scholarly journals Carrier and dilution effects of CO 2 on thoron emissions from a zeolitized tuff exposed to subvolcanic temperatures

2021 ◽  
Vol 8 (2) ◽  
Author(s):  
Silvio Mollo ◽  
Piergiorgio Moschini ◽  
Gianfranco Galli ◽  
Paola Tuccimei ◽  
Carlo Lucchetti ◽  
...  
Keyword(s):  
Noble Gas ◽  
Temperature Gradients ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Flux Rate ◽  
Advective Transport ◽  
Structural Modifications ◽  
Intermolecular Proton Transfer ◽  
Dilution Effects ◽  
Strong Dilution

Radon ( 222 Rn) and thoron ( 220 Rn) are two isotopes belonging to the noble gas radon ( sensu lato ) that is frequently employed for the geochemical surveillance of active volcanoes. Temperature gradients operating at subvolcanic conditions may induce chemical and structural modifications in rock-forming minerals and their related 222 Rn– 220 Rn emissions. Additionally, CO 2 fluxes may also contribute enormously to the transport of radionuclides through the microcracks and pores of subvolcanic rocks. In view of these articulated phenomena, we have experimentally quantified the changes of 220 Rn signal caused by dehydration of a zeolitized tuff exposed to variable CO 2 fluxes. Results indicate that, at low CO 2 fluxes, water molecules and hydroxyl groups adsorbed on the glassy surface of macro- and micropores are physically removed by an intermolecular proton transfer mechanism, leading to an increase of the 220 Rn signal. By contrast, at high CO 2 fluxes, 220 Rn emissions dramatically decrease because of the strong dilution capacity of CO 2 that overprints the advective effect of carrier fluids. We conclude that the sign and magnitude of radon ( sensu lato ) changes observed in volcanic settings depend on the flux rate of carrier fluids and the rival effects between advective transport and radionuclide dilution.

QM/MM Simulations of Organic Phosphorus Adsorption at the Diaspore-Water Interface

2019 ◽  
Author(s):  
Prasanth Babu Ganta ◽  
Oliver Kühn ◽  
Ashour Ahmed
Keyword(s):  
Interaction Energy ◽  
Dynamics Simulation ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Water Interface ◽  
Mineral Surfaces ◽  
Soil Mineral ◽  
Phosphorus Adsorption ◽  
Covalent Bonds ◽  
Binding Mechanisms

The phosphorus (P) immobilization and thus its availability for plants are mainly affected by the strong interaction of phosphates with soil components especially soil mineral surfaces. Related reactions have been studied extensively via sorption experiments especially by carrying out adsorption of ortho-phosphate onto Fe-oxide surfaces. But a molecular-level understanding for the P-binding mechanisms at the mineral-water interface is still lacking, especially for forest eco-systems. Therefore, the current contribution provides an investigation of the molecular binding mechanisms for two abundant phosphates in forest soils, inositol hexaphosphate (IHP) and glycerolphosphate (GP), at the diaspore mineral surface. Here a hybrid electrostatic embedding quantum mechanics/molecular mechanics (QM/MM) based molecular dynamics simulation has been applied to explore the diaspore-IHP/GP-water interactions. The results provide evidence for the formation of different P-diaspore binding motifs involving monodentate (M) and bidentate (B) for GP and two (2M) as well as three (3M) monodentate for IHP. The interaction energy results indicated the abundance of the GP B motif compared to the M one. The IHP 3M motif has a higher total interaction energy compared to its 2M motif, but exhibits a lower interaction energy per bond. Compared to GP, IHP exhibited stronger interaction with the surface as well as with water. Water was found to play an important role in controlling these diaspore-IHP/GP-water interactions. The interfacial water molecules form moderately strong H-bonds (HBs) with GP and IHP as well as with the diaspore surface. For all the diaspore-IHP/GP-water complexes, the interaction of water with diaspore exceeds that with the studied phosphates. Furthermore, some water molecules form covalent bonds with diaspore Al atoms while others dissociate at the surface to protons and hydroxyl groups leading to proton transfer processes. Finally, the current results confirm previous experimental conclusions indicating the importance of the number of phosphate groups, HBs, and proton transfers in controlling the P-binding at soil mineral surfaces.

Hydration States of Cholinium Phosphate-Type Ionic Liquids as a Function of Water Content

2019 ◽  
Vol 72 (5) ◽  
pp. 392 ◽  
Author(s):  
Yohsuke Nikawa ◽  
Seiji Tsuzuki ◽  
Hiroyuki Ohno ◽  
Kyoko Fujita
Keyword(s):  
Ionic Liquids ◽  
Water Content ◽  
Alkyl Chain ◽  
Hydroxyl Group ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Ion Structure ◽  
Activity Measurements ◽  
Microscopic Interactions ◽  
Dynamics Simulations

We investigated the hydration states of cholinium phosphate-type ionic liquids (ILs) in relation to ion structure, focusing on the influence of the hydroxyl group of the cation and the alkyl chain length of the anion. Water activity measurements provided information on the macroscopic hydration states of the hydrated ILs, while NMR measurements and molecular dynamics simulations clearly showed the microscopic interactions and coordination of the water molecules. The hydrogen bonding networks in these ILs were influenced by the anion structure and water content, and the mobility of water molecules was influenced by the number of hydroxyl groups in the cation and anion.

scholarly journals Quantum Chemical Calculation of Reactions Involving C20, C60, Graphene and H2O

2019 ◽  
Vol 18 (03n04) ◽  
pp. 1940008 ◽  
Author(s):  
N. A. Poklonski ◽  
S. V. Ratkevich ◽  
S. A. Vyrko ◽  
A. T. Vlassov ◽  
Nguyen Ngoc Hieu
Keyword(s):  
Gibbs Energy ◽  
Chemical Reactions ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Hydrogen Release ◽  
Graphene Sheets ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Chemical Calculation ◽  
Assisted Decomposition

Calculations of chemical reactions between C20, C60, hydrogen and water molecules are carried out using the PM3 method. Reactions with a hydrogen release at room temperature and atmospheric pressure are identified by the Gibbs energy change. The hydrogen release can be raised by increasing the number of water molecules in chlorine-assisted decomposition of fullerenes. Calculations of the Gibbs energy of chemical reactions involving water molecules between two parallel curved graphene sheets are carried out using DFT with the functional UB3LYP. During pumping between plates of an electric capacitor designed from curved graphene sheets, the water vapor with the assistance of external illumination is enriched by electrically neutral hydroxyl groups (OH)0.

Molecular recognition XI. The synthesis of extensively deoxygenated derivatives of the H-type 2 human blood group determinant and their binding by an anti-H-type 2 monoclonal antibody and the lectin 1 of Ulexeuropaeus

1992 ◽  
Vol 70 (1) ◽  
pp. 254-271 ◽  
Author(s):  
Ulrike Spohr ◽  
Eugenia Paszkiewicz-Hnatiw ◽  
Naohiko Morishima ◽  
Raymond U. Lemieux
Keyword(s):  
Monoclonal Antibody ◽  
Molecular Recognition ◽  
Blood Group ◽  
Human Blood ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Human Blood Group ◽  
Derivatives Of ◽  
Hydrogen Bonded

The relative potencies of a wide variety of deoxygenated derivatives of the methyl glycoside of α-L-Fuc-(1 → 2)-β-D-Gal-(1 → 4)- β-D-GlcNAc (the H-type 2 human blood group related trisaccharide) for the inhibition of the binding of an artificial H-type 2 antigen by the lectin I of Ulexeuropaeus confirmed the previous evidence that the key and productive interaction involves only the three hydroxyl groups of the α-L-fucose unit, the hydroxyl at the 3-position of the β-D-galactose residue, and the nonpolar groups in their immediate environment. Except for the acetamido group and the hydroxymethyl of the β-D-Gal unit, which stay in the aqueous phase, on complex formation the remaining three hydroxyl groups appear to come to reside at or near the periphery of the combining site since their replacement by hydrogen causes relatively small changes (< ± 1 kcal/mol) in the stability of the complex (ΔG0). Relatively much larger but compensating changes occur for the enthalpy and entropy terms, and these may arise primarily from the differences in the water structure about the periphery of the combining site and the oligosaccharide both prior to and after complexation. It is proposed that steric constraints lead to an ordered state of the water molecules hydrogen-bonded to the polar groups within the cleft formed by the key region of the amphiphilic combining site. Their release to form less ordered clusters of more strongly hydrogen-bonded water molecules in bulk solution would contribute importantly to the driving force for complexation. It is demonstrated that the surface used for the binding of H-type 2-OMe by a monoclonal anti-H antibody is virtually identical to that used by the Ulex lectin. Keywords: molecular recognition, H-type 2 blood group determinant and deoxygenated derivatives, lectin I of Ulexeuropaeus, anti-H-type 2 monoclonal antibody, enthalpy–entropy compensation.

The polarography of beryllium

1964 ◽  
Vol 17 (10) ◽  
pp. 1072 ◽  
Author(s):  
PJ Shirvington ◽  
TM Florence ◽  
AJ Harle
Keyword(s):  
Aqueous Media ◽  
Electrode Reaction ◽  
Complexing Agents ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Reduction Step ◽  
Current Time ◽  
Diffusion Controlled ◽  
Coordinated Water ◽  
Potentiometric Data

The polarography of beryllium in 0.5M lithium chloride has been investigated in some detail, using several polarographic and coulometric techniques. Current-time curves, microscopic examination and cinematography of the mercury drop, and the effect of complexing agents, aided in elucidating the electrode process. The experimental data show that the polarographic step for the tetraquoberyllium ion is diffusion-controlled but irreversible, and results from the reduction of two protons liberated from the coordinated water molecules, yielding beryllium hydroxide and hydrogen. The evidence suggests that this reduction takes place in a stepwise process, with a soluble beryllium hydroxy complex as an intermediate. The polarographic results can be correlated with published potentiometric data on the composition and stabilities of hydrolysed beryllium species in aqueous media. The number of electrons involved in the electrode reaction depends on the number of hydroxyl groups per beryllium atom in the beryllium complex. Beryllium oxalate and salicylate complexes also give a reduction step, but only if the complex contains coordinated water molecules. The diffusion coefficient of the tetraquoberyllium ion was found to be 6.2 � 0.3 x 10-6 cm2 sec-1 at 30�.

scholarly journals Water Adsorption Properties of Free and Dehydrated β-Cyclodextrin Studied by near Infrared Spectroscopy and Gravimetry

2016 ◽  
Vol 689 ◽  
pp. 143-147 ◽  
Author(s):  
Alfred A. Christy
Keyword(s):  
Hydrogen Bonds ◽  
Infrared Spectra ◽  
Water Adsorption ◽  
Near Infrared ◽  
Adsorption Properties ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Near Infrared Spectra ◽  
Adsorption Of Water

β-cyclodextrin, like other carbohydrates has a tendency to adsorb water molecules and the properties are attributed to the hydroxyl groups in the molecules. β-cyclodextrin, the cyclic oligomer of glucose has a hydrophobic interior and hydrophilic exterior. The cyclic structure favours the formation of hydrogen bonds between the OH groups on the adjacent glucose units and affects the formation of hydrogen bonds with water molecules. The hydoxyl groups engaged in hydrogen bondings can be eliminated at high temperatures and the adsorption properties of the dehydrated β-cyclodextrin will depend on the new functional groups formed. The aim of the report is to discuss the issue of the water adsorption properties of free and dehydrated β-cyclodextrin. Dry β-cyclodextrin and dehydrated β-cyclodextrin at temperatures 250, 300 and 350 °C were allowed to adsorb water from a humidity controlled air environmennt and the evolving near infrared spectra were measured using a near infrared spectrometer equipped with a transflectance accessory. The near infrared spectra in the region 10,000-4000 cm-1 and their second and fourth derivative profiles were used in studying the variation in the adsorption characteristics of dehydrated β-cyclodextrin. The results of the analyses show that the adsorption of water by β-cyclodextrin decreses at 300 °C compared to 200 and 250 °C. Dehydration forms more of the ethereal type-O-bonds in the molecule and explains the decrease in the water molecular adsorption at higher dehydration temperatures.

scholarly journals Crystal structures and spectral properties of new Cd(II) and Hg(II) complexes of monensic acid with different coordination modes of the ligand

2010 ◽  
Vol 8 (4) ◽  
pp. 852-860 ◽  
Author(s):  
Juliana Ivanova ◽  
Ivayla Pantcheva ◽  
Mariana Mitewa ◽  
Svetlana Simova ◽  
Heike Mayer-Figge ◽  
...  
Keyword(s):  
Toxic Metal ◽  
Molecular Geometry ◽  
Spectroscopic Properties ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Monoclinic System ◽  
Bidentate Coordination ◽  
Space Group ◽  
Intramolecular Hydrogen ◽  
Oxygen Atoms

AbstractThe single crystal X-ray structures and the spectroscopic properties of complexes of monensic acid (C36H62O11·H2O) with toxic metal ions of Cd(II) and Hg(II) are discussed. The cadmium(II) complex (1) is of composition [Cd(C36H61O11)2(H2O)2] and crystallizes in the monoclinic system (space group P2(1), Z = 2) with a = 12.4090(8), b = 24.7688(16), c = 14.4358(11) Å, β = 91.979(7)°. Two ligand monoanions are bound in a bidentate coordination mode to Cd(II) via the carboxylate and the primary hydroxyl oxygens occupying the equatorial plane of the complex. The axial positions of the inner coordination sphere of Cd(II) are filled by two water molecules additionally engaged in intramolecular hydrogen bonds. The Hg(II) complex (2), [Hg(C36H60O11)(H2O)], crystallizes in the orthorhombic system (space group P2(1)2(1)2(1), Z = 4) with a = 12.7316(2), b = 16.4379(3), c = 18.7184(4) Å. The monensic acid reacts with Hg(II) in a tetradentate coordination manner via both oxygen atoms of the carboxylate function and oxygens of two hydroxyl groups. The twofold negative charge of the ligand is achieved by deprotonation of carboxylic and secondary hydroxyl groups located at the opposite ends of the molecule. Hg(II) is surrounded by five oxygen atoms in a distorted square pyramidal molecular geometry.

scholarly journals Analysis of water state adsorbed by cellulose fibers

2019 ◽  
Vol 58 (5) ◽  
pp. 24-31
Author(s):  
Daria S. Masas ◽  
◽  
Maria S. Ivanova ◽  
Gocha Sh. Gogelashvili ◽  
Alexander S. Maslennikov ◽  
...  
Keyword(s):  
Adsorbed Water ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Active Centers ◽  
Surface Hydroxyl ◽  
Spin Lattice ◽  
Donor Acceptor ◽  
Elementary Fibrils

Modernized model of microfibril cellulose layered structure is proposed. This model considers presence of slit-shaped micropores in space between elementary fibrils and cellulose microfibrils. It’s discussed the nature of donor-acceptor hydrogen bonds formation: intra-, intermolecular, and interlayer bonds inherent in each glucopyranous cellulose link. It’s described the mechanism of water molecules specific adsorption interactions in a monolayer with active centers located on the hydrophilic surfaces of elementary fibrils. Dipole-dipole energy transition into energy of hydrogen bond is discussed during adsorption process between active centers of cellulose and water adsorptive molecules. Analysis of water molecules dipole-dipole interactions with surface hydroxyl groups of cellulose showed that at distance of 2.5-3 Å energy of this interaction transforms into energy of hydrogen bond. It is discussed the formation mechanism of water molecules donor-acceptor bonds with cellulose surface hydroxyl groups. Thermodynamic parameters characterizing adsorbate state the in these layers are determined by proton magnetic relaxation and sorption measurements. It’s established the possibility of determining adsorption net heat in bilayer considering Arrhenius nature of adsorbate thermal molecular motions correlation times. Increase in entropy of adsorbed water during adsorption process is revealed basis on Vant Hoff equation and certain adsorption equilibrium constant. The calculation established that distance between nearest active centers of cellulose is 6.5 Å. This leads to disunity of adsorbed water molecules and allows application of Langmuir and BET adsorption theory. Analysis of spin-lattice relaxation times dependence on cellulose moisture content made it possible to establish the cause of its crystallite wedging from adsorbed water molecules at adsorption initial stages. Decline of the spin-lattice relaxation unambiguously indicates the process of cellulose dispersion into its structural elements. It was established that during adsorption a part of the internal regions of crystallites passes to their surface with participation of cellulose hydroxyl groups. During desorption reverse process is observed.

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