Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Physicochemical Problems of Mineral Processing

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Influence of dissolved air on bubble attachment to highly oriented pyrolytic graphite

Krasowska M., Sellapperumage P. M. F., Ralston J., Beattie D. A.

Physicochemical Problems of Mineral Processing

2018

Vol. 54, iss. 1

163--173

The effect of air, dissolved in 0.1 M KCl solution, on bubble attachment to the smooth hydrophobic surface of highly oriented pyrolytic graphite was studied. The stability of a wetting film in such a system is governed by surface forces, i.e. electrostatic and van der Waals interactions. At the high ionic strength investigated, the electric double layer forces are both weak and of short range, therefore the stability of the wetting film is dominated by van der Waals interactions. The Hamaker coefficient for the highly oriented pyrolytic graphite-KCl aqueous solution-air system is negative and hence van der Waals interactions are repulsive. A repulsive force should stabilize the wetting film, preventing its rupture and bubble attachment to the highly oriented pyrolytic graphite surface. Many experimental studies have found that wetting films are not stable at graphite or coal surfaces, and air bubbles attach. In the present experiments, the stability of the wetting films decreased with increasing amount of dissolved air. The time required for film drainage, rupture, and air bubble attachment was shortened by two orders of magnitude when the experiments were performed in air saturated 0.1 M KCl solution. This instability was attributed to an increasing number of nano- and submicron- bubbles nucleated at the graphite surface. The Hamaker coefficient across the air-KCl aqueous solution-air system is positive and hence van der Waals interactions are attractive, resulting in wetting film rupture and macroscopic air bubble attachment to a highly oriented pyrolytic graphite surface decorated with resident nano- and submicro-metre bubbles.

The effect of sulphite on the xanthate-induced flotation of copper-activated pyrite

Khmeleva T, N., Skinner W., Beattie D. A., Georgiev T. V.

Physicochemical Problems of Mineral Processing

2002

Vol. 36

185-195

The effect of sulphite ions on the xanthate-induced flotation of copper-activated pyrite has been studied. Various techniques have been used to identify the plausible mechanisms of interaction of sulphite with both collector and pyrite surface. It was found that sulphite depressed the xanthateinduced flotation of copper-activated pyrite with nitrogen or air purging at pH 7. However, the depression effect was greater when air was used. Solution and spectroscopic studies indicated that sodium bisulphite interacted with the pyrite surface, as well as with isobutyl xanthate in solution and its adsorbed state. Based on the results obtained, a combination of possible mechanisms has been proposed to explain the depressing effect of sulphite on copper-activated pyrite. It was suggested that both the decomposition of the xanthate in solution via perxanthate formation and dixanthogen desorption from the pyrite surface were responsible for the pyrite depression. Furthermore, iron hydroxy species were formed on the pyrite surface, rendering it hydrophilic, thus preventing the formation of bubble-pyrite particle aggregates.

Do badania wpływu siarczynu sodowego na proces flotacji pirytu aktywowanego miedzią użuto szeregu technik badawczych. Ich zadaniem było wyjaśnienie mechanizmu oddziaływania siarczynu sodowego z kolektorem (ksantogenianem izobutylowym) oraz z powierzchnią pirytu. Odkryto, że siarczyn depresuje flotację pirytu aktywowanego miedzią przy udziale ksantogenianu w warunkach pH 7, przy przepływie azotu lub powietrza. Depresujący efekt był większy, gdy powietrze zostało użyte. Badania spektroskopowe wskazują, że siarczyn sodu reaguje z powierzchnią pirytu a także z izobutylowym ksantogenianem i to zarówno w roztworze jak i na powierzchni ciała stałego. Na tej podstawie zaproponowano mechanizm depresji aktywowanego pirytu przez siarczyn sodu. Wyniki badań sugerują, że zarówno dekompozycja ksantogenianu jak i desorpcja dwuksantogenu z powierzchni pirytu są czynnikami odpowiedzialnymi za depresowanie pirytu. Dodatkowo zaobserwowano powstawanie na powierzchni pirytu grup hydroksylowych, które dodatkowo depresowały piryt, powodując hydrofilizacje jego powierzchni i brak możliwości utworzenia trwałego agregatu z banieczką powietrza.