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Chapter 5

samples for making microscopy observations. In the microscopy observation of
O∕W emulsions, the pH of the aqueous phase was decreased from 8.8 to 4.5 by
adding 0.1 M HCI. The O∕W emulsion was observed for 10 min before adding HCI.
Then HCI was added at time zero. Photomicrographs of clay solids skins were
taken as the function of time.

5.5.2. Results and discussions

In the second step of the separation procedure described in section 5.4.2,
increasing pH and shaking caused formation of an oil-in-water emulsion. In order
to break this emulsion, the pH of the aqueous phase needs to be lowered in a
third step. In this section, experiments are described in which hydrochloric acid
(HCI) was used to find the optimal pH for demulsification.

Figure 5.8 shows the photomicrographs of o∕w emulsions with time when
lowering the pH from 8.8 to 4.5, as described in section 5.5.1.

Before adding HCI, the O∕W emulsions did not coalesce in 10 min. After
adding HCI, the O∕W emulsions coalesced very fast and formed continuous oil
phase finally. With the decrease of pH, soaps will form naphthenic acids and
destabilize the O∕W emulsions.

The following experiments were performed to find the optimal pH for
oil-in-water emulsion coalescence, as described in section 5.5.1. Figure 5.9

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