Adsorption Of Mono Research Articles

Adsorption of Mono- and Divalent Ions onto Dendritic Polyglycerol Sulfate (dPGS) as Studied Using Isothermal Titration Calorimetry.

The effective charge of highly charged polyelectrolytes is significantly lowered by a condensation of counterions. This effect is more pronounced for divalent ions. Here we present a study of the counterion condensation to dendritic polyglycerol sulfate (dPGS) that consists of a hydrophilic dendritic scaffold onto which sulfate groups are appended. The interactions between the dPGS and divalent ions (Mg2+ and Ca2+) were analyzed using isothermal titration calorimetry (ITC) and showed no ion specificity upon binding, but clear competition between the monovalent and divalent ions. Our findings, in line with the latest theoretical studies, demonstrate that a large fraction of the monovalent ions is sequentially replaced with the divalent ions.

Kraft Lignin and its Derivates – a Study on the Adsorption of Mono and Multielement Metals, Potential Use for Noble Metal Recycling and an Alternative Material for Solid Base Catalyst

Kraft Lignin and its Derivates – a Study on the Adsorption of Mono and Multielement Metals, Potential Use for Noble Metal Recycling and an Alternative Material for Solid Base Catalyst

Rivalry at the Interface: Ion Desolvation and Electrolyte Degradation in Model Ethylene Carbonate Complexes of Li+, Na+, and Mg2+ with PF6 - on the Li4Ti5O12 (111) Surface.

Spinel lithium titanate, Li4Ti5O12 (LTO), emerges as a “universal” electrode material for Li-ion batteries and hybrid Li/Na-, Li/Mg-, and Na/Mg-ion batteries functioning on the basis of intercalation. Given that LTO operates in a variety of electrolyte solutions, the main challenge is to understand the reactivity of the LTO surface toward single- and dual-cation electrolytes at the molecular level. This study first reports results on ion desolvation and electrolyte solvent/salt degradation on an LTO surface by means of periodic DFT calculations. The desolvation stages are modeled by the adsorption of mono- and binuclear complexes of Li+, Na+, and Mg2+ with a limited number of ethylene carbonate (EC) solvent molecules on the oxygen-terminated LTO (111) surface, taking into account the presence of a PF6– counterion. Alongside cation adsorption, several degradation reactions are discussed: surface-catalyzed dehydrogenation of EC molecules, simultaneous dehydrogenation and fluorination of EC, and Mg2+-induced decay of PF6– to PF5 and F–. Data analysis allows the rationalization of existing experimentally established phenomena such as gassing and fluoride deposition. Among the three investigated cations, Mg2+ is adsorbed most tightly and is predicted to form a thicker fluoride-containing film on the LTO surface. Gassing, characteristic for carbonate-based electrolytes with LTO electrodes, is foreseen to be suppressed in dual-cation batteries. The latter bears promise to outperform the single-ion ones in terms of durability and safety.

Renewable Eco-Friendly Activated Biochar from Tobacco: Kinetic, Equilibrium and Thermodynamics Studies for Chlorpyrifos Removal

ABSTRACT We evaluated the potential application of tobacco as a low-cost raw matter for the development of a new and ecological activated biochar, with the aim of chlorpyrifos adsorption. This was performed by means of characterization and testing the efficiency of the activated biochar based on tobacco from seized cigarettes. Chemically and thermally activated biochar were produced with different chemical modifying agents (ZnCl2 and NaOH). The treatments improved the features of adsorbent structure, with an increase of 1775x in SSA of AB-ZnCl2. The adsorption of chlorpyrifos by the activated biochar seems to occur partially by chemical and partially by physical interactions between the pesticide and the surface functional groups O–H, C–H, C=O, C–C, C–H, and C–O. The good adjustments may indicate the adsorption of mono and multilayer. The materials show great results for removal of chlorpyrifos with an estimate qm of 683.30 and 1602.40 µg g−1 for Langmuir, respectively, found for AB and for AB-ZnCl2. This way, the production of activated biochar can be an excellent alternative for the destination and use of tobacco from seized cigarettes, allowing its use in remediation and decontamination of water.

Adsorption of Mono- and Divalent 4-(Dimethylamino)pyridines on Gold Surfaces: Studies by Surface-Enhanced Raman Scattering and Density Functional Theory.

The adsorption thermodynamics of 4-(dimethylamino)pyridine (DMAP) and its five divalent derivatives di-DMAP- n (2 ≤ n ≤ 6) with gradually increasing methylene-spacer lengths n binding to planar gold surfaces has been studied by surface-enhanced Raman spectroscopy (SERS) and density functional theory (DFT). SERS intensities of the totally symmetrical breathing mode of the pyridine ring at approximately 1007 cm-1 are used to monitor the surface coverage of the DMAP and di-DMAP- n ligands on gold surfaces at different concentrations. The equilibrium constant as a measure of the binding affinity is obtained from these measurements by using a modified Langmuir isotherm. Due to multivalent binding to the gold substrate, a characteristic enhancement of the binding affinity of di-DMAP- n compared to the monovalent DMAP is observed for all divalent species. First principles calculations of the di-DMAP- n ligands on an ideal Au(111) surface model as well as step terrace models have been performed to understand the adsorption structures and the multivalent binding enhancements. Furthermore, Raman spectra of the adsorbed molecules have been studied by first principles calculations to correlate the binding affinities to experimentally determined adsorption constants. The joint experimental and theoretical investigation of an oscillatory behavior of the binding affinity as a function of the methylene-spacer length in mono- and divalent 4-(dimethylamino)pyridines reveals that the molecular architecture plays an important role for the structure-function interplay of multivalently bound adsorbates.

Adsorption of mono- and di-butyltin by a wheat charcoal: pH effects and modeling

Understanding adsorption processes of butyltins (BTs) such as monobutyltin (MBT) and dibutyltin (DBT) by black carbons is important for the evaluation of BT exposure risks to organisms and humans. However, relevant knowledge is scarce. In this study, the acidity constants pKa,1=2.3, pKa,2=3.5 and pKa,3=5.9 for MBT and pKa,1=3.0 and pKa,2=5.1 for DBT are estimated via potentiometric titration. Additionally, adsorption isotherms of BTs to a wheat charcoal were determined. The adsorption behavior was observed to be pH-dependent due to BT speciation and the pH-dependent surface charge of the charcoal. MBT adsorption to the charcoal decreases with increasing pH from 4 to 8, while the highest adsorption occurs at pH 6 for DBT. Adsorption of the BTs is successfully described in the pH range of 3–10 by using a newly developed pH-dependent Dual Langmuir model. The model has the potential to predict the interaction of BT species with charcoal, which can contribute to the risk assessments of BTs in the environment.

Adsorption of Nucleic Acid Components on Rutile (TiO2) Surfaces

Nucleic acids, the storage molecules of genetic information, are composed of repeating polymers of ribonucleotides (in RNA) or deoxyribonucleotides (in DNA), which are themselves composed of a phosphate moiety, a sugar moiety, and a nitrogenous base. The interactions between these components and mineral surfaces are important because there is a tremendous flux of nucleic acids in the environment due to cell death and horizontal gene transfer. The adsorption of mono-, oligo-, and polynucleotides and their components on mineral surfaces may have been important for the origin of life. We have studied here interactions of nucleic acid components with rutile (TiO(2)), a mineral common in many terrestrial crustal rocks. Our results suggest roles for several nucleic acid functional groups (including sugar hydroxyl groups, the phosphate group, and extracyclic functional groups on the bases) in binding, in agreement with results obtained from studies of other minerals. In contrast with recent studies of nucleotide adsorption on ZnO, aluminum oxides, and hematite, our results suggest a different preferred orientation for the monomers on rutile surfaces. The conformations of the molecules bound to rutile surfaces appear to favor specific interactions, which in turn may allow identification of the most favorable mineral surfaces for nucleic acid adsorption.

Modelling of fixed-bed adsorption of mono-, di-, and fructooligosaccharides on a cation-exchange resin

Abstract Kinetics of fixed-bed adsorption of simple saccharides (glucose, fructose, and sucrose) and fructooligosaccharides (1-kestose, 1-nystose, and 1 F -fructofuranosyl nystose) on process-size particles of cation exchanger Amberlite™ CR1320Ca was investigated. A step-up method of frontal chromatography was used when several inlet concentration steps were made in the range of 0–20 g dm −3 . The obtained experimental data were fitted simultaneously using the general rate model with two estimated parameters, which were the distribution coefficient of linear adsorption isotherm and solid-phase diffusion coefficient. The contribution of individual transport phenomena to dispersion of adsorption fronts was discussed.

DFT and In-Situ Spectroelectrochemical Study of the Adsorption of Fluoroacetate Anions at Gold Electrodes

The adsorption of mono-, di-, and trifluoroacetate anions at gold electrodes is studied in perchloric acid solutions by cyclic voltammetry and in situ infrared and Raman spectroscopies. Surface enhanced infrared reflection absorption spectroscopy experiments under attenuated total reflection conditions (ATR-SEIRAS) and surface enhanced Raman scattering (SERS) experiments were carried out with gold thin-film electrodes sputtered on silicon and on a polycrystalline gold substrate, respectively. Theoretical harmonic vibrational frequencies of trifluoroacetate species adsorbed with different geometries on Au clusters with (111), (100), and (110) orientations, as well as IR and Raman intensities, have been obtained from B3LYP/LANL2DZ, 6−31+G(d) calculations. This theoretical study was extended to di- and monofluoroacetate anions adsorbed on Au(111) clusters. The theoretical and experimental results confirm the bidentate bonding of fluoroacetate anions with the OCO plane perpendicular to the metal surface irres...

Studies on adsorption of mono- and multi-chromophoric hemicyanine dyes on silver nanoparticles by surface-enhanced resonance raman and theoretical calculations

Structural and vibrational properties of mono- and multichromophoric hemicyanine (HC) dyes in solution and adsorbed on silver-coated films have been investigated using optical absorption and resonance Raman scattering techniques, with interpretations aided by theoretical calculations. This is the first report on the Raman spectroscopic studies of multichromophoric HC derivatives. The structure of the monomer, N-propyl-4-(p-N,N-dimethylamino styryl)pyridinium bromide (HC3), and its charged and neutral silver complexes (HC3-Ag) in the ground electronic (S(0)) state were optimized using density functional calculations with the B3LYP method using the 6-31G(*) and LANL2DZ basis sets. The ground state structure of N-hexyl-4-(p-N,N-dimethylamino styryl)pyridinium bromide (HC6) and multichromophoric HC dyes were computed using the HF6-31G(*) method. The negligible shift or broadening observed in the electronic absorption and resonance Raman spectra in solution with increasing size of the HC chromophore suggests that the excitations are localized within individual monomer units in bis and tetra chromophores. However, in the tris chromophore, considerable redshift and broadening were observed, indicating a significant electronic interaction between the nonbonded electrons of the N atom and the aromatic pi-system that is supported by the calculated excitation energies using the time-dependent density functional theory method. The effect of HC dye concentration on the electronic absorption spectra of the silver-coated film showed significant broadening, which was attributed to the formation of H- and J-aggregates in addition to the formation of a metal-molecule complex. A considerable redshift along various vibrations observed in the surface-enhanced resonance Raman scattering (SERRS) spectra of the HC derivatives indicates that adsorption on the silver surface leads to a considerable interaction of the electron rich moiety of HC derivatives with the silver surface. The enhancement of various in-plane and out-of-plane vibrations, along with slight broadening and redshifts observed in the SERRS spectra, suggests that binding of the HC dyes to the silver surface occurs through the aromatic pi-system attached to the electron rich dimethylamino group, with the ring lying almost parallel to the silver surface. Theoretical results have further indicated adsorption via chemisorption for the charged HC3-Ag complexes and by physisorption for the neutral HC3-Ag complexes.

Adsorption of Mono-, Di-, Tri- and Tetra-Glycine by Mesoporous Materials FSM-16

Adsorption of mono, di-, tri- and tetra-gly by FSM-16 was attempted and isotherms for adsorption of them was drawn. The isotherms for adsorption were arranged from high to low that of tetra-, tri-, di- and mono-gly in order. The arrangement of the isotherms was dependent on the solubility of glycine and its oligomers. On the other hand, FSM-16 can function as the molecular sieve because FSM-16 has a mesopore. The effect of the molecular sieve showed very little in extend of the adsorption.

Adsorption of Methylamines on Carbon Materials at Zero Surface Coverage

This paper deals with the adsorption of mono-, di- and trimethylamine (MMA, DMA and TMA) on carbon materials at zero surface coverage studied by inverse gas−solid chromatography (IGSC). The adsorbe...

Adsorption of mono- and polynucleotides on iron oxide hydroxide polymorphs

Adsorption of mono- and polynucleotides on iron oxide hydroxide polymorphs

Adsorption of mono- and divalent metal cations on hydroxyapatite in water.

Adsorption of mono- and divalent metal cations on hydroxyapatite in water.

The influence of organocation structure on the adsorption of mono- and of bipyridinium cations by expanding lattice clay minerals: I. Adsorption by Na +-montmorillonite

Adsorption isotherms, X-ray diffraction, and microcalorimetic techniques were used to study interactions in an aqueous environment between various pyridinium and bipyridinium cations and a Na +-montmorillonite clay preparation. All of these cations had high affinities for the clay, were adsorbed to 80–125% of its cation-exchange capacity (CEC) and the adsorption processes were exothermic. Where lamellar collapse onto flattened organocations was observed, bipyridinium cations were more energetically bound to the clay than were the monopyridinoum species. This can be attributed to additional stabilization arising from charge transfer complexes in the cases of the bivalent compounds. Although 4-phenylpyridinium compounds were not flattened in the interlamellar spaces, their interactions, per equivalent, with the clay were the most highly exothermic observed because of the van der Waals interactions between the interlamellarly adsorbed aromatic rings. Significant effects could be attributed to the quaternizing groups only in cases of adsorption of 2,2′-bipyridine derivatives, and there was no evidence to indicate that altering the species of halide counterion significantly influenced adsorption.

The influence of organocation structure on the adsorption of mono- and of bipyridinium cations by expanding lattice clay minerals: II. Adsorption by Na +-vermiculite

From observation of adsorption isotherms, X-ray diffraction, and microcalorimetric data it was evident that the interactions between various pyridinium and bipyridinium cations and Na +-vermiculite clay were significantly different from the reactions of the same organocations with Na +-montmorillonite reported in Part I of this series. Uptake of adsorbate ranged from 22 to 119% of the cation-exchange capacity (CEC) of the vermiculite and, in contrast to the montmorillonite systems, the organocation-clay interactions were always endothermic initially. Van der Waals forces gave rise to secondary exothermic effects when bipyridine species (liberated from 4,4′-bipyridinium salts) and the higher concentrations of the 4-phenylpyridinium compounds were taken into the interlamellar spaces. Monopyridinium cations lacked the configurational entropy impetus of the bipyridinium species and were less extensively adsorbed. The endothermicity can be attributed to the large amount of energy required to remove bound water from the vermiculite lamellae. Thus in the interlamellar spaces the organocations assumed conformations which displaced least water and resisted the energy-releasing collapse of the lamellae so frequently observed in adsorption by montmorillonite. Quaternization with methyl groups depressed adsorption on vermiculite because the difficulty of displacing surface water increased with the size/charge ratio of the adsorbate.