High pressure injection technique for hypochlorite treatment of polysulfone hollow fibre membranes

Abstract

High pressure injection technique for hypochlorite treatment of polysulfone hollow fibre membranes has been developed. This technique allows injection of the hypochlorite solution into the channel of the fibres at a high pressure. The effect of this treatment on water flux of the membranes is studied. The results are compared with the water flux of identical membranes subjected to traditional hypochlorite treatment. Concentrated polymer solution containing polysulfone (PSf) /poly-vinyl pyrrolidone (PVP-K90)/N-Methyl-2-pyrrolidone (NMP) in weight ratio of 15/5/80 together with two types of bore fluids have been used for the production of two types of hollow fibre membranes via dry-wet-spinning process. Distilled water and mixture of NMP/ distilled water are used as bore fluids. Atomic force microscopic analysis and image processing technique (SEM microphotographs) have been employed to investigate performance of PSf hollow fibres treated with the traditional and high pressure injection techniques in relation to the composition of bore fluid. It is observed that in general both treatment methods result in the increase in water flux of the hollow fibres due to elimination of PVP (poly-vinyl pyrrolidone) swelling and alteration in pore size and pore distribution. The rate of increase in water flux in the membranes treated by high pressure injection technique is found to be higher in comparison to traditionally treated membranes. It is also found that the membranes produced using a mixture of NMP/ distilled water as bore fluid exhibit a higher rate of flux increase than those produced using distilled water. High pressure injection technique yields to production of highly permeable membranes. In addition, it is found that the composition of bore fluid controls the performance of the membranes subjected to hypochlorite treatment.