Effect of Pyrite

Pyrite (FeS2) and the related mineral marcasite (FeS2) occur frequently in coal and are recognized as the major mineral constituents of many coals (Chapter 7). Thus, it is not surprising that there has 

storing coal where it wonld be repeatedly wet (by rain) may favor pyrite oxidation. 

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

Figure 17.3 Effect of pyrite content of the ore on gold recovery in the copper-gold concentrate at 30% Cu concentrate grade (1 ore from Peru 2 ore from Indonesia).

Nakazawa, H. and Iwasaki, I., 1986. Galvanic contact between nickel arsenide and pyrrlotite and its effects on flotation. Inter. J. Miner. Process, 18 203 - 215 Nakazawa, H. and Iwasaki, 1., 1985. Effect of pyrite-pryyhotite contact on their floatabilities. 

Pozzo, R. L. and Iwasaki, I., 1987. Effect of pyrite and pryyhotite on the corrosive wear of grinding media. Minerals Metallurgical Processing, 4(2) 166-171... 

Effect of Pyrite Particle Size on Dispersion. It was suspected that a lot of the apparently non-dispersed pyrite particles shown in Figure 2 was due to the settling of hoarse particles between 10 and 37 micrometers. Pyrite has a specific gravity of about 5 0, while that of coal is around 1.2-1.3 Therefore, a pyrite suspension having only particle size below 10 micrometers was prepared and tested. The results, which are also shown in Figure 2(b), showed that the minus 10 micrometer pyrite suspension remained very stable, with only 10 - 20% weight of the particles settled or flocculated. From these observations, it is believed that the selective dispersion of pyrite will be more effective for the smaller particle sizes. 

Fig. 51 Effects of pyrite weathering on the concentrations of Fe2+, SO.,2- and H+ in the absence and in the presence of calcite...

Kolker A., Cecil B. C., Dulong F. T., and Fedarko N. (2001) Effect of pyrite composition textme, and form on acid ttrine drainage potential in coal-bearing strata of the central Appalachian Basin. Geol. Soc. Am. Ann. Meet. Abstr. Progr. Pap. 172-0. 

Table III. The Effect of Pyrite Particle Size on the Recovery of Sulfur (7)...

Stohl and Granoff (18) investigated the effects of pyrite particle sizes, pyrite defects and surface areas on coal liquefaction. They observed no effect due to surface area and concluded that the observed particle size effect was due to diffusional limitations in the transformation of pyrite to pyrrhotite. 

The effect of pyrite removal was also clearly demonstrated ( 0). For Burning Star coal (Illinois No. 6), the oil yield for run-of-mine coal (4.8% pyrite) was 47%. Conventional cleaning to 1.5% pyrite resulted in an oil yield of 42%. Deep cleaning to 0.5% pyrite followed by addition of 5.3% pyrite to the clean coal produced an oil yield of 51%, even though the operating pressure (1800 psi) was lower than in the other runs (2250 psi). 

In situ IRRAS with a Ge prism window was used by Laajalehto et al. [603] to study the effect of pyrite activation by copper and lead ions at pH 5, 6.5, and 9. It was found that the xanthate interaction with copper-activated pyrite resembles that of chalcopyrite, resulting in adsorption and dixanthogen formation. In similar experiments with lead-activated pyrite, only very weak absorption bands of the adsorbed collector were observed, implying that lead depresses rather than activates pyrite. 

R.L. Pozzo and I. Iwasaki, Effect of Pyrite and Pyrrhotite on the Corrosive Wear of Grinding Media, Miner. Metall. Process., Aug 1987, p 166-171... 

Reactions of Goal Ash. Mineral matter impurities have an important effect on the utili2ation of a coal. One of the constituents of greatest concern is pyrite because of the potential for sulfur oxide generation on combustion. The highest concentrations of pyrite are associated with coal deposition under marine environments, as typified by the Illinois Basin, including parts of Illinois, Indiana, and Kentucky. Additionally, the mineral matter... 

The last reaction cited above as shown is very effectively catalyzed by bacterial action but is very slow chemically by recycling the spent ferrous liquors and regenerating ferric iron bacterially, the amount of iron which must be derived from pyrite oxidation is limited to that needed to make up losses from the system, principally in the uranium product stream. This is important if the slow step in the overall process is the oxidation of pyrite. The situation is different in the case of bacterial leaching of copper sulfides where all the sulfide must be attacked to obtain copper with a high efficiency. A fourth reaction which may occur is the hydrolysis of ferric sulfate in solution, thus regenerating more sulfuric acid the ferrous-ferric oxidation consumes acid. 

The iron sulphide in South African coals is a mixture of pyrite and marcasite (18). Although marcasite is known to transform into pyrite at elevated temperatures, separate spiking experiments were performed to see if pyrite or marcasite would show a preferential catalytic effect. The addition of pyrite and marcasite minerals (-200 mesh), to the coal showed equivalent total conversions, and yields of oil and asphaltene. 

The Effect of Mineral Matters on the Decomposition Ethers. Recently, the effect of mineral matters of coal on the coal liquefaction has received much attention. It was shown that small amounts of FeS or pyrite are responsible for the hydro-genative liquefaction of coal. Therefore, it is interesting to elucidate the effect of mineral matters of coal on the decomposition rate and products of aromatic ethers, and so three diaryl ethers were thermally treated in the presence of coal ash obtained by low temperature combustion of Illinois No.6 coal at about 200°C with ozone containing oxygen. 

Cruz R., Bertrand, V., Monroy, M., GonzAlez, I. 2001. Effect of sulphide impurities on the reactivity of pyrite and pyritic concentrates a multi-tool approach. Applied Geochemistry, 16, 803-819. 

This method is highly sensitive to temperature. Figure 17.5 shows the effect of temperature on pyrite/arsenopyrite separation. In this particular case, most of the gold was associated with pyrite. Successful pyrite/arsenopyrite separation can also be achieved with the use of potassium peroxy disulphide as the arsenopyrite depressant. 

Figure 17.5 Effect of temperature on separation of pyrite and arsenopyrite from a bulk pyrite/ arsenopyrite concentrate.

The lower explosive limit and minimum explosive concentrations of flax, wool, cotton, jute, hemp and sisal fibres are of the same order of magnitude as those of highly explosive dusts [15], The explosibility of pyrites dusts with sulfur contents above 20% was evaluated experimentally. Dusts of 30% sulfur content gave explosion pressures of 3 bar at pressure rise rates of 16 bar/sec. Mixtures of 60% pyrites and 40% powdered limestone still showed significant pressure effects, and the proportion of limestone actually needed to suppress explosions was considerably above the values currently accepted by mining industries [16], Effects of mixtures of particle sizes in combustible dusts upon minimum ignition temperature (T ") and upon presence or absence of explosion were studied. Presence of 30% of fines in a coarse dust lowers Tf significantly [17], Experimental explosions of polyethylene,... 

Unfortunately, pyrite sulfur makes up only half the sulfur content of coal, while the other half is organically bound. Coal gasification is the only means by which this sulfur mode can be removed. Of course, it is always possible to eliminate the deleterious effects of sulfur by removing the major product oxide S02 by absorption processes. These processes impose large initial capital investments. 

Figure 1.2 Effect of pulp potential on self-induced collectorless flotation behaviors of pyrrhotite and pyrite (Heyes and Trahar, 1984)...

Figure 2.7 Effect of pulp potential on collectorless flotation behaviors of pyrite and pyrrhotite...

Sun et al. (1993a) reported the effects HS ion concentration on the adsorption of HS , the amount of extracted sulphur and sulphur-induced flotation of pyrite as shown in Fig. 3.11. The results show that dining sodium sulphide-induced collectorless flotation, it involves the adsorption of HS ion on the mineral and the HS" adsorbed can be oxidized into sulphur to render pyrite and arsenopyrite surface hydrophobic due to the fact that the adsorption density of HS" ion increases with the HS" ion concentration and the amount of extracted sulphur and hence the flotation rate increases with the increase of adsorption density. It suggests that the mechanism of sodium sulphide-induced collectorless flotation of pyrite takes place hy reactions ... 

Figure 3.11 Effects of HS" concentration on the adsorption, the amount of neutral sulphur extracted fiom pyrite surface and collectorless flotation of pyrite at pH = 11.0 (Sun et al., 1993a)...

The formation of hydroxyl iron and calcixxm sulphate precipitates makes pyrite surface very hydrophilic and inhibits other electrochemistry reaction on pyrite like collector giving rise to the depression of pyrite. The depression effect of lime on pyrite may be stronger than that of NaOH. 

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. 

Ahlberg, E. and Broo, A. E., 1996c. Oxygen reduction at sulphide minerals. 3. The effect of surface pre-treatment on the oxygen reduction at pyrite. Inter. J. Miner. Process, 47(1 - 2) 49-60... 

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