The effect of bore fluid type on performance of treated polysulfone hollow-fiber membrane

Abstract

In this work, atomic force microscopy (AFM) analysis and application of the image processing technique on scanning electron microscope microphotographs were employed to investigate the performance of polysulfone (PSf) hollow-fiber membranes treated with hypochlorite and hot water in relation to composition of bore fluid used during spinning of hollow-fiber membranes. Fiber spinning dope containing PSf/poly vinyl pyrrolidone/ N-methyl-2-pyrrolidone (NMP) in a mass ratio of 15/5/80 were used for production of two types of hollow fibers via the dry-jet wet spinning process. A mixture of NMP and water in a 1/1 ratio, as well as distilled water alone, were used as bore fluids. The membranes were treated using 95℃ water and sodium hypochlorite 4% (w/v). Structurally superior membranes were produced with the mixed bore fluid. In addition, these membranes exhibited higher permeation in comparison to membranes made using other bore fluid. Hypochlorite treatment resulted in an increase in surface roughness of the membranes, and was found to be also responsible for the increase in the average membrane pore size and water flux. The hypochlorite-treated membrane produced using NMP/water as bore fluid exhibited a higher rate of flux than those produced using distilled water. It was also found that treatment with 95℃ water affected both type of membranes. However, the effect of this treatment on the membrane produced with mixed bore fluid was more pronounced. Linear regression was used to establish the correlations between mean surface roughness parameters and hydraulic permeability. AFM analysis strongly supported the consistency of the measured values of water flux.