Novel polymer membrane can keep separating oil from water

Polymer scientists from the University of Groningen and NHL Stenden University of Applied Sciences, both in the Netherlands, have developed a polymer membrane from biobased malic acid. This superamphiphilic vitrimer epoxy resin membrane can be used to separate water and oil, and is fully recyclable. When the membrane's pores are blocked by foulants, it can be depolymerized, cleaned and subsequently pressed into a new membrane. The scientists report the new membrane in a paper in Advanced Materials

Superamphiphilic membranes that 'love' both oil and water are promising materials for cleaning up oil spills in water, but they aren't very practical yet. Existing membranes are often not robust enough for use outside the laboratory environment and their pores can clog as a result of fouling with algae and sand. Now, however, Chongnan Ye and Katja Loos from the University of Groningen and Vincent Voet and Rudy Folkersma from NHL Stenden have used a relatively new type of polymer to create a membrane that is both strong and easy to recycle.

In recent years, the researchers from both institutes have joined forces to investigate vitrimer plastics. These are polymer materials with the mechanical properties and chemical resistance of a thermoset plastic, but which also possess properties of a thermoplastic, since they can be depolymerized and reused.

This means that a vitrimer plastic has all the qualities to make a good membrane for oil spill remediation. "Furthermore, it was made from malic acid, a natural monomer," adds Loos.

"The polymers in the vitrimer are crosslinked in a reversible manner," explains Voet. "They form a dynamic network, which enables recycling of the membrane." The vitrimer is produced via base-catalyzed ring-opening polymerization between pristine and epoxy-modified biobased malic acid. It is then ground into a powder by ball milling and turned into a porous membrane through the process of sintering.

In an oil spill, both water and oil will spread out on the superamphiphilic membrane. But because much more water is present than oil, the membrane becomes covered in water, which can then pass through the pores. "The water film on the membrane's surface keeps the oil out of the pores so that it is separated from the water," says Voet.

When sand and algae clog up the pores, the membrane can be depolymerized and then recreated from the building blocks after the pollutants are removed. "We have tested this on a laboratory scale of a few square centimetres," says Loos. "And we are confident that our methods are scalable, both for the polymer synthesis and for the production and recycling of the membrane." The scientists are hoping that an industrial partner will take up further development.

Creating this new membrane for oil spill remediation shows the power of cooperation between a research university and an applied university. "A while ago, we decided that the polymer groups at the two institutes should become one, by sharing students, staff and facilities. We recently started the first hybrid research group in the Netherlands," explains Loos. This makes it easier to find applications for newly designed materials.

"Polymer chemists strive to link molecular structures to material properties and applications," adds Voet. "Our hybrid research team has the experience to do just that."

This story is adapted from material from the University of Groningen, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.