Abstract: In order to decrease the MgO content in floated copper-nickel concentrate of Northwest copper-nickel sulfide with high magnesium content，the tests on improving quality and decreasing magnesium content for the raw ores containing 1.29% nickel,0.87% copper,29.02% MgO were carried out by using disodium EDTA as Cu²⁺,Ni²⁺ complexing agent and sodium hexametaphosphate and JC as inhibitors for Mg-containing gangues.The results showed that,by the closed-circuit process of one roughing，two cleaning，three scavengings，middlings returning in proper order into the flow,final copper-nickel mixed concentrate with Ni grade of 8.95% ,Cu grade of 5.21%,nickel recovery of 82.91%,copper recovery of 71.56%，and MgO content of 6.13% was obtained.Compared with the on-site beneficiation process，the optimized process could decrease the middles regrinding operation and simplify the flotation process,while the Ni and Cu grade of final copper-nickel mixed concentrate were improved by 0.28 and 0.71 percentage points,and the nickel and copper recovery were improved by 0.35 and 1.38 percentage points respectively.MgO content was reduced by 0.59 percentage points.The optimizing process achieved good effect of beneficiation.

Key words: Copper-nickel sulfide ores, Mg-containing gangues, Complexing agent, Disodium EDTA, Inhibitors, Sodium hexametaphosphate, JC