Assessing Synergistic Ultrafiltration Membrane Fouling by TiO2 Nanoparticles and Humic Acid Using Interaction Energy Analysis

Abstract

IntroductionRecently, engineered nanoparticles have been widely used in numerous industrial products, resulting in an increasing discharge of nanoparticles into aquatic systems [1][2]. Engineered nanoparticles have been observed to be toxic to microbes, plants, animals, and ecosystems [3]. As a result, engineered nanoparticles represent an emerging category of foulants. More attention has been paid to how engineered nanoparticles will be removed by -and impact the performance of -wastewater treatment systems [4]. Ultrafiltration (UF) has been acknowledged as a promising technology for removing nanoparticles due to its high-quality effluent, reliability in operation, Pol. J. Environ. Stud. Vol. 26, No. 5 (2017), 2259-2266 AbstractThis research attempts to elucidate the effect of humic acid (HA) on TiO 2 nanoparticle ultrafiltration (UF) membrane fouling, and quantitatively analyze the synergistic membrane fouling mechanisms using interaction energies. The extended Derjaguin-Landau-Verwey-Overbeek (xDLVO) theory was employed to analyze the interaction energies and predict UF membrane fouling. Membrane fouling effects were studied during the dead-end filtration of individual TiO 2 and HA-TiO 2 mixtures using two kinds of polymeric UF membranes. It was found that HA-TiO 2 mixtures lead to greater flux declines than individual TiO 2 . For specific foulant, the hydrophobic PVDF membrane showed relative severe membrane fouling than hydrophilic PES membrane. As for the HA-TiO 2 mixture, much higher irreversible fouling was observed compared with that of individual TiO 2 . Moreover, this study highlights the importance of HA concentration in synergistic fouling effects of the HA-TiO 2 mixture. The increase of HA concentration caused an increase of contact angle and lower interaction energy, thus aggravating membrane fouling. Results illustrated that synergistic membrane fouling by TiO 2 and HA could be successfully explained using the xDLVO analysis. The extent of membrane fouling turned out to be dominated by Lewis acid-base interaction.