scholarly journals Phase Inversion and Interfacial Layer Microstructure in Emulsions Stabilized by Glycosurfactant Mixtures

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 331
Author(s):  
Rodolfo Esposito ◽  
Domenico Cavasso ◽  
Marcella Niccoli ◽  
Gerardino D’Errico
Keyword(s):  
Phase Inversion ◽  
Rational Design ◽  
Emulsion Stability ◽  
Narrow Range ◽  
Supramolecular Organization ◽  
Paramagnetic Resonance ◽  
Oil In Water ◽  
Oil Water ◽  
The Relationship ◽  
Electron Paramagnetic

Identification of strategies to prolong emulsion kinetic stability is a fundamental challenge for many scientists and technologists. We investigated the relationship between the emulsion stability and the surfactant supramolecular organization at the oil–water interface. The pseudo-phase diagrams of emulsions formed by water and, alternatively, a linear or a branched oil, stabilized by mixtures of two sugar-based surfactants, Span80 and Tween80, are presented. The surfactant ordering and dynamics were analyzed by electron paramagnetic resonance (EPR) spectroscopy. In Oil-in-Water (O/W) emulsions, which are stable for more than four days, disordered surfactant tails formed a compact and viscous layer. In Water-in-Oil (W/O) emulsions, whose stability is much lower, surfactants formed an ordered layer of extended tails pointing toward the continuous apolar medium. If linear oil was used, a narrow range of surfactant mixture composition existed, in which emulsions did not demix in the whole range of water/oil ratio, thus making it possible to study the phase inversion from O/W to W/O structures. While conductometry showed an abrupt inversion occurring at a well-defined water/oil ratio, the surfactant layer microstructure changed gradually between the two limiting situations. Overall, our results demonstrate the interconnection between the emulsion stability and the surfactant layer microstructuring, thus indicating directions for their rational design.

Low-Valent Ferrocenes

2020 ◽  
Author(s):  
Hayoung Song ◽  
Giyun Kwon ◽  
Cooper Citek ◽  
Seungwon Jeon ◽  
Kisuk Kang ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Thermodynamic Stability ◽  
Rational Design ◽  
Theoretical Studies ◽  
Paramagnetic Resonance ◽  
Orbital Interactions ◽  
Redox Flow Batteries ◽  
Low Valent ◽  
Functionalized Ligands ◽  
Electron Paramagnetic

Here, we report the first isolable low-valent biscyclopentadienyl iron complexes stabilized by NHC-functionalized ligands (NHC-Cps), which were characterized by electron paramagnetic resonance (EPR) and <sup>57</sup>Fe Mössbauer spectroscopy. Additional theoretical studies on these formally low-valent ferrocene complexes clearly explain the origin of their thermodynamic stability and the orbital interactions between iron and NHC-Cp. Exploiting the facile Fe(II/I) redox chemistry, we successfully demonstrated that the NHC-Fc compounds can be applied as anolytes for redox-flow batteries. These low-valent species will not only deepen our understanding of the intrinsic chemistry of low-valent ferrocene but have the potential to open the way for rational design of highly-reduced metallocene derivatives for various applications.

Influence of casein and different supplements into stability of Corn Oil/Water emulsions

2020 ◽  
Vol 3 (1) ◽  
pp. 9
Author(s):  
Vanya Gandova ◽  
Ivan Genov
Keyword(s):  
Phase Separation ◽  
Sodium Chloride ◽  
Potassium Chloride ◽  
Corn Oil ◽  
Emulsion Stability ◽  
Oil In Water ◽  
Oil Water

The effects of casein addition in oil-in-water emulsions made with 2 and 4 wt % protein and 10, 15, 25 and 35 wt % corn oil were investigated. A carbohydrate (starch), sodium chloride (NaCl) and potassium chloride (KCl), were used as supplements to prove the emulsion stability. Different analyses were prepared to investigation of emulsions. pH were measured and the values – connected with gravitational creaming and phase separation. Comparing the analyses’ results determined that emulsions prepared with 2 wt % of casein as protein, 25 % of corn oil and mix of carbohydrate 2 % - KCl 2 % exhibit more stability.

scholarly journals The mechanism of action of xanthine oxidase. The relationship between the rapid and very rapid molybdenum electron-paramagnetic-resonance signals

1979 ◽  
Vol 177 (1) ◽  
pp. 357-360 ◽  
Author(s):  
R C Bray ◽  
S Gutteridge ◽  
D A Stotter ◽  
S J Tanner
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Xanthine Oxidase ◽  
Low Ph ◽  
Active Centre ◽  
Paramagnetic Resonance ◽  
Alternative Pathways ◽  
Ph Values ◽  
Covalent Intermediate ◽  
The Relationship ◽  
Electron Paramagnetic

On the basis of the work of Gutteridge, Tanner & Bray [Biochem. J. (1978) 175, 887-897] and of other data in the literature, a mechanism for the reaction of xanthine oxidase with reducing substrates is proposed. In the Michaelis complex, xanthine is bound to molybdenum via the N-9 nitrogen atom. Coupled transfer of two electrons to molybdenum and the C-8 proton to the enzyme yields (Enzyme)-Mo-SH. Concerted with this process, reaction of the xanthine residue with a nucleophile in the active centre yields a covalent intermediate that breaks down to give the product by alternative pathways at high and at low pH values.

OIL SPILL DISPERSION STABILITY AND OIL RE-SURFACING

2008 ◽  
Vol 2008 (1) ◽  
pp. 661-665 ◽  
Author(s):  
Merv Fingas
Keyword(s):  
Water Column ◽  
Oil Spill ◽  
Emulsion Stability ◽  
Dispersed Phase ◽  
Water Interface ◽  
Water Emulsion ◽  
Stabilization Process ◽  
Oil In Water ◽  
Oil Water ◽  
Oil In Water Emulsion

ABSTRACT This paper summarizes the data and the theory of oil-in-water emulsion stability resulting in oil spill dispersion re-surfacing. There is an extensive body of literature on surfactants and interfacial chemistry, including experimental data on emulsion stability. The phenomenon of resurfacing oil is the result of two separate processes: de stabilization of an oil-in-water emulsion and desorption of surfactant from the oil-water interface which leads to further de stabilization. The de stabilization of oil-in-water emulsions such as chemical oil dispersions is a consequence of the fact that no emulsions are thermodynamically stable. Ultimately, natural forces move the emulsions to a stable state, which consists of separated oil and water. What is important is the rate at which this occurs. An emulsion is said to be kinetically stable when significant separation (usually considered to be half or 50% of the dispersed phase) occurs outside of the usable time. There are several forces and processes that result in the destabilization and resurfacing of oil-in-water emulsions such as chemically dispersed oils. These include gravitational forces, surfactant interchange with water and subsequent loss of surfactant to the water column, creaming, coalescence, flocculation, Ostwald ripening, and sedimentation. Gravitational separation is the most important force in the resurfacing of oil droplets from crude oil-in-water emulsions such as dispersions. Droplets in an emulsion tend to move upwards when their density is lower than that of water. Creaming is the de stabilization process that is simply described by the appearance of the starting dispersed phase at the surface. Coalescence is another important de stabilization process. Two droplets that interact as a result of close proximity or collision can form a new larger droplet. The result is to increase the droplet size and the rise rate, resulting in accelerated de stabilization of the emulsion. Studies show that coalescence increases with increasing turbidity as collisions between particles become more frequent. Another important phenomenon when considering the stability of dispersed oil, is the absorption/desorption of surfactant from the oil/water interface. In dilute solutions, much of the surfactant in the dispersed droplets ultimately partitions to the water column and thus is lost to the dispersion process. This paper provides a summary of the processes and data from some experiments relevant to oil spill dispersions.

Herbicide-Oil-Water Emulsions

1989 ◽  
Vol 3 (1) ◽  
pp. 13-19 ◽  
Author(s):  
Frank A. Manthey ◽  
John D. Nalewaja ◽  
Edward F. Szelezniak
Keyword(s):  
Soybean Oil ◽  
Seed Oil ◽  
Emulsion Stability ◽  
Seed Oils ◽  
Water Emulsion ◽  
Esterified Fatty Acids ◽  
Oil In Water ◽  
Crop Origin ◽  
Oil Water ◽  
Oil In Water Emulsion

Oil-water emulsion stability was determined for crop origin and refinement of seed oils and their methyl esterified fatty acids (methylated seed oil) as influenced by emulsifiers and herbicides. Oil-in-water emulsion stability of one-refined, degummed, and crude seed oils was affected by the emulsifier. However, emulsion stability of methylated seed oil was not affected by the refinement of the seed oil used to produce the methylated seed oil or by the emulsifier. Oils without emulsifiers or emulsifiers alone added to formulated herbicide-water emulsions reduced emulsion stability depending upon the herbicide and emulsifier. Further, emulsion stability of formulated herbicides plus oil adjuvants was influenced by the oil type, the emulsifier in the oil adjuvant, and the herbicide. Oil-in-water emulsions improved or were not affected by increasing concentration of the emulsifier in the oil. However, T-Mulz-VO at a concentration greater than 10% with soybean oil or 5% with methylated soybean oil reduced emulsion stability with sethoxydim. Emulsion stability of herbicides with adjuvants depends upon the herbicide, the emulsifier, emulsifier concentration, and the crop origin, type, and refinement of oil.

Iron in kaolinite: II. The relationship between kaolinite crystallinity and iron content

Clay Minerals ◽  
1980 ◽  
Vol 15 (1) ◽  
pp. 1-13 ◽  
Author(s):  
M. M. Mestdagh ◽  
L. Vielvoye ◽  
A. J. Herbillon
Keyword(s):  
Total Iron ◽  
Epr Spectra ◽  
External Signal ◽  
Crystalline Perfection ◽  
Paramagnetic Resonance ◽  
The Third ◽  
Internal Signal ◽  
External Signals ◽  
The Relationship ◽  
Electron Paramagnetic

AbstractCalibration of the internal and external signals appearing at geff ∼4 in the electron paramagnetic resonance (EPR) spectra of twenty-four kaolinites, has led to the recognition of two types of kaolinite-iron. The amount of iron associated with the internal signal (I iron) shows good inverse correlations with parameters used to describe the degree of crystalline perfection in kaolinite. Iron associated with the external signal (E iron) is insensitive to crystalline order. By considering both the amount and nature of the iron, the kaolinites investigated are placed in three groups. The first contains well-crystallized varieties characterized by low total iron and EPR spectra consisting mainly of an E signal. Poorly-crystallized kaolinites contain more iron and are characterized by a fifty-fifty partition of this iron into E and I sites. The third group contains samples which are intermediate with respect to both the amount and nature of the iron.

scholarly journals Low-Valent Ferrocenes

2020 ◽  
Author(s):  
Hayoung Song ◽  
Giyun Kwon ◽  
Cooper Citek ◽  
Seungwon Jeon ◽  
Kisuk Kang ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Thermodynamic Stability ◽  
Rational Design ◽  
Theoretical Studies ◽  
Paramagnetic Resonance ◽  
Orbital Interactions ◽  
Redox Flow Batteries ◽  
Low Valent ◽  
Functionalized Ligands ◽  
Electron Paramagnetic

Here, we report the first isolable low-valent biscyclopentadienyl iron complexes stabilized by NHC-functionalized ligands (NHC-Cps), which were characterized by electron paramagnetic resonance (EPR) and <sup>57</sup>Fe Mössbauer spectroscopy. Additional theoretical studies on these formally low-valent ferrocene complexes clearly explain the origin of their thermodynamic stability and the orbital interactions between iron and NHC-Cp. Exploiting the facile Fe(II/I) redox chemistry, we successfully demonstrated that the NHC-Fc compounds can be applied as anolytes for redox-flow batteries. These low-valent species will not only deepen our understanding of the intrinsic chemistry of low-valent ferrocene but have the potential to open the way for rational design of highly-reduced metallocene derivatives for various applications.

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