Affinity for surfaces

Immersion of the stepped Pt(s) [6(111) x (111)] surface into aqueous Br solutions [30] and subsequent examination of the surface by Auger spectroscopy and LEED revealed that Br has no particular affinity for surface steps. Instead, the differences in adsorption behavior of the stepped and smooth (111) surfaces are due to the fact that different long-range adsorbed layer... 

Beryllium is an alkaline-earth elements whose behavior drastically differs from that of the other alkaline-earth elements. Its low mobility in natural waters is attributed to its affinity for surfaces. Laboratory experiments have been performed to examine the partitioning of Be between sediments from natural systems and water (You et al, 1989). The partition coefficient depends strongly on pH in the range 2-7. The curve of as a function of pH (Figure 24) can be explained by a thermodynamic model by taking into account beryllium speciation in freshwater and the... 

The one-electron redox couples Mn2 1 /Mir + and Cu 1 /C u21 complete the emerging picture of metal oxygenations ( u 1 shows low affinity for surfaces, ami... 

As indicated in Table 2, the type of process by which constituent X may be mobilized (or sequestered) depends on speciation of X in the solid phase. Thus, if X is an integral constituent of an aquifer mineral, dissolution of the mineral will be required to release X into solution, whereas mineral dissolution would not be required to mobilize X if it is sorbed onto a mineral surface. Environmental conditions (including both chemical composition of pore fluids and microbial activity) will influence the extent of mobilization or sequestration of X. For metals, in particular, both the solubility and the affinity for surfaces can be strongly influenced by redox conditions and the presence of (biogenic) complexing agents. 

Initial experiments had indicated that the monomer standard BSA powder used in our experiments contained 13% dimer. Previous studies have shown that the different molecular weight species of human serum albumin exhibit varied affinities for surfaces (24). We were interested in elucidating the effect of dimer species in our adsorption experiments. The molecular weight differences of the monomer and dimer allowed us to follow the relative concentrations of each species in the effluent profile. Figure 8 illustrates the data obtained from a run in which 1.0 mg/mL BSA was applied to a... 

To sum up, polymers have a strong affinity for surfaces, but a saturation level is soon reached. The thickness of the adsorbed layer may vary from a few [nm] to several hundreds of [nm]. This is the order of magnitude of the range of interparticle forces, which are profoundly modified by the presence of polymers. 

The a, p, and 8 isomers of BHC have a relatively low affinity for surfaces, following the order S—p > a (Tsukano, 1973). For soil with 1.9% organic carbon, l/n was 0.91 andK= 10-30 for soil with 5.2% organic carbon, l/n = 0.71-0.83 andK= 30-120 for all four isomers of BHC. These data suggest that BHC isomers other than the 5-isomer will not be sorbed significantly in natural waters. King etal. (1969) observed that an equilibrium in the sorption of lindane onto soils occurred in one hour, compared... 

Dry chlorine has a great affinity for absorbing moisture, and wet chlorine is extremely corrosive, attacking most common materials except HasteUoy C, titanium, and tantalum. These metals are protected from attack by the acids formed by chlorine hydrolysis because of surface oxide films on the metal. Tantalum is the preferred constmction material for service with wet and dry chlorine. Wet chlorine gas is handled under pressure using fiberglass-reinforced plastics. Rubber-lined steel is suitable for wet chlorine gas handling up to 100°C. At low pressures and low temperatures PVC, chlorinated PVC, and reinforced polyester resins are also used. Polytetrafluoroethylene (PTFE), poly(vinyhdene fluoride) (PVDE), and... 

Collectors ndFrothers. Collectors play a critical role ia flotation (41). These are heteropolar organic molecules characterized by a polar functional group that has a high affinity for the desired mineral, and a hydrocarbon group, usually a simple 2—18 carbon atom hydrocarbon chain, that imparts hydrophobicity to the minerals surface after the molecule has adsorbed. Most collectors are weak acids or bases or their salts, and are either ionic or neutral. The mode of iateraction between the functional group and the mineral surface may iavolve a chemical reaction, for example, chemisorption, or a physical iateraction such as electrostatic attraction. 

Sulfide collectors ia geaeral show Htfle affinity for nonsulfide minerals, thus separation of one sulfide from another becomes the main issue. The nonsulfide collectors are in general less selective and this is accentuated by the large similarities in surface properties between the various nonsulfide minerals (42). Some examples of sulfide flotation are copper sulfides flotation from siUceous gangue sequential flotation of sulfides of copper, lead, and zinc from complex and massive sulfide ores and flotation recovery of extremely small (a few ppm) amounts of precious metals. Examples of nonsulfide flotation include separation of sylvite, KCl, from haUte, NaCl, which are two soluble minerals having similar properties selective flocculation—flotation separation of iron oxides from siUca separation of feldspar from siUca, siUcates, and oxides phosphate rock separation from siUca and carbonates and coal flotation. 

Organosulfur Adsorbates on Metal and Semiconductor Surfaces. Sulfur compounds (qv) and selenium compounds (qv) have a strong affinity for transition metal surfaces (206—211). The number of reported surface-active organosulfur compounds that form monolayers on gold includes di- -alkyl sulfide (212,213), di- -alkyl disulfides (108), thiophenols (214,215), mercaptopyridines (216), mercaptoanilines (217), thiophenes (217), cysteines (218,219), xanthates (220), thiocarbaminates (220), thiocarbamates (221), thioureas (222), mercaptoimidazoles (223—225), and alkaneselenoles (226) (Fig. 11). However, the most studied, and probably most understood, SAM is that of alkanethiolates on Au(lll) surfaces. 

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