The influence of solution Eh on the rate of ferrous iron oxidation by Acidithiobacillus ferrooxidans is characterized. The experimental approach was based on the use of a two-chamber bioelectrochemical cell, which can determine the ferrous iron oxidation rate at controlled potential. Results enabled the formulation of a novel kinetic model, which incorporates the effect of solution Eh in an explicit form but still integrates the effect of ferrous iron concentration and ferric inhibition. The results showed that at Eh values below 650 mV (standard hydrogen electrode, SHE) the bacterial oxidative activity is mainly dependent on ferrous iron concentration. At Eh values between 650 and 820 mV (SHE) the oxidation rate is mainly controlled by ferric inhibition. Over 820 mV (SHE) the bacterial oxidative activity is strongly inhibited by the Eh increase, being completely inhibited at Eh = 840 mV (SHE).
A modified
Pitzer model at very high ionic strengths is developed
in this work for quaternary systems consisting of three uniunivalent
salts with a common ion and water. The proposed model is a combination
of the extended Debye–Hückel model and the Pitzer model.
This model satisfactorily describes the solubilities for the ternary
LiCl+NaCl+H2O, LiCl+KCl+H2O, and NaCl+KCl+H2O systems at 25 °C, and it predicts reasonably acceptably
the solubilities of the quaternary system LiCl+NaCl+KCl+H2O at 25 °C, when comparing with the experimental results of
the literature and those obtained by the original Pitzer model with
modified parameters high concentrations. In addition, the proposed
model was applied to the process of refining muriate of potash on
an industrial plant of a Chilean mining and chemical company.
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