scholarly journals Sorption modelling by Gibbs energy minimisation: Towards a uniform thermodynamic database for surface complexes of radionuclides

2002 ◽  
Vol 90 (9-11) ◽  
Author(s):  
D. A. Kulik
Keyword(s):  
Solid Solution ◽  
Aqueous Solution ◽  
Gibbs Energy ◽  
Mineral Water ◽  
Reference Site ◽  
Surface Complexes ◽  
Common Value ◽  
Energy Minimisation ◽  
Site Density ◽  
Elemental Stoichiometry

SummaryRadionuclide sorption on mineral-water interfaces can be thermodynamically modelled, similar to solid-solution aqueous-solution systems (only in chemical elemental stoichiometry), if definitions of the standard and reference states, surface activity terms (SAT), and elemental stoichiometries of surface-bound species are unequivocally established. A pre-requisite is that a unique common value of the reference (site) density (Γ

scholarly journals Removal of Chromium from Aqueous Solution Using Modified Pomegranate Peel:Mechanistic and Thermodynamic Studies

2009 ◽  
Vol 6 (s1) ◽  
pp. S153-S158 ◽  
Author(s):  
Tariq S. Najim ◽  
Suhad A. Yassin
Keyword(s):  
Activation Energy ◽  
Solid Solution ◽  
Aqueous Solution ◽  
Adsorption Process ◽  
Batch Process ◽  
The Other ◽  
Water Molecules ◽  
Pomegranate Peel ◽  
Solution Interface ◽  
Adsorbent Surface

Modified pomegranate peel (MPGP) and formaldehyde modified pomegranate peel (FMPGP) were prepared and used as adsorbent for removal of Cr(VI) ions from aqueous solution using batch process. The temperature variation study of adsorption on both adsorbents revealed that the adsorption process is endothermic, from the positive values of ∆H˚. These values lie in the range of physisorption. The negative values of ∆G˚ show the adsorption is favorable and spontaneous. On the other hand, these negative values increases with increase in temperature on both adsorbents, which indicate that the adsorption is preferable at higher temperatures. ∆S˚ values showed that the process is accompanied by increase in disorder and randomness at the solid solution interface due to the reorientation of water molecules and Cr(VI) ions around the adsorbent surface. The endothermic nature of the adsorption was also confirmed from the positive values of activation energy, Ea, the low values of Ea confirm the physisorption mechanism of adsorption. The sticking probability, S*, of Cr(VI) ion on surface of both adsorbents showed that the adsorption is preferable due to low values of S*(0< S*< 1 ), but S*values are lower for FMPGP indicating that the adsorption on FMPGP is more preferable .

Local Environment of Surface-Polyelectrolyte-Bound DNA Oligomers

2000 ◽  
Vol 651 ◽  
Author(s):  
Sangmin Jeon ◽  
Sung Chul Bae ◽  
Jiang John Zhao ◽  
Steve Granick
Keyword(s):  
Aqueous Solution ◽  
Salt Concentration ◽  
Fluorescence Anisotropy ◽  
Local Environment ◽  
Time Resolved Fluorescence ◽  
Surface Complexes ◽  
Dna Oligomers ◽  
Time Resolved ◽  
Two Photon ◽  
Anisotropy Decay

AbstractTwo-photon time-resolved fluorescence anisotropy methods were used to study the dynamical environment when fluorescent-labelled DNA oligomers (labelled with FAM, 6-fluorescein-6-carboxamido hexanoate) formed surface complexes with quaternized polyvinylpyridine (QPVP) cationic layers on a glass surface. We compared the anisotropy decay of DNA in bulk aqueous solution, DNA adsorbed onto QPVP, and QPVP-DNA-QPVP sandwich structures. When DNA was adsorbed onto QPVP, its anisotropy decay was dramatically retarded compared to the bulk, which means it had very slow rotational motion on the surface. Motions slowed down with increasing salt concentration up to a level of 0.1 M NaCl, but mobility began to increase at still higher salt concentration owing to detachment from the surface-immobilizing QPVP layers.

scholarly journals Integrating Density Functional Theory Modeling with Experimental Data to Understand and Predict Sorption Reactions: Exchange of Salicylate for Phosphate on Goethite

Soil Systems ◽  
2020 ◽  
Vol 4 (2) ◽  
pp. 27 ◽  
Author(s):  
James D. Kubicki ◽  
Tsutomu Ohno
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Mineral Water ◽  
Surface Complexes ◽  
Functional Theory ◽  
Complex Models ◽  
Mechanical Approach ◽  
Plant Exudates ◽  
Quantum Mechanical Approach

Density functional theory (DFT) calculations are a quantum mechanical approach that can be used to model chemical reactions on an atomistic scale. DFT provides predictions on structures, thermodynamics, spectroscopic parameters and kinetics that can be compared against experimentally determined data. This paper is a primer on the basics of utilizing DFT for applications in mineral-water interfaces. In our case-study, we use DFT to model the surface complexes of phosphate and salicylate adsorbed onto the (101) and (210) surfaces of α-FeOOH (goethite), as an example of combining DFT and experiment. These three components are important in the phosphorus-organic matter interactions in soils, and by comparing the energies of the two surface complexes, the exchange energy of salicylate for phosphate onto goethite can be estimated. The structures of the surface complexes are predicted and the resulting vibrational frequencies calculated based on these structures are compared to previous observations. Upon verification of reasonable surface complex models, the potential energy of exchanging salicylate for phosphate is calculated and shown to be significantly exothermic. This model result is consistent with observations of plant exudates, such as salicylate freeing adsorbed phosphate in soils under P-limited conditions.

Thermodynamic characterization of high-temperature superconductors in the yttrium-barium-copper-oxygen system. The Y123 solid solution (Technical Report)

2000 ◽  
Vol 72 (3) ◽  
pp. 463-477 ◽  
Author(s):  
G. F. Voronin
Keyword(s):  
Solid Solution ◽  
Gibbs Energy ◽  
Thermodynamic Data ◽  
High Temperature Superconductors ◽  
Gibbs Energy Function ◽  
Data Set ◽  
Y123 Phase ◽  
Barium Copper ◽  
Self Consistent ◽  
Consistent Thermodynamic Data

The aim of this report is to inform the chemical community about a self-consistent thermodynamic data set for the YBa2 Cu3 O6+z (1 ≥ z ≥ 0) solid solution, that is well known as the Y123 phase and possesses superconducting properties at z~1 and low temperatures. About 3300 experimental points obtained in 240 miscellaneous experiments published in 78 papers have been processed simultaneously in order to obtain the most reliable Gibbs energy function of the Y123 phase in the temperature range from 250 to 1300 K and pressures up to 100 kbar. A function is recommended for approximation of the Gibbs energy, which has 16 adjustable parameters. All other thermodynamic properties of the Y123 solution, including the conditions for its internal stability, can be derived from the assessed Gibbs energy. Brief descriptions of the thermodynamic model, experimental and data assessment methods as well as examples of self-consistent thermodynamic data applications are given.

Fabrication and Stability of CoAl2O4 Ceramic Pigment for 3D Printing

2017 ◽  
Vol 898 ◽  
pp. 1935-1939 ◽  
Author(s):  
Yuan Song ◽  
Yuan Lin Zheng ◽  
Yu Fei Tang ◽  
Hai Bing Yang
Keyword(s):  
Solid Solution ◽  
Aqueous Solution ◽  
3D Printing ◽  
Zeta Potential ◽  
Spinel Structure ◽  
Sol Gel ◽  
Ceramic Pigment ◽  
Ceramic Pigments ◽  
Oxide Solid Solution ◽  
The Stability

Ceramic pigment is the key component of the ink color in the 3D printing process of ceramic products. The color performance and stability of ceramic pigments after calcination still need to be improved. In the present study the cobalt aluminate (CoAl2O4) ceramic pigment powders were fabricated by sol-gel method. The effects of fabrication processes on color properties of CoAl2O4 ceramic pigments were investigated. The compositions and morphologies of CoAl2O4 ceramic pigment powders were characterized. The stability of CoAl2O4 ceramic pigments was discussed. The results showed that the CoAl2O4 ceramic pigment with high chroma was obtained at calcination temperature of 1200°C and the Co/Al ratio is 1:3. The Zeta potential of the fabricated CoAl2O4 ceramic pigment powders in aqueous solution was-66.2 mV, which represented good dispersion stability. The chroma and saturation of the CoAl2O4 ceramic pigment increased owing to that the oxide solid solution in the spinel structure increased after being sintered at 1300 oC.

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