Sulfur oxyanions

Sulfur oxyanions are similar to nitrate and nitrite in that they are mobile in soil and can be converted to many different forms (see Chapter 4, Figure 4.8). However, they are different from the other oxyanions in that they are the source of the essential nutrient, sulfur, and are deposited on soil from the atmosphere. Sulfate species can be determined by X-ray fluoresence (XRF), making their determination easier than the other oxyanions [21,22], Sulfur is discussed in more detail in Section 6.2.23. 

DeWeerd, K. A., Concannon, F. Suflita, J.M. (1991). Relationship between hydrogen consumption, dehalogenation, and the reduction of sulfur oxyanions by D. tiedjei. Applied and Environmental Microbiology, 57, 1929-34. 

Goldhaber M. B. 1983. Experimental study of metastable sulfur oxyanion formation during pyrite oxidation at pH 6-9 and 30 °C. Am. J. Sci. 283 913-217,... 

A wide range of oxyacids is possible with more than one sulfur atom. Although the acids are not always very stable, the oxyanions are often more easily prepared. Many of these are likely intermediates in the oxidation of aqueous sulfites and occur at low concentration in water droplets in the atmosphere. Higher concentrations of sulfur oxyanions such as 8406, SsO , and S Ol can be found in mineralized acid-sulfate waters of volcanic crater lakes (e.g., Sriwana et al, 2000). 

Takano, B. 1987. Correlation of volcanic activity with. sulfur oxyanion speciation in a crater lake. Science 235 1633-35. 

Townsend, G.T. and J.M. Suflita. 1997. Influence of sulfur oxyanions on reductive dehalogenation activities in Desulfomonile tiedjei. Appl. Environ. Microbiol. 63 3594-3599. 

OCI2 to [Co(en)L ]Cl2 (HL = hydroxydihydropyrrolecarboxylic acid). A study of the redox kinetics and reaction mechanisms of some sulfur oxyanions has appeared. Whole organisms of T. tepidarius oxidize thiosulfate by a mechanistic system quite different from that previously described for T. versutus. ... 

Vanadium Sulfates. Sulfate solutions derived from sulfuric acid leaching of vanadium ores are industrially important in the recovery of vanadium from its raw materials. Vanadium in quadrivalent form may be solvent-extracted from leach solutions as the oxycation complex (VO) ". Alternatively, the vanadium can be oxidized to the pentavalent form and solvent-extracted as an oxyanion, eg, (V O ) . Pentavalent vanadium does not form simple sulfate salts. 

For nucleophiles of different atomic numbers, nucleophilicity usually does no parallel basicity. For example, for the halogens the reactivity sequence I > Br > Cl is opposite to the sequence of basicity Cl > Br > I . Similarly, sulfur anions such as HS are better nucleophiles but weaker bases than corresponding oxyanions such as HO . 

By definition,4 all oxyanions, [XO ]m, contain a central element X (generally a non-metal, such as sulfur in a sulfate anion, [S04]2", but X may also be a metal,5 such as chromium in the chromate anion, [Cr04]2-) and a number of terminal oxygen atoms (Table 1). Each terminal oxygen atom involves up to three lone pairs of electrons and consequently each oxyanion [XO ]m may be involved in coordination to n different metal atoms if each terminal oxygen atom coordinates to only one metal atom. If more than one lone pair on each terminal oxygen atom is used in coordination... 

The pattern of one-coordinate oxyanions for the pyramidal X03 and X04 type oxyanion species is somewhat different. X-atom coordination only occurs significantly via the sulfur atom of the... 

In addition to pH, the sorption of arsenic on ferrihydrites is also affected by other chemicals in the water. In many situations, lime (CaO) is used to neutralize sulfuric acid (H2SO4) mine drainage, which may contain ferrihydrite precipitates and arsenic. The addition of lime can enhance the removal of As(V) with ferrihydrite by providing abundant Ca2+ that sorb onto ferrihydrites and increase the number of positive surface charges. The positive surface charges would readily attract and sorb As(V) oxyanions (Stollenwerk, 2003, 89 Jia and Demopoulos, 2005, 9526 Wilkie and Hering, 1996, 107). 

The topics covered in this book include the above kinds of information for oxyanions of the elements which form discrete anions carbon, sulfur, nitrogen, and the halogens including ... 

What we found is that all metal ions catalyze P—O fission. Selective P—O fission by amines was increased from 80% to 100% in the presence of Mg2+ ion, which also enhanced the rate. Exclusive P—O fission also occurred in the attack by the oxyanion of PCA in the presence of Zn2+ ion. A plausible rationale is that such a path, which involves metal ion assistance in a pentacovalent intermediate as illustrated in Figure 12a, is energetically much more favorable than that of Sn2 displacement on sulfur. Conversely, if an enzyme that catalyzes the reaction of phosphosulfate is metal ion dependent, the reaction probably involves P—O fission, as suggested by Roy (4). 

The structure of NaHSOs, sodium bisulfite, is rather curious. It is an oxyanion of a sulfur(IV) compound with a lone pair of electrons—the HOMO—on the sulfur atom, but the charge is formally on the more electronegative oxygen As a third row element (third row of the periodic table, that is) sulfur can have more that )ust eight electrons—it s all right to have four or six bonds to S or P, unlike, say, B OrN. 

Included in Table I are molybdenum enzymes that are as yet unclassified due to their partial characterization (46—49, 58). These enzymes includes polysulfide reductase that accomplish sulfur reduction to sulfide (46), underlining its role in the global sulfur cycling. Chlorate and selenate reductase are examples of relatively rare enzymes using simple oxyanions of third-row elements as substrates (47 19, 58). 

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