SOLUBILIZATION OF NONAQUEOUS PHASE LIQUID HYDROCARBONS IN MICELLAR SOLUTIONS OF DODECYL ALCOHOL ETHOXYLATES

Results of an experimental investigation of hydrocarbon solubilization in 0.01 M micellar solutions of dodecyl alcohol ethoxylates at 25 deg rees C are presented. The effects of surfactant hydrophile-lipophile b alance (HLB) and hydrocarbon molar volume and polarity on the molar so lubilization ratios (MSRs) and micelle-water partition coefficients of 11 nonaqueous phase liquid (NAPL) hydrocarbons are examined. The MSRs of the alkanes (n-dodecane, n-decane, n-hexane, and cyclohexane), whi ch sharply decrease and asymptotically approach zero with increasing H LB, are shown to depend on micellar core volume and hydrocarbon molar volume and affinity for the micellar core. In contrast, the MSRs of th e:aromatic hydrocarbons (benzene, toluene, chlorobenzene, o-xylene, an d o-dichlorobenzene) and the chlorinated alkenes (trichloroethylene an d tetrachloroethylene) exhibit a maximum within the same HLB range. Th is behavior appears to be the result of two opposing effects: (i) loss of solubilization capacity with increasing HLB and (ii) enhancement o f solubilization capacity by electron donor-acceptor (EDA) complexatio n. The logarithms of the micelle-water partition coefficients for all of the hydrocarbons follow the trends of the MSRs and increase with hy drocarbon hydrophobicity.