Leaching characteristics and recovery method of nickel from low-grade nickel-pyrrhotite

In order to leach and recover nickel from high-silicon low-grade nickel-pyrrhotite, some factors were determined, including roasting pretreatment control, sulfuric acid use ratio, inoculated ThiobaciUus. ferrooxidans or uninoculated. Then sulfate-reducing bacteria (SRB) were immobilized by intact rice chaff in an up-flow anaerobic bed reactor. The leach liquor was treated by the reactor. It is shown that roasting results in the sintering of minerals and makes nickel wrapped, which is not conducive to the leaching of nickel. Thiobacillus ferrooxidans form a biofilm on the mineral surface, which plays a key role in the dissolution of minerals, and oxidizes Fe²⁺ to be Fe³⁺, which does a further dissolution of minerals. The leaching rate of nickel reaches to 92.16% and the concentration of Ni²⁺ is 973.22 mg·L^-1. When the influent passes through the reactor at a speed of 2 200 to 3 600 mL·L^-1·d^-1, the recovery of Ni²⁺, which adsorbs on the rice chaff in the form of NiS, is above 98%, and 98% of magnesium exists in the solution in the form of ions. The NiO content increases from 1.69% of the crude ore to 11.84% of the rice chaff.