OBSERVATION OF THE DISSOLUTION OF NAPL MIXTURES

The process of NAPL dissolution has been studied extensively for petroleum products where the solvent mixtures are lighter than water, but less has been done for dense solvents. An experiment to quantitatively measure the dissolution behaviour for mixtures of dense and light, chlorinated and non-chlorinated hydrocarbons, represented by an equimolar mixture of 1,1,1-trichloroethane, tetrachloroethene, 1,1,2-trichloro-1,2,2-trifluoroethane and toluene, was undertaken. The experimental system consisted of a generator column and a constant-headspace flow cell, sampled automatically and analysed using a portable gas chromatograph. The effect of ionic strength on the dissolution of the solvents was measured. Activity coefficients of the solvents in the mixture were calculated and compared with UNIFAC(C) predictions.