Aqueous solubility of Cr(VI) compounds in ferrochrome bag filter dust and the implications thereof

Authors

  • SP du Preez Chemical Resource Beneficiation, North-West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom 2520, South Africa
  • JP Beukes Chemical Resource Beneficiation, North-West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom 2520, South Africa
  • WPJ van Dalen Chemical Resource Beneficiation, North-West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom 2520, South Africa
  • PG van Zyl Chemical Resource Beneficiation, North-West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom 2520, South Africa
  • D Paktunc CanmetMINING, Natural Resources Canada, 555 Booth St., Ottawa, ON, K1A0G1, Canada
  • MM Loock-Hattingh Chemical Resource Beneficiation, North-West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom 2520, South Africa

DOI:

https://doi.org/10.4314/wsa.v43i2.13

Keywords:

hexavalent chromium, Cr(VI), ferrochromium, ferrochrome, bag filter dust, smelter waste

Abstract

The production of ferrochrome (FeCr) is a reducing process. However, it is impossible to completely exclude oxygen from all of the high-temperature production process steps, which may lead to unintentional formation of small amounts of Cr(VI). The majority of Cr(VI) is associated with particles found in the off-gas of the high-temperature processes, which are cleaned by means of venturi scrubbers or bag filter dust (BFD) systems. BFD contains the highest concentration of Cr(VI) of all FeCr wastes. In this study, the solubility of Cr(VI) present in BFD was determined by evaluating four different BFD samples. The results indicate that the currently applied Cr(VI) treatment strategies of the FeCr producer (with process water pH ≤ 9) only effectively extract and treat the water-soluble Cr(VI) compounds, which merely represented approximately 31% of the total Cr(VI) present in the BFD samples evaluated. Extended extraction time, within the afore-mentioned pH range, proved futile in extracting sparingly-soluble and water-insoluble Cr(VI) species, which represented approximately 34% and 35% of the total Cr(VI), respectively. Due to the deficiencies of the current treatment strategies, it is highly likely that sparingly water-soluble Cr(VI) compounds will leach from waste storage facilities (e.g. slimes dams) over time. Therefore, it is critical that improved Cr(VI) treatment strategies be formulated, which should be an important future perspective for FeCr producers and researchers alike.

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Published

2017-04-20

Issue

Vol. 43 No. 2 April (2017): Water SA

Section

Research paper

License

Copyright (c) 2017 SP du Preez, JP Beukes, WPJ van Dalen, PG van Zyl, D Paktunc, MM Loock-Hattingh

Creative Commons License

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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The content of this journal is licensed under a Creative Commons Attribution Licence.  Users are permitted to read, download, copy, distribute, print, search or link to the full texts of the articles in this journal under the terms of this Licence, without asking prior permission from the publisher or the author, provided the source is attributed. Copyright is retained by the authors.

How to Cite

SP du Preez (2017) “Aqueous solubility of Cr(VI) compounds in ferrochrome bag filter dust and the implications thereof”, Water SA, 43(2 April). doi:10.4314/wsa.v43i2.13.