Abstract: There are high content of soluble salts as zinc sulfate and ferrous sulfate in some high sulfur lead-zinc deposits in a Yunnan Lead-zinc Mine, so that a large number of Zn2+, Fe2+ metal ions exist in flotation pulps.When pyrite is suppressed with lime in conventional flotation process, a large amount of hydroxide precipitation is produced with reaction of these metal ions with lime, which has a strong inhibitory effect on lead-zinc ores, resulting in an ineffective separation of lead-zinc complex ores.In order to reduce the impact of soluble salts on flotation of lead-zinc ores, the alkali-free flotation is adopted under the natural pH (acid) condition.For lead separation, zinc sulfate and sodium sulfate are taken as inhibitors, and aniline and drugs and ammonium drugs as collector; For zinc, the sodium silicate, sodium, carboxymethyl cellulose are taken as a modifier, PN405 as collector of zinc.Lastly, 59.57% lead concentrate with recovery of 75.14 % and 53.93% zinc concentrate with recovery of 93.70% have been obtained.

Key words: High sulfur lead-zinc ore, Soluble salt, Alkali-free flotation