Oxygen in electrolyte solutions

Schumpe E, Adler I Deckwer W (1978) Solubility of oxygen in electrolyte solutions. Biotechnology and Bioengineering 20 145-150. 

Hung GW, Dinius RH. Diffusivity of oxygen in electrolyte solutions. J Chem Eng Data 1972 17(4) 449-51. 

Holtzapple MT, Eubank PT, Matthews MA. A comparison of 3 models for the diffusion of oxygen in electrolyte solutions. Biotechnol Bioeng 1989 34(7) 964-70. 

Schumpe. A. I. Adler, W.D. Deckwer, "SolubUlty of oxygen in electrolyte solutions", Biotech, t Bioeng., v20, ppl45-150 (1978)... 

Gubbins KE, Walker RD (1965) The solubility and diffusivity of oxygen in electrolytic solutions. J Electrochem Soc 112 469-471... 

An example of amperometric methods used for analytical purposes is the sensor proposed in 1953 by Leland C. Clark, Jr. for determining the concentration of dissolved molecular oxygen in aqueous solutions (chiefly biological fluids). A schematic of the sensor is shown in Fig. 23.1. A cylindrical cap (1) houses the platinum or other indicator electrode (2), the cylindrical auxiliary electrode (3), and an electrolyte (e.g., KCl) solution (4). The internal solution is separated by the polymer... 

H.J. Forman and I. Fridovich, Electrolytic univalent reduction of oxygen in aqueous solution demonstrated with superoxide dismutase. Science. 175, 339 (1972). 

Since the work function is very sensitive to contaminants, the most reliable measurements are done in ultrahigh vacuum conditions. From the determination of the electron work functions of Fe, Co, Ni, Cu, Au, and other metals in the presence of water adsorbed from the gas phase, it follows that water molecules are oriented with oxygen atoms toward the metal surface. The method is very sensitive to the presence of water. For example, upon adsorption of 3 x lO molecules of water per square centimeter of Co film (4% of a monolayer), the work function value is decreased by ca. 0.3 eV. However, these measurements were done at 77 K, meaning that adsorbed water was likely to be in a crystalline or amorphous ice form. Hence, the quoted results are of limited value to understanding the metal-water system in electrolyte solutions. 

Fig. 11.7 Parallel voltammetric screening of 64 Pt thin film catalysts for the electroreduction of oxygen in acidic solution. In the kinetically controlled region, the activity of all 64 catalysts shows good reproducibility. Conditions 0.5 M H2S04, oxygen saturated 20 mV s 1 anodic scan rate, 60°C, electrolyte stirring, potentials are plotted on the mercury/mercury sulfate electrode scale. Inset voltammogram of 64 Pt thin film catalysts in oxygen-free sulfuric acid, 20 mV s-1, prior to oxygen screening.

Copper (III)-Peptide Complexes. Molecular oxygen reacts with Cu(II)tetraglycine (G4) in neutral solution to produce a yellow species with an intense absorption band at 362 nm. As the oxygen in the solution is consumed, the amount of the yellow species decays (Figure 6). The uv-visible spectrum, molar absorptivity, dissociation kinetics in acid and in base, and the redox behavior of this yellow species are similar to those of Cunl(H.3G4)", which is generated by IrCl62 or by electrolytic oxidation of the corresponding Cu(II) complex. The peptide products after... 

Interphase inhibition [52] occurs where the inhibitive layer has a three-dimensional structure situated between the corroding metal and the electrolyte. The interphase layers generally consist of weakly soluble compounds such as oxides, hydroxides, carbonates, inhibitors, etc. and are considered to be porous. Non-porous three-dimensional layers are characteristic of passivated metals. The inhibitive efficiency depends on the properties of the three-dimensional layer, especially on porosity and stability. Interphase inhibition is generally encountered in neutral media, either in the presence or absence of oxygen. In aerated solutions, the inhibitor efficiency may be correlated with the reduction in the oxygen transport limited current at the metal surface. 

The Sherritt-Cominco process was developed as an alternative to smelting of sulfide concentrates. The key feature of the Sherritt-Cominco process is the removal of iron before the leaching of copper. The concentrate is thermally activated and leached with sulfuric acid to dissolve iron. Iron is precipitated as jarosite. The leach residue is pressure leached with oxygen in acid solution to convert copper sulfides to copper sulfates. The solution is purified by the coprecipitation of Te, As, Bi, Sb, Pb, and Se with Fe2C>3. The electrolyte contains 30 g L 1 Cu and 140 g L 1 sulfuric... 

The partial pressures of oxygen, po, on both sides of the membrane are used instead of activities as in electrolyte solutions. When air is used as the reference gas on one side of the membrane, the potential of the sensor will be determined by the partial pressure of oxygen in the sample gas. In some of the latest modifications air as the reference gas has been replaced by solid nickelous oxide in contact with the zirconium dioxide providing a constant concentration of ions at the platinum contact electrode. 

The RDE or RRDE in an electrochemical cell (Fig. 15.2) is widely used to study ORR kinetics on M-N4/C complexes in electrolyte solutions. Co and Fe macrocycles have been studied extensively as catalysts for oxygen reduction [27, 49-93]. Co-phthalocyanine (CoPc) and Co-tetrasufonated phthalocyanine (CoTsPc) adsorbed on carbon surfaces have been fotmd to catalyze 2e reductimi of O2 to form H2O2 in both alkaline and acid solutions, while Fe-phthalocyanine (FePc) and Fe-tetrasufonated phthalocyanine (FeTsPc) catalyze the overall 4e reduction in alkaline solutions [83-86]. hi an acid solution, certain face-to-face Co-porphyrins, which can form a dioxygen bridge between two Co-centers on graphite surface, have been shown to catalyze 4e reduction [58-60]. 

The solubility of gases in electrolyte solutions is usually expressed in a form that is relative to the solubility of the same gas in pure water under the same conditions of temperature and pressure. For oxygen and nitrogen, there exist useful empirical equations for calculating the solubility of gas, expressed as a mole fracticMi, at atmospheric pressure over a given temperature range. 

Tourillon and Gamier [27] pointed out that a non-degassed reaction system (electrolytic solution) used for the electrochemical syntheses results in film conductivities lower than those obtained from a carefully degassed system. They attributed these lower conductivities to the involvement of chemical disorder (due, for example, to the introduction of carbonyl groups that are suspected to result fi-om the presence of oxygen and/or water involved in electrolytic solution). 

Oxygen. The rotational motion of liquid water has been shown to be anisotropic by and Ti measurements. NMR spectroscopy has been used to study the dynamics of supercritical water. Temperature and pressure effects on Ti values of solvent molecules in electrolyte solutions have been examined. The diffusion coefficients of DMSO, Mc2S02, D N03 and T>2 0 in D2SO4 have been determined. ... 

In EW and ER, an aggregation of acid drops suspended above the electrolytic cells is a phenomenon known as acid mist, which comes from bursting bubbles of hydrogen and even oxygen in acid solutions. Therefore, spraying acid drops into the atmosphere are detrimental to health and equipment. One can alleviate the hazardous of acid mist by implementing a ventilation system [1,13] or using close-ended cylindrical cells [40]. 

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