Separation of Fe(III) and Cr(III) from tannery sludge bioleachate using organophosphorus acid extractants

Abstract

The presented work focused on extraction and separation of Fe(III) and Cr(III) from tannery sludge bioleachate using di(2-ethylhexyl) phosphoric acid (D2EHPA) as extraction agent; the effect of adding tributyl phosphate (TBP) was also investigated. Leachate containing 3.4 g/L Cr(III) and 2.0 g/L Fe(III) was selected as feed solution. The results indicated that Fe(III) can be completely removed from the leachate under conditions of 5 vol% D2EHPA in kerosene and equilibrium pH 2.2. In addition, the removal efficiency of Fe(III) could be enhanced while the extraction rate of Cr(III) exhibited a decline on adding TBP at above 10 vol%. HCl solution was then used to strip Fe(III) and Cr(III) from the loaded organic. It can be concluded from the stripping experiments that 97 % of the Fe(III) could be recovered using 9 mol/L HCl solution as stripping agent for 20 min. However, the recovery efficiency decreased when adding TBP to the organic, which can be attributed to the isolation of the extraction actions because TBP surrounding effect to D2EHPA.