Ferrous sulfide

Schwefel-einschlag, m. sulfur match (for casks) sulfuring (of casks), eisen, n. iron sulfide (usiially ferrous sulfide, Iron(II) sulfide), -entfernung,/. removal of sulfur, desulfurization. -erz, n. sulfur ore. -faden, m. sulfured wick, sulfur match, -farbe, /. sulfur color sulfur dye (of wool) stoved shade. 

Ferrous ions (Fe ) combine with sulfide ions (S ) to form black ferrous sulfide FeS) ... 

Hydrogen sulfide also is formed, and this instantly reacts with iron and steel to form thin deposits of black ferrous sulfide in the superheater tubes ... 

Dissolution based on oxidation, the last but one of the chemical processes as the listing goes in Table 5.2, may best be described in a brief manner by taking a typical example of ferrous sulfide, the dissolution of which occurs as a consequence of oxidation of sulfide ion to sulfate ... 

Dissolution occurring to belong to protonation involves the processes highlighted out in Table 5.2. The dissolution of calcium carbonate in acids, the decomposition of calcium fluoride by concentrated sulfuric acid, the dissolution of ferrous sulfide in hydrochloric acid are some of the examples that can be pointed out as protonation-based dissolution. 

Most of the pollutants may be effectively removed by precipitation of metal hydroxides or carbonates using a reaction with lime, sodium hydroxide, or sodium carbonate. For some, improved removals are provided by the use of sodium sulfide or ferrous sulfide to precipitate the pollutants as sulfide compounds with very low solubilities. After soluble metals are precipitated as insoluble floes, one of the water-solid separators (such as dissolved air flotation, sedimentation, centrifugation, membrane filtration, and so on) can be used for floes removal.911 The effectiveness of pollutant removal by several different precipitation methods is summarized in Tables 5.15-5.17. 

Alternatively, hexavalent chromium can be reduced, precipitated, and floated by ferrous sulfide. By applying ferrous sulfide as a flotation aid to a plating waste with an initial hexavalent chromium concentration of 130 mg/L and total chromium concentration of 155 mg/L, an effluent quality of less than 0.05 mg/L of either chromium species can be achieved if a flotation-filtration wastewater treatment system is used.15... 

Ferrous sulfide acts as a reducing agent at pH 8 to 9 for reduction of hexavalent chromium and then precipitates the trivalent chromium as a hydroxide in one step without pH adjustment.5162 So, the hexavalent chromium in the nickel-chromium plating wastewater does not have to be isolated and pretreated by reduction to the trivalent form. The new process is applicable for removal of all heavy metals. All heavy metals other than chromium are removed as insoluble metal sulfides, M(II)S. 

Ferrous sulfide can also react with metal hydroxide to form insoluble metal sulfide ... 

Ferrous sulfide itself is also a relatively insoluble compound. Thus, the sulfide ion concentration is limited by its solubility, which amounts to only about 0.02 g/L, and the inherent problems associated with conventional sulfide precipitation are significantly minimized. 

The newly developed flotation-filtration process involving the use of ferrous sulfide as a flotation aid offers a distinct advantage in the treatment of nickel-chromium plating wastewater that contains hexavalent chromium, nickel, iron, and other metals. 

Another innovative flotation-filtration wastewater treatment system adopts the innovative use of the chemical ferrous sulfide (FeS), which reduces the hexavalent chromium and allows separation of chromium hydroxide, nickel hydroxide, and ferric hydroxide in one single step at pH 8.5. Figure 6.7 illustrates the entire system. Again, a DAF-filtration clarifier plays the most important role in this wastewater treatment system. 

The chemical name of compounds composed of only two elements usually ends with the suffix ide. The chemical name for water, for example, which is composed of two atoms of hydrogen and one of oxygen, and whose chemical formula is H20, is, therefore, hydrogen oxide. The chemical name for common table salt, composed of one atom of sodium and one of chlorine, and has the formula is NaCI, is sodium chloride. Pyrite, an iron ore composed of one atom of iron (ferrum in Latin) and one of sulfur, has the formula FeS, and its chemical name is ferrous sulfide. 

Brassert A modified blast furnace process for making iron. Less limestone is added than in the usual process, so the product contains more sulfur. The molten iron product is mixed with sodium carbonate, with which the ferrous sulfide reacts yielding sodium sulfide and iron oxide. These float on the molten iron and are skimmed off. 

Sulfex [Sulfide extraction] A process for removing heavy metals from waste streams by adding ferrous sulfide to precipitate them as their sulfides. Developed by the Permutit Company and now owned by U.S. Filter/Warrendale. Not to be confused with SULF-X or Sulph-X. 

A picture of the last step, the casting, can be seen in Figure 5.1. The processing steps are done under strictly controlled temperatures (up to roughly 1220 °C). During these, several chemical reactions take place and these enable the separation of copper from other materials. A typical reaction during the conversion is to remove the ferrous sulfides (FeS) by oxidization to iron oxides (FeO), which react with silica and can be thereafter removed as slag that is collected on the top of a ladle. As a side product, sulfur dioxide is formed and it is quite common to reuse it in a combined sulfuric acid plant. These two reactions are shown in (A) and (B) ... 

The HS formed further dissociates to (pK = 13.9). However in most submerged soils the concentration of Fe + in the soil solution is sufficient that virtually all is precipitated as amorphous ferrous sulfide and very small concentrations of H2S and HS remain in solution. The relations between the S04 -HS and Fe(OH)3-Fe " systems at neutral pH are shown in Figure 4.12. Amorphous ferrous sulfide may gradually crystallize as mackinawite (FeS). Under some circumstances pyrite is then formed, e.g. FeS(s) + S(s) FeS2(s), leading to potential acid sulfate soils (Section 7.3). 

In this method, sodium sulfide, potassium sulfide, and/or ferrous sulfide can be dosed to the spent fixer during mixing at an alkaline pH range, for precipitation of silver ions as insoluble silver sulfide precipitates [87]. Figure 7 [19,59] indicates that the residual silver concentration in the sulfide precipitation treated effluent can be below 10 mg/L in the entire alkaline range, and can be as low as 10 mg/L at pH 10.5. 

This technology involves the addition of chemical reagents to cause insoluble compounds to form. A common method nsed to precipitate metal ions is pH adjustment. The desired pH is one in which the metals exhibit low solubilities in water and therefore precipitate. Common reagents nsed for pH adjnstment include aUcahs such as lime, caustic soda, or magnesium hydroxide slurries to precipitate metal hydroxides. Sulfides such as sodium sulfide or ferrous sulfide slurries are often nsed to precipitate metal snlfides. Other reagents, such as xanthates, can also be nsed to precipitate metal ions. 

The use of a stopcock in the reaction flask during the saturation with hydrogen permits the occasional expulsion of hydrogen gas, which would otherwise accumulate. Apparently, commercial ferrous sulfide contains free iron as an impurity. 

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