Oxygen dissolution

Damjanovic A, Bockris JO M. 1966. The rate constants for oxygen dissolution on bare and oxide-covered platinum. Electrochim Acta 11 376-377. 

Estimate the mass-transfer coefficient for the oxygen dissolution in water 25°C in a mixing vessel equipped with flat-blade disk turbine and sparger bv using Calderbank and Moo-Young s correlations. 

Eq. (9.32) predicts that the the mass-transfer coefficient for the oxygen dissolution in water 25°C in a mixing vessel is 4.58 x lO m/s, regardless of the power consumption and gas-flow rate as illustrated in the previous example problem. Lopes De Figueiredo and Calderbank (1978) reported later that the value of kL varies from 7.3 x 10"4 to 3.4 x 1CT3 m/s, depending on the power dissipation by impeller per unit volume (Pm/v) as... 

Lopes De Figueiredo, M. M. and P. H. Calderbank, "The Scale-Up of Aerated Mixing Vessels for Specified Oxygen Dissolution Rates," Chem. Eng. Sci. 34 (1979) 1333-1338. 

It is widely known that oxygen dissolution in a medium is highly dependent on the medium s viscosity. The decrease observed in the dissolved oxygen concentration is probably associated with the increase in the viscosity observed along the process. The two observations, the decrease in oxygen concentration and the increase in viscosity, were simultaneously observed during the production of EPS by Rhizobium sp. EQ1. 

A more attractive example is with the dissolution of molecular oxygen on platinum and platinum alloys in concentrated phosphoric acid at temperatures above 100°C. Now here the value of a for the oxygen dissolution is 1.5, and that is helpful. It means the reaction goes faster a fuel cell in which the cathodic reaction of oxygen is often an r.d.s. is faster for the same electrode potential, which is good economics. 

The stirring system works either by shaking, by oxygen circulation, or by means of an externally powered magnetic bar. Stirring must be sufficient for the kinetic measurements to be meaningful and not dependent on the rate of oxygen dissolution. 

Exposure of TijAl or TigAl-base alloys to oxygen at higher temperatures leads to oxidation on the one hand and to oxygen dissolution in the alloy on the other (Rowe, 1990 Kim and Froes, 1990 Froes etal.,... 

Although mostly it is accepted that the corrosion reaction requires the existence of the oxygen reduction reaction, Hoffmann has concluded that, in the absence of oxygen, dissolution can be compensated by reduction of iron oxyhydroxides [87]. 

Another possibility for oxygen dissolution is peroxycarbonate formation ... 

The peculiarities of the defect structure of TiC and TiN allow for oxygen dissolution on the first stage of oxidation. Titanium oxides appear later, when the material structure is saturated with oxygen. Anatase was observed at lower temperatures and/or short oxidation times (5 min). With increasing time and temperature, rutile is formed as the only oxidation product [108]. 

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