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An efficient, antibacterial water filtration membrane

An article based on this release appeared in The Hindu.

An antibacterial membrane for water purification made of polyethylene and graphene oxide has been designed at IISc. This can possibly supplement the reverse osmosis (RO) based water purification systems that are in use today.

The matrix of the membrane is polyethylene, which we all know and is used commonly in polyethylene bags. Polyethylene is an excellent choice for the matrix because it is easy to process, cheap and resistant to chemicals.

Embedded in the polyethylene matrix are graphene oxide sheets. Graphene oxide is a compound of carbon, hydrogen and oxygen in variable ratios; it has a unique property of forming paper like sheets of one-molecule thickness – very, very thin.

To create microscopic pores in the membrane, the researchers mixed polyethylene with polyethylene oxide (PEO) during manufacture. “PEO was added so that it could later be removed to create tiny pores in the membranes,” said Suryasarathi Bose, the corresponding author of the paper, in an interview.

Once the components are mixed by melt mixing process, PEO was “etched out”, or removed, by using water. “This makes the process eco-friendly, since only water is used during the manufacture process,” said Dr. Bose.

Now the porous membrane was ready for testing. When PEO is etched out, it leaves behind tiny, irregularly placed pores. Bacteria are larger than these pores and get filtered out. Suspended solids larger than the pore size are similarly left behind when water is passed through this membrane. Since the pores are not symmetric, even particles smaller than the pores find it hard to move through the membrane, making it an efficient filter.

Graphene oxide per se has been shown to have antibacterial properties. In this study, an amine group (-NH2) has been attached on to the surface to increase the antimicrobial properties of graphene oxide.

“This membrane can be used to support the traditional reverse osmosis set ups”, said Dr. Bose. “It can be a first round of treatment. RO plants end up wasting a lot of water. Using this membrane and RO membrane in combination can increase the efficiency and reduce wastage,” he added.

About the authors:

 

The corresponding author, Suryasarathi Bose is an Assistant Professor in the Department of Materials Engineering, Indian Institute of Science, Bangalore.

Contact: sbose@materials.iisc.ernet.in; Tel: 22933407

The paper has authors from Center for Nano Science and Engineering, Department of Chemical Engineering and Department of Materials Engineering, Indian Institute of Science, Bangalore.

A collaborator is from Polymer Science Diagnostic Center, Steer Engineering Pvt. Ltd, Bangalore-560058.