Adsorption Of Bis Research Articles

Adsorption of bis(2-hydroxy-3-chloropropyl) dodecylamine on quartz surface and its implication on flotation

Abstract In order to clarify the effect of polar group modification on flotation performance of amine collector, flotation properties of quartz and hematite using bis(2-hydroxy-3-chloropropyl) dodecylamine (N23) as a collector were investigated. And the adsorption mechanism of N23 on quartz surface was established by zeta potential measurements, SEM/EDS measurements, and molecular structure analysis. Single mineral flotation results indicated that N23 showed stronger collecting ability on quartz and hematite than DDA-CH 3 COOH. However, starch could depress the flotation of hematite. Flotation recovery of 98.10% for quartz could be achieved, when N23 concentration was 43.33 mg/L and starch concentration was 16.67 mg/L at natural slurry pH. Separation of artificially mixed minerals of hematite and quartz was achieved effectively using N23 as the collector. The optimized separation result with 66.29% iron grade and 90.06% iron recovery in concentrate was obtained when slurry pH was 7.34 with 43.33 mg/L N23 and 23.33 mg/L starch. The interaction energies of N23 with mineral surface also showed well consistency with flotation results. SEM/EDS analyses and zeta potential measurements revealed that N23 could absorb on quartz surface in the forms of strong electrostatic and hydrogen bonding interaction. Compared with DDA, N23 had a higher HLB value and better water-solubility, which resulted in better dispersion in water and stronger adsorption on mineral surface.

On the use of the experimentally determined enzyme inhibition constant as a measure of absolute binding affinity

Defined as a state function representing an inhibitor's absolute affinity for its target enzyme, the experimentally determined enzyme inhibition constant (Ki) is widely used to rank order binding affinities of different inhibitors for a common enzyme or different enzymes for a common inhibitor and to benchmark computational approaches to predicting binding affinity. Herein, we report that adsorption of bis(7)-tacrine to the glass container surface increased its Ki against Electrophorus electricus acetylcholinesterase (eeAChE) to 3.2 ± 0.1 nM (n = 5) compared to 2.9 ± 0.4 pM (n = 5) that was determined using plastic containers with other assay conditions kept the same. We also report that, due to binding or “adsorption” of bis(7)-tacrine to the inactive eeAChE, the bis(7)-tacrine Ki increased from 2.9 ± 0.4 pM (n = 5) to 734 ± 70 pM (n = 5) as the specific eeAChE activity decreased from 342 U/mg to 26 U/mg while other assay conditions were kept the same. These results caution against using Kis to rank order binding potencies, define selectivity, or benchmark computational methods without knowing detailed assay conditions.

Surface modification of iron particles with a polyfluorinated disulfude: Effect of solvent and temperature

Adsorption of bis(2-chloro-3-oxaperfluorobutyl) disulfide from nonaqueous solutions onto the surface of carbonyl iron particles was studied with the aim of modification of these particles. The adsorption parameters were calculated using the Langmuir equation from the adsorption isotherms obtained in the interval 20-60°C. With an increase in temperature and in the solvent affinity for the modifying agent, the limiting amounts of the reagent that has interacted with the iron particle surface increase. This fact suggests the chemisorption nature of the process. The products of the reaction of iron with the disulfide can be desorbed from the particle surface.

Anti‐corrosion properties of bis(benzimidazole) derivatives for N80 steel in H2S solution

In this work, we systematically investigated the effect of four bis(benzimidazole) derivatives containing different heteroatoms in molecular structures on inhibiting corrosion of N80 steel in 0.5 mmol·l−1 H2S solution by potentiodynamic polarization, electrochemical impedance spectroscopy and metallographic microscope. The results showed that within the range of 0.1–1.0 mmol·l−1, the adsorption of bis(benzimidazole) derivatives on N80 steel surface was found to follow Langmuir adsorption isotherm. Meanwhile, stable adsorbing monolayer between inhibitors and the metal surface was formed, which was confirmed by thermodynamic adsorption parameters (Kads, ). This series of bis(benzimidazole) derivatives exhibited obvious corrosion inhibitory properties for N80 steel. Moreover, they could both slow down the anodic dissolution of iron and the cathodic reduction reaction as mixed type corrosion inhibitors. The optimal inhibition efficiency was obtained for 1,3‐bis(benzimidazl‐2‐yl)‐2‐thiapropane (BBMS). Hopefully, this series of inhibitors might find applications in anti‐corrosion and many other areas. Copyright © 2012 John Wiley & Sons, Ltd.

Ag(I)/Ag electrode reaction in amide-type room-temperature ionic liquids

Ag(I)/Ag electrode reaction was investigated in some amide-type room-temperature ionic liquids composed of different cations. The morphology of silver deposits and the electrochemical behavior were not sensitive to the difference in the cations of ionic liquids. On the other hand, it was suggested that the adsorption of bis(trifluoromethylsulfonyl)amide (TFSA −) is more important for electrodeposition of silver in both ionic liquids and aqueous solutions. The diffusion coefficients of silver cation in the ionic liquids indicated the silver cation is surrounded by TFSA − to form a bulky species. The rate of crystal growth of silver particles in the ionic liquids by electrochemical Ostwald ripening was much slower than that in a nitrate aqueous solution, suggesting the charge transfer in the ionic liquids is slower than that in the aqueous solution.

Synthesis, characterization and catalytic epoxidation of styrene using molecular oxygen over “neat” and host–guest nanocomposite materials

The complexes of Fe(II) were synthesized with the azamacrocyclic ligands; [12]aneN 4: 1,4,7,10-tetraazacyclododecane-2,3,8,9-tetraone; [14]aneN 4: 1,4,8,11-tetraazacyclotetradecane-2,3,9,10-tetraone; Bzo 2[12]aneN 4: dibenzo-1,4,7,10-tetraazacyclododecane-2,3,8,9-tetraone and Bzo 2[14]aneN 4: dibenzo-1,4,8,11-tetraazacyclotetradecane-2,3,9,10-tetraone. Iron(II) complexes with azamacrocyclic ligand were entrapped in the nanocavity of zeolite-Y by a two-step process in the liquid phase: (i) adsorption of bis(diamine)iron(II); in the supercages of the zeolite, and (ii) in situ condensation of the iron(II) precursor complex with diethyloxalate. The new nanocomposite materials were characterized by several techniques: chemical analysis, spectroscopic methods (DRS, BET, FTIR and UV/vis). Analysis of the data indicated that the Fe(II) complexes were encapsulated in the nanodimensional pores of zeolite-Y and exhibited different from those of the free complexes, which can arise from distortions caused by steric effects due to the presence of sodium cations, or from interactions with the zeolite matrix. The encapsulated nanomaterials are active catalyst for the epoxidation of styrene using molecular oxygen as an oxidant. By comparing the performance of the heterogeneous system with the free complex in the oxidation of styrene using O 2, protection effect of the matrix over the active center was evidenced by a higher conversion and yield of products.

Host (nanocavity of zeolite-Y)/guest (Mn(II), Co(II), Ni(II) and Cu(II) complexes of pentadendate Schiff-base ligand) nanocomposite materials (HGNM): application in the heterogeneous oxidation of cyclohexene

Transition metal (M = Mn(II), Co(II), Ni(II) and Cu(II)) complexes with pentadendate Schiff-base ligand; N,N′-bis(salicylidene)-2,6-pyridinediaminato, H2 [sal-2,6-py]; was entrapped in the nanocavity of zeolite-Y by a two-step process in the liquid phase: (i) adsorption of bis(salicylaldiminato)metal(II); [M(sal)2]-NaY; in the supercages of the zeolite, and (ii) in situ Schiff condensation of the metal(II) precursor complex with the corresponding 2,6-pyridinediamine; [M(sal-2,6-py)]-NaY. The new materials were characterised by several techniques: chemical analysis, spectroscopic methods (DRS, BET, FTIR and UV/Vis), conductometric and magnetic measurements. Analysis of the data indicates that the M(II) complexes are encapsulated in the nanodimensional pores of zeolite-Y and exhibit different from those of the free complexes, which can arise from distortions caused by steric effects due to the presence of sodium cations, or from interactions with the zeolite matrix. The Host–Guest Nanocomposite Materials (HGNM); [M(sal-2,6-py)]-NaY; catalyzes the oxidation of cyclohexene with tert-butylhydroperoxide (TBHP). Oxidation of cyclohexene with HGNM gave 2-cyclohexene-1-one, 2-cyclohexene-1-ol and 1-(tert-butylperoxy)-2-cyclohexene. [Mn(sal-2,6-py)]-NaY shows significantly higher catalytic activity than other catalysts.

Oxidation of cyclohexene with tert-butylhydroperoxide catalysted by host (nanocavity of zeolite-Y)/guest (Mn(II), Co(II), Ni(II) and Cu(II) complexes of N, N′-bis(salicylidene)phenylene-1,3-diamine) nanocomposite materials (HGNM)

Transition metal (M = Mn(II), Co(II), Ni(II) and Cu(II)) complexes with tetradendate Schiff-base ligand; N, N′-bis(salicylidene)phenylene-1,3-diamine, H 2[sal-1,3-phen]; was entrapped in the nanocavity of zeolite-Y by a two-step process in the liquid phase: (i) adsorption of bis(salicylaldiminato)metal(II); [M(sal) 2]-NaY; in the supercages of the zeolite, and (ii) in situ Schiff condensation of the metal(II) precursor complex with the corresponding phenylene-1,3-diamine; [M(sal-1,3-phen)]-NaY. The new materials were characterised by several techniques: chemical analysis, spectroscopic methods (DRS, BET, FTIR and UV–vis), conductometric and magnetic measurements. Analysis of the data indicates that the M(II) complexes are encapsulated in the nanodimensional pores of zeolite-Y and exhibit different from those of the free complexes, which can arise from distortions caused by steric effects due to the presence of sodium cations, or from interactions with the zeolite matrix. The host–guest nanocomposite materials (HGNM); [M(sal-1,3-phen)]-NaY; catalyzes the oxidation of cyclohexene with tert-butylhydroperoxide (TBHP). Oxidation of cyclohexene with [M(sal-1,3-phen)] gave 2-cyclohexene-1-one, 2-cyclohexene-1-ol and 1-( tert-butylperoxy)-2-cyclohexene whereas, oxidation with [M(sal-1,3-phen)]-NaY resulted in the formation of 2-cyclohexene-1-one and 2-cyclohexene-1-ol. [Mn(sal-1,3-phen)]-NaY shows significantly higher catalytic activity than other catalysts.

Loosely Packed Hydroxyl-Terminated SAMs on Gold

We report the preparation of loosely packed hydroxyl-terminated self-assembled monolayers (SAMs) on gold by the adsorption of bis(11,11'-dithioundecyl)perfluoroheptanoate and base-mediated cleavage of the fluorocarbon terminal group. As shown through complementary characterization methods, the partially fluorinated SAM exhibits a structure in which the outer surface contains mostly -CF(3) groups, the fluorocarbon groups are slightly canted on average, and the hydrocarbon chains underneath are in a fluidlike state. Upon cleavage of the fluorocarbon group, the hydroxyl-terminated alkyl chains relax into an increasingly canted, fluidlike state. The resulting monolayer packing exposes both methylene and hydroxyl functionalities, yielding an intermediate surface energy (theta(a)(H(2)O) approximately 68 degrees ). As compared to a densely packed hydroxyl-terminated SAM prepared from bis(11-hydroxyundecyl)disulfide, the cleaved films are thinner because of the greater average chain cant and exhibit a approximately 50% higher capacitance and a factor of 5 lower charge-transfer resistance. The addition of THF to the electrolyte solution as a cosolvent intercalates into the loosely packed SAM to double the charge-transfer resistance and increase the capacitance by approximately 20% but does not affect the capacitance of the densely packed SAM. The loosely packed SAM is also more easily exchanged upon exposure to a solution of n-docosanethiol.

Acid-catalysed degradation of the organomercury intermediates of pentafluorophenylmercury bromide reduction near a mercury electrode

The acid-catalysed protolysis of intermediates, formed either during one-electron reduction of substituted arylmercury salt (C6F5HgBr) or by the adsorption of bis(arylalkynyl)mercury compound [(PhC C)2Hg] on a Hg electrode has been found in lowacidic media (3

Adsorption of Cationic Surfactants on Highly Dispersed Silica

Comparative study was made of adsorption of cationic surfactants, decamethoxine, ethonium, and cetyltrimethylammonium bromide, on a highly dispersed amorphous silica at different pH values. Contrary to the adsorption of monoquaternary ammonium compound, cetyltrimethylammonium bromide, the adsorption of bis(quaternary ammonium) compounds, ethonium and decamethoxine, was found to be caused mainly by electrostatic interaction. The adsorption of antiseptic decamethoxine is reversible at pH 6; this may be used to design carriers capable of controlled drug release into the surrounding medium.

On the inhibition effect of dialkyl phosphates in the depassivation of metals

The inhibition effect and adsorption of bis(2-ethylhexyl) phosphate (EHP) and dioctyl phosphate (DOP) anions ((C8H17-O)2P(O)OH) in the depassivation of iron, aluminum, and zinc in neutral solutions were studied by electrochemical and ellipsometric methods. Both the anions exhibit high passivating properties; DOP is superior to EHP in passivating iron and has a considerable aftereffect. The adsorption of dialkyl phosphates on passive iron from a borate buffer is governed by the Frumkin isotherm.

The adsorption of bis(he×afluoroacetylacetonato)zinc(II) on Si(111)-7×7

The adsorption of the organometallic compounds bis(hexafluoroacetylacetonato)zinc(II) (Zn(hfac)2) and bis(hexafluoroacetylacetonato)nickel(II) (Ni(hfac)2) on the surface of Si(111)-7×7 were studied by a combination of scanning tunnelling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). These compounds are analogues of the compound bis(hexafluoroacetylacetonato)copper(II), which is an important precursor for the chemical vapour deposition of copper that we have previously studied. Both XPS and STM results indicate that the Zn(hfac)2 is adsorbed intact on the surface, and remains intact on the surface at temperatures up to 300 K. The XPS shows a transition from a physisorbed state to a chemisorbed state at temperatures between 160 and 300 K. At higher temperatures Zn(hfac)2 decomposed to form Zn and fluorocarbon fragments. The metal component diffused into the substrate. The Ni(hfac)2 complex could not be successfully adsorbed on the Si surface: it was shown that this was due to decomposition of the molecule in the vapour phase, probably due to the higher temperatures needed to evaporate this relatively involatile compound.

Adsorption of tetrasulfide-functional silane on high surface area silica treated with aqueous and non-aqueous solutions

The adsorption of bis-[3-(triethoxysilyl)propyl]tetrasulfide (Si-69) coupling agent onto fumed silica is affected by the solvent polarity and the silane concentration. Chemisorbed silane onto silica studied by quantitative FTIR reveals that polar solvents, especially water and ethanol, yield significantly more chemisorbed silane than non-polar solvents. In contrast, physisorbed silane is dominant in non-polar solvents. In the case of silane concentration effect, the chemisorbed silane increases with silane concentration until the saturation point. By varying silane concentration, physisorbed silane in both polar and non-polar solvents is found to increase as the silane concentration increases.

Adsorption of bis(triethanolammonium) 1,10-decanedicarboxylate on magnetite from aqueous solution

Adsorption of bis(triethanolammonium) 1,10-decanedicarboxylate on magnetite from aqueous solution

Effect of pH on the electron transfer of cytochrome c on a gold electrode modified with bis(4-pyridyl)disulphide

The adsorption of bis(4-pyridyl)disulphide (PySSPy) and 4,4′-bipyridyl (PyPy) on a gold electrode was studied using cyclic voltammetry. The adsorption isotherms and equilibrium constants ( 1 × 10 6 mol −1 1 for PyPy and 6 × 10 6 mol −1 1 for PySSPy) were determined. The effect of pH on the electrochemical behaviour of cytochrome c was studied on the PySSPy-modified gold electrode. The results show that cytochrome c can only transfer electrons on a deprotonated electrode surface. When the pH is decreased, the standard heterogeneous rate constant of cytochrome c on the modified gold electrode decreases and the electrochemical behaviour changes from a quasi-reversible to an irreversible process.