Differences of Bioleaching of Pyrites from Different Geo-Genetic Deposits by <i>Leptospirillum ferriphilum</i>

Abstract

In this paper, the bioleaching behavior of three pyrites from different geological origins (high-temperature hydrothermal, low-temperature hydrothermal and coal sedimentary) by L. ferriphilum was studied. The internal structure of three pyrite samples were investigated using optical microscope. The results show that the physical characteristics and internal structures of pyrites from different geological origins are different, and this causes the divergences of their bioleaching behavior. High-temperature hydrothermal pyrite (n-type semiconductor tested) is not almost dissolved and the leaching rate is only 0.58%, while the leaching rate of low-temperature hydrothermal pyrite and coal sedimentary pyrite (both of p-type semiconductor tested) are 15.25% and 27.50% respectively. The Leica optical microscope test of p-type semiconductor pyrites indicates that coarse particle of low-temperature hydrothermal pyrite is crystallized well and sedimentary pyrite consists of fine-grained crystal with poor crystallinity. This was suggested to cause the divergences of the bioleaching rate of both p-type semiconductor pyrites. In view of mineralogy, the semiconductive type of pyrite is the primary factor affecting its bioleaching. Furthermore, the different internal structure of pyrites will further have an influence on bioleaching for the same semiconductive type.Key words: pyrite; bioleaching; L. ferriphilum; geo-genetic