Effect of a cationic surfactant on the volatilization of PAHs from soil

Purpose

Cationic surfactants are common in soils because of their use in daily cosmetic and cleaning products, and their use as a soil amendment for the mitigation and remediation of organic contaminated soils has been proposed. Such surfactant may affect the transfer and fate of organic contaminants in the environment. This study investigated the effect of a cationic surfactant, dodecylpyridinium bromide (DDPB), on the volatilization of polycyclic aromatic hydrocarbons (PAHs) from a paddy soil.

Materials and methods

The volatilization of PAHs from moist soil amended with different concentrations of DDPB was tested in an open system. The specific effects of DDPB on the liquid?Cvapor and solid?Cvapor equilibriums of PAHs were separately investigated in closed systems by headspace analysis.

Results and discussion

DDPB affects both liquid?Cvapor and solid?Cvapor processes of PAHs in soil. At DDPB concentrations below the critical micelle concentration (CMC), movement of PAHs from the bulk solution to the gas?Cliquid interface appeared to be facilitated by interaction between PAHs and the surfactant monomers adsorbed at the gas?Cliquid interface, promoting the volatilization of PAHs from solution. However, when DDPB was greater than the CMC, volatilization was inhibited due to the solubilization of PAHs by micelles. On the other hand, the formation of sorbed surfactant significantly inhibited the solid?Cvapor volatilization of PAHs.

Conclusions

The overall effect of the two simultaneous effects of DDPB on liquid?Cvapor and solid?Cvapor processes was a decreased volatilization loss of PAHs from soil. Inhibition of PAH volatilization was more significant for the soil with a lower moisture content.