Conductivity study on the w/o microemulsion of a saponified mono(2-ethylhexyl) phosphoric acid extractant system

Abstract Conductivities of water-in-oil (w/o) microemulsions of the sodium salt of mono(2-ethylhexyl)phosphoric acid- n -hexane- n -pentanol-water system have been measured during dilution processes with varying amounts of water present. The conductivity does not change significantly if the microemulsion is continually diluted, but does change significantly with different amounts of water added at the beginning of microemulsion formation. The water amount added at the beginning affects the structure parameters of the microemulsion, such as the radius of the water pool ( r ) and the mean aggregation number of the surfactant molecules in a droplet ( n ∗ ), indicating that an optimum r and/or n ∗ value may exist that gives maximum conductivity. The conductivity behaviour of the microemulsions has also been studied based on charge carrier transition by the “sticky collision of droplet” mechanism. The activation energy ΔE was determined. The results showed that there was a maximum in the ΔE value when the water content increased up to the percolation threshold value.