Formulating Surfactant Blends

We provide surfactant formulations specific to site geochemistry and NAPL composition.  Our chemistry is based on a decades of research and product testing.  

The force that prevents NAPL from flowing inside an aquifer is called the capillary force.  This force arises because of the high energy surface that exists between oil and water.  Because physical systems move to the lowest energy environments (thermodynamics), the oil and water seek to minimize the contact between them.  The NAPL cannot flow because flowing involves increasing the area of contact.

Surfactants can help increase the rate of removing NAPL from an aquifer by tow different mechanisms.  One mechanism is called solubilization.  Here, surfactant micelles provide little mobile pools of oil that can dissolve some of the NAPL, so it can be removed within the flowing ground water.  This will work, but requires that the volume of surfactant exceeds the volume of NAPL, which can be very expensive.

The other way that surfactants help remove NAPL is to lower the energy of the area of contact between the oil and water.  The interfacial tension between the oil and water is direct measure of the energy of the interface.  When surfactants adsorb at the oil/water interface, the energy of the interface decreases.  When the energy of the interface decreases, the barrier that prevents the NAPL from flowing in the subsurface also decreases and more of the NAPL can be pumped directly to the surface as a separate non-aqueous phase liquid (NAPL).

Because there is a direct connection between oil/water interfacial tension and mobilization of subsurface NAPL, we focus our formulation efforts on minimizing the interfacial tension between the oil and water.  This is why we always requests samples of site ground water, site NAPL, and site soil before finalizing a site-specific surfactant formulation.   Laboratory testing with site materials results in a surfactant system which produces the lowest possible oil/water interfacial tension.  Please note that for well characterized sites it may be possible to  use a pre-formulated surfactant blend (i.e. a blend developed and applied to a site with similar characteristics) without having to first conduct laboratory testing.