Magnetic nanoparticles can separate oil and water in seconds, according to new research from the UT Petroleum and Geosystems Engineering department.

Current methods in the oil and gas industry use a technique called gravitational separation, which can’t separate very small oil droplets, just microns in size. The resulting water is not safe for human use due to these droplets, and can be difficult to dispose of, according to Saebom Ko, Petroleum and Geosystems research associate and lead author.

“Our technology aims to remove these tiny oil droplets as the post treatment,” Ko said.

The new technique involves making magnetic nanoparticles from iron salts in alkaline solutions at high temperatures and coating them with a specific polymer. These salts are mixed with the oil-water mixture, and the negatively-charged oil droplets attach to the positively-charged magnetic nanoparticles. Then, a magnet easily separates the treated water and the nanoparticles attached to the oil.  

“For the best results, the particles and the mixture are mixed for 10 to 15 minutes. The oil is removed in a matter of seconds,” Hugh Daigle, Petroleum and Geosystems assistant professor, said. The research team also includes Thomas Milner of the UT Biomedical Engineering department.

Millions of gallons of water used in hydraulic fracturing can be treated effectively using the new technique, according to the study. The magnetic nanoparticles can also clean up oil spills that would have otherwise been disastrous, and could potentially remove lead and other toxic chemicals from drinking water.

Although a research group at MIT has used nanoparticles that soak into the oil and employed a skimming machine to clean up spills, Daigle said this is the first time magnetic nanoparticles have been used to completely separate the oil from water.

Ko said the research team first got the idea through extensive magnetic separations and nanoparticle research in the mining, food and biomedical industries, but they initially had difficulties finding the proper polymers to be coated on the nanoparticles.

“First we used commercially available magnetic nanoparticles, then we switched to synthesize particles in our lab,” Ko said.

For now, the researchers are working to produce magnetic nanoparticles on a large scale, create a continuous flow system for oil droplet removal and design a method to reuse the particles.

Daigle said that the biggest potential problem could come in the form of dissolved solids, such as little pieces of dust or organic matter. Organic contaminants, which have very similar properties to oil, might be picked up along with the oil droplets, he said.

“Currently, some of the nanoparticles conglomerate, or stick together,” Milner said. “We’re looking at using a laser to help break them apart.”