STUDIES OF THE DISSOCIATION OF OXIDE SURFACES AT THE LIQUID–SOLID INTERFACE

1966 ◽  
Vol 44 (14) ◽  
pp. 1663-1670 ◽  
Author(s):  
Syed M. Ahmed
Keyword(s):  
Surface Charge ◽  
Double Layer ◽  
Zero Point ◽  
Specific Adsorption ◽  
Hydroxyl Groups ◽  
Surface Hydroxyl ◽  
Charge Densities ◽  
Coulombic Interactions ◽  
Solution Interface ◽  
Effect Of Surface

The dissociation of surface hydroxyl groups of crystalline SiO2, ZrO2, and ThO2, in aqueous suspensions, has been studied as a function of pHs at different ionic strengths of KNO3. The surface groups of quartz dissociate as weak acids, while those of ZrO2 and ThO2 dissociate amphoterically. A reversible double layer is formed at the oxide–solution interface, and H+ and OH− function as the potential-determining ions. Quantitative data have been obtained on (a) surface charge densities, (b) zero point of charge, (c) differential capacities of the double layer on quartz and ZrO2, and (d) the effect of surface charge density and ionic strength on the interfacial tension. The differential capacities indicate specific adsorption of NO3−on ZrO2 and ThO2 while NO3− has zero affinity for quartz surfaces. At low negative charge densities, solvated K+ are adsorbed on quartz and ZrO2 through coulombic interactions while at pHs > 10 specific adsorption of K+ predominates. ThO2 appears to exhibit a greater tendency for the specific adsorption of K+.

Phase transition of capillary condensed liquids in porous silica: effect of surface hydroxyl groups

1995 ◽  
Vol 267 ◽  
pp. 159-167 ◽  
Author(s):  
T. Takei ◽  
T. Konishi ◽  
M. Fuji ◽  
T. Watanabe ◽  
M. Chikazawa
Keyword(s):  
Phase Transition ◽  
Porous Silica ◽  
Hydroxyl Groups ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
Effect Of Surface

Effect of surface hydroxyl groups on heat capacity of mesoporous silica

2018 ◽  
Vol 112 (20) ◽  
pp. 201903 ◽  
Author(s):  
Michal Marszewski ◽  
Danielle Butts ◽  
Esther Lan ◽  
Yan Yan ◽  
Sophia C. King ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Mesoporous Silica ◽  
Hydroxyl Groups ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
Effect Of Surface

scholarly journals The effect of surface hydroxyl groups on the adsorption properties of nanocrystallineTiO2films

2005 ◽  
Vol 7 (4) ◽  
pp. 163-168 ◽  
Author(s):  
Angela Šurca Vuk ◽  
Robi Ješe ◽  
Boris Orel ◽  
Goran Dražc
Keyword(s):  
Integral Intensity ◽  
Dip Coating ◽  
Pluronic F127 ◽  
Hydroxyl Groups ◽  
Surface Hydroxyl ◽  
Photocatalytic Effect ◽  
Anatase Nanoparticles ◽  
Ir Analysis ◽  
Ir Bands ◽  
Effect Of Surface

NanocrystallineTiO2/Brij andTiO2/Pluronic films were prepared with a view to their application in electrochromic and Grätzel cells and examination of their photocatalytic effect. The films were prepared from titanium (IV) isopropoxide with the addition of Brij 56 or Pluronic F127. Films were deposited by dip-coating, thermally treated at 500∘Cand analysed by XRD, TEM and IR analysis. XRD and TEM analyses revealed the presence of anatase nanoparticles embedded in the amorphous phase. The presence of the latter was also confirmed by a broad high-frequency shoulder of the Ti-O stretching mode at 436cm−1that was found for films prepared with both kinds of surfactants. Addition of surfactants decreased the size of the particles and increased the surface roughness, and consequently in IR spectra the surface hydroxyl Ti-OH modes appear between 3800 and 3600cm−1. IR measurements also revealed thatTiO2films with surfactants have a higher photocatalytic effect which was tested for stearic acid by following the integral intensity of C-H and C=O IR bands.

Soil Chemistry

2003 ◽  
Author(s):  
Anthony S. R. Juo ◽  
Kathrin Franzluebbers
Keyword(s):  
Surface Charge ◽  
Functional Groups ◽  
Soil Chemistry ◽  
Chemical Properties ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Surface Hydroxyl ◽  
Mineral Structure ◽  
Ph Dependent ◽  
Soil Colloids

Soil chemistry deals with the chemical properties and reactions of soils. It is essentially the application of electrochemistry and colloid chemistry to soil systems. Major topics include surface charge properties of soil colloids, cation and anion sorption and exchange, soil acidity, soil alkalinity, soil salinity, and the effects of these chemical properties and processes on soil biological activity, plant growth, and environmental quality. The ability of the electrically charged surface of soil colloids to retain nutrient cations and anions is an important chemical property affecting the fertility status of the soil. There are two major sources of electrical charges on soil organic and inorganic colloids, namely, permanent or constant charges and variable or pH-dependent charges. Permanent or constant charges are the result of the charge imbalance brought about by isomorphous substitution in a mineral structure of one cation by another of similar size but differing valence (see also section 2.3.2). For example, the substitution of Mg2+ for Al3+ that occurs in Al-dominated octahedral sheets of 2:1 clay minerals results in a negative surface charge in smectite, vermiculite, and chlorite. The excess negative charges are then balanced by adsorbed cations to maintain electrical neutrality. Permanent negative charges of all 2:1 silicate minerals arise from isomorphous substitutions. The l:l-type clay mineral, kaolinite, has only a minor amount of permanent charge due to isomorphic substitution. The negative charges on kaolinite originate from surface hydroxyl groups on the edge of the mineral structure and are pH-dependent. Variable or pH-dependent charges occur on the surfaces of Fe and Al oxides, allophanes, and organic soil colloids. This type of surface charge originates from hydroxyl groups and other functional groups by releasing or accepting H+ ions, resulting in either negative or positive charges. Other functional groups are hydroxyl (OH) groups of Fe and/or Al oxides and allophanes and the COOH and OH groups of soil organic matter. Variable-charge soil colloids bear either a positive or a negative net surface charge depending on the pH of the soil. The magnitude of the charge varies with the electrolyte concentration of the soil solution.

Adsorption at solid-liquid interfaces. II. Models of the electrical double layer at the oxide-solution interface

1973 ◽  
Vol 26 (6) ◽  
pp. 1191 ◽  
Author(s):  
HJL Wright ◽  
RJ Hunter
Keyword(s):  
Zeta Potential ◽  
Surface Charge ◽  
Double Layer ◽  
Liquid Interfaces ◽  
Nernst Equation ◽  
Oxide Systems ◽  
Solution Interface ◽  
Gel Layer ◽  
Solid Liquid ◽  
Mineral Oxide Surfaces

An extension has been made to Gouy-Stern-Grahame models of the double layer on mineral oxide surfaces.1 In this work and an earlier paper,2 the Stern isotherm is used for adsorption of p.d. ions at the surface. This is essentially an inversion of the modified Nernst equation given by Levine and Smith.3 The development of the surface charge and potential is considered by two different but related methods. Comprehensive calculations show that the zeta potential of oxide systems may be reasonably simulated with such models but the calculated surface charge is much less than that found experimentally. It is suggested that a model in which this surface charge is incorporated into a gel layer may be more appropriate.

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