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Impact of media coating on simultaneous manganese removal and remineralization of soft water via calcite contactor

Hamed Pourahmad, Maryam Haddad, Dominique Claveau-Mallet and Benoit Barbeau

Article (2019)

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Abstract

The aim of this study was to investigate the negative impact of a newly-formed manganese (Mn)-layer on calcite dissolution in the long-term operation of a calcite contactor. Simultaneous removal of Mn and remineralization of soft water in an up-flow calcite contactor was conducted and led to a progressive loading of Mn into the calcite matrix. The calcite contactor demonstrated high Mn removal; however, the hardness release decreased from 32 to 20 mg CaCO₃ L-1 after 600 h of operation on a high Mn concentration (5 mg L-1) feed. For an elevated Mn concentration (i.e. 5 mg Mn L-1) in the feed water, the coated layer was mainly composed of Mn which inhibits the mass transfer from the calcite core to the liquid phase. The superficial layer was identified as 5.2% Mn oxides (MnOx) by X-ray photoelectron spectroscopy (XPS). Therefore, it is postulated that Mn removal starts with an ion exchange sorption reaction between soluble Mn2+ from aqueous phase and Ca2+ from the CaCO₃ matrix which is followed by a slow recrystallization of MnCO₃ into MnO₂. On the other hand, when the Mn content in the feed water was lower (i.e. 0.5 mg Mn L-1), a considerably lower amount of MnOx was detected on the coated media. For all the examined conditions, the formation of this coating improved Mn removal due to the autocatalytic nature of the adsorption/oxidation of dissolved manganese by MnOx. A mechanistic model based on calcite dissolution and the progressive formation of a MnO₂ layer was implemented in PHREEQC software to predict the reduction in hardness release expected in long-term operation. The model was calibrated with experimental data and resulted in realistic breakthrough curves. In order to accurately predict the pH of the effluent stream, a slow-rate recrystallization of MnCO₃ into MnO₂ was implemented (compared to the fast precipitation of MnO₂ or the absence of MnO₂ formation).

Uncontrolled Keywords

Calcite Contactor, Manganese Removal, Soft water Remineralization, Groundwater supplies, sorption, PHREEQC

Subjects: 1400 Mining and mineral processing > 1400 Mining and mineral processing
1500 Environmental engineering > 1501 Water quality, pollution
1500 Environmental engineering > 1502 Waste water treatment
Department: Department of Civil, Geological and Mining Engineering
Funders: CRSNG/NSERC
Grant number: 312139
PolyPublie URL: https://publications.polymtl.ca/5305/
Journal Title: Water Research (vol. 161)
Publisher: Elsevier
DOI: 10.1016/j.watres.2019.06.037
Official URL: https://doi.org/10.1016/j.watres.2019.06.037
Date Deposited: 16 Jul 2020 16:44
Last Modified: 10 Apr 2024 20:53
Cite in APA 7: Pourahmad, H., Haddad, M., Claveau-Mallet, D., & Barbeau, B. (2019). Impact of media coating on simultaneous manganese removal and remineralization of soft water via calcite contactor. Water Research, 161, 601-609. https://doi.org/10.1016/j.watres.2019.06.037

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