Microbial ferrous iron oxidation in acidic solution

Abstract

Microbial ferrous iron oxidation in a dilute sul furic acid medium at low pH was investigated. Part of a study of acidic leach solution chemistry and chemical speciation the effects on metal-sulfide oxidation these studies were performed to un derstand the processes that accompany microbial extraction of metals from ores, and to learn of similar reactions that may occur naturally. Results showed that pH values of 1.0 to 2.4 affected microbial oxidation rate very little. Microbial yield coefficients were experimentally determined and agreed with predictions from thermodynamic considerations. The maximum specific growth rate coefficient and the half-velocity coefficient represented ex perimental data. Oxidation occurred rapidly and the minimum sludge age value was about 0.4 day. Attached film processes may be the most appropriate systems for achieving microbial oxidation of ferrous iron. J. Water Pollut. Control Fed., 60, 518 (1988). rooxidans). Microbial leaching of mineral ores involves metals dis solution caused by biological and chemical reactions. This paper presents the study results of one aspect of these microbial leaching reactions: the chemical and biological factors that affect microbial ferrous iron oxidation by Thiobacillus ferrooxidans at pH values between 1.0 and 2.4. This study was part of an investigation of certain chemical and biological processes associated with the dis solution of chalcocite (Cu2S), a metal sulfide ore. The pur pose was to obtain information that could be used to im prove understanding of microbiological ore leaching op erations, as well as to provide knowledge on related chemical and biological reactions that may occur naturally in the environment as in the case of mine acid drainage. This paper provides the biological kinetics of ferrous iron oxidation in a dilute sulfuric acid medium with additional information to explain chemical speciation during ferrous iron oxidation. Batch and continuous flow-through re actors were used to evaluate Thiobacillus ferrooxidans oxidation of Fe(II) in an acidic sulfate leach medium typ ical of that which may be formed from the reaction of ferric iron for dissolution of metal sulfide and uranium