Extractive ultrafiltration.
Extractive ultrafiltration is a separation process by which liquid extraction in series with ultrafiltration removes contaminants from water. The toxin is extracted into an organic-in-water emulsion which is then separated by an ultrafilter. The ultrafilter thus replaces the settler in a conventional mixer-settler process; the extraction and emulsification allow ultrafiltration to remove much smaller molecules than is indicated by the nominal molecular weight cut-off of the membrane. In the present study, the toxins, toluene and monochlorobenzene, were individually extracted from water into heptane and hexane, respectively, reducing their concentration in the permeate water five to ten fold, at fluxes in excess of 60% of the pure water flux for the membrane. The operating temperature, organic to water ratio, and amount of surfactant used to stabilize the emulsion, were independently varied to determine the optimum values of each quantity, consistent with highest possible permeate flux through the membrane and maximum removal of the contaminant. General conclusions drawn were that the optimum permeate was obtained 1. at ambient temperature 2. when surfactant concentration was a minimum 3. when a minimum amount of extraction solvent was used.