Development and characterization of nanoporous carbon membranes for protein ultrafiltration

Nanoporous carbon ultrafiltration membranes could be very attractive for bioprocessing applications, but existing carbon membranes tend to have very low hydraulic permeability due to the large thickness of the carbon layer. We have developed a new method for producing nanoporous carbon membranes using a stainless steel support that has first been modified by slip-casting silica particles into the macropores of the support. The nanoporous carbon membrane is then formed by pyrolysis of polyfurfuryl alcohol with polyethylene glycol used as the pore forming agent. The sub-micron-sized silica particles allow thin integral membranes to be formed after only two or three coats of the polyfurfuryl alcohol. Dextran sieving curves for the nanoporous carbon were similar to those of a commercial 100 kDa polyethersulfone ultrafiltration membrane, with a slightly broader pore size distribution. Performance characteristics for the nanoporous carbon were only slightly below those of commercial polymeric ultrafiltration membranes, but the nanoporous carbon was stable even after prolonged exposure to 3N NaOH. These results demonstrate that high performance nanoporous carbon ultrafiltration membranes can be made using silica-modified stainless steel supports.