Surface Chemistry of Carbonate Minerals

Morse J.W. (1986) The surface chemistry of carbonate minerals in natural waters An overview. Mar. Chem. 20, 91-112. 

The ideas developed here are largely based on the concept of the coordination at the (hydr)oxide interface the ideas apply equally well to silicates. Somewhat modified concepts for the surface chemistry of carbonate, phosphate, sulfide and disulfide minerals have to be developed. 

Dolomite is one of the most abundant sedimentary carbonate minerals but its mode of formation and its surface properties are less well known than for most other carbonate minerals. As we have mentioned, the nucleation of dolomites and its structural ordering is extremely hindered. There is a general trend for the "ideality" of dolomite to increase with the age of dolomite over geological time (Morse and Mackenzie, 1990). Most dolomites that are currently forming in surfacial sediments and that have been synthesized in the laboratory are calcium-rich and far from perfectly ordered. Such dolomites are commonly referred to as "protodolomites . Morse and Mackenzie (1990) have reviewed extensively the geochemistry (including the surface chemistry of dolomites and Mg-calcites. 

The application of IR spectroscopy to catalysis and surface chemistry was later developed in the fifties by Eischens and coworkers at Texaco laboratories (Beacon, New York) in the USA [7] and, almost simultaneously, by Sheppard and Yates at Cambridge University in the UK [8]. Mapes and Eischens published the spectra of ammonia chemisorbed on a silica-alumina cracking catalyst in 1954 [6], showing the presence of Lewis acid sites and also the likely presence of Br0nsted acid sites. Eischens, Francis and Pliskin published the IR spectra of carbon monoxide adsorbed on nickel and its oxide in 1956 [9]. Later they presented the results of an IR study of the catalyzed oxidation of CO on nickel at the First International Congress on Catalysis, held in Philadelphia in 1956 [10]. Eischens and Pliskin also published a quite extensive review on the subject of Infrared spectra of adsorbed molecules in Advances in Catalysis in 1958, where data on hydrocarbons, CO, ammonia and water adsorbed on metals, oxides and minerals were reviewed [11]. These papers evidence clearly the two tendencies observed in subsequent spectroscopic research in the field of catalysis. They are the use of probes to test the surface chemistry of solids and the use of spectroscopy to reveal the mechanism of the surface reactions. They used an in situ cell where the catalyst sample was... 

Surface chemistry of the oxide-water interface is emphasized here, not only because the oxides are of great importance at the mineral-water (including the clay-water) interface but also because its coordination chemistry is much better understood than that of other surfaces. Experimental studies on the surface interactions of carbonates, sulfides, disulfides, phosphates, and biological materials are only now emerging. The concepts of surface coordination chemistry can also be applied to these interfaces. This chapter is designed... 

A deactivating agent for copper-activated sphalerite is any species that has sufficient affinity for copper(I) or (II) to compete for it with sulfide ions in the surface lattice of the mineral, thus removing it from the surface. Ligands such as cyanide or ethylenediamine, which coordinate strongly to copper, have therefore been found to be the most effective. A knowledge of the stability of the species present in a system composed of H+, Zn +, Cu +, and CN ions has enabled the extent of deactivation Ijy cyanide ion to be predicted the results of these predictions are compared with experimental observations in Figure 2. This approach has been successfully extended to the effects of pH and the presence of other ions such as carbonate on the activation and deactivation processes, and is a pertinent example of the quantitative application of coordination chemistry to complex systems. 

Depending on the particle-surfactant system, one or more of the above contributions can be responsible for adsorption. The dominating one would depend on the nature and concentration of the surfactant, the surface chemistry of the particle, and solution properties such as pH and ionic strength. Electrostatic and lateral interaction forces are usually the major factors determining the adsorption of surfactants on oxides and other non-metallic minerals. Chemical interactions become more dominant for surfactant adsorption on salt-type minerals, such as carbonates and sulfides. 

The important characteristics of carbon are PSD, surface chemistry (functionality) and mineral matter content. The adsorption capacity depends on the accessibility of the organic molecules to the microporosity which is dependent on their size. Thus, under appropriate... 

Cu and Zn enter sedimentary material in substantial proportions, both in the structure of minerals (carbonates, clays) and adsorbed on surfaces. Boyle (1981) showed that foraminiferal tests may contain Zn in excess of a few ppm. Partitioning of Cu and Zn between water and carbonates has been investigated by Rimstidt et al. (1998). The crystal chemistry of Cu and Zn in goethite has been investigated by EXAFS by Manceau et al. (2000). Typical Zn and Cu concentrations in FeMn nodules and encrustations are 500-1000 ppm and 800-6000 ppm, respectively (e.g., Albarede et al. 1997b). 

Core and valence level photoemission studies of iron oxide surfaces and the oxidation of iron. Surface Sd. 68 459—468 Bruno, J. Sturam, J.A. Wersin, P. Brand-berg, E. (1992) On the influence of carbonate on mineral dissolutions I. The thermodynamics and kinetics of hematite dissolution in bicarbonate solutions at T = 25°C. Geo-chim. Cosmochim. Acta 56 1139—1147 Brusic.V. (1979) Ferrous passivation. In Corrosion Chemistry, 153—184 Bruun Hansen, H.C. Raben-Lange, R. Rau-lund-Rasmussen, K. Borggaard, O.K. 

This paper is devoted to the sorption of uranyl, which exhibits a complex aqueous and surface chemistry. We review briefly the sorption behaviour of An in the environment, and illustrate the variety of environmental processes using published data of uranyl sorption in the Ban-gombe natural reactor zone. After summarizing the general findings of the mechanisms of An sorption, we then focus particularly on the current knowledge of the mechanisms of uranyl sorption. A major area of research is the influence of the aqueous uranyl speciation on the uranyl surface species. Spectroscopic data of U(VI) sorbed onto silica and alumina minerals are examined and used to discuss the role of aqueous uranyl polynuclear species, U02(0H)2 colloids and uranyl-carbonate complexes. The influence of the mineral surface properties on the mechanisms of sorption is also discussed. 

A number of attempts have been made to understand the mechanism of the adsorption of chelates on oxide minerals. For instance, IR spectroscopic studies10 have indicated the presence of a basic monosalicylaldoximate copper complex as well as the bis-salicylaldoximate complex on the surface of malachite (basic copper carbonate) treated with salicylaldoxime. However, other workers4 have shown that the copper chelate is partitioned between the surface and dispersed within the solution, and that a dissolution-precipitation process is responsible for the formation of the chelate. Research into the chemistry of the interaction of chelating collectors with mineral surfaces is still in its infancy, and it can be expected that future developments will depend on a better understanding of the surface coordination chemistry involved. 

In natural systems, carbonates react with a variety of solutions at different pressures and temperatures. The processes involved in these reactions are complex, but depend significantly on the solubilities of the carbonate minerals, their surface chemistries, and dissolution and precipitation kinetics. In this chapter, we have... 

Before the dawn of synthetic chemistry the natural cycle had resulted in a fair degree of stability in the chemistry of the earth s surface, although in certain ecological niches, massive buildups of substances that would not break down (in those niches) have occurred, most notably in the deposits of mineral oil, natural gas, and carbon. 

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