Iron sulfide accumulation

Microsensors have been used to develop profiles in mixed species biofilms. Figure 10 shows concentration profiles of sulfide, oxygen, and pH in a biofilm accumulated on the surface of a mild steel corrosion coupon. The concentration of sulfide is highest near the metal surface, where iron sulfide forms quickly and covers the steel surface if both ferrous and sulfide ions are available. At low ferrous ion concentrations, adherent and temporarily protective films of iron sulfides are formed on the steel surface, with a consequent reduction in corrosion rate. High rates of SRB-induced corrosion of mild steel are maintained only in high concentrations of ferrous ion. 

The upper electrode is grounded to ihe vessel and any conductive material between ihe electrodes can cause a short circuit. The charged electrode can also short to the vessel or to the oil water interface. Any accumulation of water, bsltw, iron sulfides, or similar material can result in a short circuit. The most common cause of short ing is an interface buildup. 

The iron sulfide (or pyrophorric iron) accumulates as a blackish-gray deposit inside the tubes. 

Iron monosulfides comprise about 20% of the iron sulfide minerals in the noneuxinic sediment and about 50% in the euxinic sediment. Their greater preservation in the euxinic sediment, as in sediment from Walker Lake, is probably a result of insufficient elemental sulfur formation in this extremely reducing environment. Seasonally aerobic conditions at the sediment-water interface of the noneuxinic sediment would promote elemental sulfur formation from the oxidation of H2S that accumulates in pore water. 

Similary, in freshwater and non-sulfidic brackish environments with strong O2 demand, dissolved ferrous-iron may accumulate in groundwaters and anoxic bottom waters. Significant iron oxidation will occur where the water... 

S04 was —5%c at 1.0 m bis. Although dissolved sulfide concentrations in the plume were low (0.3-5.0 p.M), analysis of the sediment cores indicated that iron sulfides have accumulated in the aquifer. The highest concentrations of iron sulfides were detected just beneath the water table where increased sulfate reduction rates were measured (Figure 7). 

In the Lake Vechten sediments referred to above, stratification of the two groups of orgcmisms appeared to be due Isurgely to the sensitivity of methane producers to HjS which became inhibitory above about 0.1 mM (Cappen-berg, 1975). In many sediments, however, H2S does not accumulate to a significant extent due to its fixation as iron sulfides and its diffusion from the sediment. Winfrey emd Zeikus (1977), for example, reported that, in Lake Mendota sediments, the amount of sulfide which could be added before free HjS appeared in the pore waters was about 25 times the concentration of sulfate required to inhibit methanogenesis. 

Like Fe(II) oxidation, Fe(III) reduction can proceed rapidly due to strictly chemical mechanisms (Figure 9.1). Iron(III) reduction by sulfides is the dominant abiotic reduction mechanism whereby sulfides accumulate following 804 ... 

In this paper, we present data for total organic carbon (TOC), sulfur and iron contents in sediment samples from piston and box cores taken from the shelf and slope off southwestern Taiwan. We also present data of acid soluble iron, sulfidic iron and porewater sulfate in selected samples. The goal of this study is to illuminate the unusual inter-relationships among carbon, sulfur and iron in the rapidly accumulating sediments off southwestern Taiwan, which may serve as a typical example of sedimentation environments around high-standing islands with rapid denudation rates. 

Apart from iron, the availability of sulfate can also limit the production of iron sulfides in sediments, once the rate of sulfate consumption exceeds the diffusive supply, especially in environments of rapid sediment accumulation. However, the measured sulfate concentrations... 

This tower was used to steam-strip hydrogen sulfide from an amine solution. This is a somewhat corrosive service. Thus, iron sulfide particles (products of corrosion) accumulate in the circulating amine solution. The regenerator was equipped with stainless steel valve trays. It had been onstream for three years before the trouble started. 

The primary deposit will be iron sulfide, and some coke may be found above the stripping steam inlet. The drums may have an accumulation of sludge, if the bottom connections extend into them. Overhead drums are susceptible to corrosion as a result of the water/H2S mixture, so if possible check this vessel before cleaning to determine if FeS is present. Copious amounts of ammonia were also found in the linings of these drums, so care should be taken when water flushing, and so on. 

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