Electrochemical Study of the Chalcopyrite Biooxidation in Presence and Absence of Sulfuro- and Ironoxidizing Microorganisms
Authors: Lopez-Cazares Maria Irene , Garcia-Meza Jessica Viridiana , Larios Duran E. R. , Cruz Gaona R. 
Published: February 2020

The chalcopyrite (CuFeS2) is one of the main mineral sulfides (MS) used for the leaching of Cu; during its oxidation, generates insoluble sulfur species or secondary phases of sulfur (by example S°, Sn
2- and intermediate products ) that may form a passivation layer on the mineral surface, which decreases the dissolution kinetics.[
1-7
]

Iron and sulfur oxidizing microorganisms (IOM and SOM, respectively) may prevent such effect throughout the biooxidation of reduced sulfur species [8, 9]. It has been found that the electrochemical formation of S° and Sn
2- phases on mineral surface facilitates initial attachment of microorganisms; in addition, it has been reported that the electrochemical activity degree of sulfur species, directly influences on the physicochemical and biological characteristics of the biofilm developed during the biooxidation[10,11]. This research assessed the biooxidation process of CuFeS2, correlating the initial presence of S° and/or Sn
2- with changes in the hydrophobic domains (HD) of extracellular polymeric substances (EPS) of the formed biofilm. For this, the behavior of two different microbial cultures were compared, one SOM culture (containing only Acidithiobacillus thiooxidans) and a mixed SOM-IOM culture (Acidithiobacillus thiooxidans + Leptospirillum sp.). Massive Electrodes of chalcopyrite were electrochemically oxidized to form the sulfur secondary species (S° and Sn
2-) previous to the mineral-bacteria contact. The evolution of secondary [RL1] species during biooxidation process in each culture was followed by Raman Spectroscopy. The spacetime changes of the biofilm and interfacial electrochemical study were evaluate by Electrochemical Impedance Spectroscopy (EIS and Scanning Electron Microscopy (SEM). The previous results showed that there are important differences in the biooxidation process, depending on the sulfur species produced initially, the type of culture used, and the incubation time; in addition, it was found that both types of cultures efficiently remove S° and Sn
2- by dissimilar mechanisms that seem to be associated with the IOM role in the bioleaching process.

Key Words chalcopyrite, passivation layer, IOM, SOM, biooxidation.
1.- Habashi F. (1978). Chalcopyrite. Its chemistry and metallurgy. McGraw-Hill.
2.- Dutrizac JE (1989) Elemental sulphur formation during the ferric sulphate leaching of
chalcopyrite. Can Metall Q 28:337–44.
3.-Dutrizac JE (1992)The leaching of sulphide minerals in chloride media. Hydrometallurgy 29:1–45.
3.- Antonijevic MM, Jankovic Z, Dimitrijevic M (1994) Investigation of the kinetics of
chalcopyriteoxidation by potassium dichromate. Hydrometallurgy 35:187–201.
4.- Harmer SL (2002) Surface layer control for improved copper recovery for chalcopyrite
leaching. University of South Australia.

5. Xian YJ, Wen SM, Deng JS, Liu J, Nie Q (2012) Leaching chalcopyrite with sodium chlorate in
hydrochloric acid solution. Can Metall Q 51:133–40.
6.- Parker AJ, Paul RL, Power GP (1981) Electrochemistry of the oxidative leaching of copper
from chalcopyrite. J Electroanal Chem Interfacial Electrochem 118:305–16.
7.- Hackl RP., Dreisinger DB, Peter SE, King JA (1995). Passivation of chalcopyrite during
oxidative leaching in sulfate media. Hydrometallurgy 39: 25–48.
8.- Pan HD, Yang HY, Tong LL, Zhong CB, Zhao YS (2012) Control method of chalcopyrite
passivation in bioleaching. Trans. Nonferrous Met Soc China 22:2255−2260.
9.- Anjum F, Shahid M, Akcil, A (2012) Biohydrometallurgy techniques of low grade ores: A
review on black shale. Hydrometallurgy (1-12):117-118 doi:10.1016/j.hydromet.2012.01.007.
10.-González D, Lara R, Valdez-Pérez D, Alvarado K, Navarro-Contreras H, Cruz R, García-Meza
JV (2012) Evolution of biofilms during the colonization process of pyrite by Acidithiobacillus

thiooxidans. Appl Microbiol Biotechnol 93:763–775.
11.- Lara R, García-Meza V, González I, Cruz R (2012) Influence of the surface speciation on
biofilm attachment to chalcopyrite by Acidithibacillus thiooxidans. Appl Microbial Biotechnol.
doi 10.1007/s00253-0112-4099-8.