High- and low-molecular-weight lignosulfonates and Kraft lignins as oil/water-emulsion stabilizers studied by means of electrical conductivity

Electrical conductivity measurements were used to study the creaming rates in oil/water emulsions stabilized with five lignosulfonates and one Kraft lignin. The creaming process resulted in a narrow dispersion band separating the water-rich and the oil-rich phases. An electrode was designed to follow this zone in the emulsion as a function of time. This makes it possible to calculate the amount of water separated from the emulsion directly from the creaming profiles. The stability concerning creaming was also evaluated with data obtained from visual inspection. Equivalent creaming profiles indicate that the electrode design used is suitable for stability measurements in the systems examined. Droplet interaction in diluted emulsions was studied with video-enhanced microscopy. Received: 10 September 1998 Accepted in revised form: 18 December 1998