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1

Influence of adsorption of n-alkyltrimethylammonium bromides (C8, C12, C16) and bubble motion on kinetics of bubble attachment to mica surface

Niecikowska A., Zawala J., Malysa K.

Physicochemical Problems of Mineral Processing

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2011

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Vol. 47

237-248

EN

Influence of adsorption of n-alkyltrimethylammonium bromides (C8, C12, C16) and formation of motion induced dynamic architecture of adsorption layer (DAL) over surface of the colliding bubble on kinetics of three-phase contact (TPC) formation at mica surface was studied. The dynamic phenomena occurring during the bubble collisions were monitored using a high-speed camera of frequency 1040 Hz. The effect of solution concentration and the DAL formation, due to the bubble motion, was determined. It was showed that stability of the wetting film formed between the colliding bubble and mica surface was governed by the electrostatic interactions between the film interfaces. It was found that when the distance covered by the bubble (i.e. the distance between the capillary and the mica surface) was L=3 mm (location "close") then the time of the three phase contact formation (tTPC), was significantly shorter than for the L=100 mm (location "far"). The differences between the tTPC for the locations "close" and "far" were the largest at lowest concentration. The mechanism responsible for significant differences in the tTPC values for the location "close" and "far" is described.

PL

Badano wpływ adsorpcji n-alkilotrimetyloamoniowych bromków (C8, C12, C16) oraz utworzenia na powierzchni pęcherzyka, ruchem indukowanej dynamicznej architektury warstwy adsorpcyjnej (DAL), na kinetykę powstawania kontaktu trójfazowego (TPC) na powierzchni miki. Zjawiska zachodzące podczas kolizji pęcherzyka były rejestrowane przy użyciu szybkiej kamery o częstotliwości 1040 Hz. Określono wpływ stężenia roztworów i utworzenia DAL na kinetykę powstawania TPC. Wykazano, że stabilność ciekłego filmu, powstającego w trakcie kolizji pomiędzy pęcherzykiem a powierzchnią miki, jest determinowana przez siły elektrostatyczne pomiędzy granicami faz, które tworzą ciekły film. Kiedy pęcherzyk pokonywał odległość (od kapilary do powierzchni miki) L=3 mm (lokalizacja "blisko") czas powstawania kontaktu trójfazowego był znacznie krótszy, w porównaniu z odległością L=100 mm ("daleko"). Różnice obserwowane dla L=3 mm i L=100 mm wzrastały wraz ze zmniejszeniem stężenia. Przedstawiono mechanizm wyjaśniający znaczące różnice w czasie powstawania kontaktu trójfazowego dla położenia "blisko" i "daleko"

2

Kinetics of random sequential adsorption of interacting particles on partially covered surfaces

Weroński P.

Bulletin of the Polish Academy of Sciences. Chemistry

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2003

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Vol. 51, No. 3-4

221-239

EN

The random sequential adsorption (RSA) approach was used to analyse adsorption kinetics of charged spheres at charged surfaces precovered with smaller sized, likely charged particles. The algorithm of M. R. Oberholzer et al. [20] was exploited to simulate adsorption allowing electrostatic interaction in three dimensions, that is, particle-particle and particle-surface interactions during the approach of a particle to the substrate. The calculation of interaction energies in the model was achieved with the aid of a many-body superposition approximation. The effective hard particle approximation was used for determination of corresponding simpler systems of particles, namely: the system of hard spheres, the system of particles with perfect sink model of particle-interface interaction, and the system of hard discs at equilibrium. Numerical simulations were performed to determine adsorption kinetics of larger particles for various surface concentration of smaller particles. It was found that in the limit of low surface coverage the numerical results were in a reasonable agreement with the formula stemming from the scaled particle theory with the modifications for the sphere-sphere geometry and electrostatic interaction. The results indicate that large particle-substrate attractive interaction significantly reduces the kinetic barrier to the large, charged particle adsorption at a surface precovered with small, likely charged particles.

3

Electrostatic interactions of colloid particles in mixed electrolytes

Warszyński P., Adamczyk Z.

Bulletin of the Polish Academy of Sciences. Chemistry

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2001

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Vol. 49, No. 1

101-114

EN

Electrostatic interactions of two spherical particles immersed in an electrolyte mixture were analyzed theoretically. A numerical scheme was developed for solving the governing Poisson-Boltzmann equation expressed in the bispherical co-ordinate system. The method was based on the alternating direction over-relaxation procedure using the Newton-Raphson iteration. The novelty of the algorithm consists in using the grid transforming functions enabling a more uniform distribution of mesh points in regions characterized by strong electric field. Using the numerical method, electric potential distribution (within and outside the sphere) was calculated which allowed one to determine the effective surface potential of a spherical particle immersed in a mixture of electrolytes. The interaction energy of particles as a function of their separation was also determined numerically for various amounts of a 2:1 electrolyte added to a 1:1 electrolyte. These energy profiles were compared with analytical approximations derived using the linear superposition approach (LSA) exploiting the effective potential determined previously. It was demonstrated that the LSA can be used as a good estimate of the potential distribution and interaction energy for distances between particles exceeding the double-layer thickness. It was also shown that a small addition of the 2:1 electrolyte decreased significantly the interaction energy between particles, which has implications for colloid stability.