Mineral surface chemistry, effect

This interface is critically important in many applications, as well as in biological systems. For example, the movement of pollutants tln-ough the enviromnent involves a series of chemical reactions of aqueous groundwater solutions with mineral surfaces. Although the liquid-solid interface has been studied for many years, it is only recently that the tools have been developed for interrogating this interface at the atomic level. This interface is particularly complex, as the interactions of ions dissolved in solution with a surface are affected not only by the surface structure, but also by the solution chemistry and by the effects of the electrical double layer [31]. It has been found, for example, that some surface reconstructions present in UHV persist under solution, while others do not. 

This book deals only with the chemistry of the mineral-water interface, and so at first glance, the book might appear to have a relatively narrow focus. However, the range of chemical and physical processes considered is actually quite broad, and the general and comprehensive nature of the topics makes this volume unique. The technical papers are organized into physical properties of the mineral-water interface adsorption ion exchange surface spectroscopy dissolution, precipitation, and solid solution formation and transformation reactions at the mineral-water interface. The introductory chapter presents an overview of recent research advances in each of these six areas and discusses important features of each technical paper. Several papers address the complex ways in which some processes are interrelated, for example, the effect of adsorption reactions on the catalysis of electron transfer reactions by mineral surfaces. 

Abstract Two systems are discussed in this chapter, which are copper activating zinc-iron system with and without depressants. Firstly, the system in the absence of depressants is discussed. And it is obtained that at a specific pH the activation for each mineral occurs in a certain range. Through the electrochemical methods and surface analysis the entity contributing to the activation can be identified which are usually copper sulphides and vary for different minerals. Secondly, the system with depressants is researched. And also the effects of pulp potential on the activation are discussed. The same conclusion can be obtained as the one from the former system. Furthermore, zeta potential are involved in the discussion of activation and die mechanism can be explained firom the changes of zeta potential. Similarly, the activation mechanism of this system is also studied through solution chemistry, bonding of activator with mineral surfaces and surface analysis. 

Mineral segregation in industry relies heavily on the selective adsorption of macromolecules onto the surfaces of those minerals that have particular industrial applications. This selectivity is governed mainly by the surface chemistry of the mineral and the type of polymer used as a flocculant. " Effectiveness of flocculation depends upon the charge, concentration and molecular weight of the polymer, and also the pH and salt concentration of the clay suspension. The bonding between the anionic flocculant polyacrylamide (PAM) and clay mineral surfaces has been effectively reviewed recently by Hocking et al and the reader is referred to this should they require an in-depth literature review. For more information on general colloidal chemistry of clay suspensions the reader is referred to the review of Luckham and Rossi." ... 

In the present paper the chemistry of plutonium is reviewed, with particular reference to the ambient conditions likely to be encountered in natural waters. In addition, experimental work is presented concerning the effects of such variables as pH, plutonium concentration, ionic strength, and the presence of complexing agents on the particle size distributions of aqueous plutonium. In subsequent papers it will be shown that these variables, as they influence the particle size distribution of the aqueous plutonium, greatly affect its interaction with mineral surfaces. The orientation of these studies is the understanding of the likely behavior and fate of plutonium in environmental waters, particularly as related to its interaction with suspended and bottom sediments. 

Three specific areas can be identified to serve as foci for expanding the research on this material (i) The nature of the organic components interactions need to be ascertained. Do the lipids (whose chemistry is dominated by aliphatic components) and humic (whose chemistry is dominated by aromatic, carboxyl, and carbohydrate components) actually exist as distinct domains in organo-mineral complexes (ii) What is the effect of the mineral surface on adsorbed macromolecule conformation How does conformation impact the adsorption of additional NOM components (iii) Finally, a better understanding of the interfacial chemistry of these organo-mineral composites needs to be developed in order to understand the fate of many organic contaminants introduced into natural systems. 

We monitored the pH and Eh of the column effluents by means of in-line sampling cells equipped with glass and platinum electrodes, respectively. Effluent samples were collected with a fraction collector. Three separate tests were conducted with columns of identical diameter but different lengths 11, 22, and 44 cm. The different column lengths allowed us to investigate the effect on solution chemistry of residence time in the column and surface area of minerals contacted by the solution. At the flow rates used in our experiment, the residence times were approximately 1, 2, and 4 days, respectively, for the three columns. The mineral surface area contacted by the solutions is proportional to the column lengths. 

Because of the importance of the surface chemistry of bone mineral in physiological systems, we have undertaken a series of gas adsorption studies on hydroxyapatite in the form of anorganic bone. In a recent publication from this laboratory (4) results of calorimetric studies of the adsorption of water and methanol vapors on bone mineral and on synthetic hydroxyapatite were reported. The adsorption potential for nitrogen on dehydrated hydroxyapatite, whether from bone or from synthetic sources, was rather profoundly altered by the addition to the surface of chemisorbed methanol or water prior to the adsorption of nitrogen at —195° C. This effect was reflected in the specific surface areas, in the BET C values, and in the resultant values of Ex — EL (net heats of adsorption) as shown in Table I of the above paper. 

The filter cakes obtained from mineral and chemistry industrials are mostly wastes and sent to the transportation and storage without any thermal operations. The stability properties of the filter cakes such as tensile, shear and compression strength are very important for the deposit of slimes (5). The shear strength of the mineral filter cakes is influenced by the particle size, shape and surface tension as well as the applied pressure and the saturation degree (6, 7). It was mentioned in the recent studies that particle shape has also a very substantial effect on the shear strength of the cake. The shear strength of the mineral filter cake is defined as follows F... 

Hochella M. E., Jr. (1993) Surface chemistry, structure, and reactivity of hazardous mineral dust. In Health Effects of Mineral Dusts, (eds. G. D. Guthrie and B. T. Mossman). Rev. Min. 28, Mineralogical Society of America, Washington, DC, pp. 275-308. 

Table 2. Mechanical properties of specimen effect of mineral size/surface chemistry.

Ward, D.B. and Brady, P.V., Effect of Al and organic acids on the surface chemistry of kaolinite. Clays Clay Miner., 46, 453, 1998. 

Dissolution rate constants for major elements are summarized as a function of temperature in Fig. 2. Apparent activation energies have the same relationship as dissolution rate. Alkali metal and alkali earth metal ion have -20 to 40 kJ/mol apparent activation energy, due to a diffusion effect from the mineral surface. The existing reaction condition does not correspond to the critical reaction rate, but this condition is more applicable for natural water-rock interactions, because the nature of incongruent dissolution on the mineral surface controls fluid chemistry and metastable reaction processes. 

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