addition of KOH to any solvent
used as a component of extraction–flocculation solvents significantly improves the sludge removal and decreases the oil loss. The
determination of a KOH optimal concentration may be identified
by comparing the settling curves obtained for a fixed solvent to
oil composition and several KOH concentrations. Fig. 5 quite sharply
shows the existence of an optimal concentration of 2 g, this is
in agreement with the findings of Ping et al