Pyrite determination

Przybylowicz, W.J. 2004. Trace element zoning In pyrite determined by PIXE elemental mapping evidenoe for varying ore-fluid composition and eleotroohemical precipitation of gold at the Spitskop deposit, Saldania Belt, South Afrioa. X-Ray... 

We present here the preliminary results of our attempt to develop a new method for the analysis of pyrite in coal and lignite. It is well known that sulfur in coal is present in different forms. In particular, although the iron sulfide in coal is generally pyrite ( 1), other iron sulfides are frequently present. For example, iron disulfide occurs as marcasite, a rhombic crystalline form, as well as pyrite, a cubic crystalline form. Perhaps the term disulfide sulfur should be used to replace the pyritic sulfur more commonly quoted, as recently suggested by Youh (2). Since the chemical reactivity of these two disulfides of iron is similar, our method will record them equally well. Nonetheless, we will continue to refer to the pyrite determinations here, although we are really talking about the chemical species FeS2 rather than a particular crystalline structure. 

Two methods have been proposed for the analysis of sulfur in impure samples of pyrite, EeS2. Sulfur can be determined in a direct analysis by oxidizing it to S04 and precipitating as BaS04. An indirect analysis is also possible if the iron is precipitated as Ee(OH)3 and isolated as Ee203. Which of these methods will provide a more sensitive determination for sulfur What other factors should be considered in deciding between these methods ... 

Data for which no reference is given are from the Slrukturbericht of P. P. Ewald and C. Hermann. 6 R. W. G. Wyckoff, Z. Krisl., 75,529 (1930). W. H. Zachariasen, ibid., 71, 501, 517 (1929). d The very small paramagnetic susceptibility of pyrite requires the presence of electron-pair bonds, eliminating an ionic structure Fe++S2. Angles are calculated for FeS2, for which the parameters have been most accurately determined. The parameter value (correct value = 0.371) and interatomic distances for molybdenite are incorrectly given in the Slrukturbericht. 

Bomite-chalcopyrite—pyrite assemblage also defines /sj -temperature region. Combining the FeS content of sphalerite coexisting with bomite-chalcopyrite-pyrite, /s2-temperature can be determined (Kouda, 1977). 

Table V Analyses of Unwashed Coals Used to Determine the Effect of Pyrites...

Once the pure mineral powders characterized, 3 mixtures were manually prepared and named ML1, ML2 and ML3. They contain each of the 8 minerals in different proportions reproducing 3 mine tailings falling in the uncertainty zone of the static test used. The 3 synthetic tailings were characterized with the same techniques as for the pure minerals. Cp and Sp weight fractions were evaluated from their chemical element tracers (respectively Cu and Zn) obtained from ICP-AES analysis. Qz, Dol, and Sid samples are considered pure and their percentages in the mixtures are not corrected. Table 1 presents the fraction of each mineral in the three mixtures before and after correction taking into consideration the contamination of Po sample by pyrite and calcite, as previously determined. The corrected mineral proportions are used for calculation of the static test parameters based on... 

The minerals that influence gold recovery in these ores are iron sulphides (i.e. pyrite, marcasite, etc.), in which gold is usually associated as minute inclusions. Thus, the iron sulphide content of the ore determines gold recovery in the final concentrate. Figure 17.3 shows the relationship between pyrite content of the ore and gold recovery in the copper concentrate for two different ore types. Most of the gold losses occur in the pyrite. 

Iron sulphides are ubiquitous in marine and freshwater sediments. They are usually present either as pyrite or as monosulphides, which can be liberated by hydrochloric acid. These acid volatile sulphides give rise to an intense black colour that is characteristic of anoxic sediments. They play an important role in recent diagenetic processes in sediments and the ratio of pyrite to acid volatile sulphides has been used as an historical indicator to determine whether sediments were formed in marine or freshwater conditions. They can be present over a wide range of... 

Morse and Cornwell [112] investigated methods for determining acid volatile sulphides and pyrites in marine sediments from several typical... 

Pyrite Oxidation. The oxidation of Fe(ll) minerals by Fe3+ is also of importance in the oxidation of pyrite by 02. This process is mediated by the Fe(II)-Fe(III)system. Pyrite is oxidized by Fe3+ (which forms a surface complex with the pyrite (cf. formula VI in Fig. 9.1) (Luther, 1990). The rate determining step at the relatively low pH values encountered under conditions of pyrite dissolution is the oxygenation of Fe(II) to Fe(III) usually catalyzed by autotrophic bacteria (Singer and Stumm, 1970 Stumm-Zollinger, 1972). Thus, the overall rate of pyrite dissolution is insensitive to the mineral surface area concentration. Microbially catalyzed oxidation of Fe(II) to Fe(III) by oxygen could also be of some significance for oxidative silicate dissolution in certain acid environments. 

Figure 1.9 Determination of corrosion currents for pyrite-mild steel (Py-MS) pyrrhotite-mild steel (Po-MS) and pyrite-pyrrhotite-mild steel (Py-Po-MS)systems under abrasion in a quartzite slurry by adjusting to the surface area ratios of ground minerals and steel balls (Pozzo and Iwasaki, 1987)...

The h-pH diagrams of surface oxidation of arsenopyrite and pyrite are shown in Fig. 2.16 and Fig. 2.17, respectively. Figure 2.16 shows that jBh-pH area of self-induced collectorless flotation of arsenopyrite is close to the area forming sulphur. The reactions producing elemental sulphur determine the lower limit potential of flotation. The reactions producing thiosulphate and other hydrophilic species define the upper limit of potential. In acid solutions arsenopyrite demonstrates wider potential region for collectorless flotation, but almost non-floatable in alkaline environment. It suggests that the hydrophobic entity is metastable elemental sulphur. However, in alkaline solutions, the presence of... 

Abstract The sodium sulphide-induced collectorless flotation of several minerals are first introduced in this chapter. The results obtained are that sodium sulphide-induced collectorless flotation of sulphide minerals is strong for pyrite while galena, jamesonite and chalcopyrite have no sodium sulphide-induced collectorless flotability. And the nature of hydrophobic entity is then determined through J h-pH diagram and cyclic voltammogram, which is element sulphur. It is further proved widi the results of surface analysis and sulphur-extract. In the end, the self-induced and sodium sulphide-induced collectorless flotations are compared. And it is found that the order is just reverse in sodium sulphide-induced flotation to the one in self-induced collectorless flotation. 

The influence of potential on the floatability of pyrite with butyl xanthate as a collector has been determined and the result is given in Fig. 4.23. It follows that flotation begins at 0.1 V for an initial KBX concentration of 10 mol/L. The flotation potential ranges from 0.10 V to +0.31 V. 

Figtire 7.12 is the polarization curves of pyrite electrode in xanthate solution with different concentration for dipping for 48 hours. Electrochemistry parameters determined by the computer PARcal are listed in Table 7.2. Inhibiting efficiency can be calculated by Eq. (7-7), Rp- is the polarization resistance after adding collector, Rp is the polarization resistance without collector. It can be seen from Fig. 7.12 and Table 7.2 diat, with the increase of xanthate concentration, corrosive potential and corrosive current of the pyrite electrode decrease gradually while polarization resistance increases, indicating the formation of surface oxidation products. 

We shall now return to the determination of amounts of iron, e.g. as extracted from an iron-containing ore such as pyrite. Iron can exist in solution in many possible forms, with the most obvious being the ferrous and ferric aquo ions. Metallic iron is normally a good choice of redox electrode for determining the amounts of these ions in solution. 

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