Mechanisms of arsenate removal and membrane fouling in ferric based coprecipitation–low pressure membrane filtration systems

•Both MF and UF membranes showed similar arsenic and iron removal efficiency.•No differences were observed for arsenic removal between the filtration cycles.•Arsenic coprecipitation with iron was dependent on ionic composition of water.•Cake-layer formation was the main fouling mechanism for As bear...

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Bibliographic Details
Published in:Separation and purification technology 2020-06, Vol.241, p.116644, Article 116644
Main Authors: Ahmad, Arslan, Rutten, Sam, de Waal, Luuk, Vollaard, Peter, van Genuchten, Case, Bruning, Harry, Cornelissen, Emile, van der Wal, Albert
Format: Article
Language:English
Subjects:
Arsenic removal
Coprecipitation
Groundwater treatment
Iron chloride
Microfiltration
Ultrafiltration
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Summary:•Both MF and UF membranes showed similar arsenic and iron removal efficiency.•No differences were observed for arsenic removal between the filtration cycles.•Arsenic coprecipitation with iron was dependent on ionic composition of water.•Cake-layer formation was the main fouling mechanism for As bearing-ferric precipitates. Ferric based coprecipitation–low pressure membrane filtration is a promising arsenic (As) removal method, however, membrane fouling mechanisms are not fully understood. In this study we investigated the effect of feed water composition and membrane pore size on arsenate [As(V)] removal and membrane fouling. We observed that As removal efficiency was independent of the membrane pore size because the size of the Fe(III) particles was larger than the pore size of the membranes, attributed to a high calcium concentration in the feed water. Arsenic coprecipitation with Fe(III) (oxyhydr)oxides rapidly reached equilibrium before membrane filtration, within 1 min. Therefore, As removal efficiency was not improved by increasing residence time before membrane filtration. The removal of As(V) was strongly dependent on feed water composition. A higher Fe(III) dose was required to reduce As(V) to sub-µg/L levels for feed water containing higher concentration of oxyanions such as phosphate and silicate, and lower concentration of cations such as calcium. Cake-layer formation was observed to be the predominant membrane fouling mechanism.
ISSN:1383-5866
1873-3794
1873-3794
DOI:10.1016/j.seppur.2020.116644