SORPTION OF TRICHLOROETHYLENE ONTO A ZEOLITE ACCOMPANIED BY METHANOTROPHIC BIOTRANSFORMATION

The rate and extent of trichloroethylene (TCE) sorption from aqueous phase onto a synthetic hydrophobic zeolite, silicalite, were measured. Equilibrium sorption fit the Langmuir isotherm with parameters of Q(o) = 201 mg of TCE/g of silicalite and b = 0.52 L/mg. Rate studies showed that TCE uptake by silicalite was rapid (equilibrium approached within 25 min) as was desorption following perturbation of equilibrium by chloroform (CF) addition to the aqueous phase. The availability of sorbed TCE for cometabolic transformation by methanotrophic bacteria was evaluated, and a model was developed based upon the hypothesis that the TCE transformation rate is proportional to the concentration of TCE in solution and independent of the mass of sorbed TCE. A comparison between experimental and model results for concurrent sorption/biotransformation supported the validity of the hypothesis and model assumptions. In the presence of silicalite, the methanotrophic transformation of solution-phase TCE induced desorption of TCE from the silicalite, resulting in bioregeneration of the sorption sites. The potential for using silicalite in an advanced waste treatment process incorporating bioregeneration is discussed.