Free-standing membranes made of activated boron nitride for efficient water cleaning

Developing membranes with excellent mechanical strength and chemical stability is a practically important issue for efficient removal of pollutants from wastewater. In this work, we report on a free-standing membrane fabrication from an activated boron nitride (ABN) micro-ribbon. The membrane techniques we used, combine the intrinsic active adsorption competence of ABN and the mechanical advantages of conventional membrane filtration. The obtained membranes show an excellent removal ability of water pollutants through a simple filtration adsorption process. The examined pollutants include toxic metallic ions and organics. We showed that the dye (like methylene blue) removal ability significantly exceeded that of activated carbon by an order of magnitude at least; lead ions (Pb2+) in wastewater can be nearly fully removed, the starting 5 mg L−1 concentration was reduced to less than 0.01 mg L−1 after the 600 μm-thickness membrane adsorption filtration. Moreover, the membranes can be stacked together to further improve the adsorption capacity because of their high permeability. The excellent reusable performance of the filtration membranes was also confirmed. We believe that the reported work should open the way toward the practical application of ABN membranes in the field of wastewater purification.