• The highest mass-transfer coefficients are observed for the smallest surfactants
with branched tails as they desorb and diffuse faster
• the NAPL solubilization rate increases with C S and with the hydrophilic character
of surfactants
• the NAPL solubilization rate increases with the hydrophilic character of HOCs
• SC increases with the micelle size, i.e., the number of aggregated monomers
• The partition coefficient K m for any contaminant increases with its hydrophobic
character (K ow )
Cationic surfactants cannot be used for SW/SF because of the usual anionic
charge of soil materials and their biocide activity on Gram-negative bacteria (Simoes
et al. 2005; Bera et al. 2013). Conversely, calcite material may be positively charged
below pH 9.5, so anionic surfactants can be lost by adsorption onto these surfaces
(Ma et al. 2013). Neutral surfactants are preferred over anionics, because of lower
CMC values (Rosen and Kunjappu 2012), lower toxicity and less sensitivity of their
aqueous solubility to salinity and temperature variations (Holmberg et al. 2002). For
example, high salinities may be observed in zones polluted by halogenated organic
compounds where reductive dehalogenation occurs. Alternatively, anionic surfactants may precipitate in soil pores if the GW temperature is below their Krafft point.
Fig. 1.11 Scheme of an indirect solubilization of a NAPL by micelles [Adapted from Bernardez
(2005)]
26
N. Fatin-Rouge
with branched tails as they desorb and diffuse faster
• the NAPL solubilization rate increases with C S and with the hydrophilic character
of surfactants
• the NAPL solubilization rate increases with the hydrophilic character of HOCs
• SC increases with the micelle size, i.e., the number of aggregated monomers
• The partition coefficient K m for any contaminant increases with its hydrophobic
character (K ow )
Cationic surfactants cannot be used for SW/SF because of the usual anionic
charge of soil materials and their biocide activity on Gram-negative bacteria (Simoes
et al. 2005; Bera et al. 2013). Conversely, calcite material may be positively charged
below pH 9.5, so anionic surfactants can be lost by adsorption onto these surfaces
(Ma et al. 2013). Neutral surfactants are preferred over anionics, because of lower
CMC values (Rosen and Kunjappu 2012), lower toxicity and less sensitivity of their
aqueous solubility to salinity and temperature variations (Holmberg et al. 2002). For
example, high salinities may be observed in zones polluted by halogenated organic
compounds where reductive dehalogenation occurs. Alternatively, anionic surfactants may precipitate in soil pores if the GW temperature is below their Krafft point.
Fig. 1.11 Scheme of an indirect solubilization of a NAPL by micelles [Adapted from Bernardez
(2005)]
26
N. Fatin-Rouge