Selective Filtration of Fluids in Materials with Slit-Shaped Nanopores

Resumo

Problems associated with a qualitative increase in the selectivity of fluid filtration remain the major challenge in a variety of areas such as fluid transport through porous materials and media, ion separation, water desalination and purification, and many others. A promising way to solve these problems is to design and develop membranes with slit-shaped nanopores. In the paper, we studied the selectivity and permeability of slitshaped nanosized pores in the natural mineral (hydroxyapatite) with the use of the nonequilibrium molecular dynamics approach with all-atom models. We showed that the subnanometer-wide slit-shaped pores in hydroxyapatite are able to demonstrate both good salt rejection and relatively high water permeability. In particular, the numerically predicted water permeability of hydroxyapatite with 0.4 nm thick slit-shaped nanopores reaches about 200 L/(m² h bar) that is higher than that of commercial membranes and has the same order of magnitude as the theoretically predicted water permeability through single-layer MoS₂ nanoporous membranes. An increase in the nanopore thickness is accompanied by a multiple growth in permeability, which is comparable with advanced 2D-CAP (2D-conjugated aromatic polymer) membranes, but in so doing the filtration selectivity is lost. The results show that nanoporous materials with the connected network of slit-shaped nanopores is a promising filter material for water treatment including seawater desalination and other important technical and environmental applications.