Faculty of Engineering and Information Technologies, School of Chemical and Biomolecular Engineering
Abstract
This study aims to develop the carbon nanotube composite membrane for the purpose of enhancing low pressure driven membrane process that encounters several challenging issues such as limited rejection efficiency and fouling. First, we synthesized multiwall carbon nanotubes/polyaniline(MWCNTs/PANI) complex by in-situ polymerization. The MWCNTs/PANI membrane removed natural organic matter 4 fold (80 %) which cannot be effectively removed by low-pressure driven membranes, as well as delivering 30 times higher water product (1400 LMH/bar) than the PES membrane. Further research on physical/chemical properties of the membrane revealed that the hydroxyl functionalized MWCNTs/PANI complex increased the hydrophilicity, porosity and slip length of the membrane by improving the membrane structure. It also altered the surface charge of the membrane, which contributed to the increase in electrostatic interaction between the membrane surface and the negatively charged organic matter, compared that currently used polymeric membranes are negatively charged. A second part of the research targeted to the application for enhanced organic matter removal in seawater pre-treatment. By enhanced natural organic matter removal and delivering high permeate flux, the MWCNTs membrane contributed to minimizing sludge volume generated from seawater desalination plant by reducing PAC dosage (1.5 g/L to 0.5 g/L). Lastly, protein fouling behavior in the MWCNTs membrane was examined under different solution chemistry (pH and ionic strength) for the wide application of MWCNTs membrane in wastewater reclamation and recovery of bioprocess industry. For the MWCNTs membrane, two dominant fouling mechanisms – complete/intermediate blocking and cake filtration operated under different pH and increasing ionic strength. Consequently, protein fouling of the MWCNTs membrane was found to be alleviated by controlling electrostatic interaction with charged proteins via pH and ionic strength
