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Acknowledgement to Reviewers of Colloids and Interfaces in 2018
Open AccessArticle

Membrane Filtration of Anionic Surfactant Stabilized Emulsions: Effect of Ionic Strength on Fouling and Droplet Adhesion

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Wetsus European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911 MA Leeuwarden, The Netherlands
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Membrane Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
*
Author to whom correspondence should be addressed.
Colloids Interfaces 2019, 3(1), 9; https://doi.org/10.3390/colloids3010009
Received: 1 December 2018 / Revised: 8 January 2019 / Accepted: 9 January 2019 / Published: 10 January 2019
Membranes hold great potential to be used for the successful treatment of oily waste water, but membrane fouling leads to substantial decreases in performance. Here we study the impact of ionic strength on membrane fouling from an emulsion stabilized by the anionic surfactant sodium dodecyl sulfonate (SDS). For this we use a unique combinatorial approach where droplet adhesion to a cellulose surface in a flow cell is compared to membrane fouling (flux decline) on a cellulose membrane. In the initial membrane fouling stages droplet adhesion dominates. While the flow cell demonstrates a high number of droplets adhering especially at high ionic strengths (100 mM NaCl), the strongest flux decline is observed at intermediate (10 mM NaCl) ionic strength. This suggests that the fouling mechanism must be different, with pore blocking expecting to dominate at intermediate ionic strength. At the later fouling stages the porosity of the cake layer plays a key role in the flux reduction. At low ionic strength, oil droplets repel each other strongly and an open, more permeable, cake layer is formed. However at higher ionic strength, a screening of charge interactions leads to a lower porosity and thereby a lower flux. This leads to a clear trend: with a higher ionic strength a higher flux decline is observed. Flux recovery is high at all ionic strengths, in line with the observation in the flow cell that oil droplets can easily be sheared of a cellulose surface at all ionic strengths. This work thus highlights the critical effect of the ionic strength on membrane fouling by anionically stabilized emulsions. Moreover it shows how the use of an optical flow cell can provide key insights to help explain observations in more standard membrane fouling experiments. View Full-Text
Keywords: filtration; membranes; microscopy filtration; membranes; microscopy
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MDPI and ACS Style

Dickhout, J.M.; Lammertink, R.G.H.; de Vos, W.M. Membrane Filtration of Anionic Surfactant Stabilized Emulsions: Effect of Ionic Strength on Fouling and Droplet Adhesion. Colloids Interfaces 2019, 3, 9.

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