Sulfur fresh water iron

Vanadium is stripped from the organic solution with 1.5 mol dm sulfuric acid to a concentration of about 50gdm V. After an iron removal step with strong sulfuric acid, the organic solution is washed with water and recycled. From the vanadium strip liquor, ammonium polyvanadate (APV) is precipitated by oxidation and addition of ammonia. The APV slurry is thickened and pumped to a vacuum belt filter, where the APV cake is carefully washed with fresh water. The APV filter cake is dried and then calcined to vanadium pentoxide. 

Reduced forms of sulfur, such as sulfide and thiols, also react rapidly with Mn02 (26-28) as well as with FeOx. However, sulfur in fresh water is often present in substoichiometric amounts with respect to iron. Thus little or no free reduced S is present even under strongly anoxic conditions because of the formation of very insoluble FeS x species. Our equilibrium calculations (29) indicate that complexation with reduced sulfur species is not a quantitatively important aspect of Mn speciation in Lake Richard B. Russell (RBR). However, this result does not rule out the occurrence of such species as transient intermediates. 

The scatter diagram of TS vs. TOC illustrates the S/C ratios of our samples (Fig. 7). Although the study area is a normal marine environment Le. clastic sediments overlain by oxic waters of typical oceanic salinity), most of the S/C ratios in the sediments are considerably lower than the average ratio of 1/2.8 obtained for reduced sulfur and organic carbon in sediments beneath oxygenated seawater (Berner, 1982). By contrast, the S/C ratios in our samples are mostly lower than 1/10, typically occurring in fresh water environments. Similarly, low S/C ratios have been observed in Amazon inner shelf muds (Alter et al, 1986 Alter and Blair, 1996). The authors attribute the low ratios to the oxidation power of iron oxides and reworking of sediments. Unlike the Amazon case, our samples are mostly from the slope and submarine canyons rather than the shelf and, therefore, deserve further discussion. 

In the LO-CAT II process, sulfur is recovered by filtration and then washed to remove iron and salts. The washed filtercake is then reslurried with fresh water before melting (Reicher, 1995). As the LO-CAT U and LO-CAT processes utilize similar iron concentrations, the LO-CAT II molten sulfur product should be at least as pure a.s indicated in Table 9-20. 

In the determination of sulfate, 2 to 5 g of the analysis sample is mixed with HC1 (2 volumes concentrated HC1 + 3 volumes of water), and the mixture is gently boiled for 30 minutes. After filtering and washing, the undissolved coal may be retained for the determination of pyrite sulfur, or it may be discarded and a fresh sample used for pyrite sulfur. Saturated bromine water is added to the filtrate to oxidize all sulfur forms to sulfate ions and ferrous ions to ferric ions. After boiling to remove excess bromine, the iron is precipitated with excess ammonia and filtered. This precipitate must be retained for the determination of nonpyrite iron if a fresh sample of coal was used for the determination of the pyrite iron. The sulfate is then precipitated with ISaCE, and the BaSC>4 is determined gravimetrically. 

In addition, one of the commonly reported major elemental components of the ashes from woods in marine sediments is iron, which has very low concentrations in fresh wood (45). This iron is probably immobilized as pyrite (FeS2) and other reduced iron minerals as a result of sulfide released by sulfate-reducing bacteria (26, 59). These minerals are significant because they indicate in situ degradation and can affect density measurements in wood. However, from the perspective of the conservator, it is more important that when exposed to oxygen, iron-sulfur minerals tend to oxidize and release sulfuric acid (26). For example, Barbour measured a pH of 3.0 in the interstitial waters of a buried alder wood that had been stored for only 6 months at 2 °C (59). At such high acidities the hydrolysis of polysaccharides should be expected (4). Such mineral phases in buried wood from marine waters can have a deleterious effect any time the material is exposed to molecular oxygen. 

The chemical components of calcium carbonate — dissolved calcium ions and carbon dioxide — are widely distributed. Calcium is the fifth most common element in the earth s crust (after oxygen, silicon, aluminium and iron). It was extracted from early igneous rocks by the combined effects of erosion by the weather and corrosion by acidic gases (oxides of sulfur, oxides of nitrogen and carbon dioxide dissolved in rain water). Carbon dioxide makes up about 0.03 % by volume of the earth s atmosphere and is dissolved in both fresh and sea water. Combination of dissolved calcium ions and carbon dioxide resulted in the sedimentary deposition of calcium carbonate, which was subsequently converted into limestone rock. Early limestones (Precambrian — Table 2.1) are believed to have been deposited as precipitates of CaCOa, and/or as a result of the biochemical activity of very simple organisms, such as bacteria. 

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