Mineral surface characterization

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. 

The light incident on a mineral surface divides itself in a number of ways. It is partly reflected, partly transmitted, and partly absorbed. Minerals exhibiting metallic bonding have a high reflectivity. Those characterized by ionic or covalent bonding have a high transmissivity. The optical properties are anisotropic they are different in different directions and depend on the arrangement of atoms in the crystals. 

This step is characterized by bulk precipitation of lead xanthate on the mineral surface. Electrochemical phenomena... 

The sessile drop method has several drawbacks. Several days elapse between each displacement, and total test times exceeding one month are not uncommon. It can be difficult to determine that the interface has actually advanced across the face of the crystal. Displacement frequency and distance are variable and dependent upon the operator. Tests are conducted on pure mineral surfaces, usually quartz, which does not adequately model the heterogeneous rock surfaces in reservoirs. There is a need for a simple technique that gives reproducible data and can be used to characterize various mineral surfaces. The dynamic Wilhelmy plate technique has such a potential. This paper discusses the dynamic Wilhelmy plate apparatus used to study wetting properties of liquid/liquid/solid systems important to the oil industry. 

Zeitner, W. A., E. C. Yost, M. L. Machesky, M. I. Tejedor-Tejedor, and M. A. Anderson (1986), "Characterization of Anion Binding on Goethite Using Titration Calorimetry and Cylindrical Internal Reflec-tion-Fourier Transform Infrared Spectroscopy", in J. A. Davis and K. F. Hayes, Eds., Geochemical Processes at Mineral Surfaces, Am. Chem. Soc., Washington, 142-161. 

Sorption processes are influenced not just by the natures of the absorbate ion(s) and the mineral surface, but also by the solution pH and the concentrations of the various components in the solution. Even apparently simple absorption reactions may involve a series of chemical equilibria, especially in natural systems. Thus in only a comparatively small number of cases has an understanding been achieved of either the precise chemical form(s) of the adsorbed species or of the exact nature of the adsorption sites. The difficulties of such characterization arise from (i) the number of sites for adsorption on the mineral surface that are present because of the isomorphous substitutions and structural defects that commonly occur in aluminosilicate minerals, and (ii) the difference in the chemistry of solutions in contact with a solid surface as compound to bulk solution. Much of our present understanding is derived from experiments using spectroscopic techniques which are able to produce information at the molecular level. Although individual methods may often be applicable to only special situations, significant advances in our knowledge have been made... 

In order to characterize the adsorption species on mineral surface, DDTC is oxidized into the dimmer by adding definite H2O2 into the DDTC solution, which then is extracted by cyclohexane to determine its UV spectrum. As seen from the UV spectrum in Fig. 4.33, there are three UV absorbance peaks at 230 nm, 261 nm, 280 nm respectively. The maximum absorbance peak is at 230 nm, the next peak is at 260 nm, and the weak peak is at 280 nm. The peak at 230 nm can serve as a characteristic absorbance peak, and the peak at 260nm results from absorbance overlapping of diethyl dithiocarbamate and its dimmer. 

Clay minerals are characterized by a high surface charge and a very small particle size. A detailed presentation of two types of layered silicate clay (kaoUnite and smectite) is given in Chapter 1. 

The polymetallic veins are poorly exposed at surface and are characterized by the presence of gossans with remnants of breccias with quartz matrix and oxidized sulfide clasts. Hypogene polymetallic mineralization is characterized by the presence of massive and banded sulfide veins and sulfide breccias up to 13 m thick. This mineralization is developed In... 

Min. Soc. Am., Washington, 87-132 Hochella, M.E.Jr. (1995) Mineral surfaces their characterization and their chemical, physical and reactive nature. In Vaughan, D.J. Pat-trick, R.A.D. (eds.) Mineral surfaces. Min. 

Zeltner,W.A. Yost, E.C. Machesky M.L. Teje-dor-Tejedor, M.I. Anderson, M.A. (1986) Characterization of anion adsorption on goethite using titration calorimetry and CIR-ETIR. In Davis, J.A. Hayes, K.E. (eds.) Geochemical processes at mineral surfaces. 

Eusden, J. D. Jr. Francis, C. A. 1999secondary mineral. Surface Science Spectra, 6, 184-192. 

Minerals containing bound water (OH) or water molecules (H20) adsorbed onto mineral surfaces give rise to prominent spectral absorptions near 3 pm that are observed in some asteroid classes (Rivkin et al., 2002). These absorptions have different shapes (Fig. 12.14) -the hydroxl feature is sharp and the H20 feature is more subdued. Infrared spectra for asteroids with high albedos are generally characterized by the water feature, whereas spectra of low-albedo asteroids tend to have the sharp OH feature. Although the hydroxl band is partly obscured when viewed through the Earth s atmosphere (the dashed lines in Fig. 12.14), it is still an easily recognizable feature in the spectra of some asteroid classes. 

Tables 7.6 and 7.7 compare the binding affinities of sites on the a-Al203 (0001), a-Al203 (1-102), and a-Fe203 (0001) surfaces and those in various types of bacteria, natural organic matter, and polyacrylic acid (PAA). The metal oxide substrates and humic acid are characterized by two binding sites, one strong and one weak, for Pb(II). The stability constant for the PAA-Pb(II) complex (i.e., ML2 species) is typically larger than those of higher affinity mineral surface binding sites (i.e., Mj).

Surface and interfacial phenomena of importance in mineral processing are reviewed. Examples of a fundamental and an applied nature are taken from the recent literature to illustrate how the use of several different surface characterization techniques makes it possible to delineate a detailed molecular-scale picture of interfaces. Lack of... 

In mineral processing, surface characterization techniques are used primarily to study mechanisms of various subprocesses. These studies are carried out mostly in research laboratories using model systems so as to keep the system simple and amenable to interpretation by known laws of physics and chemistry. For these very reasons, some of the newer surface characterization techniques have been used to investigate pure solids, often single crystals. In mineral processing operations, one necessarily deals with particles of complex ores with an objective to recover the valuable minerals contained in the ore. Experience, both in industry and laboratory, shows that complex ore particles behave differently from simple solids in many ways. In process evaluation and in optimization of operating plants, it is necessary to characterize the ore particles as they undergo various treatments. In recent years ESCA has been found to be a useful technique for... 

Adsorption of NOM onto mineral surfaces produces a composite that possesses physical and chemical properties distinct from either of its constituent components. The ill-defined, heterogeneous nature of NOM makes the interpretation of data from the characterization of naturally occurring OMN complexes problematic. In this respect, studies involving NOM- component classes (e.g., lipids, proteins, etc.) and reference minerals may offer insights. The characterization of model NOM-mineral composites provides the opportunity to employ techniques specific to the interaction of interest. 

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