SURFACTANT-ENHANCED DISSOLUTION OF PHENANTHRENE INTO WATER FOR LAMINAR-FLOW CONDITIONS

The effects of surfactant solutions on processes influencing subsurfac e remediation are of significant environmental concern, We previously investigated the dissolution of solid phenanthrene into aqueous soluti ons containing nonionic surfactants in a well-mixed system and develop ed a mechanistic model to describe the dissolution process. In the pre sent work, we challenged this model by collecting data from a flow-thr ough system in which the hydrodynamics are well defined and provided i ndependent measurements of all parameters in the model, The dissolutio n process is assumed to be governed by the diffusion of phenanthrene a way from the hydrocarbon-water interface in both the aqueous phase and micelles, and transport is formulated in a three-dimensional advectiv e-diffusive model. The trends in model predictions and experimental da ta compare favorably, lending further support to the proposed mechanis tic model. In particular, effluent concentrations of phenanthrene from the experimental apparatus were both predicted and observed to be sub stantially lower than saturation (equilibrium) concentrations, and thi s difference increased at increasing surfactant concentration over the range of laminar flow rates tested. Better quantitative agreement bet ween the model and experimental data may require a more accurate measu rement of the micellar diffusion coefficient or a more complex descrip tion of interfacial processes. However, the proposed dissolution model provides an important step toward understanding the influence of surf actants on hydrocarbon dissolution and transport.