Batch bioleaching experimental set up.

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... total number of eleven pH controlled batch experiments were conducted for bioleaching of a pyrite concentrate using a mixed microbial culture (Figure 9). Ten different oxidic by-products and slaked lime as reference material were used to control the pH in the bioreactor during the experiment. ...

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... the maintenance coefficient was much higher when no chloride was added ( Figure 9 and Table IV Modeling studies suggested a probability of inhibition of specific Fe 2+ utilization rate due to chloride at lower growth rates, whereas a higher dilution rates specific ferrous utilization is stimulated ( Figure 8, Paper VII). Similarly the effect of chloride would also be more pronounced at lower substrate level as the growth rate will decrease with the increment of the chloride concentration at a given residual substrate concentration ( Figure 3, Paper VII). ...

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... phenomenon of growth uncoupled Fe 2þ oxidation has been previously reported in At. ferrooxidans batch growth ( Breed et al., 1999;Kelly and Jones, 1978). In Figure 9 the biomass yield was plotted versus the logarithm of the Fe 3þ /Fe 2þ ratio. The figure shows that for different total iron concentrations the biomass yields were at the same level until the dilution neared the critical rate. ...

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... per the Pirt theory, the biomass yield increased with increasing dilution rate (Figure 7), as growth uncoupled Fe 2+ oxidation cannot be ignored (Equations 3 and 7), and was in agreement with previous studies (Sundkvist et al., 2008, Becker andMärkl, 2000). The plots of specific Fe 2+ oxidation rate versus dilution rate (Equation 8; Figure 8) and specific Fe 2+ oxidation rate versus the log of the Fe 3+ to Fe 2+ ratio (Equations 8 and 9; Figure 9) showed that the specific Fe 2+ oxidation rate was relatively constant and insensitive to both dilution rate and the Fe 3+ to Fe 2+ ratio. When working under chemostat conditions, the true maintenance coefficient was the intercept in figure 8 and was valid in the entire range where the chemostat conditions were fulfilled. ...

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... the maintenance coefficient was much higher when no chloride was added ( Figure 8 and Table V). The contribution from maintenance activities to the calculated maximum specific Fe 2+ utilization rate in the experiments with 0 g L -1 , 2 g L -1 , and 3 g L -1 chloride was 93%, 24%, and 23%, respectively ( Figure 9). The calculated maintenance coefficient based on the Pirt theory (Table V) showed that the introduction of 2-3 g L -1 chloride into the growth medium in the feed to the bioreactor decreased the maintenance coefficient by 70% when compared to the experiment without chloride. ...