Effect of polyvinylpyrrolidone molecular weights on morphology, oil/water separation, mechanical and thermal properties of polyetherimide/polyvinylpyrrolidone hollow fiber membranes

Abstract

ABSTRACT:We prepared polyetherimide (PEI) hollow fiber membranes using polyvinylpyrrolidones (PVP) with different molecular weights (PVP 10,000, PVP 40,000, and PVP 1,300,000) as additives for oil/water separation. Asymmetric hollow fiber membranes were fabricated by wet phase inversion technique from 25 wt % or 30 wt % solids of 20 : 5 : 75 or 20 : 10 : 70 (weight ratio) PEI/PVP/N-metyl-2-pyrrolidone (NMP) solutions and a 95 : 5 NMP/water solution was used as bore fluid to eliminate resistance on the internal surface. Effects of PVP molecular weights on morphology, oil-surfactant-water separation characteristics, mechanical, and thermal properties of PEI/PVP hollow fiber membranes were investigated. It was found that an increase in PVP molecular weight and percentage in PEI/PVP dope solution resulted in the membrane morphology change from the finger-like structure to the spongy structure. Without sodium hypochlorite posttreatment, hollow fiber membranes with higher PVP molecular weights had a higher rejection but with a lower water flux. For oil-surfactant-water emulsion systems (1600 ppm surfactant of sodium dodecylbenzenesulfonate and 2500 ppm oil of n-decane), experimental results illustrated that the rejection rates for surfactant, total organic carbon, and oil were 76.1 Ϸ 79.8%, 91.0 Ϸ 93.0%, and more than 99%, respectively. Based on the glass transition temperature values, PVP existed in hollow fiber membranes and resulted in the hydrophilicity of membranes. In addition, using NaOCl as a posttreatment agent for membranes showed a significant improvement in membrane permeability for PVP with a molecular weight of 1300 K, whereas the elongation at break of the treated hollow fiber membranes decreased significantly.

Hollow fiber ultrafiltration membranes made from blends of PAN and PVP

“…This could be attributed to the reaction between hypochlorite and PVP that caused chain scission of PVP molecules and the eventual leaching of PVP from the membrane matrix [8], which was subsequently confirmed by the SEM images. The results in this study were also in agreement with the previous work [10][11][12]. Table 3 also indicates that there were no significant changes in both pure water flux and retention of the membranes treated under different concentrations of 500 and 1000 mg l −1 , which suggested that there was an optimum hypochlorite concentration around 500 mg l −1 for the treatment to achieve a high flux PAN membrane.…”

“…1a and b reveal that the cross-section of the as-spun fiber had a finger-like structure going through from the inside to the outer side of the fiber. This indicates that the addition of 3% PVP 360K in the dope solution was not enough to suppress macrovoids, which was in agreement with [10]. Fig.…”

“…The air gap length during spinning impacts performance of the final fibers and it has been investigated by a number of researchers [5][6][7][8]. Hypochlorite treatment has been applied to increase flux of MF/UF membranes made from a blend of PVP and hydrophobic polymers [8][9][10][11][12].…”

Functional Properties of Punica granatum L. Juice Clarified by Hollow Fiber Membranes

“…The enhancement in membrane hydrophilicity could be related to the presence of the hydrophilic PVP into the polymeric matrix and not washed away during membrane post-treatment with water [29][30][31]. The water permeability is reported in Table 2.…”

Development of a LCST membrane forming system for cellulose acetate ultrafiltration hollow fiber

“…However, the addition of PVP with high molecular mass results in a low flux membrane due to swelling of the residual PVP at the surface of pore walls when water passes through the membrane pores [14]. Therefore, hypochlorite treatment has been applied to increase flux of MF/UF membranes made from a blend of PVP and hydrophobic polymers [14][15][16][17]. Recently, the authors [18,19] have investigated hypochlorite treatment over different time and different concentrations to achieve high flux membranes spun from blends of CA and PVP.…”