The right blend of polymers enables rapid and molecule-selective filtering of tiny particles from water.
A method of fabricating polymer membranes with nanometer-scale holes that overcomes some practical challenges has been demonstrated by researchers at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia.
Porous membranes can filter pollutants from a liquid, and the smaller the holes, the finer the particles the membrane can remove. The KAUST team developed a block copolymer membrane with pores as small as 1.5 nanometers but with increased water flux, the volume processed per hour by a membrane of a certain area.
A nanofilter needs to be efficient at rejecting specific molecules, be producible on a large scale, filter liquid quickly and be resistant to fouling or the build-up of removed micropollutants on the surface.
Block copolymers have emerged as a viable material for this application. Their characteristics allow them to self-assemble into regular patterns that enable the creation of nanoporous materials with pores as small as 10 nanometers.
However, reducing the size further to three nanometers has only been possible by post-treating the membrane (depositing gold, for example). Moreover, smaller holes usually reduce the water flux.
Klaus-Viktor Peinemann from the KAUST Advanced Membranes & Porous Materials Center and Suzana Nunes from the KAUST Biological and Environmental Science and Engineering Division formed a multidisciplinary team to find a solution.
“We mixed two block copolymers in a casting solution, tuning the process by choosing the right copolymer systems, solvents, casting conditions," explained Haizhou Yu, a postdoctoral fellow in Peinemann’s group. This approach is an improvement on alternatives because it doesn’t require material post-treatment.
Peinemann and colleagues blended polystyrene-b-poly(acrylic acid) and polystyrene-b-poly(4-vinylpyridine) in a ratio of six to one. This created a sponge-like layer with a 60 nanometer film on top. Material analysis showed that nanoscale pores formed spontaneously without the need for direct patterning1.
The researchers used their nanofiltration material to filter the biological molecule protoporphyrin IX from water. The filter simultaneously allowed another molecule, lysine, to pass through, demonstrating its molecular selectivity. The researchers were able to filter 540 liters per hour for every square meter of membrane, which is approximately 10 times faster than commercial nanofiltration membranes.
The groups teamed up with Victor Calo from the University's Physical Science and Engineering Division to develop computer models to understand the mechanism of pore formation. They showed that the simultaneous decrease in pore size and increase in flux was possible because, while the pores are smaller, the pore density in the block copolymer is higher.
“In the future, we hope to optimize membranes for protein separation and other applications by changing the copolymer composition, synthesizing new polymers and mixing with additives,” said Nunes.
Angewandte Chemie International Edition
Michelle D'Antoni | Research SEA
Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery
20.01.2017 | GSI Helmholtzzentrum für Schwerionenforschung GmbH
Seeking structure with metagenome sequences
20.01.2017 | DOE/Joint Genome Institute
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
20.01.2017 | Awards Funding
20.01.2017 | Materials Sciences
20.01.2017 | Life Sciences