A super-strong membrane for industrial filtration

Scientists from the Imperial College London have developed an ultrathin membrane that is suitable for a range of industrial filtration processes. Their prototype solves the problems associated with typical membranes, which are not as energy-intensive as other separation methods but are also costly to scale up and are not resistant to organic solvents.

“Membranes are currently used for a range of important tasks, such as making water drinkable and life-saving kidney filtering,” said study co-author Professor Andrew Livingston. “The drawback has been that industry hasn’t been able to use membranes in organic liquid systems more widely because they’ve had cost and design limitations.”

The team created their own membrane with nanoscale crumples, providing an increased surface area for filtering substances that remains strong and does not buckle — even under extreme pressures. The prototype membrane is said to be extremely thin and permeable, able to filter organic liquids at pressures of around 50 bar (the equivalent to the pressure at around 500 m below the ocean’s surface), durable and resistant to a range of organic solvents.

To test the effectiveness of the membrane in the lab, the team mixed together a solution containing a solvent, alcohol and dyed molecules of different colours and sizes. They then made the solution percolate through the membrane at high pressures, using a device called a dead-end cell, to see if they could filter out everything apart from the alcohol. The team observed the process using an absorption spectroscopy device, which uses light at different wavelengths to determine what molecules are passing through the membrane.

The membrane was found to be completely effective, with only the alcohol passing through. When comparing the prototype to a conventional membrane, the researchers found it could separate substances 400 times faster. The results of their study have been published in the journal Science.

The prototype is 80 mm in diameter, but the team is confident that it can be scaled up for use in industries such as pharmaceuticals, manufacturing and oil refining. Their ultimate goal is for the crumpled membrane to improve or completely replace industrial processes that process organic solvents, which currently rely on energy-intensive evaporation and distillation techniques.

“We now want to work even more closely with industry to further refine our membranes so that they can meet their needs,” said co-author Dr Santanu Karan. “We hope our work will lead to new collaborations and, ultimately, improvements in the way industries use separation processes.”

Image credit: Imperial College London.