EFFECT OF BACTERIAL ADAPTATION ON KINETICS AND MECHANISMS OF BIOLEACHING FERROUS SULFIDES

Thiobacillus ferrooxidans bacteria were used in this work to study the effect of bacterial adaptation on bioleaching of three iron-bearing s ulfide minerals, namely, pyrite (FeS2), chalcopyrite (CuFeS2), and ars enopyrite (FeAsS). It was found that bacterial adaptation prior to bio leaching, enhanced the degree of sulfide leaching 2-4 fold over non-ad apted bacteria. Also the bacterial activity was enhanced by 2-4.8 fold . The pH of leaching solution was decreased by the increase in both ad aptation period and bioleaching time. A mechanistic model for bioleach ing of sulfides with T. ferrooxidans is described. The model explains the role of bacteria in direct and indirect biochemical leaching react ions. It also reconciles such observed behaviors and phenomena as lag time, adaptation, pH increase during lag time, and electrochemistry of bioleaching. The model shows how direct and indirect biochemical inte ractions are involved in bioleaching of ferrous sulfides.