Oil famously does not mix with water but when joined together, the two liquids can be very difficult to separate.
Several methods can get the job done depending on the relative amount of water and oil or the size of oil droplets. For emulsified oil, the most efficient way is to use a membrane that can filter tiny droplets out of the water.
However, membranes immediately get "fouled" and would need to be cleaned.
In a paper published in the journal Applied Materials and Interfaces, a team of researchers from MIT discussed an imaging tool that enables the development of a new membrane material that can resist fouling.
What Is Inside A Membrane?
Gregory Rutledge, a professor of chemical engineering and one of the authors of the paper, said that the fouling process is nearly impossible to observe. The filtration membranes are usually tightly packed and "tend to be very hard to look inside of."
"There's a lot of effort to develop new types of membranes, but when they get put in service, you want to see how they interact with the contaminated water, and they don't lend themselves to easy examination," he explained in a press release.
The solution they proposed involves the use of two lasers to scan the material layer by layer. The technique is called confocal laser scanning microscopy.
When the two laser beams cross, the material marked with a fluorescent dye glows. For their experiment, the researchers used two dyes: one on the oil in the fluid and the other on the fibers of the membrane.
More Efficient Way To Separate Oil And Water
The technique allowed for the creation of a full 3D image of the way the droplets of oil are dispersed throughout the membrane. This can provide a better understanding of how the separation between oil and water take place and of what fouling really is.
"The hope is that with a better understanding of the mechanism of fouling, people will be able to spend more time on the techniques that are more likely to succeed," Rutledge said. He added that engineers can design different types of membranes to deal with varying effluents.
The researchers believe that the technique can also be used in the study of how mixed fluids interact and to observe the separation of other kinds of mixtures, such as solid particles in liquids.