Marangoni Effects in Liquid Jets of Non-Ionic Surfactants

2005 ◽  
Vol 58 (9) ◽  
pp. 678 ◽  
Author(s):  
Daniel M. Colegate ◽  
Colin D. Bain
Keyword(s):  
Diffusion Coefficients ◽  
Laser Doppler Velocimetry ◽  
Surface Velocity ◽  
Liquid Jets ◽  
Adsorption Model ◽  
Diffusion Controlled ◽  
Air Water Interface ◽  
Marangoni Effects ◽  
Controlled Adsorption ◽  
Best Fit

The adsorption of nonionic surfactants in the CnE8 family at the air–water interface has been studied on the millisecond timescale in a free liquid jet. The amount of adsorbed surfactant was measured by ellipsometry. The rates of adsorption are compared with a diffusion-controlled adsorption model. In the case of C10E8, which is below its cmc, the monomer diffusion coefficient provides a good fit to the experimental data. For n = 12, 14, and 16, micelles control the mass transport. The best fit diffusion coefficients are close to, but not identical with, the literature values for the micellar diffusion coefficients. Laser Doppler velocimetry was used to measure the change in surface velocity arising from adsorption of the surfactant, for n = 12, 14, and 16. There was a qualitative correlation between the retardation of the surface velocity and the surface tension gradients.

Fo and Ni Relations in Olivine Differentiate between Crystallization and Diffusion Trends

2020 ◽  
Author(s):  
Boris Gordeychik ◽  
Tatiana Churikova ◽  
Thomas Shea ◽  
Andreas Kronz ◽  
Alexander Simakin ◽  
...  
Keyword(s):  
Diffusion Coefficients ◽  
Computational Models ◽  
Three Dimensional ◽  
Crystal Shape ◽  
Diffusion Anisotropy ◽  
Progressive Loss ◽  
Theoretical And Computational Models ◽  
Diffusion Controlled ◽  
Mafic Magmas ◽  
And Diffusion

Abstract Nickel is a strongly compatible element in olivine, and thus fractional crystallization of olivine typically results in a concave-up trend on a Fo–Ni diagram. ‘Ni-enriched’ olivine compositions are considered those that fall above such a crystallization trend. To explain Ni-enriched olivine crystals, we develop a set of theoretical and computational models to describe how primitive olivine phenocrysts from a parent (high-Mg, high-Ni) basalt re-equilibrate with an evolved (low-Mg, low-Ni) melt through diffusion. These models describe the progressive loss of Fo and Ni in olivine cores during protracted diffusion for various crystal shapes and different relative diffusivities for Ni and Fe–Mg. In the case when the diffusivity of Ni is lower than that for Fe–Mg interdiffusion, then olivine phenocrysts affected by protracted diffusion form a concave-down trend that contrasts with the concave-up crystallization trend. Models for different simple geometries show that the concavity of the diffusion trend does not depend on the size of the crystals and only weakly depends on their shape. We also find that the effect of diffusion anisotropy on trend concavity is of the same magnitude as the effect of crystal shape. Thus, both diffusion anisotropy and crystal shape do not significantly change the concave-down diffusion trend. Three-dimensional numerical diffusion models using a range of more complex, realistic olivine morphologies with anisotropy corroborate this conclusion. Thus, the curvature of the concave-down diffusion trend is mainly determined by the ratio of Ni and Fe–Mg diffusion coefficients. The initial and final points of the diffusion trend are in turn determined by the compositional contrast between mafic and more evolved melts that have mixed to cause disequilibrium between olivine cores and surrounding melt. We present several examples of measurements on olivine from arc basalts from Kamchatka, and published olivine datasets from mafic magmas from non-subduction settings (lamproites and kimberlites) that are consistent with diffusion-controlled Fo–Ni behaviour. In each case the ratio of Ni and Fe–Mg diffusion coefficients is indicated to be <1. These examples show that crystallization and diffusion can be distinguished by concave-up and concave-down trends in Fo–Ni diagrams.

scholarly journals Bacterial leaching kinetics for copper dissolution from a lowgrade Indian chalcopyrite ore

2013 ◽  
Vol 66 (2) ◽  
pp. 245-250 ◽  
Author(s):  
Abhilash ◽  
K.D. Mehta ◽  
B.D. Pandey
Keyword(s):  
Phase Identification ◽  
Low Grade ◽  
Bacterial Leaching ◽  
Copper Dissolution ◽  
Diffusion Controlled ◽  
Shrinking Core ◽  
Copper Mines ◽  
Chalcopyrite Ore ◽  
Best Fit

Bio-leaching of copper (0.3%) from a low grade Indian chalcopyrite ore of Malanjkhand copper mines, using a native mesophilic isolate predominantly Acidithiobacillus ferrooxidans (A.ferrooxidans), is reported. A bio-recovery of 72% Cu was recorded in the presence of this culture (not adapted), which increased to 75% with an ore adapted culture after 35 days at 35ºC and pH 2.0 with <50fim particles. The kinetic data showed best fit for the diffusion-controlled shrinking core model, exhibiting linear plots for [1- 2/3X-(1-X)2/3] vs time (X-fraction leached). Apparently, the role of the bacteria is to convert the ferrous ion to the ferric state, which oxidizes the chalcopyrite in order to dissolve copper, while maintaining a high redox potential. The activation energy value (E) was calculated to be 96 and 108 kJ/mol for the un-adapted culture and the ore adapted culture respectively in the temperature range 25-35ºC. This leaching mechanism was corroborated by XRD phase identification and SEM studies of the leach residue.

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