An alternative method to assess permeation through disposable gloves.

Previously, we have demonstrated the capability of activated charcoal cloth (ACC) to assess dermal exposure to VOCs. Here we investigated whether ACC patches can be used as an under-glove indicator to evaluate the ingress of toluene through disposable gloves in a controlled environment, and compared these results to the amount of toluene ingress determined from the standardized test methods for determining chemical permeation through PPE. In a test chamber, with plugs for air sampling, five to six ACC patches were placed on a mannequin hand underneath disposable gloves (latex, nitrile, neoprene, polymer laminate). Three work-exposure scenarios were simulated to assess toluene ingress through the different gloves: vapor exposure; spray exposure, and immersion. The standard permeation test, using a diffusion cell, was carried with glove material of the palm, with continuous contact conditions. In all of ACC test, the order of toluene ingress was latex > neoprene > nitrile > Barrier, but for the standardized testing, the order of the neoprene and nitrile was reversed, and nitrile had higher levels of toluene ingress. These results show the need to think beyond standard testing techniques for occupational exposure to hazardous substances, and the added value of "application style" testing.

Model study of enhanced oil recovery by flooding with aqueous surfactant solution and comparison with theory.

With the aim of elucidating the details of enhanced oil recovery by surfactant solution flooding, we have determined the detailed behavior of model systems consisting of a packed column of calcium carbonate particles as the porous rock, n-decane as the trapped oil, and aqueous solutions of the anionic surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT). The AOT concentration was varied from zero to above the critical aggregation concentration (cac). The salt content of the aqueous solutions was varied to give systems of widely different, post-cac oil-water interfacial tensions. The systems were characterized in detail by measuring the permeability behavior of the packed columns, the adsorption isotherms of AOT from the water to the oil-water interface and to the water-calcium carbonate interface, and oil-water-calcium carbonate contact angles. Measurements of the percent oil recovery by pumping surfactant solutions into calcium carbonate-packed columns initially filled with oil were analyzed in terms of the characterization results. We show that the measured contact angles as a function of AOT concentration are in reasonable agreement with those calculated from values of the surface energy of the calcium carbonate-air surface plus the measured adsorption isotherms. Surfactant adsorption onto the calcium carbonate-water interface causes depletion of its aqueous-phase concentration, and we derive equations which enable the concentration of nonadsorbed surfactant within the packed column to be estimated from measured parameters. The percent oil recovery as a function of the surfactant concentration is determined solely by the oil-water-calcium carbonate contact angle for nonadsorbed surfactant concentrations less than the cac. For surfactant concentrations greater than the cac, additional oil removal occurs by a combination of solubilization and emulsification plus oil mobilization due to the low oil-water interfacial tension and a pumping pressure increase.