Volatilization reduction of monoaromatic compounds in nonionic surfactant solutions

Changes in the overall mass transfer coefficient (KOL) of several volatile organic compounds (VOCs) in surfactant (Triton X-100, Triton X-305, and Triton X-405) solutions are investigated. Different surfactant concentrations, from below to above the critical micelle concentration (CMC), are used to examine the possible inhibition effects on the volatilization of VOCs. The volatilization reduction (or the decrease in the KOL value) of the monoaromatic solutes from the surfactant solutions is considered to be a result of the effects of solubility enhancement and gas–liquid interface hindrance. For the solubility enhancement effect, the extent of volatilization reduction would generally be larger when a surfactant contains less polar ethylene oxide (EO) and when a monoaromatic compound has lower water solubility. On the other hand, gas–liquid interface hindrance may inhibit the volatilization of VOCs due to the aggregation of surfactants at the interface. Both the two-film and surface-depletion rate-limiting (SDRL) models are applied to elucidate the volatilization reduction of VOCs in surfactant solutions.