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Kinetic study of sulfide leaching by galvanic interaction between chalcopyrite, pyrite, and sphalerite in the presence of T. ferrooxidans (30°C) and a thermophilic microorganism (55°C)
Author(s) -
Mehta A. P.,
Murr L. E.
Publication year - 1982
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.260240413
Subject(s) - sphalerite , chalcopyrite , dissolution , leaching (pedology) , galvanic cell , sulfide , chemistry , bioleaching , zinc , metal , sulfide minerals , metallurgy , pyrite , nuclear chemistry , copper , inorganic chemistry , materials science , mineralogy , geology , soil science , soil water
A systematic, kinetic study and comparison of the leaching of mixed metal sulfides by galvanic conversion and in the presence of bacteria has been carried out for the first time using both powder (−100 to −400 mesh) and larger (bulk) specimen systems. The rates of dissolution of copper from chalcopyrite and zinc from sphalerite as single, electrically isolated (separate) systems were compared with electrically contacting (galvanically coupled) systems involving CuFeS 2 /FeS 2 and ZnS/FeS 2 , with and without bacteria and at temperatures of 30 and 55°C. The dissolution of Cu was observed to increase by a factor of 4.6 when the galvanic leaching of CuFeS 2 /FeS 2 was compared to CuFeS 2 leaching at 30°C. When bacteria were present, Cu dissolution increased by an additional factor of 2.1 in the CuFeS 2 /FeS 2 system. At 55°C, the corresponding ratios for Cu were 4.3 and 2.7, respectively. The galvanic leaching of Zn in the ZnS/FeS 2 system compared to ZnS leaching increased by a factor of 2 at 30°C; in the presence of bacteria the dissolution of Zn from the ZnS/FeS 2 system increased by an additional factor of 1.3 at the same temperature. By comparison, the ratio of Cu dissolution from CuFeS 2 in acid‐bacterial medium and sterile controls (without bacteria) was 5.5. The corresponding ratio for Zn from ZnS was 2.2 at both 30 and 55°C. The order of reaction was found to be essentially first order for the leaching of powder systems at both 30 and 55°C (with T. Ferrooxidans and thermophilic microorganisms, respectively). The corresponding reaction rate constants were observed to be 12.6 and 22.9 for T. ferrooxidans and the thermophilic microorganisms, respectively. Activation energies for the various systems were also determined.