In contemporary era, the research and development of bioleaching have been always focused on achieving effective recovery of valuable metals by improving the efficiency of bioleaching microorganisms, which may be determined mainly by sulfur oxidation activities of sulfur-oxidizing microbes and the speciation of intermediate compounds formed during bioleaching processes. However, the correlation between sulfur oxidation activities of sulfur-oxidizing microbes and the speciation of intermediate compounds has remained elusive. A team from Key Lab of Biometallurgy of Ministry of Education of China,School of Minerals Processing and Bioengineering,Central South University has gained insight into sulfur oxidation activities of thermophiles and sulfur speciation in bioleaching of chalcopyrite. Their research has been published on November 26th, 2010 in Bioresource Technology.

The team identified the mixed thermophiles, with contributing significantly to the raising of leaching rate and accelerating the formation of leaching products, had a higher sulfur oxidation activity than the pure culture, and jarosite was the main passivation component hindering the dissolution of chalcopyrite, and elemental sulfur seemed to have no influence on the dissolution of chalcopyrite. In addition, The team supported that covellite might be converted from chalcocite during the leaching experiments, and the elemental sulfur may partially be the derivation of covellite and chalcocite.

Sulfur K-edge spectra of chalcopyrite leaching with mixed thermophilic archaea using synchrotron radiation at BSRF：Besides the features of chalcopyrite in Fig. a, the spectra presented a new peak at 2.4804KeV that could be assigned to sulfate ions. And the chalcopyrite peak kept declining when the sulfate ions peak kept increasing. The fitted XANES spectra of the surface residues at day 6 suggests that the surface residue mainly contained chalcopyrite, jarosite, covellite and chalcocite with the fraction of 47.5%, 38.2%, 13.5% and 0.7%, respectively (Fig.b).

The research provides the scientific community clues to promote the understanding of the synergistic effect of the thermophiles as well as bioleaching mechanism by the mixed thermophilic culture, and to devise an efficient way to enhance the yield of chalcopyrite bioleaching. In their works, Sulfur K-edge X-ray absorption near-edge structure (XANES) of BSRF was proved to be a particularly useful technique to investigate the variations in the sulfur species, ranging from sulfide, sulfite, and sulfate; in addition, it is able to differentiate various sulfides based on the shape and the position of the XANES features, thus providing useful site-specific information for sulfur species of catalysis.

Published article：

Wei Zhua, Jin-lan Xiaa,*, Yi Yanga, Zhen-yuan Niea, Lei Zhengb, Chen-yan Mab, Rui-yong Zhanga, An-an Penga, Lu Tanga, Guan-zhou Qiua Sulfur oxidation activities of pure and mixed thermophiles and sulfur speciation in bioleaching of chalcopyrite. Bioresource Technology, 2011, 102: 3877–3882.

a. Key Lab of Biometallurgy of Ministry of Education of ChinaSchool of Minerals Processing and Bioengineering Central South University Changsha 410083, China

b. Beijing Synchrotron Radiation Facility Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049, China

*Correspondence: jlxia@mail.csu.edu.cn；Tel. +86 731 88836944