Destabilization of water in bitumen emulsion by washing with water

In order to get more information about the mechanism of stabilization of wa ter-in-diluted-bitumen emulsion, bitumen diluted with toluene (10%, 25%, an d 50% in volume) was "washed" using different amounts of water (0-20% in vo lume). The washing water was emulsified and then separated by high-speed ul tra-centrifugation. The supernatant was then used to create a second w/o em ulsion with the addition of new water. Stability of the new emulsion was me asured in terms of the water separation rate under a low centrifugal force. It has been found that a very stable w/o emulsion was obtained in original diluted bitumen. However, after the diluted bitumen was pre-washed with a f ew per cent of water, the second emulsion became unstable. This indicates a significant effect of pre-washing with water on emulsion stability, possib ly through the removal of emulsion stabilizing agents. Based on analytical results such as surface tension, and FTIR spectra, it appears that a small fraction of bitumen, mostly polar compounds such as carbonic acids and othe r oxygen-containing compounds, are responsible for the emulsion stabilizati on. Emulsion stability decreases with increasing volume of washing water bu t increases with the bitumen concentration.