Effects of Pre-ozonation on Membrane Filtration of Oil-in-water Emulsions Using Different Polymeric (PES, PAN, PTFE) Ultrafilter Membranes

Abstract

ABSTRACTEmulsified oily contaminants of wastewaters cannot be eliminated effectively by conventional treatments, but they pose significant risks both to the environment and to human health, therefore their efficient elimination is imperative. Membrane filtration is a promising technique for the effective purification of oil-in-water emulsions; however, the accumulation of hydrophobic contaminants on the membrane surface quickly leads to significant water flux reduction, which is a limiting factor of the economic utilization. In the present comparative study short-term ozonation was investigated as a suitable pre-treatment to achieve lower flux reduction during the separation of micro- or even nanoscale crude oil droplets by ultrafiltration with different membranes. Results confirmed that pre-ozonation modifies the surface charge (zeta-potential) of the oil droplets which resulted in the reduced accumulation of contaminants on the membrane surface and higher fluxes in the case of every investigated ultrafilter membranes: polyethersulfone (PES), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE). Filtration experiments were carried out using ultrapure and model groundwater matrices for a more thorough discussion of achievable advantages, and it was concluded that in the case of low ionic strength the PES membrane provided the highest flux; however, in the case of realistic water matrix (model groundwater) the application of acetone-conditioned PTFE ultrafilter membrane – combined with pre-ozonation – was much more beneficial. Overall, pre-ozonation decreased the total resistance in all cases; however, the reversibility of the measured filtration resistance and flux reduction was strongly dependent on both the matrix and the membrane surface material.