APPLICATION OF SOLVENT SUBLATION TO THE SIMULTANEOUS REMOVAL OF EMULSIFIED COAL TAR AND DISSOLVED ORGANICS

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Abstract
Solvent sublation is a unique bubble-separation method which combines features of foam fractionation and solvent extraction in a single unit operation. Surfactant introduced into a flotation column serves to remove emulsions and other colloids, while simultaneously transporting dissolved organics into a solvent layer for retention. The extracting solvent is placed directly on the surface of the aqueous phase. The objective of this research was to test the feasibility of using the solvent sublation process to remove phenols and particulates from underground coal gasification (UCG) wastewater. Previous work with separate flotation, adsorption, solvent extraction and coagulation processes indicated that a combined approach might have added utility in increasing pollutant removal. Further, the combined process could have greater efficiencies of operation. All experiments were performed in the batch mode using methylisobutyl ketone (MIBK) solvent and ethylhexadecyldimethylammonium bromide (EHDA-Br) surfactant. The solvent-aqueous ratios, pH, and surfactant doses were independently varied in this investigation, while the air flow rate was held constant. The final process configuration employed removed 93 percent of the phenols and over 90 percent of the 2–10 μm diameter particles from the UCG wastewater. In addition, some precipitate flotation was observed in select operational modes. This served to remove color bodies and additional colloids previously immune to treatment. Measurement of residual MIBK in effluents showed that solvent-sublation left less residual solvent than did solvent-extraction in these wastewaters.