Hydrolysis differences of polyacrylonitrile support membrane and its influences on polyacrylonitrile-based membrane performance

As polyacrylonitrile (PAN)-based membrane plays an important role in the processes of pervaporation, bioproduct purification and water treatment, this study aims at better understanding the hydrolysis differences by using different alkaline species, and how the hydrolysis degree affect the subsequent modification of hydrolyzed PAN membranes. The ATR-FTIR spectra and the measurements of ion exchange capacity (IEC) demonstrated the differences of hydrolysis degree among the KOH, NaOH and LiOH hydrolyzed PAN membranes. The microtopographical changes on membrane surfaces were characterized by atomic force microscopy. It was found that the membrane surface roughness decreased with the increase in the hydrolysis degree. The molecular weight cut-off (MWCO) of the hydrolyzed membranes was determined by filtration studies using poly(ethylene glycol) and Cytochrome C solutions. It was noted that the MWCO of the PAN membranes decreased from 20,000 to 6000 after hydrolysis with 2 N NaOH or 2 N KOH for 1 h at 65°C. Subsequently, the polyethyleneimine (PEI) was deposited on the top surface of the hydrolyzed PAN membrane to form a composite membrane. The pervaporation performance and ions rejection property of the PAN/PEI composite membrane clearly demonstrated that the hydrolysis difference had a great influence on subsequent modification of the PAN-based membrane.