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Abstract
Calcium and magnesium are commonly present in flotation process waters in the order of 500 and 50 ppm, respectively. The effect of Ca (500 ppm) and Mg (50 ppm) ions on the uptake of copper and xanthate on sphalerite and flotation of Cu-activated sphalerite was investigated as a function of pH. Copper and xanthate uptake showed no change due to the presence of Ca and Mg. Flotation recovery was significantly reduced when pH exceeded that for the formation of the corresponding hydroxide precipitate. The recovery decrease was more pronounced for Mg, reflecting the lower pH for the onset of hydroxide precipitation (≈pH 9) than for Ca (≈pH 12). Imaging by X-ray photoelectron spectroscopy and scanning electron spectroscopy indicated that coverage by Mg(OH)2(s) was general. Attachment of Mg(OH)2(s) is probably a heterocoagulation process. The coating appears to be porous to Cu and xanthate. The depressant mechanism is attributed to competition by hydrophilic hydroxide sites with hydrophobic (xanthate) sites.
Calcium and magnesium are commonly present in flotation process waters in the order of 500 and 50 ppm, respectively. The effect of Ca (500 ppm) and Mg (50 ppm) ions on the uptake of copper and xanthate on sphalerite and flotation of Cu-activated sphalerite was investigated as a function of pH. Copper and xanthate uptake showed no change due to the presence of Ca and Mg. Flotation recovery was significantly reduced when pH exceeded that for the formation of the corresponding hydroxide precipitate. The recovery decrease was more pronounced for Mg, reflecting the lower pH for the onset of hydroxide precipitation (≈pH 9) than for Ca (≈pH 12). Imaging by X-ray photoelectron spectroscopy and scanning electron spectroscopy indicated that coverage by Mg(OH)2(s) was general. Attachment of Mg(OH)2(s) is probably a heterocoagulation process. The coating appears to be porous to Cu and xanthate. The depressant mechanism is attributed to competition by hydrophilic hydroxide sites with hydrophobic (xanthate) sites.
Le calcium et le magnésium sont communément présents dans les eaux du procédé de flottation dans des proportions de 500 et 50 ppm, respectivement. On a fait une étude en fonction du pH de l'effet des ions de Ca (500 ppm) et de Mg (50 ppm) sur la capture de cuivre et de xanthate sur la galène et la flottation de la galène activée par le Cu. La capture de cuivre et de xanthate n'a pas montré de changements dus à la présence du Ca et du Mg. La récupération de la flottation était significativement réduite quand le pH excédait celui de la formation du précipité hydroxyde correspondant. La diminution de récupération était plus prononcée pour le Mg, réfléchissant le pH plus faible pour le début de la précipitation de l'hydroxyde (aux environs du pH 9) que pour le Ca (aux environs du pH 12). Des images par spectroscopie de photoélectrons de rayons x et par spectroscopie électronique à balayage indiquaient que la couverture par le Mg(OH)2(s) était générale. L'attachement du Mg(OH)2(s) se produit probablement par un procédé d'hétéro coagulation. Le revêtement a l'air poreux au Cu et au xanthate. Le mécanisme de dépression est attribué à la compétition par les sites hydroxydes hydrophiles avec les sites hydrophobes (xanthate).
