Ultrasonic-assisted Oxidation Leaching of Nickel Sulfide Concentrate

The feasibility of oxidation leaching process of nickel from nickel sulfide ore and the form of different components in the lixivium has been studied at first. The method of leaching nickel sulfide concentration directly by oxidants with existence of ultrasonic has been advanced. The process of leaching nickel from nickel sulfide concentration by using the system of persulfate and silver has been determined. The~influence~of~different~factors~on the leaching rates of nickel, such as with and without ultrasonic, the concentration of Na2S2O8, liquid-solid ratio and the concentration of AgNO3 have been explored. The results show that: (1) in the oxidative leaching system, nickel can be leached completely as Ni2+ or NiSO4(aq.)from nickel sulfide concentration in theory; (2) the nicopyrite can not exist steadily in the persulfate acid leaching system, but Ni2+can. Meanwhile, sulfur may be existed steadily in the leaching process; (3) nicopyrite with much lower electrostatic potential may be leached earlier than chalcopyrite and sideropyrite; and (4) the overall reaction rate of the leaching process can be enhanced with ultrasonic radiation, but it does not change the mechanism of leaching. The more oxidant concentration or higher liquid-solid ratio is, the higher leaching percentage of nickel. The leaching percentage of nickel can be increased significantly by adding a small amount of AgNO3 during the leaching processes. Under the same conditions, the higher concentration of AgNO3 is, the higher leaching yields of nickel will be obtained.