Iron sulphides

Bacterial activity often plays a major part in determining the corrosion of buried steel. This is particularly so in waterlogged clays and similar soils, where no atmospheric oxygen is present as such. If these soils contain sulphates, e.g. gypsum and the necessary traces of nutrients, corrosion can occur under anaerobic conditions in the presence of sulphate-reducing bacteria. One of the final products is iron sulphide, and the presence of this is characteristic of attack by sulphate-reducing bacteria, which are frequently present (see Section 2.6). 

Although iron sulphide also forms a eutectic with the metal this melts at 988°C, and at temperatures in the region of 700 to 800°C alloys with substantial proportions of nickel replaced by iron and a chromium level maintained at about 20% show advantages over nickel-chromium-base alloys in resistance to sulphur attack. 

Kassner used a rotating disc, for which the hydrodynamic conditions are well defined, to study the dissolution kinetics of Type 304 stainless steel in liquid Bi-Sn eutectic. He established a temperature and velocity dependence of the dissolution rate that was consistent with liquid diffusion control with a transition to reaction control at 860 C when the speed of the disc was increased. The rotating disc technique has also been used to investigate the corrosion stability of both alloy and stainless steels in molten iron sulphide and a copper/65% calcium melt at 1220 C . The dissolution rate of the steels tested was two orders of magnitude higher in the molten sulphide than in the metal melt. 

The ER system has been used successfully in a range of industries for process plant monitoring. As ER can be applied in any liquid or gaseous environment the areas of application are considerable. However, there is a problem with ER if a conductive corrosion product is produced as is the case with sour crude oil or gas due to the deposition of iron sulphide. 

Tacconi NR, Medvedko O, Rajeshwar K (1994) Cathodic electrosynthesis of metal sulphide thin films at a sulphur-modified gold surface application to the iron sulphide system. 1 Electroanal Chem 379 545-547... 

Maeda, H., Ito, Y., Aragane, T. and Sato, i. (1981) Modes of occurrence and properties of electrum from the Shimokawa cupriferous iron sulphide deposits in comparison with those from the Kuroko deposits. Mining Geology Special Is.sue, 10, 193—202 (in Japanese with English abst ). 

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. 

Metallic compositions serving as siccatives catalyze the well-known oxidation and polymerization of oil in paints and other finishes. Likewise, ferrous and other metallic objects boost self-heating in piles of lignocellulosics. Among the known catalyzing substances are iron sulphides and iron oxides from combustion gases of... 

The floatability of gold from gold-containing copper gold ores depends on the nature and occurrence of gold in these ores, and its association with iron sulphides. 

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. 

Many iron ores also contain iron sulphide, which is commonly called fool s gold. 

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... 

Doctor et al. (2000) point out the technical problems in the transport infrastructure that could arise from impurities in the C02. Any transport system requires the C02 to be dried to prevent the formation of C02 hydrates. Considerable problems with the formation of iron sulphide in natural gas pipelines indicate that C02 also has to be cleaned of hydrogen sulphide content. 

Pye K, Dickson JAD, Schiavon N, Coleman ML, Cox M (1990) Formation of siderite-Mg-calcite-iron sulphide concretions in intertidal marsh and sandflat sediments, north Norfolk, England. Sedimentology 37 325-343... 

Abstract In the beginning, the mixed potential model, which is generally used to explain the adsorption of collectors on the sulphide minerals, is illustrated. And the collector flotation of several kinds of minerals such as copper sulphide minerals, lead sulphide minerals, zinc sulphide minerals and iron sulphide minerals is discussed in the aspect of pulp potential and the nature of hydrophobic entity is concluded from the dependence of flotation on pulp potential. In the following section, the electrochemical phase diagrams for butyl xanthate/water system and chalcocite/oxygen/xanthate system are all demonstrated from which some useful information about the hydrophobic species are obtained. And some instrumental methods including UV analysis, FTIR analysis and XPS analysis can also be used to investigated sulphide mineral-thio-collector sytem. And some examples about that are listed in the last part of this chapter. 

Role of Polyhydroxyl and Poly Carboxylic Xantfaate in the Flotation of Zinc-Iron Sulphide... 

Flotation Behavior of Zinc-Iron Sulphide mth Polyhydroxyl and Polycarboxylic Xanthate as Depressants... 

Table 5.1 Potential area of flotation of zinc-iron sulphide with butyl xanthate as a collector in the presence of GX2...

Figure 5.27 presents the adsorption isotherms of 2,3-dihydroxyl propyl dithiocarbonic sodium (GX2) on marmatite, arsenopyrite and pyrrhotite. The adsorption of GX2 on these three zinc-iron sulphides is increased with its... 

Figure 5.31 Zeta potential of zinc-iron sulphide minerals as a function of pH...

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