Adsorption anionics

Fluoride is a natural component of most types of soil, in which it is mainly bound in complexes and not readily leached. The major source of free fluoride ion in soil is the weathering and dissolution of fluoride rich rock that depends on the natural solubility of the fluoride compound in question, pH, and the presence of other minerals and compounds and of water. The major parameters that control fluoride fixation in soil through adsorption, anion exchange, precipitation, formation of mixed solids and complexes are aluminium, calcium, iron, pH, organic matter and clay [19,20]. 

Anion-induced adsorption -> induced adsorption Anion vacancies -> vacancies... 

Comparison of Protein Adsorption Anion-Exchange Interaction onto Porous Hollow-Fiber Membrane and Gel Bead-Packed Bed, J. Membrane Sci.,... 

The structure of the adsorbate systems formed by mercaptobenzothiazole and analogue molecules on CdS (1010) surface was studied quantum chemically using density functional theory [57]. Preliminary calculations of the free adsorptive molecules indicate an energetic preference of their thione form compared to the thiol form. For the anions of the adsorptive molecules, the role of the endocyclic nitrogen and the exocychc sulfur as possible donor atoms was examined by means of known chelate complexes. Geometry optimizations showed that the structure of the adsorbate systems is dominated by the formation of two coordinative bonds from the donor atoms of the adsorptive anions to two adjacent Cd atoms of the surface. It showed that the molecular plane of the adsorptives is tilted with respect to the normal of the crystal face. They have shown that the tilt angle is mainly determined by the tendency of the surface Cd atoms to continue the tetrahedral coordination from the bulk [57]. 

Metal-organic frameworks are largely used for their host-guest properties, such as gas adsorption, anion exchange and chemical separation, much like zeolites. The following section will deal with some of these aspects individually. 

Adsorption Anion resin Palm kernel Ethanol 63 Oliveira and Vladimir Oliveira, 2001... 

Keywords Radiotracer technique Spedlic adsorption Nonspedlie adsorption Anions 7-AI2O3... 

Key words Fillers — flotation — adsorption — anionic surfactant — cationic polyelectrolyte... 

Fig. V-11. Electrocapillary curves (a) adsorption of anions (from Ref. 113) (b) absorption of cations (from Ref. 6) (c) electrocapillary curves for -pentanoic acid in QAN HCIO4. Solute activities from top to bottom are 0, 0.04761, 0.09096, 0.1666, and 0.500 (from Ref. 112).

Note Some of Grahame s values for and included in this table. For a common cation, the sequence of anions in order of increasing adsorption is similar to that of the Hofmeister series in coagulation studies, and it is evident that specific adsorption properties are involved. 

Electrolyte adsorption on metals is important in electrochemistry [167,168]. One study reports the adsorption of various anions an Ag, Au, Rh, and Ni electrodes using ellipsometry. Adsorbed film thicknesses now also depend on applied potential. 

In general, then, anion-forming adsorbates should find p-type semiconductors (such as NiO) more active than insulating materials and these, in turn, more active than n-type semiconductors (such as ZnO). It is not necessary that the semiconductor type be determined by an excess or deficiency of a native ion impurities, often deliberately added, can play the same role. Thus if Lr ions are present in NiO, in lattice positions, additional Ni ions must also be present to maintain electroneutrality these now compete for electrons with oxygen and reduce the activity toward oxygen adsorption. 

The fact that more than one molecule of water may be displaced for each anion adsorbed, and that the adsorption energy of these water molecules will show a complex dependence on the electrode potential. 

Wliether the potentials are derived from quantum mechanical calculations or classical image forces, it is quite generally found that there is a stronger barrier to the adsorption of cations at the surface than anions, in agreement with that generally. ... 

STM has been used to study adsorption on surfaces as it relates to corrosion phenomena [6, 7]. Sulfiir is a well known corrosion agent and is often found in air (SO2, FI2S) and in aqueous solution as dissolved anions ( HSO7) or dissolved gas (FI2S). By studying the interaction of sulfur with surfaces, insights can be gained into... 

Biggs S, Mulvaney P, Zukoski C F and Grieser F 1994 Study of anion adsorption at the gold-aqueous solution interface by atomic force microscopy J. Am. Chem. Soc. 116 9150... 

Horanyi G and Rizmayer E M 1984 Radiotracer study of anion adsorption at silver electrodes in acidic medium J. Electroanal. Chem. 176 339-48... 

Wang J, Ocko B M, Davenport A J and Isaacs H I 1992 In situ diffraction and reflectivity studies of the Au(111 )/electrolyte interface Reconstruction and anion adsorption Phys. Rev B 34 10 321-38... 

Wu S, Lipkowski J, TylizczakT and Hitchcock H P 1995 Effect of anion adsorption on early stages of copper electrocrystallization at Au(111) surface Prog. Surf. Sc/. 50 227-36... 

Example of copredpitation (a) schematic of a chemically adsorbed inclusion or a physically adsorbed occlusion in a crystal lattice, where C and A represent the cation-anion pair comprising the analyte and the precipitant, and 0 is the impurity (b) schematic of an occlusion by entrapment of supernatant solution (c) surface adsorption of excess C. 

Another example of vims clearance is for IgM human antibodies derived from human B lymphocyte cell lines where the steps are precipitation, size exclusion using nucleases, and anion-exchange chromatography (24). A second sequence consists of cation-exchange, hydroxylapatite, and immunoaffinity chromatographies. Each three-step sequence utilizes steps based on different properties. The first sequence employs solubiUty, size, and anion selectivity the second sequence is based on cation selectivity, adsorption, and selective recognition based on an anti-u chain IgG (24). 

Hydrophobic Interaction Chromatography. Hydrophobic interactions of solutes with a stationary phase result in thek adsorption on neutral or mildly hydrophobic stationary phases. The solutes are adsorbed at a high salt concentration, and then desorbed in order of increasing surface hydrophobicity, in a decreasing kosmotrope gradient. This characteristic follows the order of the lyotropic series for the anions ... 

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