Abstract: Main metallic minerals of a high iron and sulfur marmatite ore in Mongolia are mainly magnetite,sphalerite,pyrite,etc.Sphalerite is distributed in irregular granular and closely embedded with pyrite,magnetite,etc.The process of one roughing-three cleaning-two scavenging,tailings of one stage cleaning return to grinding for zinc flotation process is adopted,while the index is poor.To improve the zinc concentrate index,tests on reagent dosages of zinc flotation are made,as well as comparison tests of zinc flotation before and after process optimization.Results indicated that,zinc concentrate with zinc grade of 50.98% and recovery of 91.10% is obtained through simulated on-site closed circuit process,while zinc concentrate with zinc grade of 52.02% and recovery of 92.39% is obtained through optimized process of one scavenging concentrate also returned to grinding.Zinc grade and recovery are increased by 1.04 and 1.29 percentage points respectively through optimization.

Key words: Sphalerite, Marmatite, Middlings return, Process optimization