scholarly journals Determination of intrinsic equilibrium constants at alumina/electrolyte interface

2004 ◽  
Vol 69 (12) ◽  
pp. 1063-1072 ◽  
Author(s):  
Zaklina Todorovic ◽  
Slobodan Milonjic
Keyword(s):  
Equilibrium Constants ◽  
Point Of Zero Charge ◽  
Ionization Constants ◽  
Hydroxyl Groups ◽  
Alkali Cations ◽  
Binding Model ◽  
Complexation Constant ◽  
Mean Values ◽  
Surface Hydroxyl ◽  
Electrolyte Interface

Intrinsic ionization and complexation constants at an alumina/electrolyte interface were studied by the site binding model, while the sorption of alkali cations from aqueous solutions was interpreted by the triple-layer model. The surface properties of alumina were investigated by the potentiometric acid-base titrationmethod. The point of zero charge (pHpzc) of alumina obtained by thismethod was found to be 7.2. The obtained mean values of the intrinsic protonation and ionization constants of the surface hydroxyl groups and the intrinsic surface complexation constant, in different electrolytes, are pKinta1 = 4.4, pKinta2 = 9.6 and pKintM+ = 9.5 respectively.

The surface chemistry of kaolinite. III. Microelectrophoresis

1972 ◽  
Vol 25 (9) ◽  
pp. 1857 ◽  
Author(s):  
AS Buchanan ◽  
RC Oppenheim
Keyword(s):  
Ph Dependence ◽  
Equilibrium Constants ◽  
Particle Surface ◽  
Electrolyte Solutions ◽  
Ionic Species ◽  
Hydroxyl Groups ◽  
Electrophoretic Study ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
Aluminium Species

Aqueous suspensions of kaolinite from Mt. Egerton, Victoria, have been leached at pH 6.0. In agreement with a theoretical prediction derived from a combination of solubility data and equilibrium constants, more silicon species than aluminium species were found in the leaching liquor. The electrophoretic mobility increases (ie. moves to less negative values) as the leaching at pH 6 proceeds. This has been correlated with the surface hydroxyl groups being more effectively under the control of the less electropositive metal, aluminium. In a binary oxide mineral like kaolinite, the electrical double layer at the particle surface is influenced by the pH dependence of the ionic species in the solution as well as by the pH dependence of the nature of the surface. The results of an electrophoretic study of unleached kaolinite in various aqueous electrolyte solutions is also presented.

scholarly journals Humic Ion-Binding Model VII: a revised parameterisation of cation-binding by humic substances

2011 ◽  
Vol 8 (3) ◽  
pp. 225 ◽  
Author(s):  
E. Tipping ◽  
S. Lofts ◽  
J. E. Sonke
Keyword(s):  
Organic Matter ◽  
Metal Binding ◽  
Environmental Chemistry ◽  
Equilibrium Constants ◽  
Laboratory Data ◽  
Cation Binding ◽  
Model Parameters ◽  
Ion Binding ◽  
Binding Model ◽  
Mean Values

Environmental contextNatural organic matter exerts a powerful control on chemical conditions in waters and soils, affecting pH and influencing the biological availability, transport and retention of metals. To quantify the reactions, we collated a wealth of laboratory data covering 40 metals and acid–base reactions, and used them to parameterise the latest in a series of Humic Ion-Binding Models. Model VII is now available to interpret field data, and contribute to the prediction of environmental chemistry. AbstractHumic Ion-Binding Model VII aims to predict the competitive reactions of protons and metals with natural organic matter in soils and waters, based on laboratory results with isolated humic and fulvic acids (HA and FA). Model VII is simpler in its postulated multidentate metal binding sites than the previous Model VI. Three model parameters were eliminated by using a formal relationship between monodentate binding to strong- and weak-acid oxygen-containing ligands, and removing factors that provide ranges of ligand binding strengths. Thus Model VII uses a single adjustable parameter, the equilibrium constant for monodentate binding to strong-acid (carboxylate) groups (KMA), for each metallic cation. Proton-binding parameters, and mean values of log KMA were derived by fitting 248 published datasets (28 for protons, 220 for cationic metals). Default values of log KMA for FA were obtained by combining the fitted values for FA, results for HA, and the relationship for different metals between log KMA and equilibrium constants for simple oxygen-containing ligands. The equivalent approach was used for HA. The parameterised model improves on Model VI by incorporating more metals (40), providing better descriptions of metal binding at higher pH, and through more internally consistent parameter values.

Catalytic ozonation of p-chloronitrobenzene over pumice-supported zinc oxyhydroxide

2013 ◽  
Vol 68 (8) ◽  
pp. 1895-1900 ◽  
Author(s):  
Lei Yuan ◽  
Jimin Shen ◽  
Zhonglin Chen
Keyword(s):  
Hydroxyl Radicals ◽  
Underlying Mechanism ◽  
Catalytic Ozonation ◽  
Point Of Zero Charge ◽  
Hydroxyl Groups ◽  
Ozone Decomposition ◽  
Surface Hydroxyl ◽  
Heterogeneous Catalytic ◽  
Surface Hydroxyl Groups ◽  
Catalytic Ozone

The catalytic ozonation of p-chloronitrobenzene (pCNB) in an aqueous solution using pumice-supported zinc oxyhydroxide (ZMP) as the catalyst was investigated. ZMP significantly enhanced the degradation efficiency in the heterogeneous catalytic ozonation compared with ozonation alone. The decomposition rate of the aqueous ozone increased 2.84-fold in the presence of ZMP. Catalytic ozone decomposition showed that pCNB is oxidized primarily by hydroxyl radicals (•OH) in ozonation/ZMP processes. This modification increases the density of surface hydroxyl groups as well as the pH at the point of zero charge (pHPZC) of pumice, resulting in the appearance of new ZnO and Zn(OH)2 crystalline phases. An investigation of the underlying mechanism confirms that ZnOOH loading promotes •OH initiation, which enhances the degradation of pCNB.

The synthesis and structure of silica-supported bis(h5-cyclopentadienyl)dichlorotitanium(IV) complexes

1986 ◽  
Vol 51 (7) ◽  
pp. 1430-1438 ◽  
Author(s):  
Alena Reissová ◽  
Zdeněk Bastl ◽  
Martin Čapka
Keyword(s):  
Free Surface ◽  
Hydroxyl Groups ◽  
Titanium Complex ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
Free Hydroxyl ◽  
Cyclopentadienyl Anion

The title complexes have been obtained by functionalization of silica with cyclopentadienylsilanes of the type Rx(CH3)3 - xSi(CH2)nC5H5 (x = 1-3, n = 0, 1, 3), trimethylsilylation of free surface hydroxyl groups, transformation of the bonded cyclopentadienyl group to the cyclopentadienyl anion, followed by coordination of (h5-cyclopentadienyl)trichlorotitanium. The effects of single steps of the above immobilization on texture of the support, the number of free hydroxyl groups, the coverage of the surface by cyclopentadienyl groups and the degree of their utilization in anchoring the titanium complex have been investigated. ESCA study has shown that the above anchoring leads to formation of the silica-supported bis(h5-cyclopentadienyl)dichlorotitanium(IV) complex.

scholarly journals High catalytic activity for formaldehyde oxidation of an interconnected network structure composed of δ-MnO2 nanosheets and γ-MnOOH nanowires

2020 ◽  
Vol 8 (4) ◽  
pp. 429-439
Author(s):  
Ying Tao ◽  
Rong Li ◽  
Ai-Bin Huang ◽  
Yi-Ning Ma ◽  
Shi-Dong Ji ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Network Structure ◽  
Manganese Oxides ◽  
Active Oxygen Species ◽  
Low Cost ◽  
High Dispersion ◽  
Hydroxyl Groups ◽  
High Catalytic Activity ◽  
Interconnected Network ◽  
Surface Hydroxyl

AbstractAmong the transition metal oxide catalysts, manganese oxides have great potential for formaldehyde (HCHO) oxidation at ambient temperature because of their high activity, nontoxicity, low cost, and polybasic morphologies. In this work, a MnO2-based catalyst (M-MnO2) with an interconnected network structure was successfully synthesized by a one-step hydrothermal method. The M-MnO2 catalyst was composed of the main catalytic agent, δ-MnO2 nanosheets, dispersed in a nonactive framework material of γ-MnOOH nanowires. The catalytic activity of M-MnO2 for HCHO oxidation at room temperature was much higher than that of the pure δ-MnO2 nanosheets. This is attributed to the special interconnected network structure. The special interconnected network structure has high dispersion and specific surface area, which can provide more surface active oxygen species and higher surface hydroxyl groups to realize rapid decomposition of HCHO.

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