FLOTATION USING MICROGAS DISPERSIONS FOR THE REMOVAL OF PENTACHLOROPHENOL FROM AQUEOUS-SOLUTIONS

Microgas dispersions called colloidal gas aphrons (CGAs) were generate d using cationic, anionic, and nonionic surfactants, and were used in an adsorptive bubble flotation process in a semibatch mode to remove p entachlorophenol (PCP) from the aqueous phase. The aqueous solution wa s maintained at pH values by using buffers. CGAs generated with Tergit ol, which is a nonionic surfactant, were found to be the most efficien t for the removal of PCP; the efficiency remained nearly independent o f pH. In the case of an anionic surfactant, sodium dodecylbenzene sulf onate (DDBS), the efficiency of removal improved from 15 to 36% with a change in pH from 10.1 to 3.0. For a cationic surfactant, hexadecyltr imethylammonium bromide (HTAB), the removal at pH 10.1 was 81%, which decreased to 68. 1% at pH 3.0. The charges on the encapsulating film o f CGAs may explain the higher percentage of adsorption of PCP on the C GAs generated using HTAB as compared to CGAs generated using DDBS. For all the surfactants, an increase in concentration improved the remova l efficiency. These results were compared with the removal efficiencie s using conventional flotation techniques used by other researchers. S olvent sublation appears to be effective in the removal of PCP, but ev en in the presence of a surfactant it required 300% more air volume pe r volume of liquid when compared with CGA flotation.