Dextrin as a Regulator for the Selective Flotation of Chalcopyrite, Galena and Pyrite

Abstract

The adsorption of both dextrin and xanthate ions at the pyrite/aqueous solution and the galena/aqueous solution interfaces have been studied through batch adsorption tests. Batch flotation tests were also carried out on a chalcopyrite ore and a chalcopyrite-galena scavenger concentrate using dextrin. Dextrin adsorption isotherms on two types of surfaces of pyrite show that the greater the initial surface density of iron hydroxides, the higher the adsorption of dextrin is. These adsorption isotherms exhibit two plateaus suggesting that dextrin adsorbs on pyrite not only on ferric hydroxide sites, but also on ferrous hydroxide sites. Adsorption of xanthate ions gives rise to a partial desorption of dextrin lowering the surface hydrophilicity of pyrite. This desorption of dextrin is proposed to occur due to the dissolution of ferric hydroxide which is associated with the oxidation of xanthate ions to dixanthogen. It is shown that dextrin is an effective depressant for pyrite in flotation of copper in the chalcopyrite ore at pH 8, but the pulp needs to be aereated in order to promote the surface oxidation of pyrite and enhance the adsorption of dextrin. On galena, adsorption of xanthate ions also leads to the desorption of dextrin, but, dextrin can be an effective depressant only if the surface of galena is sufficiently oxidized to have dextrin left on the surface after xanthate adsorption. This surface oxidation of galena is more effective with pyrite than using air. Results are presented on the flotation of chalcopyrite from a chalcopyrite-galena bulk concentrate high in pyrite using dextrin as a depressant for galena and pyrite at pH 8.

The adsorption of both dextrin and xanthate ions at the pyrite/aqueous solution and the galena/aqueous solution interfaces have been studied through batch adsorption tests. Batch flotation tests were also carried out on a chalcopyrite ore and a chalcopyrite-galena scavenger concentrate using dextrin. Dextrin adsorption isotherms on two types of surfaces of pyrite show that the greater the initial surface density of iron hydroxides, the higher the adsorption of dextrin is. These adsorption isotherms exhibit two plateaus suggesting that dextrin adsorbs on pyrite not only on ferric hydroxide sites, but also on ferrous hydroxide sites. Adsorption of xanthate ions gives rise to a partial desorption of dextrin lowering the surface hydrophilicity of pyrite. This desorption of dextrin is proposed to occur due to the dissolution of ferric hydroxide which is associated with the oxidation of xanthate ions to dixanthogen. It is shown that dextrin is an effective depressant for pyrite in flotation of copper in the chalcopyrite ore at pH 8, but the pulp needs to be aereated in order to promote the surface oxidation of pyrite and enhance the adsorption of dextrin. On galena, adsorption of xanthate ions also leads to the desorption of dextrin, but, dextrin can be an effective depressant only if the surface of galena is sufficiently oxidized to have dextrin left on the surface after xanthate adsorption. This surface oxidation of galena is more effective with pyrite than using air. Results are presented on the flotation of chalcopyrite from a chalcopyrite-galena bulk concentrate high in pyrite using dextrin as a depressant for galena and pyrite at pH 8.

On a étudié l'adsorption des ions tant de dextrine que de xanthate aux interfaces pyrite/solution aqueuse et galène/solution aqueuse par des essais d'adsorption en lot. On a également effectué des essais de flottation en lot avec un minerai de chalcopyrite et un concentré épurateur de chalcopyrite-galène utilisant de la dextrine. Les isothermes d'adsorption de la dextrine sur deux types de surface de pyrite montrent que, plus grande est la densité de la surface initiale des hydroxydes de fer, plus élevée est l'adsorption de la dextrine. Ces isothermes d'adsorption exhibent deux plateaux, suggérant que la dextrine s'adsorbe sur la pyrite non seulement sur les sites d'hydroxyde ferrique, mais également sur les sites d'hydroxyde ferreux. L'adsorption des ions xanthate donne naissance à une désorption partielle de la dextrine, abaissant l'hydrophilicité de la surface de la pyrite. On propose que cette désorption de la dextrine se produit à cause de la dissolution de l'hydroxyde ferrique qui est associée à l'oxydation des ions xanthates en dixanthogène. On montre que la dextrine est un déprimant efficace de la pyrite lors de la flottation du cuivre dans le minerai de chalcopyrite au pH de 8, mais qu'il est nécessaire d'aérer la pulpe afin de promouvoir l'oxydation de la surface de la pyrite et d'augmenter l'adsorption de la dextrine. Sur la galène, l'adsorption des ions xanthate conduit également à la désorption de la dextrine, mais la dextrine peut être un déprimant efficace seulement si la surface de la galène est suffisamment oxydée pour avoir encore de la dextrine à la surface après l'adsorption du xanthate. Cette oxydation de la surface de la galène est plus efficace avec la pyrite qu'avec l'utilisation d'air. On présente les résultats de la flottation de la chalcopyrite à partir d'un concentré en vrac de chalcopyrite-galène élevé en pyrite en utilisant la dextrine comme déprimant de la galène et de la pyrite à un pH de 8.