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| The impact of pH on microfiltration membrane fouling by sodium alginate: mechanism analysis using xDLVO theory. |
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Abstract Extended Derjaguin-Landau-Verwey-Overbeek (xDLVO) theory was used to quantitatively evaluate the role of interfacial interactions, i.e. Lifshitz van der Waals (LW), acid-base (AB) and electrostatic (EL) interactions, involved in microfiltration (MF) membrane fouling by sodium alginate (SA) at various pH. In the pH range of 5~9, the AB interaction energy played a dominant role and determined the nature and magnitude of the total interaction energy. As pH increased from 5to 9, fouling potential (K) for SA fouling of MF membrane decreased in the order of pH 5 > pH 7 > pH 8 > pH 9. During initial filtration stage, the hydrophobic membrane was subject to more severe fouling due to its attractive total interfacial interaction with SA. During subsequent fouling stage, no significant difference was found between fouling behaviors of hydrophobic and hydrophilic membranes because of the identical repulsive interfacial interaction between SA themselves for both membranes. Fouling potentials of initial and subsequent fouling stages correlated well with the interfacial free energies of membrane-SA and SA-SA combinations, respectively. This indicated that the xDLVO theory could effectively predict SA fouling behavior of MF membrane at different solution pH.
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Received: 20 August 2013
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