The Role of Outer-Sphere Surface Acidity in Alkene Epoxidation Catalyzed by Calixarene−Ti(IV) Complexes

2007 ◽  
Vol 129 (50) ◽  
pp. 15585-15595 ◽  
Author(s):  
Justin M. Notestein ◽  
Leandro R. Andrini ◽  
Felix G. Requejo ◽  
Alexander Katz ◽  
Enrique Iglesia
Keyword(s):  
Surface Acidity ◽  
Outer Sphere ◽  
Sphere Surface

scholarly journals Electrochemical Perspective on Hematite–Malonate Interactions

2021 ◽  
Vol 5 (4) ◽  
pp. 47
Author(s):  
Karolina Kędra ◽  
Marzena Łazarczyk ◽  
Tajana Begović ◽  
Danijel Namjesnik ◽  
Karolina Lament ◽  
...  
Keyword(s):  
Surface Potential ◽  
Electrostatic Interactions ◽  
Surface Acidity ◽  
Outer Sphere ◽  
Diffuse Layer ◽  
Point Of Zero Charge ◽  
Oxide Surface ◽  
Layer Potential ◽  
Ph Range

Organic matter (OM) interactions with minerals are essential in OM preservation against decomposition in the environment. Here, by combining potentiometric and electrophoretic measurements, we probed the mode of coordination and the role of pH-dependent electrostatic interactions between organic acids and an iron oxide surface. Specifically, we show that malonate ions adsorbed to a hematite surface in a wide pH window between 3 and 8.7 (point of zero charge). The mode of interactions varied with this pH range and depended on the acid and surface acidity constants. In the acidic environment, hematite surface potential was highly positive (+47 mV, pH 3). At pH < 4 malonate adsorption reduced the surface potential (+30 mV at pH 3) but had a negligible effect on the diffuse layer potential, consistent with the inner-sphere malonate complexation. Here, the specific and electrostatic interactions were responsible for the malonate partial dehydration and surface accumulation. These interactions weakened with an increasing pH and near PZC, the hematite surface charge was neutral on average. Adsorbed malonates started to desorb from the surface with less pronounced accumulation in the diffuse layer, which was reflected in zeta potential values. The transition between specific and non-specific sorption regimes was smooth, suggesting the coexistence of the inner- and outer-sphere complexes with a relative ratio that varied with pH.

Influence of aluminium impregnation on activated carbon for enhanced desulfurization of DBT at ambient temperature: Role of surface acidity and textural properties

2016 ◽  
Vol 303 ◽  
pp. 489-500 ◽  
Author(s):  
Saheed A. Ganiyu ◽  
Khalid Alhooshani ◽  
Kazeem O. Sulaiman ◽  
Muhammad Qamaruddin ◽  
Idris A. Bakare ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Ambient Temperature ◽  
Surface Acidity ◽  
Textural Properties

scholarly journals Reflections on the outer-sphere mechanism of electron transfer

1996 ◽  
Vol 74 (5) ◽  
pp. 631-638 ◽  
Author(s):  
Thomas W. Swaddle
Keyword(s):  
Electron Transfer ◽  
Large Change ◽  
Outer Sphere ◽  
Pressure Effects ◽  
Spherical Approximation ◽  
Mean Spherical Approximation ◽  
Redox Kinetics ◽  
Electron Transfer Processes ◽  
Low Pressures

The quantitative efficacy of the Stranks–Marcus–Hush theory of volumes of activation ΔV‡ for outer-sphere electron transfer between metal complexes in solution is assessed. The theory predicts ΔV‡ accurately for several couples in aqueous solution, but is satisfactory for polar nonaqueous solvents only at pressures of ca. 100 MPa and above, and accuracy is not improved when the molecular nature of the solvent is allowed for through the Mean Spherical Approximation approach. At low pressures, the calculations become numerically unstable when the isothermal compressibility of the solvent is high and its relative permittivity is low, particularly for the more highly charged couples. For aqueous systems, departures from the predicted ΔV‡ afford insights into the role of the counterions, the incursion of inner-sphere pathways, the enhanced reactivity of CoIII/II cage complexes relative to conventional chelates, and the question of "spin forbiddenness" of electron transfer processes that involve a large change in spin multiplicity. Key words: redox kinetics, inorganic reaction mechanisms, pressure effects, Marcus–Hush theory, activation volumes.

scholarly journals Waste Brick Dust as Potential Sorbent of Lead and Cesium from Contaminated Water

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1647 ◽  
Author(s):  
Barbora Doušová ◽  
David Koloušek ◽  
Miloslav Lhotka ◽  
Martin Keppert ◽  
Martina Urbanová ◽  
...  
Keyword(s):  
Amorphous Material ◽  
Surface Complexation ◽  
Total Pore Volume ◽  
Zero Point ◽  
Outer Sphere ◽  
Aqueous System ◽  
Sphere Surface ◽  
Adsorption Condition ◽  
Weak Adsorption ◽  
Brick Dust

Adsorption properties of waste brick dust (WBD) were studied by the removing of PbII and CsI from an aqueous system. For adsorption experiments, 0.1 M and 0.5 M aqueous solutions of Cs+ and Pb2+ and two WBD (Libochovice—LB, and Tyn nad Vltavou—TN) in the fraction below 125 µm were used. The structural and surface properties of WBD were characterized by X-ray diffraction (XRD) in combination with solid-state nuclear magnetic resonance (NMR), supplemented by scanning electron microscopy (SEM), specific surface area (SBET), total pore volume and zero point of charge (pHZPC). LB was a more amorphous material showing a better adsorption condition than that of TN. The adsorption process indicated better results for Pb2+, due to the inner-sphere surface complexation in all Pb2+ systems, supported by the formation of insoluble Pb(OH)2 precipitation on the sorbent surface. A weak adsorption of Cs+ on WBD corresponded to the non-Langmuir adsorption run followed by the outer-sphere surface complexation. The leachability of Pb2+ from saturated WBDs varied from 0.001% to 0.3%, while in the case of Cs+, 4% to 12% of the initial amount was leached. Both LB and TN met the standards for PbII adsorption, yet completely failed for any CsI removal from water systems.

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