MASS-TRANSFER OF POLYNUCLEAR AROMATIC-HYDROCARBONS FROM COMPLEX DNAPLMIXTURES

Parameters governing the rates of mass transfer of the individual comp onents of four synthetic dense non-aqueous phase liquid (DNAPL) mixtur es into the aqueous phase were evaluated. The DNAPL mixtures, composed of toluene and eight polynuclear aromatic hydrocarbons (PAHs), were d esigned to serve as models for coal tars and creosotes. The reactor em ployed provided a relatively stable interface between internally mixed but segregated aqueous and DNAPL phases. Two parameters, the aqueous phase concentration at equilibrium and the overall film mass transfer coefficient, were quantified by simulating aqueous concentration profi les with a mass-transfer-limited rate model using a statistical parame ter search and data fitting routine. DNAPL phase activity coefficient values for the various compounds derived from equilibrium aqueous phas e concentrations were typically within a factor of 2 of Raoult's law p rediction of unity; refinement of fugacity ratio estimates for the sol id PAHs brought the values even closer to unity. Film transfer coeffic ients for all components of the mixtures studied were similar in magni tude, in the range 0.8-3 x 10(-3) cm/s. No significant variations of t he film transfer coefficient for naphthalene were noted across the DNA PL mixtures, over which the mole fraction of this compound was varied from 0.05 to 0.25.