Is O2 Soluble In Water

Oxygen Solubility

Low oxygen solubility in the water leads to a depression charge per unit of oxygen reduced by the controlled-ring electrons, which relates to an accumulation of the electrons in a semiconductor that consequently enhances the charge per unit of recombination of the photogenerated electrons and the holes [35].

From: Interface Science and Technology , 2021

Oxygen Solubility, Diffusion Coefficient, and Solution Viscosity

Wei Xing , ... Jiujun Zhang , in Rotating Electrode Methods and Oxygen Reduction Electrocatalysts, 2014

one.3.ane Solubility in Pure Water

Oxygen solubility in pure or fresh water at 25 °C and 1.0 atm of O_ii pressure is about 1.22 × ten⁻³ mol dm⁻³ (the values are varied from i.eighteen to 1.25 mol dm⁻ⁱⁱⁱ every bit reported in different literature). ^iii,iv In air with a normal composition, the oxygen partial pressure is 0.21 atm, the O₂ solubility would become 2.56 × 10⁻⁴ mol dm⁻³. The solubility of oxygen in water has been the subject of much literature. Currently the oxygen polarographic probe is usually used to measure solubility of O₂ in aqueous solutions. ^five

Normally, oxygen solubility is strongly dependent on (1) the amount of dissolved electrolyte common salt(s) (decreases at higher concentration of electrolyte), (2) temperature (decreases at higher temperatures), and (iii) pressure (increases at higher pressure). Nosotros will give some detailed discussion about these factors and their furnishings on the O₂ solubility in the following subsections.

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Advances in Microfluidic Fuel Cells

Erik Kjeang , ... David Sinton , in Micro Fuel Cells, 2009

three.4.2 Gas-Permeable Cathodes

The oxygen solubility limitation, common to many microfluidic fuel cells discussed thus far, may be addressed by incorporating cathodes that access the surrounding air. Ambient air has four orders of magnitude higher diffusivity (0.two cm² s^−one) and several times higher concentration (10 mM) than dissolved oxygen in aqueous media [29]. Hydrophobic porous gas diffusion electrodes are cardinal components for PEM-based fuel cells that allow gaseous reactants to pass, while limiting liquid transport. Jayashree et al. [29] introduced the start microfluidic fuel cell with an integrated air-animate cathode, using a graphite plate anode covered with Pd black nanoparticles and a porous carbon paper cathode covered with Pt black nanoparticles. A schematic of the fuel cell is provided in Effigy three.iii (also Effigy three.2e). To facilitate ionic transport to the cathodic reaction sites and sufficient separation betwixt the interdiffusion zone and the cathode, the air-breathing cell compages requires a blank cathodic electrolyte stream. With this cell a summit power density of 26 mW cm⁻ⁱⁱ was achieved using 1 M formic acid in 0.5 Thou sulfuric acid anolyte and a blank 0.five M sulfuric acid catholyte flowing at 0.3 mL min^−one per stream. The air-breathing cell architecture was also evaluated using methanol [28], which enables college overall free energy density than formic acid. Relatively pocket-size power densities were obtained with ane M methanol fuel (17 mW cm⁻²), however, improved reaction kinetics resulted in an increment in the open-circuit prison cell voltage from 0.93 Five to one.05 5. The air-breathing cells also enabled significantly college coulombic fuel utilization than the cells based on dissolved oxygen, upwardly to a maximum of 33% [29].

The scale-up and integration of multiple air-breathing fuel cells, while maintaining sufficient oxidant admission, tin be complicated. INI Power Systems (Morrisville, NC) is developing direct methanol microfluidic fuel cells with integrated gas diffusion cathode for commercial applications. Notably, recent improvements of electrodes and catalysts, optimization of methanol concentration and catamenia rates, and the addition of a gaseous period field on the cathode side accept resulted in impressive power densities on the order of 100 mW cm⁻² [46]. As compared to other direct methanol fuel cells, these microfluidic fuel cells are competitive.

Very recently, Tominaka et al. [47] developed a monolithic microfluidic fuel cell with air-breathing capabilities. The architecture of their silicon-based device is shown schematically in Figure 3.4. In this case a microchannel is employed that is open to the atmosphere on ane side. The configuration provides air-breathing access to oxidant at the porous cathode. The liquid fuel is contained in the microchannel by capillary forces; however, there is some potential for fuel evaporation.

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Oxygen in Silicon, Precipitation of

H. Bender , in Encyclopedia of Materials: Science and Technology, 2001

3 Oxygen Precipitation

From the oxygen solubility dependence, information technology follows that the oxygen is present in a supersaturated state and hence it will tend to cluster during thermal treatments. Once the clusters reach a critical size they become nuclei for precipitates which will further grow past the addition of oxygen atoms. Precipitates of subcritical size dissolve while the larger ones grow. The disquisitional size of the precipitates depends on the strain and interface energy, the temperature, and the supersaturation of oxygen, vacancies, and silicon self-interstitials. The formation of stoichiometric SiO ₂ precipitates is associated with a 125% book expansion. The resulting lattice strain is relieved by intrinsic bespeak defect interactions, i.eastward., past the generation of silicon self-interstitials and past the absorption of vacancies.

The oxide precipitate germination has been explained variously as a homogeneous, a heterogeneous, or a combined homogeneous/heterogeneous process. Homogeneous nucleation is a continuous machinery which occurs randomly and continuously throughout the fabric, whereas heterogeneous precipitation requires pre-existing nuclei to exist present in the starting material. The observed nucleation rate, i.e., the precipitate density per unit of time, decreases steeply in a higher place 850°C and can be reasonably well predicted past the homogeneous nucleation theory. The saturation precipitate density reaches a maximum effectually 700–800°C. Oxygen precipitation is not observed for an initial interstitial oxygen concentration below ∼5×10¹⁷atomscm⁻³. However, as the presence of carbon strongly increases the oxygen atmospheric precipitation rate, the precipitation is non a truly homogeneous process. This is also confirmed past the observation that the unlike thermal histories of wafers from seed and bottom ends of the crystals have a strong impact on the precipitation kinetics.

Depending on the anneal conditions ii dominant types of oxide precipitates are found. Plate-like precipitates (Fig. one(a)) form during single-step annealings in the temperature range 650–1050°C, and are besides nowadays in two-step heat-treated material with the offset amalgamate in a higher place 900°C. High-resolution manual electron microscopy shows that the precipitates are baggy. Past analysis with electron free energy loss spectroscopy the composition is adamant equally SiO _x , with ten between 1 and ii. The habit plane of the plates is parallel to the {001} silicon planes with the edges of the platelet forth 〈110〉 directions. The edges of the precipitates show a wedge-shaped thickness variation and the larger precipitates are also truncated at the corners of the plates. The larger precipitates are often broken up into smaller parts with parallel habit planes. The thickness of the plates is <4nm for anneals upwardly to 900°C. One time this thickness is reached the plates grow laterally. The precipitate growth rate is express by the rate of oxygen diffusion. The border size of the plate-like oxide precipitates follows a t ^0.75 time dependence. The plate-like precipitates are nether a loftier stress. The release of the volume expansion is of the lodge of 60–80% and is obtained by the emission of self-interstitials, the assimilation of vacancies, or the generation of dislocation loops.

Octahedral precipitates (Fig. 1(b)) occur in two-step low–high-temperature annealed material when the kickoff treatment is performed below 900°C. The smaller precipitates have a truncated octahedral shape. These precipitates too consist of baggy SiO _x . They derive from the plate-like precipitates previously formed. The octahedral precipitates are free of stress, indicating the full release of the volume deviation by interaction with intrinsic indicate defects. Their shape is adamant by a balance betwixt the strain energy, which is high for spherical precipitates, and the interface and oxygen-transport costless energies, which are high for plate-similar precipitates.

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Inclusion Engineering

Lauri Holappa , Olle Wijk , in Treatise on Process Metallurgy: Industrial Processes, 2014

1.7.3.one General Aspects

Pure iron has an oxygen solubility of most 2300 ppm (0.23 wt%) at 1600 °C. This solubility is not reached in normal steelmaking procedure, just the oxygen content is limited by other elements dissolved in liquid steel. When raw steel is produced by refining hot metal in converter or by melting scrap in electric arc furnace some oxygen is dissolved into steel. The lower the carbon content in the steel is afterward decarburization, the higher is the oxygen, typically in the range of 200–800 ppm (0.02–0.08 wt% [O]). When the raw steel is deoxidized, strong oxide-forming elements are added into steel and the content of dissolved oxygen drops downwardly. The equilibrium content of oxygen when calculation an element Me to the steel tin be calculated from the equilibrium:

(ane.7.i) $x [Me] + y [O] = {Me}_{x} O_{y}$

Nearly important deoxidation equilibria in liquid steel at 1600 °C are given in Chapter 1.6.ii.1. In Si–Mn deoxidation, the dissolved oxygen contents in liquid steel are in the range from 100 to 50 ppm. Addition of aluminum strongly decreases the equilibrium oxygen; for instance at the dissolved aluminum content of 0.030%, the oxygen content at equilibrium is around 5–3 ppm depending on the temperature. Compared with the dissolved oxygen content in liquid steel during borer, this value is just 1:100 or and so.

When deoxidizing addition is made into a liquid steel, an intensive nucleation of small inclusions occurs. After this initial nucleation, the inclusions grow in size due to diffusion growth, coalescence, and collisions. Of these factors, collisions between the particles are regarded as the virtually dominating factor [ii,three]. Considering of the rapid initial deoxidation reaction, the dissolved oxygen content decreases to a value close to the equilibrium shortly later on the addition and can exist regarded as nigh constant until the casting. Still, the total oxygen content, which means the sum of the dissolved oxygen and the oxygen bound to the inclusions, i.e., deoxidation products, is decreasing relatively slowly during the subsequent ladle metallurgical operations. In add-on to these primary inclusions, a further nucleation of secondary inclusions and growth of existing inclusions occur during the casting stage equally a issue of decreasing temperature.

All the inclusions formed every bit products of the deoxidation process are endogenous; i.e., they are formed in the melt as a result of the addition of the deoxidant which reacts with dissolved oxygen. Nonetheless, in practical steelmaking, a number of other factors tin influence the amount of oxide inclusions in the steel. In ladle metallurgy and casting, in that location are numerous possibilities for reoxidation of the steel. In the ladle, reoxidation can occur because of an oxidizing top slag, reactions with the air temper via an open slag-free "centre" formed due to too vehement gas stirring and reactions between the refractory in the ladle and the deoxidized steel. Oxygen can even fall into steel from different alloying additions which retain minor merely varying amounts of oxides. In startup of casting, there can be problems with opening the slide gate nozzles which impels the addition of oxygen. Sometimes, casting is started by teeming steel from the ladle to tundish without a protecting tube between the ladle and the tundish. During continuous casting, reactions might occur between the isolating powder added to the tundish, betwixt deoxidants and mold powders. In ingot casting, reactions might occur between the casting pulverisation and the liquid steel. In add-on to all these factors, it is important to forbid the access of exogenous inclusions in the different product steps as well equally the end-up of exogenous inclusions from the alloys in the steel. What has been said to a higher place gives an idea of the great complexity of steelmaking. Strict control of the composition and size distribution of nonmetallic inclusions in liquid steel requires business firm knowledge well-nigh all production steps and critical influencing factors. Of course the demands depend on the products that are produced. In some steel shops, it might be unnecessary to make a certain special treatment, while in another constitute, the aforementioned activeness is a "must" because of dissimilar product mix.

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Lithium-air batteries for medium- and large-scale free energy storage

A. Rinaldi , ... R. Yazami , in Advances in Batteries for Medium and Big-Calibration Energy Storage, 2015

11.7.1 PFC additive in the Li-O₂ battery

Perfluorocarbons, such every bit the perfluoroalkyl group, have the highest oxygen solubility amongst the organofluorine compounds. However, perfluoroalkyls are immiscible in most organic solvents, except in several nonpolar hydrocarbons like hexane and isooctane. ( Babiak et al., 2008) Therefore, fluorinated ether one-methoxyheptafluoropropane was called as an additive, because of its ability to dissolve in DME and TEGDME solvent. Throughout the manuscript, 1-methoxyheptafluoropropane will be referred simply every bit PFC.

Anhydrous DME, TEGDME, and anhydrous lithium perchlorate were purchased from Sigma Aldrich for the basic electrolyte mixture. Fluorinated ether, 1-methoxheptafluoropropane, HFE 7000 99.5% was obtained from 3M. Graphitized acetylene black (Sigma Aldrich) was utilized as the carbon cathode with PVDF-HSV 900 (Arkema, Inc.). The graphitized grade of acetylene black was expected to be more stable chemically against superoxide radicals (Itkis et al., 2013). Anhydrous Northward-methyl-2-pyrrolidone (Sigma Aldrich) was used to dissolve the PVDF binder for cathode fabrication.

The assembly of the cell and electrolyte preparation were performed in an argon environment glovebox with less than 1 ppm of O₂ and 0.5 ppm of H₂O. All the experiments were conducted in ECC-air fabricated by EL-CELL GmbH (EL-CELL GmbH, n.d.). The oxygen menstruation to the cell was prepare to 0.05 ml/min and the experiments were washed at laboratory room temperature (22 °C). Galvanostatic discharge was performed using an Arbin bombardment tester BT2000. The current densities used in this study were fifty, 250, and 500 mA g_c ^{− 1} (based on the weight of the carbon in the cathode).

Effigy eleven.28 shows the galvanostatic Li-O₂ cell discharge curves for porous carbon cathode at 250 mA yard_c ^{− i} in O_ii-purged 0.1 1000 LiClO₄:DME with and without 20 vol% PFC additive. The galvanostatic discharge experiments clearly showed an increase of discharge voltage with the addition of the PFC. At 250 mA thou_c ^{− 1} the average discharge voltage plateau of the jail cell with 10% PFC condiment was 2.5 $V_{Li / {Li}^{+}}$ , whereas the cell without the additive showed a lower plateau at 2.45 V _Li. The increase of the discharge potential in the cell with the additive was consistent in a wide range of belch currents. Figure xi.29 presents the summary of discharge plateaus (taken at a discharge capacity of 150 mAh m_c ^{− 1}) observed at various belch currents for cells with and without the additive. The average discharge voltage plateau increased by 55-70 mV at different electric current rates, even at lower current rates of 50 mA grand_c ^{− 1}. The average electrolyte resistance obtained from the high-frequency region of the AC impedance measurements for cell without and with 20 vol% PFC were 76.8 and 88.5 Ω, respectively. The literature viscosity value of the DME and PFC solvent (Table xi.three) was very close, thus information technology should not accept significantly afflicted the belch functioning. Therefore, the increase in belch voltage could not exist explained by either the increment of electrolyte resistance or a alter in the viscosity. The additive upshot on discharge chapters withal was less obvious. The total belch capacities of the cell with and without the condiment scattered without a clear trend.

Table 11.3. Properties of diverse solvents for electrolyte

Solvent	Kinematic viscosity (cSt)	Dynamic viscosity (cPs)	Solubility of air/oxygen in solvent	Dielectric constant
PFC	0.32 ^a	0.45	~ 35 vol% (Air) ^a	vii.forty ^a
DME	0.47 ^b	0.40	21.43 vol% (O₂) ^c	7.08 ^b
TEGDME	iv.05 ^d	iv.08	ix.7 vol% (O₂) ^c	7.79 ^e

a: HFE 7000 product catalogue (1-methoxyheptafluoropropane) (3M, 2005).
b: Nonaqueous electrochemistry (Blomgren, 1991).
c: Read et al. (2003).
d: Marcus properties of solvent (Marcus, 1998).
due east: Rivas et al. (2006).

The effect of the PFC additive in tetraglyme (TEGDME) solvent with 0.1-Grand LiClO_four at 250 mA g_c ^{− 1} was investigated and the results are shown in (Figure 11.xxx). In TEGDME, the discharge voltage increased considerably with the add-on of PFC. At a 250 - mA grand_c ^{− one}, discharge current in the electrolyte containing twenty vol% additive the discharge voltage increased to 200 mV. TEGDME has lower O₂ solubility and college viscosity compared to the PFC and DME (Table 11.iii). The addition of 20 vol% PFC to the TEGDME solvent decreased the viscosity around 15% (Table 11.4). It is thus not surprising that the effect of PFC condiment especially on the discharge voltage was more pronounced with TEGDME than with DME.

Tabular array 11.4. Viscosity of TEGDME and PFC mixture of different compositions

DI h2o	TEGDME	PFC	Viscosity (cPs)
	100%	0%	2.77
	90%	10%	2.64
	80%	20%	2.36
100%			0.99

The increase in the belch voltage (and decrease of discharge overpotential) for the two glyme solvents shown in a higher place is in agreement with the idea that the PFC additive may increase the oxygen solubility and/or the oxygen send backdrop.

The correlation betwixt oxygen solubility, oxygen improvidence in the organization, and overpotential has been adult by Read et al. and other authors (Equation xi.i). The equation describes the oxygen concentration profile during discharge by modeling the cathode as a semi-space transport condition medium (Crank, 1975; Read et al., 2003; Sandhu et al., 2007; Zhang et al., 2010).

(eleven.1) $\frac{C (x)}{C_{0}} = exp (\frac{- xj}{nF C_{0} D_{eff}}) .$

C(x) is the concentration of oxygen at x electrode thickness, C ₀ is the concentration of oxygen soluble, x is the electrode thickness, j is the current density, n is the number of electrons transferred, F is the Faraday abiding, and D _eff is the effective oxygen improvidence coefficient.

Meanwhile, the discharge reaction rate tin be described by Equation (11.2) (Sandhu et al., 2007; Zhang et al., 2010), in which R(x) is the oxygen conversion rate, k is the electrochemical reduction rate, ɛ(ten) is the porosity inside the air cathode, η is the overpotential, and 0.5 is the charge-transfer coefficient assuming one electron transfer of superoxide formation as the rate determining pace during discharge.

(11.two) $R (x) = g \in (x) C (x) exp (\frac{0.5 F}{RTη}) .$

Equations (11.1) and (xi.2) explain that as the oxygen is depleted during constant current discharge (Equation 11.i), the belch overpotential will increase to sustain the abiding electrochemical rate (Equation 11.ii).

Meanwhile, the oxygen concentration profile suggests that there is an exponential decrease of oxygen concentration with a linear increase in cathode thickness (Equation eleven.ane). The correlation between the O₂ concentration contour and cathode thickness can exist exploited to dilate the expected enhancement result of O_two diffusivity and/or solubility of additive n in an Li-O_two organization. Thus the experiment was designed by varying the cathode thickness to test the effect of PFC additives on the discharge voltage.

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Mass Transfer

Pauline M. Doran , in Bioprocess Engineering Principles (2d Edition), 2013

10.8 Estimating Oxygen Solubility

The concentration divergence $(C_{AL}^{*} - C_{AL})$ is the driving force for oxygen mass transfer. Considering this difference is usually very small, it is important that the solubility $C_{AL}^{*}$ be known accurately. Otherwise, small errors in $C_{AL}^{*}$ will event in large errors in $(C_{AL}^{*} - C_{AL}) .$

Air is used to provide oxygen in near industrial fermentations. Values for the solubility of oxygen in water at various temperatures and 1 atm air force per unit area are listed in Table 10.2 . However, fermentations are not carried out using pure water, and the gas limerick and pressure can be varied. Because the presence of dissolved material in the liquid and the oxygen partial force per unit area in the gas stage bear on oxygen solubility, the values in Table 10.2 may non be straight applicable to bioprocessing systems.

Table 10.2. Solubility of Oxygen in H2o nether one atm Air Force per unit area

Temperature (°C)	Oxygen solubility under one atm air pressure (kg k⁻ⁱⁱⁱ)	Henry'due south abiding (m³ atm gmol⁻¹)
0	1.48×x⁻²	0.454
10	i.15×10⁻²	0.582
xv	one.04×10⁻²	0.646
20	9.45×10⁻³	0.710
25	eight.69×10⁻³	0.774
26	8.55×10⁻ⁱⁱⁱ	0.787
27	8.42×10⁻³	0.797
28	8.29×10⁻³	0.810
29	8.17×10⁻³	0.822
30	viii.05×ten⁻³	0.835
35	7.52×10⁻³	0.893
40	vii.07×10⁻³	0.950

Calculated from data in International Critical Tables, 1928, vol. 3, McGraw-Hill, New York, p. 257.

10.8.1 Consequence of Oxygen Fractional Pressure level

Every bit indicated in Henry's law, Eq. (10.45) , oxygen solubility is straight proportional to the total gas pressure level and the mole fraction of oxygen in the gas stage. The solubility of oxygen in water as a function of these variables tin can exist determined using Eq. (10.45) and the values for Henry'south constant listed in Table 10.2.

10.viii.two Effect of Temperature

The variation of oxygen solubility with temperature is shown in Table x.two for h2o in the range 0 to 40°C. Oxygen solubility falls with increasing temperature. The solubility of oxygen from air in pure water betwixt 0°C and 36°C has been correlated using the following equation [29]:

(x.48) $C_{AL}^{*} = xiv.161 - 0.3943 T + 0.007714 T^{2} - 0.0000646 T^{3}$

where $C_{AL}^{*}$ is oxygen solubility in units of mg l^−one, and T is temperature in °C.

10.8.3 Effect of Solutes

The presence of solutes such as salts, acids, and sugars affects the solubility of oxygen in water every bit indicated in Tables 10.3 and 10.4. These data testify that the solubility of oxygen is reduced by the improver of ions and sugars that are normally required in fermentation media. Quicker et al. [30] take developed an empirical correlation to correct values of oxygen solubility in water for the effects of cations, anions, and sugars:

Table 10.iii. Solubility of Oxygen in Aqueous Solutions at 25°C under 1 atm Oxygen Pressure

	Oxygen solubility at 25°C nether i atm oxygen pressure (kg k⁻³)
Concentration (M)	HCl	½ H₂SO₄	NaCl
0	4.14×10⁻²	4.xiv×10⁻²	4.xiv×x⁻²
0.5	three.87×ten^−two	3.77×10⁻ⁱⁱ	3.43×10⁻²
ane.0	3.75×ten⁻²	three.60×10⁻²	2.91×ten⁻²
2.0	3.l×10⁻²	3.28×10⁻²	ii.07×10⁻ⁱⁱ

Calculated from data in International Critical Tables, 1928, vol. 3, McGraw-Hill, New York, p. 271.

Table x.4. Solubility of Oxygen in Aqueous Solutions of Sugars under 1 atm Oxygen Pressure

Sugar	Concentration (gmol per kg H_twoO)	Temperature (°C)	Oxygen solubility under 1 atm oxygen pressure level (kg one thousand^−three)
Glucose	0	20	4.50×10⁻ⁱⁱ
	0.seven	xx	three.81×x⁻²
	1.five	twenty	3.18×10⁻²
	3.0	xx	2.54×x^−two
Sucrose	0	15	4.95×10⁻²
	0.4	15	4.25×10⁻²
	0.9	15	3.47×10⁻ⁱⁱ
	ane.2	15	3.08×10^−two

Calculated from data in International Critical Tables, 1928, vol. Three, McGraw-Hill, New York, p. 272.

(10.49) $\log_{ten} (\frac{C_{AL0}^{*}}{C_{AL}^{*}}) = 0.5 \sum_{i} H_{i} z_{i}^{2} C_{i Fifty} + \sum_{j} K_{j} C_{j L}$

where

$C_{AL0}^{*}$ =oxygen solubility at zero solute concentration (mol m⁻³)

$C_{AL}^{*}$ =oxygen solubility in the presence of solutes (mol thou^−three)

H _i =constant for ionic component i (m³mol⁻¹)

z _i=charge (valence) of ionic component i

C _iL=concentration of ionic component i in the liquid (mol m⁻³)

K _j=abiding for nonionic component j (chiliad³mol⁻¹)

C _jL=concentration of nonionic component j in the liquid (mol m⁻³)

Values of H _i and 1000 _j for apply in Eq. (10.49) are listed in Table 10.5. In a typical fermentation medium, the oxygen solubility is between 5% and 25% lower than in water equally a result of solute furnishings.

Table 10.5. Values of H _i and One thousand _j in Eq. (10.49) at 25°C

Cation	H _i×10³ (m³mol^−ane)	Anion	H _i×10³ (m³mol⁻¹)	Sugar	1000 _j×10ⁱⁱⁱ (thouⁱⁱⁱmol⁻¹)
H⁺	−0.774	OH⁻	0.941	Glucose	0.119
Chiliad⁺	−0.596	Cl⁻	0.844	Lactose	0.197
Na⁺	−0.550	CO_iii ⁱⁱ⁻	0.485	Sucrose	0.149*
NH₄ ⁺	−0.720	SO₄ ²⁻	0.453
Mg²⁺	−0.314	NO_three ⁻	0.802
Ca²⁺	−0.303	HCO₃ ⁻	1.058
Mn²⁺	−0.311	H_iiPO₄ ⁻	one.037
		HPO₄ ²⁻	0.485
		PO_four ³⁻	0.320

*: Approximately valid for sucrose concentrations upwards to about 200 g 50^−one.

From A. Schumpe, I. Adler, and W.-D. Deckwer, 1978, Solubility of oxygen in electrolyte solutions. Biotechnol. Bioeng. xx, 145–150; and K. Quicker, A. Schumpe, B. König, and Westward.-D. Deckwer, 1981, Comparison of measured and calculated oxygen solubilities in fermentation media. Biotechnol. Bioeng. 23, 635–650.

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Scale-Up Considerations for Biofuels

David Humbird , Qiang Fei , in Biotechnology for Biofuel Production and Optimization, 2016

20.3.3 Temperature

Culture temperature affects cell growth charge per unit, productivity of desired products, oxygen solubility, and ultimately the product toll. ^33, ³⁷ The minimum and maximum temperatures that define limits of growth and evolution of a particular microbe are chosen the cardinal temperatures. Between these exists an optimum temperature where the growth rate is highest. Although some microorganisms are able to grow at temperature below 0 °C or above 90 °C, the optimum temperature for well-nigh microorganisms is in the range of 20-forty °C. ⁴⁷

In process optimization, it is important to realize that temperature may influence cell growth charge per unit and production synthesis rate independently. These ii objective functions must exist optimized accordingly during a bioprocess evolution. For example, a temperature shift is used to induce the accumulation of lipids and/or fatty acids in the cultivation of diverse microbes (bacterial, yeasts, and microalgae) for the production of biofuels. ^48–52

In lab- and small-calibration bioprocessing, reactor temperature is mostly controlled with a jacket and circulating coolant. The ratio of heat transfer area to the reactor book in a jacket becomes insufficient at medium scale, so internal coils are used instead. ⁵³ In some reactor configurations, these coils double as agitation baffles. At the biofuel-scale, however, neither option will have enough surface area to fairly control the culture temperature, requiring a forced circulation loop through external rut exchangers, as shown in Figure 20.1.

Oestrus removal can be substantial for a large-scale performance, ⁹ and higher temperatures are ordinarily preferred for commercial product to minimize cooling capital. Cooling water delivered through an evaporative cooling tower tin can nominally maintain a culture at 38 °C (100 °F); anything lower requires a refrigeration loop providing chilled water or glycol mixture, and a cooling belfry of equal duty, every bit likewise shown in Effigy xx.1.

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Corrosion phenomena induced by liquid metals in Generation Iv reactors

C. Fazio , F. Balbaud , in Structural Materials for Generation 4 Nuclear Reactors, 2017

2.iv.2 Oxidation process

In the case of pure atomic number 82 or Pb-Bi eutectic blend, for concentrations higher than the one necessary for the magnetite formation, but beneath the oxygen solubility in lead (which will lead to the atmospheric precipitation of pb oxide in the organisation), an oxide layer tin can class at the surface of steels.

The oxidation mode is characterized by the germination of an oxide scale for ferritic-martensitic steels with a chromium concentration below or equal to 12 wt% and for austenitic steels (304, 316SS). This oxide scale is duplex in all cases observed in the literature [36–45].

This duplex oxide layer is constituted of a Fe-Cr spinel oxide layer in the case of Fe-Cr steels and a Fe-Cr-Ni spinel oxide layer in the example of Iron-Cr-Ni steels which is in contact with the steel. Above this layer, a porous magnetite layer is observed which is in contact with the liquid blend. Both layers have similar thicknesses and the interface between them corresponds to the original interface steel/Lead-(Bi).

For Atomic number 26-9Cr steel, the nature of these layers remains identical any the test temperatures between 470°C upwards to 8000 h and 600°C for durations lower than k h. Even so for T91 and 316 type steels, afterward 2800 h in oxygen-saturated Atomic number 82-Bi at 560°C, Pb diffuses in the external magnetite layer to course plumboferrite, which is a mixed oxide containing Atomic number 82-O-Atomic number 26 [45].

The stoichiometry of the Fe-Cr spinel is Fe_2.threeCr_0.7O_iv for T91 at temperatures between 470 and 600°C. It does non vary during the oxidation process. Few information exist for austenitic steel 316.

The external magnetite layer seems porous and lead penetrations can exist observed by SEM observations. Traces of atomic number 82 tin also exist observed in the Fe-Cr-(Ni) spinel layer which appears, however, more compact.

For T91, when temperature is above 550°C, internal oxidation occurs with chromium-rich oxide precipitates localized along the grain boundaries. For austenitic steels, a pronounced intergranular oxidation is observed.

Similar oxidation kinetics is observed for lead and lead-bismuth eutectic for same dissolved oxygen concentrations. Moreover, at 500°C and upwardly to 10,000 h, the oxidation kinetics obtained prove that the thicknesses of the oxide layers (spinel and magnetite layers) grow co-ordinate to a parabolic law co-ordinate to:

$h = \sqrt{{thousand}_{p} t}$

with t, oxidation duration; k _p, parabolic constant.

Oxidation kinetics obtained for various steels are presented in Fig. two.12 [36]. In this figure, it can exist observed that the oxidation kinetics of the various steels is parabolic and that the oxidation rates are higher for ferritic-martensitic steels than for austenitic steels. In this Figure is also represented the oxidation kinetics of an aluminized 316L (316L protected by an aluminized layer deposited by aluminization performed past pack cementation). This kinetics is very low. Moreover, for ferritic-martensitic steels, the improver of silicon in the fabric (e.thou., the Russian steel named EP823 which contains 1.three% Si) leads to a decrease of the oxidation kinetics.

In this oxidation mode, austenitic steels can be used as structural material upwards to temperatures around 400–450°C and martensitic steels up to 450–500°C.

Every bit has already been said, the increment of the silicon content increases the resistance to corrosion of ferritic-martensitic steels, even so their mechanical properties can be strongly impacted past the liquid metallic environment [46]. Another steel component which is interesting regarding oxidation resistance is aluminum. Tests performed with PM2000 ODS steel (containing five.5 wt% Al) showed fantabulous corrosion resistance results subsequently immersion for 600 h in flowing liquid pb-bismuth at 535°C with an oxygen concentration of 10^−vi wt%: a very dense, thin and protective oxide layer is formed due to the loftier Al content of the material (compared, for instance, to MA956 steel which contains four.5 wt% Al) [47]. Moreover, every bit it will be described in section 2.7 of this chapter, aluminum-based coatings (performed by pack cementation or past GESA procedure) evidence also very good corrosion results [48].

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Working principle of typical bioreactors

P. Jaibiba , ... Due south. Hariharan , in Bioreactors, 2020

ten.two.1 Aerobic reactors

In an aerobic reactor, the product conversion rate or the deposition charge per unit is mainly based on the chimera size and gas-to-liquid mass transfer rate. Oxygen solubility is a main parameter that should be optimally maintained considering the presence of salt may hinder the solubilizing property of oxygen. Unproblematic aerobic bioreactors can be synthetic with aerated lagoons or oxidation ponds for the storage of the waste in the open environment and with a rotating deejay that contains the microbe as a biofilm for regular churning.

Examples of commonly used aerobic bioreactors at an industrial scale include stirred tank bioreactors, airlift bioreactors, and inverse fluidized bed bioreactors. The most common aerobic reactor is the stirred tank reactor where air is sparged from the bottom of the reactor. In the airlift bioreactor mixing is provided by the turbulence created by gas. The oxygen transfer coefficient is high for airlift reactors compared to that of stirred tank reactors. The air is introduced from the bottom of the reactor resulting in a circulatory motion of contents within the reactor that helps obtain a maximum transfer of gas as shown in Fig. ten.1A.

The inverse fluidized bed reactor (FBR) is particularly used for wastewater treatment where inert particles coated with biofilm represent the solid phase, while the oxygen or air supply is the gaseous stage and the liquid stage is the wastewater. The gas flows in the countercurrent management of the liquid flow, which improves the mass transfer rate and makes the bed piece of cake to refluidize.

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Hydrogen production by polymer electrolyte membrane water electrolysis

P. Millet , in Compendium of Hydrogen Energy, 2015

9.5.2 Pressurized PEM water electrolysis

In PEM h2o electrolyzers, as discussed, ion-conducting polymer materials are used for the double purpose of carrying electric charge and separating reaction products. Hydrogen and oxygen solubility and diffusivity in perfluorinated ion-exchange polymers used equally SPE in state-of-fine art PEM h2o electrolyzers are adequately low and gas cross-permeation during operation (hydrogen diffusion beyond the membrane from cathode to anode and oxygen improvidence from anode to cathode) tin can be neglected. This is true only when PEM h2o electrolysis cells are operated in near-atmospheric pressure conditions. In such cases, gaseous cantankerous-permeation is negligible; as a upshot, faradic efficiency is close to unity and the hydrogen concentration in evolving oxygen (in the anodic compartment) and the oxygen concentration in evolving hydrogen (in the cathodic compartment) are negligible. The situation differs when the operating pressure is increased (Ogumi, Takehara, & Yoshizawa, 1984). Pressurized PEM water electrolysis is an interesting operating choice because information technology creates the possibility of direct storage of pressurized gases with no need for external compressors. The PEM jail cell acts as an electrochemical compressor (more details are provided in Chapter 10). Most commercial electrolyzers can exist operated at low to medium pressures (up to 50 bars). Reports in the literature indicate that the applied science can be operated at much higher pressures (to a higher place 100 confined). Keeping in mind that hydrogen used in the automotive industry (H_two–air fuel cell powered cars) is unremarkably stored at 350 or 700 bars, the involvement in high-pressure PEM h2o electrolysis can easily exist understood.

From a physical viewpoint, the driving force for gas cross-permeation through the polymer electrolyte is acquired by the slope of hydrogen and oxygen chemical potentials prepare beyond the membrane as a result of the desirable separation of evolving gases. Thermodynamics of gases teaches u.s. that the chemical potential of a gaseous species is proportional to its partial pressure (at low pressure values) and to its fugacity at college pressure. Because pure gases are evolving in each cell compartment during electrolysis, the slope set across the membrane is proportional to the slope of force per unit area. Nafion^® can be seen as a 2-stage medium, a combination of hydrophobic fluorinated organic courage impregnated by a percolating aqueous phase in which pending sulfonic groups and their hydrated proton counter-ions tend to cluster. Gas cross-permeation takes place because both hydrogen and oxygen solubility in Nafion^® materials is not-zero. Solubility is water content dependent just gases as well deliquesce in the organic stage (Sakai, Takenaka, & Torikai, 1986). As a result of this solubility, two concentration gradients of dissolved gases and of opposite directions are set beyond the membrane, and dissolved gaseous species catamenia across the membrane according to Fick's laws of diffusion. H₂ and O_two permeability (Eqn (ix.14)) and their diffusion coefficients (Eqn (9.xv)) are compiled in Table 9.2 (Mann, Amphlett, Peppley, & Thurgood, 2006; Sakai, Takenaka, Wakabayashi, Kawami, & Torikai, 1985).

Tabular array 9.ii. H₂ and O₂ permeability and diffusion coefficient in hydrated Nafion^® 117 at different temperatures

T (°C)	10	20	xl	60	85
${P^{thou}}_{O_{2}} ({cm}^{ii} / Pa s)$	2.one × x⁻¹²	2.iii × 10⁻¹²	three.7 × x⁻¹²	5.3 × 10⁻¹²	8.4 × 10⁻¹¹
$D_{O_{2}} ({cm}^{2} / due south)$	two.1 × 10⁻⁷	2.five × ten⁻⁷	iv.2 × x⁻⁷	half dozen.5 × 10⁻⁷	1.one × 10⁻⁶
${P^{m}}_{H_{ii}} ({cm}^{ii} / Pa s)$	iii.8 × 10⁻¹²	4.vi × x⁻¹²	7.6 × 10⁻¹²	i.two × 10⁻¹¹	two.0 × 10⁻¹¹
$D_{H_{ii}} ({cm}^{ii} / s)$	three.9 × ten⁻⁷	4.nine × 10^−seven	8.7 × 10^−seven	1.v × 10⁻⁶	two.6 × 10⁻⁶
$D_{H_{2}} / D_{O_{2}}$	1.9	2.0	2.one	2.3	2.4

A fraction of the 2 gaseous flows across the membrane is consumed at the opposite electrode: Hydrogen is re-oxidized into protons at the anode and oxygen is reduced as h2o at the cathode. As the result, the faradic efficiency of the prison cell decreases. However, part of these flows tin meet the surface-bounded porous electrodes and exist released into gaseous gas production. As a effect, oxygen is contaminated by hydrogen. The level of contagion depends on both operating current density and operating pressure level (Figure 9.17). Experimentally, it is observed that the hydrogen concentration in oxygen is inversely proportional to the current density. This is because the hydrogen crossover flow that comes across the membrane to contaminate oxygen product is proportional to the constant difference in pressure set beyond the membrane. At low current densities, the oxygen production is small; therefore, hydrogen contagion is more elevated (Fateev et al., 2011). Effigy 9.17 provides model curves obtained using a simple permeation model. The significant disagreement observed at low electric current densities occurs because during performance, the faradaic efficiency is non constant. Chapter 11 provides more details about the unlike mass send phenomena involved and the process and details about a model that tin be used to analyze experimental results.

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