Metal removal from spent pickling solutions of high zinc(II) concentration
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Poznan University of Technology
Publication date: 2004-01-01
Corresponding author
Jan Szymanowski   

Institute of Chemical Engineering and Technology, Poznan University of Technology, pl. M. Sklodowskiej-Curie 2, 60-965 Poznan, Poland
Physicochem. Probl. Miner. Process. 2004;38(1):121-129
The extraction of zinc(II), iron(III) and iron(II) with TBP from hydrochloric acid solutions containing high zinc(II) concentration is studied. Two technological approaches for the separation are considered. Firstly, the selective extraction of iron(III) (iron(II) is oxidized to iron(III)) over zinc(II) with TBP deficiency. Secondly, iron(III) reduction to iron(II) followed by zinc(II) selective extraction with an excess of TBP. The total removal of iron(III) needs several successive extractions with fresh TBP portions. Such a process is not technologically reasonable. Stripping both of zinc(II) and iron(III) can be effectively accomplished with water but is not selective. Prior stripping, the organic phase can be washed with small amounts of water. Scrubbing of TBP solutions containing iron(III) contaminated with zinc(II) gives always a mixture of zinc(II) and iron(III) which must be recycled to the extraction step in continuous process. Scrubbing of TBP solutions containing zinc(II) and iron(II) enables the removal of iron(II) with some amounts of zinc(II). Again, the solution must be recycled. Scrubbing is more advantageous than multistage extraction with small volume of TBP. The following technological concept is proposed: reduction of iron(III) to iron(II), extraction of zinc(II) with 5-10 volume excess of TBP, washing of TBP phase contaminated with iron(II) with small volumes of water and recycling of the scrubbings and stripping of zinc with water.
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