Effect of sodium sulfide additions on the pulp potential and amyl xanthateflotation of cerussite and galena

The flotation response of cerussite and galena treated with sodium sulfide solutions open to the atmosphere was assessed at pH 9.5 using amyl xanthate as the collector Since both the hydrosulfide and xanthate anions are elect rochemically active, the redox potential of the suspensions was measured wi th a smooth-platinum/saturated calomel electrode system. Mineral flotation depends on the sulfide dosage and is strongly affected by the potential. Ce russite flotation is poor under sulfide-deficient and sulfide-rich conditio ns. Low sulfide dosages are consumed by aqueous lead dissolved from the min eral and precipitate as lead sulfide. These colloidal particles seem to dep osit onto the cerussite surface and react with the collector. As a result, a peak in the flotation curve is noted. High sulfide dosages oversulfidize the mineral surface, shift the potential to reducing conditions, and depres s the mineral. At two different collector additions, optimum flotation of s ulfide-treated cerussite occurs in the potential range from -100 mV to abou t 150 mV. Galena flotation ceases above a certain sulfide dosage that lower s the potential to reducing values thus inhibiting the chemisorption of xan thate onto the mineral surface. The results of this research work indicate that the xanthate flotation of sulfidized, mixed oxide-sulfide lead ores ma y be controlled by monitoring the pulp potential. (C) 1999 Elsevier Science B.V. All rights reserved.