Materials

Bacterial biofilm wrings oil out of water

Bacterial biofilm wrings oil o...
A microscope image of the bacterial biofilm, made of cellulose, that the researchers used to filter water and oil
A microscope image of the bacterial biofilm, made of cellulose, that the researchers used to filter water and oil
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A microscope image of the bacterial biofilm, made of cellulose, that the researchers used to filter water and oil
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A microscope image of the bacterial biofilm, made of cellulose, that the researchers used to filter water and oil

Once oil gets into water, it can be difficult to separate the two, which can make polluted water tricky to clean up. Now, researchers at North Carolina (NC) State University have found that a bacterial biofilm membrane can effectively let water through while keeping oil out.

Oil can be a major environmental hazard. Obviously that includes huge oil spill disasters like Deepwater Horizon, but even on smaller scales contamination can occur from industrial processes. New clean-up solutions are always in demand.

For the new study, the NC State researchers turned to bacteria to help out. To protect themselves from environmental hazards, bacteria often produce slimy substances called biofilms, which you’ve probably seen forming on everything from your bathroom tiles to your teeth. They’re often considered a pest that needs to be broken down, but perhaps some bacterial biofilms could be put to work for us.

The team found that a bacteria called Gluconacetobacter hansenii creates a particularly useful biofilm. It’s made of cellulose, the substance plants use to build their cell walls, but in this case as a crystalline form.

“It’s one of the purest, if not the purest, forms of cellulose out there,” says Lucian Lucia, corresponding author of the study. “It’s very well structured. It’s very water loving, and it’s got a very high crystallinity, so it packs very beautifully. Once you strip out the bacteria, you have this amazingly tough material that has a real robustness, or toughness.”

The key factor there is that the biofilm is hydrophilic, or “water loving,” while at the same time it’s oleophobic, or “oil hating.” That means it readily takes up water through its pores, while repelling oil.

In experiments, placing the membrane into a mixture of water and oil worked to extract water and leave the oil behind. It even worked in solutions where the water and oil were very thoroughly mixed together.

The team says the material shows promise for applications like cleaning contaminated water. In further studies, the researchers say they will investigate how the material could be modified chemically to make it more suited for different uses. And of course there’s the ever-present question of scalability to contend with.

The research was published in the journal Langmuir.

Source: North Carolina State University

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