The overall aim of this research is to develop unique conducting polyaniline (PANI) membranes that can be electrically tuned to achieve different fluxes and selectivity. The target application is in a tuneable membrane reactor, where these membranes allow the fouling layer to be pushed off/through membranes by application of external potential.To achieve this, several different types of PANI membranes were examined. The permeation properties of HCl-doped PANI membranes can be modified electrically to produce in-situ tuneable separations. However, acid dopant leaching and membrane brittleness limit the further application of these membranes. Polymer acid doped PANI membranes using poly(2-acrylamido-2-methyl-1-propanesulfonic acid) or PAMPSA were investigated as a solution. These PAMPSA doped PANI membranes displayed improved mechanical strength and filtration stability. However, the membranes showed decreased electrical conductivity, leading to a limited tuneable permeance and selectivity under applied potential. To overcome this new challenge, expanded graphite and a large acid (dodecylbenzene sulfonic acid or DBSA) were incorporated into the PAMPSA doped PANI membranes to increase the conductivity. Despite increasing both conductivity and electrical tuneability, the resulting membranes were more porous with looser molecular weight cut-off (outside of the desired NF/low UF MWCO range) than without modification. Efforts to tighten PAMPSA doped membranes to the same MWCO as HCl doped membranes using volatile co-solvents (THF and acetone) were unsuccessful: porosity was due to the large acid dopants.Membranes were examined for their potential for in-situ fouling removal of model foulant bovine serum albumin under applied voltage. This was successful and defouling extent was found to be closely related to membranes with higher conductivity and greater acid stability.Overall, it has been demonstrated that the conducting polyaniline composite membranes can be made to be stable to acid leaching and be more mechanically robust, whilst also being externally electrically tuned to different molecular selectivities with the potential for in-situ fouling control.
|Date of Award||26 Apr 2017|
|Supervisor||Darrell Patterson (Supervisor) & Emma Emanuelsson Patterson (Supervisor)|