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Membranes (Basel). 2019 Oct 24;9(11). pii: E137. doi: 10.3390/membranes9110137.

Electrowinning of Iron from Spent Leaching Solutions Using Novel Anion Exchange Membranes.

Author information

1
Focus Area: Chemical Resource Beneficiation, Faculty of Natural Sciences, North-West University, Potchefstroom 2520, South Africa. 24250643@nwu.ac.za.
2
Focus Area: Chemical Resource Beneficiation, Faculty of Natural Sciences, North-West University, Potchefstroom 2520, South Africa. 22114688@nwu.ac.za.
3
Institute of Chemical Process Engineering, University of Stuttgart, D-70199 Stuttgart, Germany. hyeongrae.cho@icvt.uni-stuttgart.de.
4
Focus Area: Chemical Resource Beneficiation, Faculty of Natural Sciences, North-West University, Potchefstroom 2520, South Africa. J.Kerres@gmx.de.
5
Institute of Chemical Process Engineering, University of Stuttgart, D-70199 Stuttgart, Germany. J.Kerres@gmx.de.
6
Bruinsma Solutions, 10 Mclagen Str., Potchefstroom 2531, South Africa. dolf.bruinsma@gmail.com.
7
Focus Area: Chemical Resource Beneficiation, Faculty of Natural Sciences, North-West University, Potchefstroom 2520, South Africa. Henning.Krieg@nwu.ac.za.

Abstract

In the Pyror process, electrowinning (EW) is used to recover acid and iron from spent leaching solutions (SLS), where a porous Terylene membrane acts as a separator between the cathode and anode. In this study, a novel anion exchange membrane (AEM)-based EW process is benchmarked against a process without and with a porous Terylene membrane by comparing the current efficiency, specific energy consumption (SEC), and sulfuric acid generation using an in-house constructed EW flow cell. Using an FAP-PK-130 commercial AEM, it was shown that the AEM-based process was more efficient than the traditional processes. Subsequently, 11 novel polybenzimidazole (PBI)-based blend AEMs were compared with the commercial AEM. The best performing novel AEM (BM-5), yielded a current efficiency of 95% at an SEC of 3.53 kWh/kg Fe, which is a 10% increase in current efficiency and a 0.72 kWh/kg Fe decrease in SEC when compared to the existing Pyror process. Furthermore, the use of the novel BM-5 AEM resulted in a 0.22 kWh/kg Fe lower SEC than that obtained with the commercial AEM, also showing mechanical stability in the EW flow cell. Finally, it was shown that below 5 g/L Fe, side reactions at the cathode resulted in a decrease in process efficiency, while 40 g/L yielded the highest efficiency and lowest SECs.

KEYWORDS:

acid regeneration; anion exchange membranes; electrowinning; iron sulphate disposal; waste treatment

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