Interactions of aqueous NOM with nanoscale TiO2: Implications for ceramic membrane filtration-ozonation hybrid process

Jeonghwan Kim, Wenqian Shan, Simon H.R. Davies, Melissa J. Baumann, Susan J. Masten, Volodymyr V. Tarabara

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Abstract

The combined effect of pH and calcium on the interactions of nonozonated and ozonated natural organic matter (NOM) with nanoscale TiO2 was investigated. The approach included characterization of TiO2 nanoparticles and NOM, extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) modeling of NOM-TiO2 and NOM-NOM interactions, batch study on the NOM adsorption onto TiO2 surface, and bench-scale study on the treatment of NOM-containing feed waters using a hybrid process that combines ozonation and ultrafiltration with a 5 kDa ceramic (TiO2 surface) membrane. It was demonstrated that depending on pH and TiO2 loading, the adsorption of NOM species is controlled by either the availability of divalent cations or by preozonation of NOM.XDLVO surface energy analysis predicts NOM adsorption onto TiO2 in the ozone-controlled regime but not in the calcium-controlled regime. In both regimes, shortrange NOM-NOM and NOM-TiO 2 interactions were governed by acid-base and van der Waals forces, whereas the role of electrostatic forces was relatively insignificant. Ozonation increased the surface energy of NOM, contributing to the hydrophilic repulsion component of the NOM-NOM and NOM-TiO2 interactions. In the calcium-controlled regime, neither NOM-TiO2 nor NOM-NOM interaction controlled adsorption. Non-XDLVO interactions such as intermolecular bridging by calcium were hypothesized to be responsible for the observed adsorption behavior. Adsorption data proved to be highly predictive of the permeate flux performance.

Original languageEnglish
Pages (from-to)5488-5494
Number of pages7
JournalEnvironmental Science & Technology
Volume43
Issue number14
DOIs
StatePublished - 15 Jul 2009

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