Pyrite function

As noted already, the Ag content of electrum in equilibrium with argentite and FeS content of sphalerite in equilibrium with pyrite are expressed as a function of fyj and temperature, we can estimate temperature from Ag content of electrum and FeS content of sphalerite. 

Fig. 2.33. H2Saq concentration.s as a function of temperature for hot spring fluids at midocean ridges as a function of redox. Assuming AMPC (anhydrite-magnetite-pyrite-calcite) and PPM (pyrite-pyrrhotite) buffers redox in sub-seafloor reaction zones and a pressure of 500 bars, dissolved H2Saq concentrations indicate temperatures of approximately 370-385°C. Solid star Okinawa. (Modified after Seyfried and Ding, 1995.)...

Pyrite is not only one of the key compounds in Wachtershauser s theory, but could also have fulfilled an important function for phosphate chemistry in prebiotic syntheses. A group in Rio de Janeiro studied the conditions for phosphate sorption and desorption under conditions which may have been present in the primeval ocean. In particular, the question arises as to the enrichment of free, soluble inorganic phosphate (Pi), which was probably present in low concentrations similar to those of today (10 7-10 8M) (Miller and Keffe, 1995). Experiments show that acid conditions favour sorption at FeS2, while a weakly alkaline milieu works in an opposite manner. Sorption of Pi can be favoured by various factors, such as hydrophobic coating of pyrite with molecules such as acetate, which could have been formed in the vicinity of hydrothermal systems, or the neutralisation of mineral surface charges by Na+ and K+. 

Figure 3.9 Anodic current and contact angle as a function of potential for sulphidized pyrite compared with flotation recovery (Heyes and Trahar, 1984)...

Figure 4.23 Recovery of pyrite as a function of pulp potential in the presence of condition (BX 10 mol/L, KNO3 0.1 mol/L, flotation time 2 min)...

Figure 5.3 Flotation recovery of galena and pyrite as a function of butyl xanthate concentration by using lime and sodium hydroxide at pH = 12...

Figure 7.16 is the polarization curves of the pyrite electrode in dithiocarbamate solution at different concentration for dipping for 48 hours. Electrochemistry parameters determined by the computer PARcal are listed in Table 7.3. It can be seen from Fig. 7.16 and Table 7.3 that the corrosive potential of pyrite electrode decreases gradually from 187 to 160 mV and the corrosive current decreases from 10.78 to 6.01 xA/cm without or with the DDTC addition of 5 x 10 mol/L, while polarization resistance increases from 6.2 to 10.1 kfl with the increase of dithiocarbamate concentration. It indicates the formation of surface oxidation products. Comparing with xanthate, DDTC has less effect on corrosive potential, current and polarization resistance. It indicates that collector function of DDTC on pyrite is less than that of xanthate. 

Abstract In the light of quantum chemistry, sulphide minerals and the interaction of them with reagents are investigated in this chapter. With the density functional theory pyrite is first researched including its bulk properties about energy band and frontier orbitals and the property of FeS2 (100) surface. 

Density Functional Theory Research on Oxygen Adsorption on Pyrite (100) Surface... 

A lot of work (Opahle et al, 2000 Andrew et al, 2002a,b Muscat et al, 2002 Edelbro et al, 2003) has been performed on bulk and surface properties of FeS2 using various kinds of density functional theory. These works have shown that such methods are capable of producing calculated bulk properties such as lattice constants which agree well with experiment, and has provided a reference for the study of pyrite surfaces. 

In order to find a reasonable configuration for our calculation, we take test calculation to optimize the bulk structure of pyrite with GGA and LDA exchange-correlation functional. In the calculation, the plane wave cutoff energy set is 280 eV and the key point set is 4 x 4 x 4, the convergence tolerances set is 10 eV/atom. The optimized cell parameter of the two methods is 0.5415 nm and 0.5425 nm respectively, which is in good agreement with the experiment data (0.5417 nm) reported. It indicates that this configuration is sufficient to satisfy the request of accuracy. 

Figure 10.2 Recovery of flotation of pyrite as a function of pulp potential (Butyl xanthate 2.9 x 10 mol/L Butyl ether alcohol 7.5 mg/L from Wang, 1992)...

Sun Wei, Hu Yuehua, Qiu Guanzhou, Qin Wenqing, 2004a. Oxygen adsorption pyrite (100) surface by density functional theory. J. Cent. South Univ. Technol., 11(4) 385 - 390 Sun Wei, Hu Yuehua, Qin Wenqing, 2004b. DFT research on activation of sphalerite. Trans. Nonferrous Met. Soc. China, 14(2) 376-382... 

The model deformation densities for all three compounds show a peak between the metal atom and the bonded sulfur, located closer to the sulfur atoms, in a region not covered by Fig. 10.7. A local density functional calculation of pyrite by Zeng and Holzwart (1994) gives a theoretical deformation density which closely reproduces the features of the experimental densities, including the Fe—S bond peak. No orbital populations are as yet available from this calculation. 

In all of the functional group tests of kerogen, the inorganic material removed from the oil shale by attrition grinding was used as a mineral blank. Because pyrite was concentrated with the kerogen and was not separated with the mineral, pyrite equivalent to that present in the kerogen concentrate was added to the mineral blank. 

Colmer and Hinkle (14) identified T. ferrooxidans in acidic mine waters. Subsequent studies by Silverman et al. (15,16) confirmed that T. ferrooxidans could be utilized to oxidize FeSo in coal in 3 to 4 days, and the rate of oxidative dissolution was a function of the particle size and rank of the coal. Dugan and Apel (4,5) showed that a mixed culture of T. ferrooxidans and T. thiooxidans was most effective at a pH of 2 to 2.5 when the nutrient was enriched with NH " -. They reported 97% removal of pyritic sulfur from a coal sample with 3.1 weight percent sulfur. Norris and Kelly (17) reported that other acidophilic bacteria, Leptospirillum ferrooxidans in mixed cultures with T. thiooxidans, was effective for FeS2 removal. ... 

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