Bill is currently a postdoctoral research associate working in the Elimelech group. The focus of his research efforts are membrane-based water purification technologies. Recent advances in the characterization of materials at the nanoscale allow for correlations to be made between a material’s nano-structure and chemistry and the membrane’s macroscale properties. Understanding this link between nano-scale and macro-scale properties allows for the development of new membranes from novel self-assembled nanomaterials, which offer improved performance and efficiency compared to current commercial membranes. In particular, research efforts will focus on the use of nanoscale ionic materials and copolymers to improve forward osmosis, reverse osmosis and nanofiltration membranes.
Bill received his Ph.D. from the University of Minnesota – CEMS department working with Professor Ed Cussler. The research focus of his graduate studies was the use of block polymer thin films to perform selective membrane separations. These films, made of a polymer with two or more chemically distinct segments, self-assemble into a wide variety of structures. Depending on the constituent polymers and microstructure used, the transport properties of these films can vary dramatically.
Two different membrane types were the focus of his efforts. The core work of his thesis focused on making membranes with monodisperse 20 nm pores which span the membranes thickness. Controlling the solvent evaporation rate allows for membranes up to 100 cm2. in area to be made. These membranes are compared to phase inversion membranes which do not have a well defined pore size and can contain anomalous macrovoids which compromise the desired separation.
A second type of thin film research on which he focused was ammonia selective membranes. These membranes, made of crosslinked block polymers containing a sulfonated styrene block, are over one hundred times more permeable to ammonia than to nitrogen and hydrogen. This selectivity, measured with mixed gases, is the same as that expected from the fluxes of pure gases. So, the actual selectivity is within experimental error the same as the ideal selectivity. These membranes may find application in the Haber process reactor.
