FILTERS FOR SEPARATION OF PARTICLES OF DIFFERENT SIZES AND OIL FROM EMULSIONS

Abstract

With increasing concerns over water contamination, the purification of water is critical. For water purification, filtration is widely used for its convenience, low cost, and efficiency. In this thesis, two types of filters are developed for the separation of particles of different sizes and for the separation of oil from emulsions. First reported is the fabrication of an inverse size-selective membrane templated by an electrospun nanofiber mat. The electrospinning of a polymethyl methacrylate (PMMA) solution yielded long nanofibers that folded into mats. The nanofiber mats were then annealed at selected high temperatures under pressure to fuse fiber section at junctions. Infusing partially hydrolyzed polyvinyl acetate (HPVAc) into the voids between these fiber sections, crosslinking the infusing polymer, and subsequently removing the nanofiber template produced an inverse porous membrane. Liquid flux across such membranes increased by increasing the annealing temperature of the fiber mats and by etching the surfaces of the final membrane with plasma to expose the encapsulated nanochannels. The membrane could also separate particles with different sizes and the cut-off size of the separation increased as the mat annealing temperature increased. Thus, the extent of nanofiber fusion at their junctions determined the size selectivity of the membrane. Secondly, sintered glass funnels were hydrophobicized by running a treatment solution through and the hydrophobicized funnels could separate oil from water-in-oil emulsions. Chloro(dimethyl)octadecylsilane (CDMOS) was the modifying agent used for the funnels. Glass funnels with three pore sizes were modified with the same concentration of CDMOS to investigate the effect of varied pore size on the wetting properties and separation performance of the glass filters. Water sliding angles increased as filter pore size increased. However, transparent oil could be separated from water-in-oil emulsion only for h the fine- and medium- pore funnels. The separation occurred most likely due to the blocking of the water droplets by hydrophobic pores.