Single-side hydrolysis of hollow fiber polyacrylonitrile membrane by an interfacial hydrolysis of a solvent-impregnated membrane

Abstract

a b s t r a c tIn this paper, a new method was proposed to improve the mechanical strength and flux of polyacrylonitrile (PAN)-based membrane by a single-side hydrolysis of hollow fiber PAN substrate membrane. A non-water miscible solvent of cyclohexane was firstly incorporated into membrane pores to form cyclohexane-impregnated hollow fiber PAN membrane by stepwise solvent replacement method. Alkaline aqueous solution was then fed into lumen side to introduce interfacial hydrolysis reaction on the inner surface of hollow fiber by using the cyclohexane/water phase interface. After the reaction, the cyclohexane incorporated was displaced by water to remain the pore pathway. The ATR-FTIR and EDX analyses confirmed that the alkaline hydrolysis did not occur in the membrane pores. SEM and AFM were also conducted to further understand the microtopographical changes on membrane surfaces. During the assembly of PAN-based polyelectrolyte pervaporation composite membranes, both flux and mechanical strength was highly improved by using single-side hydrolysis of PAN substrate membrane while the selectivity was still kept at a relatively high level.

Surface modification of PAN hollow fiber membrane by chemical reaction

“…This changing color has been reported also in previous researches on PAN fibers [2]. The reason can be probably the long heating time during reaction process (temperatures > 60 o C).…”

“…In the diagram related to PAN sample, regardless to previous investigations [2,15,26], the peak observed at 2937 cm -1 can be attributed to C-H bond, or so-called CH stretching. The peak at 2243 cm -1 is related to the nitrile group (-CN).…”

“…Hollow fiber ultrafiltration membranes are widely used for water/waste water treatment and also as an RO pretreatment [1][2][3]. Because of its high degree of solvent resistance and good chemical and thermal stability, polyacrylonitrile has been successfully used in preparation of microfiltration and ultrafiltration membranes [4][5][6].…”

“…Zhang et al [2] studied the hydrolysis of PAN hollow fibers in the lumen side. They observed a subtle increment in separation of PEG-20 kDa, from almost 85.75 percent for intact fibers to nearly 87.23 percent for hydrolyzed ones.…”

Surface-modified polyacrylonitrile nanofibres as supports

“…Zhang et al [29] made use of series of steps to immobilize ligands on PAN nanofibres. The first step involved alkaline hydrolysis with NaOH to generate a surface structure of polyacrylamide and polyacrylic acid.…”