Influence Mechanism Of Surfactant On Volatilization Rates Of Organic Pollutants In Air-water Interface

This work was devoted to the study of the volatilization rates of organic pollutants in Air-water Interface. Four volatilization models were summarized: two-film theory,reviewed two-film theory, D.Mackay's volatilization rate model, and the volatilization rate model advanced by C.T.Chiou.Otherwise, the paper introduced the solubilization of organic pollutants enhanced by surfactants, and special performance of mixed-surfactants.The influence rule of surfactants on Henry's law constants of organic pollutants was also involved.Based on the multimedia environment with complex pollution, the study discussed the influence of surfactants on volatilization rates of volatile organic compounds(VOCs) in the interface of water/gas.In chief,It studied the effects of mixed-surfactant on the volatilization rates of naphthalene and BTEX from the static water and the corresponding mechanisms.Compared to phenomena in static state, the influence of surfactant on the volatilization rate of naphthalene in stirred water was investigated primarily.The main conclusions of this work were drawn as follows:(1) The main reason for the decrease of volatilization rate of BTEX from static water was that the presence of surfactant increased the resistance constant(r_L) in liquid film.That is, the transfer constant(k_L) became smaller,which lead to the mass transfer constant(K_L) in the liquid and then the volatilization rate( K_v) diminished.Thereby,the volatilization of BTEX was inhibited.It was concluded that with the increase of surfactant concentration,the resistance of liquid film increased accordingly,and the inhibition was more obvious. In addition, the positive relation was found between the restraining ability of a surfactant and lgK_ow of BTEX.(2) Mix-surfactants inhibited the volatilization rates of naphthalene and BTEX synergistically.Compared to the single-surfactant solution,mixed-surfactants inhibited the volatilization more efficiently.It was attributed to that the restraining ability of mixed-surfactant was stronger than that of single-surfactant.In the study,the inhibition caused by Mixed-surfactant solutions containing SDS was stronger than that by solutions containing SDBS. Data analysis showed that the evaporative loss weakening caused by mixed-surfactant synergistically was positively correlated to the degree ofsolubility enhancement.(3) The volatilization of naphthalene was enhanced by agitation. In solutions without SDS,when the rate of agitation was 51rpm/min,the volatilization rate K_v was5.63 times as K_v^o in static state;while K_v of naphthalene from static water in the presence of 2500mg/L SDS was 0.59 times as K_v^o .The volatilization rate decreasedwith either the increase of concentration of SDS or the increase of agitation rate.Agitation at low rates had the biggest contribution to the volatilization rate.In the other hand,the increase of volatilization rate was most obvious in the process from static water turn to the state with low rate of agitation.(4) In solutions containing SDS,the decrement of naphathalene's volatilization rate increased with the increase not only of SDS's concentration but also of agitation rate.It could be explained that the solution was mixed more completely with stirring.That made the molecule of naphathalene transfer to the interface more easily,and reinforced the decrease of naphathalene in liquid film caused by volatilization process.In the result,the mass transfer resistance in liquid diminished greatly,and then,the volatilization rate increased. Simultaneously,agitation enhanced combiness of naphthalene with SDS micelle, which astricted the molecule of naphthalene.And thus,the volatilization was inhibited.As described in this paper,effects of surfactants on the volatilization of organic matter from static water and the corresponding mechanisms have been beat out in the main,while rules that surfactants effect on the volatilization in the stirred state have been understood primarily.These support for the studies theoretically,which concerned to the fate o...