Iron sulfide stability

S8 Paknikar, KM., Nagpal, V., Pethkar, A.V. and Rajwade, J.M. (2005) Degradation of lindane from aqueous solutions using iron sulfide nanoparticles stabilized by biopolymers. Science and Technology of Advanced Materials, 6, 370-374. 

Stability of iron sulfides in lake sediments has not been thoroughly examined. Pyrite undergoes dynamic seasonal oxidation in salt marshes and coastal marine sediments (142, 184, 191-195). Pyrite oxidation is mediated... 

Figure 8. Hypothetical e vs. pH diagram showing how the presence of various iron silicates may affect the stability relations in the Fe-S-Si-H20 system. The full lines refer to iron species, heavy dashed lines to the system H2S-HS"-SO/ Thin dashed lines indicate how the presence of iron silicates may decrease the highest pH at which iron sulfides are stable...

The presence of solids further complicates the performance requirements for a demulsifier. Emulsions stabilized by fine particles can usually be broken if the wettability of the particles is reversed. Inorganic particles, such as iron sulfides or clay minerals, can be made water-wet, causing them to leave the interface and diffuse into the water phase, or they can be made oil-wet so that they leave the interface and diffuse into the oil phase [68]. Organic particles, such as paraffins and asphaltenes, can be removed from interfaces by dissolution [461,463,466]. 

Berner, R.A., 1964b. Stability fields of iron minerals in anaerobic sediments. J. Geol., 72 826-834. Berner, R.A., 1967. Thermodynamic stability of sedimentary iron sulfides. Am. J. Sci., 265 773-785. Berner, R.A., 1%9. Migration of iron and sulfur within anaerobic sediments during early diagenesis. Am. J. Sci., 267 19-42. 

Also, the greater stability of iron sulfide could be the reason for the separation of manganese from iron in hydrothermal solutions. These processes have not yet been investigated in more detail. 

Solids Wetting. In most crude oil, solids such as iron sulfide, silt, clay, drilling mud solids, and paraffin complicate the demulsification process. Often such solids are the primary stabilizing material, and their removal is all that is necessary to achieve satisfactory treatment. To remove solids from the interface, they can either be dispersed in the oil or water-wetted and removed with the water. 

Judging from the ease with which models of Fc4S4 are prepared under a variety of conditions and their relative stability, the Fe4S4 " core structure seems to be a relatively stable entity, a local thermodynamic minimum in the multitude of possible iron-sulfide-thiolate complexes. The initial preparation and structural characterization of the models showed that synthetic chemistry can duplicate the biological centers in far-simpler chemical systems, which can be more easily studied in great detail. 

Suspended solids and polymers generally tend to stabilize foams. One example is iron sulfide particles in amine solutions (26, 239, 318) also see item 7 above. In one case (107), precipitation of sodium chloride in a solvent-water separation column caused foaming. 

There is a need to develop the concept of stability diagrams to complex systems such as real alloys in concentrated acids or organic solvents. In such systems, it is critical to accurately represent the standard state properties as well as the activity coefficients. Recently, approaches have been developed and applied to a range of problems such as the formation of iron sulfide scales [7]. 

Redox Reactions Oxidation and reduction processes which affects the stability and persistence of electron acceptors (e.g., oxygen, ferric iron, nittate, etc.) and donors (e.g., organic matter, ferrous iron, sulfide, etc.) often mediated by microbial activity. 

At the same time, A1 helps NaAlCl4 melt to penetrate into the pores in electrode. Iron sulfide is added in order to stabilize the Ni particle size. The plateau can be found in the potential region in 2-1.6 V. 

The discoloration was found to be caused by trace amounts of hydrochloric acid which form when Neoprene oxidizes on aging. This acid reacts with iron to form ferric chloride, which in turn reacts with the thiuram disulfide modifier to form a black iron sulfide compound. Acid acceptors such as magnesia and zinc oxide were found to be effective in preventing this discoloration. However, their addition tended to decrease the viscosity stability of adhesive cements even further. 

Chemical Stabilization of Polysaccharide Polymers. Several experiments were conducted to determine the effect of certain chemical agents on polysaccharide polymer stability. The chemical agents tested were those expected to contact the polymer in a reservoir containing H2S. Ferrous and ferric iron, iron sulfide, and citric acid were most extensively tested. Citric acid (15 j m) was included in these evaluations because it was added to the polymer solutions to improve injectivity. None of the chemical agents caused any significant problem with regard to polymer stability. 

Bismuth oeeurs mainly as bismite (a-Bi203), bismuthinite (Bi2S3) and bismutite [(Bi0)2C03] very oeeasionally it oeeurs native, in assoeiation with Pb, Ag or Co ores. The main eommereial souree of the element is as a byproduet from Pb/Zn and Cu plants, from whieh it is obtained by special processes dependent on the nature of the main product. Sulfide ores are roasted to the oxide and then reduced by iron or charcoal. Because of its low mp, very low solubiUty in Fe, and fairly high oxidative stability in air, Bi can be melted and cast (like Pb) in iron and steel vessels. Like Sb, the metal is too brittle to roll, draw, or extrude at room temperature, but above 225°C Bi can be worked quite well. 

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