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Removal of phosphorus, fluoride and metals from a gypsum mining leachate using steel slag filters

Dominique Claveau-Mallet, Scott Wallace, Yves Comeau

Article (2013)

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Abstract

The objective of this work was to evaluate the capacity of steel slag filters to treat a gypsum mining leachate containing 11-107 mg P/L ortho-phosphates, 9-37 mg/L fluoride, 0.24-0.83 mg/L manganese, 0.20-3.3 zinc and 1.7-8.2 mg/L aluminum. Column tests fed with reconstituted leachates were conducted for 145 to 222 days and sampled twice a week. Two types of electric arc furnace (EAF) slags and three filter sequences were tested. The voids hydraulic retention time (HRTv) of columns ranged between 4.3 and 19.2 h. Precipitates of contaminants present in columns were sampled and analyzed with X-ray diffraction at the end of tests. The best removal efficiencies over a period of 179 days were obtained with sequential filters that were composed of Fort Smith EAF slag operated at a total HRTv of 34 h which removed 99.9% of phosphorus, 85.3% of fluoride, 98.0% of manganese and 99.3% of zinc. Mean concentration at this system's effluent was 0.04 mg P/L ortho-phosphates, 4 mg/L fluoride, 0.02 mg/L manganese, 0.02 zinc and 0.5 mg/L aluminum. Thus, slag filters are promising passive and economical systems for the remediation of mining effluents. Phosphorus was removed by the formation of apatite (hydroxyapatite, Ca5(PO4)3OH or fluoroapatite, Ca5(PO4)3F) as confirmed by visual and X-ray diffraction analyses. The growth rate of apatite was favored by a high phosphorus concentration. Calcite crystals were present in columns and appeared to be competing for calcium and volume needed for apatite formation. The calcite crystal growth rate was higher than that of apatite crystals. Fluoride was removed by precipitation of fluoroapatite and its removal was favored by a high ratio of phosphorus to fluoride in the wastewater.

Uncontrolled Keywords

Wastewater treatment, slag filters, mining remediation, hydroxyapatite growth

Subjects: 1000 Civil engineering > 1000 Civil engineering
1000 Civil engineering > 1006 Hydrologic engineering
1400 Mining and mineral processing > 1400 Mining and mineral processing
Department: Department of Civil, Geological and Mining Engineering
Funders: CRSNG/NSERC, Missouri Remediation Trust, Fonds de recherche du Québec Nature et technologies
PolyPublie URL: https://publications.polymtl.ca/9141/
Journal Title: Water Research (vol. 47, no. 4)
Publisher: Elsevier
DOI: 10.1016/j.watres.2012.11.048
Official URL: https://doi.org/10.1016/j.watres.2012.11.048
Date Deposited: 08 Sep 2021 15:38
Last Modified: 16 Nov 2022 04:15
Cite in APA 7: Claveau-Mallet, D., Wallace, S., & Comeau, Y. (2013). Removal of phosphorus, fluoride and metals from a gypsum mining leachate using steel slag filters. Water Research, 47(4), 1512-1520. https://doi.org/10.1016/j.watres.2012.11.048

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