Smart membranes, made in water
At the University of Twente, Wiebe de Vos, who was recently appointed associate professor, is working on a clean alternative that is just as simple. An added benefit of his method is that an even greater variety of membranes can be produced. "This development can be compared to the transition we saw with paint. That used to be full of harmful solvents, but now most of the paint you buy in the hardware store is based on water. With our new production method, we are on the verge of a similar transition to a cleaner product in membrane technology. And the nice thing for manufacturers is that they only need to make minor adjustments to their current equipment."
De Vos's method is called Aqueous Phase Separation and is based on charged polymers. "We prepare a solution of two different polymers with a high pH value. Under those circumstances, one of the two polymers is negatively charged, the other is still neutral. By immersing a film of this solution in an acidic bath, the second polymer gains a positive charge. The oppositely charged polymers attract each other and cluster, forming a new complex material. This complex then precipitates as a porous film: the membrane. The speed at which the polymers cluster determines the final structure of the membrane. The faster the clustering, the smaller the holes. By varying parameters like the composition and concentration of the two polymers, or the acidity of the solutions, you can create different types of membranes according to your needs."
In a recent article in the journal Advanced Functional Materials De Vos and his colleagues prove that this method leads to reproducible membranes in which the pore size can be controlled very accurately. In addition, they show that the resulting membranes are robust and perform well in common applications such as drinking water filtration.
SOURCE ON PHYS.ORG