Abstract
Stibnite (Sb(2)S(3)) is an important but difficult to biologically leach mineral, so it is important to find a potential scheme for improving the bioleaching rate of Sb(2)S(3). In this study, by combining experiments and first-principles density functional theory (DFT) calculations, the impact and related mechanisms of pyrite (FeS(2)) on stibnite (Sb(2)S(3)) bioleaching were studied for the first time. The bioleaching results revealed that FeS(2) obviously improved the Sb(2)S(3) bioleaching rate, and in the 0.5FeS(2):0.5CuFeS(2) system, the bioleaching rate of Sb(2)S(3) increased from 2.23 to 24.6%, which was the best mass mixing ratio. The XPS and XANES results revealed that during the bioleaching process, Sb(2)S(3) was transformed to Sb(2)O(3) and Sb(2)O(5). The electrochemical results revealed that after FeS(2) was mixed, a FeS(2)-Sb(2)S(3) galvanic cell formed, which promoted the electron transfer efficiency and redox reaction of Sb(2)S(3). The DFT results show that between the Sb(2)S(3) (0 1 0) and FeS(2) (1 0 0) surfaces, S-Fe, S-S, S-Sb, and Sb-Fe bonds are formed, and the direction of electron transfer is from Sb(2)S(3) to FeS(2); the work functions for Sb(2)S(3) after addition of FeS(2) decrease, implying that faster electron transfer occurs; Fe(III)-6H(2)O derived from FeS(2) adsorbs on the surface more easily than does glucose, which is the major component of the extracellular polymeric substances in bacteria, indicating that during the bioleaching process, Fe(III)-6H(2)O plays an important role; after mixing, both Fe(III)-6H(2)O and glucose adsorb on the Sb(2)S(3) (0 1 0) surface more easily, with stronger bonds and larger adsorption energies, which are in good agreement with the experimental results.