Copper surface properties

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. 

Coatings of tin produced from tin-containing aqueous solutions by chemical replacement may be used to provide special surface properties such as appearance or low friction, but protect from corrosion only in non-aggressive environments. Copper and brass may be tinned in alkaline cyanide solutions or in acid solutions containing organic addition agents such as thiourea. Steel may be first coated with copper and then treated... 

Fig. 1. Protein factors which may affect type I copper site properties. Schematic view from the protein surface closest to the copper center.

Froth flotation is an application of foams that is used to separate mineral components from each other based on their having different surface properties, typically their wettability and surface electrical charge. For example, froth flotation is the classic process used to separate copper from lead ore. The process involves having hydrophobic particles attach to gas bubbles which rise through a turbulent suspension to create a surface foam called a froth. Figure 10.2 shows an illustration of a mechanical flotation cell. This is the classic flotation device [53,91,625], First, the flotation feed particles are well dispersed into a particle suspension. Together with chemical flotation aids, such as collectors and frothers, this constitutes what is called the flotation pulp. In a mechanical flotation cell, air is fed in the form of fine bubbles and introduced near the impeller (see Figure 10.2). In addition to mechanical flotation cells, there are also pneumatic cells and cyclone flotation cells. Pneumatic... 

Co. surface area = 300 m2/g ) with aqueous solutions of Cu, Cr, Mg, Ca, Sr, and Ba in Nitrate. All the catalysts have Cu to Si02 weight ratio of 14/86. For promoted catalyst, the Cr to Cu molar ratio was varied from 1/4 0 to 1/4, and the alkaline earth metal to Cu molar ratio was kept at 1/10. The impregnated catalysts were dried at 100 °C overnight, calcined at 450 for 3 h and then reduced in a stream of 10% H2 in Ar at 300 °C for 2 h. The copper surface areas of catalysts were determined by the N20 decomposition method described elsewhere [4-5J. The basic properties of the catalysts were determined by temperature-programmed desorption ( TPD ) of adsorbed carbon dioxide. Ethanol was used as reactant for dehydrogenation reaction which was performed in a microreactor at 300°C and 1 atm. 

No more complete study of a single catalysed reaction has ever been published than that of Palmer and Constable,2 extending over eight years, on the dehydrogenation of alcohols by heated copper surfaces. Aldehydes are formed from primary and ketones from secondary alcohols by this reaction. The work has resulted in a considerable increase in our knowledge of the mode of formation and properties of the active centres on the surface of copper, and much of it may be applicable also to other metallic catalysts. The reactions are... 

Table 4 shows the surface properties of skeletal copper catalysts produced by leaching a 50wt% Cu alloy in aqueous sodium hydroxide solution at 293 K. It shows that the surface area decreases with increasing particle size of the alloy. Table 5 shows the effect of temperature of extraction on the surface area and pore structures of completely leached 1000-1180 fim particles of the 50wt% Cu alloy. The results show... 

The measurements have shown that the catalytic activity of the copper sample is determined by its surface properties and also by the composition of the subsurface region. 

Mudhivarthi S, Zantye P, Kumar A, Kumar A, Beerbom M, Schlaf R. Effect of temperature on tribological, electrochemical, and surface properties during copper CMP. Electrochem Solid-State Lett 2005 8(9) G241-G245. 

In this study, activated carbon fibers (ACFs) deposited by copper metal were prepared by electroplating technique to remove nitric oxide (NO). The surface properties of ACFs were determined by FT-IR and XPS analyses. N2/77K adsorption isotherm characteristics, including the specific surface area, micropore volume were investigated by BET and t-plot methods respectively. And, NO removal efficiency was confirmed by gas chromatographic technique. From the experimental results, the copper metal supported on ACFs appeared to be an increase of the NO removal and a decrease of the NO adsorption efficiency reduction rate, in spite of decreasing the BET S specific surface area, micropore volume, and micro-porosity of the ACFs. Consequently, the Cu content in ACFs played an important role in improving the NO removal, which was probably due to the catalytic reactions of C-NO-Cu. 

The influence of the preparation method of methanol catalysts composed of copper associated with rare earth oxides (eg Cu-La2Zr207 and ZnO promoted Cu-La2Zr20y systems) on the catalytic behaviour is discussed. Good activities and improved aging properties are always associated with a high copper surface area and a reasonnable crystallinity of the La2Zr207 pyrochlore. 

It can also be observed that despite the same copper surface areas of 12 m2/g the Cu-LaZr ([ex carbonate] 550) system has a noticiable different catalytic behavior that Cu-LaZr ([ex oxalate] 710). This proves that, appart the copper surface areas, variation of morphology, presence of impurities as well as other factors related with the preparation can be responsible for difference of catalytic properties related to the preparation technique. 

In the case of Cu 100 -c(2x2)-Pd, ARUPS studies have identified a marked withdrawl of the Pd d-band from the Fermi level due to the absence of Pd-Pd nearest neighbour bonding [25,26,27]. The Pd atoms substituted within the copper surface appears to adopt a closed d-band electronic configuration, hence would be expected to have significantly different chemisorption and reactivity properties with respect to pure Pd surfaces. In agreement with its Cu 100 -c(2x2)-Au counterpart, the Pd d-band emission shows little or no dispersion as a function of photon energy in normal emission ARUPS, consistent with formation of a largely two-dimensionally confined surface alloy. 

An example of a polyamine dendrimer functionalised by 2-pyridylethyl- substituents is (167).269 The interaction of (167) with copper(II) acceptors gives metal derivatives containing one metal for each bis[2-(2-pyridyl)ethyl]amine moiety. (167) is found to bind approximately 32 Cu ions. Polyamidoamine species containing Cu ions can be reduced in solution to zerovalent copper nanoclusters, providing a metal nanocomposite.270 Such copper(O) solutions are stable for several months, owing to the surface properties of the host dendrimer molecules. 

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