Leaching process and mechanism of high magnesium low-grade nickel sulfide ore

The leaching process and mechanism of high magnesium low grade nickel sulphide ore were studied by ammonium sulfate roasting-water leaching-bacterial leaching technology,and the mineral transformation mechanism was also researched.The results show that the leaching rates of Ni,Cu,Mg and Fe are 93.24%,92.07%,62.67%and63.39%,respectively.The roasting and bacterial leaching processes are selective for minerals.The serpentine with high iron content is easy to react with ammonium sulfate in the roasting process.Iron element in serpentine generates anhydrous ammonium alum.Magnesium element in serpentine generates(NH_4)_2Mg_2(SO_4)_3 and forsterite,which dissolve into the solution in the process of water and bacterial leaching with olivine in the ore.The serpentine with low iron content basically does not change in the process,only a small amount of iron element is leached in the bacterial leaching process,while magnesium is not easy to be leached and finally left in bacterial leaching slag.Copper and nickel sulfide minerals react with ammonium sulfate to form sulfate,which dissolve in solution in the water and bacterial leaching process.Pyrrhotite generates hematite in the roasting process,little part of which is leached in the water and bacterial leaching process.The remaining part is left in the bacterial leaching residue,resulting in the loss of iron oxide.