PNNL

Abstract

Bilgewater formed from the shipboard is regarded as a major pollutant in the marine environment. Bilgewater exist in a stable oil-in-water emulsion form. However, little is known about the oil-in-water (O/W) liquid-liquid (l-l) interface. Traditional bulk characterization approach is not capable of capturing the O/W l-l interface. Although surfactants are deemed important in droplet formation, their roles in bilge stabilization are not fully revealed. We have employed novel in situ chemical imaging tools including in situ scanning electron microscopy (SEM) and in situ time-of-flight secondary ion mass spectrometry (ToF-SIMS) to study the evolving O/W interface using a NAVY bilge model for the first time. Our results show that the droplet size distribution changes from fresh to aged bilge emulsions. The O/W interface is not static. Of particular interest, the contribution of surfactants to the aged bilge droplets becomes more significant as droplet size grows. We provide the first three dimensional images of the evolving O/W interface, demonstrating that in situ chemical imaging tools are powerful to reveal the complex and dynamic l-l interface in the liquid state.