Mineral species distribution diagrams

Mineral-surfactant equilibria. Mineral-surfactant equilibria determine adsorption of various surfactants on minerals, hemimicellization, interactions among dissolved mineral species and reagents and electrochemical interactions. The optimum conditions for mineral-surfactant interactions as well as flotation can be calculated from data for such parameters as the solubility product and complex formation constants and species distribution diagrams with the helps of plots of logC-pH, AG°-pH, log/3, iih-pH, etc. 

The species distribution diagrams calculated from these equilibria are shown in Figs. 3.6a-3.6c. For wolframite, both Mn + and Fe are dominant species for pH < 2.8. The mineral... 

Fig. 3.6. Species distribution diagrams for mineral-water open systems (a) hubnerite, (b) ferberite, and (c) scheelite (Hu and Wang, 1985).

Correlation of oleate adsorption and flotation maximum at about pH 7.5 for a variety of minerals and high abstraction (adsorption + surface precipitation) below this pH with the species distribution diagram (Fig. 4.9) suggests that the role of acid-soap dimer and precipitated oleic acid can be significant in controlling the adsorption and resultant flotation behavior. 

Due to a variety of possible solution reactions, flotation reagents exist in many forms such as undissociated molecules, ions, hydroxylated species and polymeric species under different solution conditions of pH and concentration. The fraction of species plotted as a function of the total concentration, pC, yields the species distribution diagram for the system. Such plots can be used to explain mechanisms by which reagents act in mineral flotation. 

Fig. 4.49. Species distribution diagrams of metallic ions-citric acid systems and its depression for mineral flotation (a) Fe(III)/quartz (b) Mn(II), Fe(II)/wolframite (Wang and Bai, 1983).

The pH of a system determines the reactions that define the concentration of many dissolved chemical species in water containing salts and minerals, supplied by weathering reactions, rain, runoff, and lixiviating processes. The pH is a key parameter for biological growth and for the sustainment of life for the different aquatic flora and fauna species. As discussed in Chapter 2 the contribution of the different species will affect the final pH and vice versa (i.e., the pH on its own often determines the form of the species present). That is why the distribution diagrams of chemical species are frequently defined as functions of pH (Section 2.1.2). In summary, the main environmental processes that affect the pH and the alkalinity of natural waters include ... 

Fig.1. Eh-pH diagram for the system Fe-U-S-C-H2O at 25 °C showing the mobility of uranium under oxidizing conditions, the relative stability of iron minerals, and the distribution of aqueous sulfur species. Heavy line represents the boundary between soluble uranium (above), and insoluble conditions (below), assuming 1 ppm uranium in solution.

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