Buckminsterfullerene (C60) nanoparticle fouling of microfiltration membranes operated in a cross-flow configuration

Manufactured nanomaterials, like buckminsterfullerene (C60), present unique challenges with regards to their impacts on the performance of microfiltration (MF) membranes. Of particular concern is the ability of existing physical and chemical cleaning processes to remove nanoparticle deposits on the surface and from the interior of MF membranes. The objective of this research was therefore to characterize C60 nanoparticle fouling of hollow fiber MF membranes and assess the ability of hydraulic backwashing and different cleaning solutions to remove nanoparticle deposits from fouled MF membranes. Two nanoparticles, a manufactured C60 and a carboxylated nanosphere, were studied and found to similarly affect membrane performance. Nanoparticle fouling resulted in a more substantial impact on membrane performance relative to that resulting from a colloidal foulant. This was attributed to the ability of the nanoparticles to form comparatively more dense surface deposits and to pass through the MF membrane resulting in standard pore blocking and cake layer formation on the filtrate side of the membrane. Using nanoparticle free backwash water was found to remove these cake structures on the filtrate side of the membrane and to displace the internal nanoparticle deposits. The C60 cake structures were poorly removed using conventional cleaning solutions, with the exception of hydrogen peroxide; however, removal with the hydrogen peroxide was incomplete and resulted more rapid fouling after normal operation was resumed.