Sulfite Oxidation Data

There are data using excess sodium sulfite with suitable catalysts which keep the dissolved oxygen level at zero, and the data have been obtained on small and large size fermentation tanks on this basis. One caution is that the data should have been taken when the tank was completely clean of antifoams which may be residual from the fermentation process. This antifoam can cause marked differences in the mass transfer coefficient. 

If someone has a relationship between the sulfite oxidation number and the performance required in the fermenter, this is a perfectly valid way to specify equipment and tests can be run to give an indication of the overall mass transfer rate ensuing. 

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GL 27] [R 3] ]P 29] By means of sulfite oxidation, the specific interfacial area of the fluid system nitrogen/water was determined at Weber numbers ranging from lO " to 10 [10]. In this range, the interface increases from 4000 m m to 10 000 m m . The data are - with exceptions - in accordance with optically derived analysis of the interface and predictions from calculations. At stiU larger Weber number up to 10, the specific interfacial area increases up to 17 000 m m, which was determined optically. 

It is a well-known fact that bubbles produced by mechanical force in electrolyte solutions are much smaller than those in pure water. This can be explained by reduction of the rate of bubble coalescence due to an electrostatic potential at the surface of aqueous electrolyte solutions. Thus, k a values in aerated stirred tanks obtained by the sulfite oxidation method are larger than those obtained by physical absorption into pure water, in the same apparatus, and at the same gas rate and stirrer speed [3]. Quantitative relationships between k a values and the ionic strength are available [4]. Recently published data on were obtained mostly by physical absorption or desorption with pure water. 

By incorporating the film theory into the mathematical model for the batch slurry oxidation, a mass transfer coefficient of 0.015 cm/sec was obtained by matching the model to highly catalyzed (2000 ppm Mn added) slurry oxidation data. Saturation concentration of sulfite is most important in determining mass transfer coefficient(32). A correlation is given... 

Cooper et al. (C9) were the first to determine mass-transfer coefficients by measuring the oxidation rate of sodium sulfite in an aqueous solution catalyzed by cupric ions. Their data were taken for a vaned-disk agitator with 16 blades and for a flat paddle. The ratio of agitator-to-tank diameter was 0.4, and the ratio of paddle to tank diameter was 0.25. The tank was equipped with four baffles, with baffle-width to tank diameter ratio of 0.1. 

The oxo-transfer chemistry of molybdenum in sulfite oxidase is probably the best characterized, in terms of synthetic models, structural and mechanistic data, of all the elements we have described up till now. The reaction cycle (Figure 17.5) involves binding of sulfite to the oxidized MoVI, two-electron reduction of the Mo centre and release of sulfate. The Movl centre is restored by successive one-electron transfers from a cytochrome (bs in mammals). The primary oxo-transfer reaction ... 

The continuous-flow nonsteady state measurements can be made after the reactor has reached steady state, which usually takes at least 3 to 5 times the hydraulic retention time under constant conditions. Then an appropriate amount of the compound to be oxidized (e. g. Na2S03) is injected into the reactor. An immediate decrease in the liquid ozone concentration to c, 0 mg L-1 indicates that the concentration is correct. Enough sulfite has to be added to keep cL = 0 for at least one minute so that it is uniformly dispersed throughout the whole reactor. Thus a bit more than one mole of sodium sulfite per mole ozone dissolved is necessary. The subsequent increase in cL is recorded by a computer or a strip chart. The data are evaluated according to equation 3-24, the slope from the linear regression is - (2/,/Vj + KLa(03)). 

Figure 10.9. Typical data of mass transfer coefficients at various power levels and superficial gas rates for oxidation of sodium sulfite in aqueous solution. d/D = 0.25-0.40 (Oldshue, 1983).

As with xanthine oxidase, the sulfido ligand of the active form of aldehyde oxidoreductase is readily replaced by an oxido ligand to yield a cofactor with a structure that resembles that of oxidized sulfite oxidase and assimilatoiy nitrate reductase. Both x-ray and EXAFS data are available for the bis(oxido) form, and, with the exception of the oxido replaced sulfido ligand, few changes are obvious in the overall structure of the oxidized form of the desulfo cofactor. Upon reduction of the enzyme the oxido ligand is presumably reduced to hydroxido, an observation that is supported by EPR data for the Mov state. 

High temperature thermodynamic data are available only for three sulfites calcium, potassium, and sodium. Most sulfites are fairly unstable, decomposing at relatively low temperatures. The decomposition reactions are not always exactly known, with diverse decomposition products, including sulfur, being reported. There are two major decomposition reactions (1) decomposition to the oxide and S02, and (2) oxidation-reduction (disproportionation) to the sulfate and oxide and S02, i.e.,... 

Thermodynamic data at 298.15 K were mostly taken from Wagman et al.3 High temperature data for the above-mentioned three sulfites were taken from the HSC database referred to in Chapter 1.1. No thermodynamic data for oxides are included, since they were already given in Chapter 2, and sulfates, which may also be decomposition products, are described in Chapter 4. Therefore, when only minimal data are available, they are given in the text rather than in individual tables. 

The average concentrations of reduced inorganic sulfur species in the anoxic zone of the Black Sea measured using a new colorimetric method developed by Volkov [61,62] are summarized in Table 3. Presented elemental sulfur data refer to the stun of elemental sulfur allotropes (zero-valent sulfur) and the zero-valent sulfur derived from some fraction (n - 1) of the original polysulfide S 2. Thiosulfate data in the table represent the total amount of thiosulfate, sulfite, and polythionates. At some stations in the Black Sea, Volkov [61] observed a concentration maximum of elemental sulfur at the oxic/anoxic interface associated with sulfide oxidation by dissolved oxygen and/or Mn oxyhydroxides. Increasing with depth, elemental sulfur concentrations are probably explained by the ongoing process of polysulfide formation... 

Application of laser Raman multichannel spectroscopy to a kinetic investigation in the liquid phase has been reported by Crunelle-Cras and Merlin (1977). A multichannel spectrometer with photoelectric image devices, interfaced with a data aquisition and handling system, permits the study of fast processes, exemplified by the fast oxidation of the sulfite ion by the bromate ion in an acidic medium. 

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