Ultrafiltration membrane synthesis by nanoscale templating of porous carbon

A novel method for producing carbon membranes for ultrafiltration applications is presented using a spray deposition and pyrolysis of poly(furfuryl alcohol)/poly(ethylene glycol) mixtures on macroporous stainless steel supports. The poly(ethylene glycol) or PEG employed as a carbonization template creates a mesoporosity that leads to pores in the ultrafiltration range. Scanning electron microscopy (SEM) shows that the membranes consisted of 12- to 15-μm thick carbon films. Gas permeation and water permeability data were used for the calculation of mean pore sizes, which were found to decrease with decreasing average molecular weight of the PEG template. Ultrafiltration of a polydisperse dextran solution was used to quantify the retention properties of the membranes. Molecular weight cutoffs determined from dextran retention data were shown to vary with template molecular weight: values of 2 × 10⁴, 3.5 × 10⁴, and 6 × 10⁴ g mol^-1 dextran were measured for respective templates of 2000, 3400, and 8000 g mol^-1 PEG. For PEG molecular weights of 2000 or below, the templating effect was ill defined, membrane film cracking became more prominent, and membrane selectivity and reproducibility were adversely affected.