Information of Water/Oil Emulsions

 The crucial point about applying ultrasound energy to destroy or decompose the pollutants in the oil-based sample is to make good water/oil emulsions. It is important to define, therefore, what is a good water/oil emulsion. Both light microscope and scanning electron microscope (SEM) have been used to study the size distribution of emulsion by direct observation.The resolution and depth of field from SEM are significantly better than in comparison to what can be achieved through optical microscopy. The optical and electron microscopic techniques, however, are quite complimentary in terms of the information that they can provide.Optical microscopy, in fluorescence mode or with polarized light, can provide information about the organic phases in the emulsion. Electron microscopy, through the X-rays excited in the sample, can provide information about the inorganic and mineral phases present (Schramm, 1992). The practical lower limit of emulsion sizing with optical microscopy is at the level of 0.5 um,with the limit as low as 0.1um or less for electron microscopy with direct observation of the frozen sample.Even lower limit such as 0.01um or less can be achieved with replicas and transmission or electron microscopy.

Light polarizing microscopy (Leitz, model SM-LUX-POL) is initially used to observe the emulsion. First, we only checked if water and oil were in good emulsifying state. Later, we measure the micelle size if necessary,which may be needed for determining optimized ultrasound frequency. Since preparation of suitable emulsion samples for SEM observation is difficult, there is no intention to utilize SEM as a tool at this time unless the data from light microscope are not sufficient to provide information for this study.