The effects of TBP concentration on the extraction yields of
Fe(III) and sulfuric acid were investigated. The TBP concentration
varied within 3–15 vol.% at the phase ratio of 1:1, and TOA concentration
was 35 vol.%. The experimental results are presented
in Fig. 3. The results indicate that the extraction yields of iron(III)
and sulfuric acid increase slightly from 85.4% and 97.6% to 90.1%
and 98.4% respectively with the increase of TBP concentration. This
phenomenon shows that the improvement of extraction yields is
obtained by the increase of the complex solubility with the addition
of TBP. However, with the increases of TBP continually, the
extraction rates of Fe(III) and sulfuric acid remain constant.