. (1992a) X-ray absorption spectioscopic study of the sorption of Cr(III) at the oxide/water interface. II. Adsorption, coprecpitation, and surface precipitation on hydrous ferric oxide. J. Colloid Interface Sd. 148 443-458 Charlet, L. Manceau, A.A. (1992) X-ray absorption spectroscopic study of the sorption of Cr(III) at the oxide-water interface. J. Colloid Interface Sd. 148 425-442 Chatellier, X. Fortin, D. West, M.M. Leppard, G.G. Ferris, F.G. (2001) Effect of the presence of bacterial surfaces during the synthesis of Fe oxides by oxidation of ferrous ions. Fur. J. Mineral. 13 705-714 Cheetham, A.K. Fender, B.E.F. Taylor, R.I. (1971) High temperature neutron diffraction study of Fei. O. J. Phys. C4 2160-2165 Chemical Week (1988) Glidderfs anti rust secret is out." 15 10... 

Christl, I. R. Kretzschmar (1999) Competitive sorption of copper and lead at the oxide-water interface Implications for surface site density. Geochim. Cosmochim. Acta 63 2929-2938... 

Jambor, J.L. Dutrizac, J.E. (1998) Occurrence and constitution of natural and synthetic fer-rihydrite, a widespread iron oxyhydroxide. Chem. Rev. 98 2549-2585 James, R.O. ElealyT.W. (1972) Adsorption of hydrolyzable metal ions at the oxide-water interface. Ill A thermodynamic model of adsorption. J. Colloid Interface Sci. 40 65-81 James, R.O. Parks, G.A. (1982) Characterization of aqueous colloids by their electrical double layer and intrinsic surface chemical properties. Surface Colloid Sci. 12 119-126... 

Vasudevan, D. Dorley, P.J. Zhuang, X. (2001) Adsorption of hydroxy pyridines and quinolines at the metal oxide-water interface Role of tautomeric equilibrium. Environ. Sci. 

Yates, D.E. Healy,T.W. (1975) Mechanism of anion adsorption at the ferric and chromic oxide/water interfaces. J. Colloid Interface Sd. 52 222-228... 

Davis, J. A., James, R. O. Leckie, J. O. 1978. Surface ionization and complexation at the oxide/water interface. I. Computation of electrical double layer properties in simple electrolytes. Journal of Colloid and Interface Science, 63, 480-499. 

Bargar, J. R., Brown, G. E. Jr, and Parks, G. A. (1997a). Surface complexation of Pb(II) at oxide water interfaces I. XAFS and bond valence determination of mononuclear and polynuclear Pb(II) sorption products on aluminum oxides. Geochim. Cosmochim. Acta 61, 2617-37. 

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