Understanding the Ion Transport Through the Charged Nanochannel Systems

Here I present a comprehensive study of the ion transport properties through the charged nanochannel systems was done by developing several types of boron nitride nanostructures including the CVD deposited boron nitride- alumina oxide (BN-AAO) membranes and boron nitride – SiO2 nanochannels, lamellar boron nitride flake membranes, and 3-nm boron nitride nanotube dispersed polyurethane composite (BNNT-polyurethane) membranes. Membrane transport properties through the different nanostructures were studied by testing the effect of surface properties and solution properties on the ion transport. We systematically investigate the effect of membrane structure (pore size, pore density and membrane morphologies) and the surface properties (surface defects, crystal structures and surface chare density) on the ion transport properties via various experimental and numerical methods. The membrane morphology was characterized experimentally by scanning electronic microscope (SEM) and atomic force microscope (AFM) while the surface properties were measured using Raman spectroscopy, X-Ray Diffraction (XRD) and conductance-based surface charge density measurement. The ion transport properties of the membrane were measured by a number for diffusion-based measurements and electrochemical methods. Molecular dynamic (MD) simulation studies were also employed to help investigate the interaction between membranes and the ions species. After understanding the transport characteristics, the BN-AAO membranes were explored for their applications for osmotic power generation while the h-BN lamellar membranes and BNNT-polyurethane membranes were tested for their ion separation and water purification performance. The BN-AAO membranes show an improved performance compared to most other nanofluidic reverse electrodialysis systems while the h-BN flake membranes show a high rejection with a better permeability than most other 2D-layered membranes.