Influence Mechanism Of Surfactant On Behavior Of Naphthalene In Air-water Interface

Volatilization is an important phenomenon in the transfer and destination of volatile organic compounds (VOCs). The natural water body is a complicated system. Facters, such as air-turbulence, air pressure, temperature, humidity and other compound co-existed, all influence the volatilization behavior of contaminants in the air/water interface. So it is very difficult to predict the volatilization rate under these conditions. The main volatilization models include the double-film theory, the surface renewal theory, and the C.T.Chiou's volatilization rate model.Based on the environment with complex pollutants, the influences of single and mixed surfactant on volatilization of naphthalene in the interface of air/water with and without dynamic factors were investigated. Main conclusions of this work drawn were as follows:(1) Naphthalene was solubilized synergistically by mixed anionic-nonionic surfactant solutions. This synergism resulted from a reduced critical micelle concentration (CMC) of the mixed surfactant and the increased micellar partition coefficient (K_mc) of naphthalene between micelles and aqueous phase. The volatilization of naphthalene from water was reduced significantly in the presence of single surfactant, and further reduction in volatilization was observed by synergistic effects of mixed surfactants. A positive linear correlation was found between the synergistic solubilization ratio ( ΔS ) and the synergistic inhibitory ratio on volatilization (ΔC) of naphthalene in the presence of mixed surfactant.(2) Under a certain agitating velocity, volatilization of naphthalene was inhibited when the concentration of surfactant was higher than CMC, and it was hightened slightly when the concentration of surfactant was lower than CMC, that is Δr<0. When the concentration of surfactant was set, the inhibitory ability followed the order of CTMAB ≥ Tween20 > SDBS > SDS, and the inhibitory effect increased with the HLB value for the nonionic surfactant, under all turbulence intensities.In addition, volatilization of naphthalene was enhanced by agitation. The volatilization rate (Kv) increased and resistance of the liquid phase decreased as theturbulence intensity enhanced. A maximum value of volatilization was found in every surfactant concentration whatever the agitating speed was. The main enhancement on volatilization of naphthalene lied in the slowly agitatied phase, that is, the lower theturbulence intensity, the bigger the increase of Kv value. When the mixation was good, increasing the turbulence intensity further, namely G>175s'', would not resulted in the significantincrease of the Kr value. The Kv value exhibited good linearcorrection with the agitating speed when the concentration of the surfactant was the same. The slopes the linear curves were in the range of 0.0097 to 0.0146 and the correlation coefficients were higher than 0.98. All the phenomena can be explained by surface-renewal theory and micellar solubilization of surfactant in the turbulent water.Besides, the inhibitory ability of SDBS on volatilization was enhanced remarkably by decreasing CMC, which was caused by the addition of salt with very lowconcentration (O.Olmol/L).As investigated in this paper, effects of mixed surfactant on the volatilization of naphthalene from static water and the corresponding mechanism have been proposed. Furthermore, the effects of surfactants on the volatilization in the stirring state have been interpreted. These results provide the theoretical bases for the studies of transfer and destination of oganic compounds in the environment and the removal of organic conpounds from the solution, which were previously used in the remediation of polluted soil and groundwater.