3.2. Separation time vs salt content
Before identifying the effects of salt content on microwave
demulsification tests the effect of salinity on untreated emulsions
was investigated. Fig. 4 shows the separation time of four different
emulsions made with pure water, 15 g/L and 35 g/L NaCl. The addition
of salt causes a decrease in separation time for the 80/20, 90/
10 and 95/5 oil/water emulsions, with the most significant decrease
with the 95/5 emulsions where the separation time was reduced
from 10,000 s to 7000 s. The separation time of the 70/30
emulsion underwent a slight increase when NaCl was added. The
addition of electrolytes is known to alter the interfacial tension
of an emulsion [1], and the general effect is to improve the probability
of coalescence. However, in this case the technique for emulsion
manufacture was kept constant and it could be that the
salinity affects the droplet size distribution. It is not possible,
therefore, to completely decouple the effects of interfacial tension
and droplet size in Fig. 4. It does show, however, that with the exception of the 95/5 oil/water emulsion, the addition of salt has
little effect on the settling time of untreated emulsions.