Enargite (Cu_3AsS_4) and chalcopyrite (CuFeS_2) usually occur in the same ore deposit. Due to their similar surface characteristics, both minerals are usually floated together in a copper concentrate by conventional flotation process. The contamination of arsenic in the concentrate would cause problems in the consequent metallurgical extraction process. Thus, the arsenic removal from the concentrate is required. The conventional depressants, such as lime, cyanide, sulfide and permanganate, are no effective to separate those two minerals. This investigation has found two ways to separate enargite from chalcopyrite by selective flotation. One method is to depress chalcopyrite and float enargite with 20 mg/1 potassium amyl xanthate by adjusting the pulp potential at -250 mV while maintaining the pH at 9.0. Other method is to depress enargite and float chalcopyrite by a 250 mg/1 magnesium-ammonium mixture (MAA) under same pH and xanthate concentration. The infrared spectra of the mineral surface indicated that the ammonia complexes has formed on enargite surface and caused its hydrophilic while there is no such complex formed on chalcopyrite surface. A copper concentrate contains 1.73% As can be reduced to 0.14% As. The arsenic reduction was 92%.
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