Use of additives to enhance the selectivity of liquid surfactant membranes

This study is aimed at attempting to improve both the selectivity and the permeation rates for the separation of 1-methylnaphthalene from dodecane using aqueous surfactant membranes. This enhancement is achieved by adding various water-soluble chemical compounds (“additives”) to the water phase. Seven different additives were tried in this study and their efficacy was determined by carrying out mass transfer permeation experiments to determine both the rates of transfer and the selectivity of separation. In line with our previous work (Sharma et al. 5]; Krishna et al. 6]), we have corrected the mass transfer coefficients for emulsion breakage, and found these coefficients, and the selectivity, to correlate well with the work of transfer of the additive-containing surfactant system. The increase in selectivity in the presence of the additive has been shown to be due to the relative increase in the activity coefficient of 1-methylnaphthalene in the aqueous solution with respect to that of dodecane. The presence of the additive increases the selectivity by about one order of magnitude, and the present study should aid in the development of a viable liquid membrane separation process for the selective removal of aromatics from kerosene, a process which is required for the production of aviation turbine fuel from crudes having a high aromatic content in the lighter distillates.