Effect of poly(vinyl pyrrolidone) concentration and coagulation bath temperature on the morphology, permeability, and thermal stability of asymmetric cellulose acetate membranes

Abstract

Cellulose acetate (CA) is widely used in membrane processes. In this study, CA (weight-average molecular weight ¼ 52,000) was mixed with poly(vinyl pyrrolidone) (PVP; weight-average molecular weight ¼ 15,000) as an additive in 1-methyl-2-pyrrolidone as a solvent. The phase-inversion method was used for the preparation of flat-sheet membranes. The effects of PVP concentration and coagulation bath temperature (CBT) on the morphology, pure water permeation flux, and thermal stability of the prepared membranes were studied and are discussed in this article. The solute rejection of the developed CA membranes was quantified with an insulin protein solution. The results showed that an increase in the CBT levels from 0 to 23C along with an increase in the PVP concentration in the cast film from 0 to 1.5 wt % resulted in an increase in the macrovoid formation in the membrane sublayer, an increase in the pure water flux (PWF), and a decrease in insulin rejection. Further increases in the PVP concentration from 1.5 to 3, 6, and 9 wt % resulted in gradual suppression of the macrovoid formation, a decrease in PWF, and an increase in insulin rejection. Higher PVP concentrations and lower CBT levels also appeared to result in higher glass-transition temperatures.

Preparation of modified polyethersulfone membranes using variation in coagulation bath temperature and addition of hydrophilic surfactant

“…4). The aforementioned observations are in agreement with the literature [3,20]. In general, it can be said that the formation of more porous structure occurs under quick precipitation conditions, and the precipitation is faster at higher temperatures.…”

Preparation and characterization of poly (ethersulfone) nanofiltration membranes for amoxicillin removal from contaminated water

“…Details of membrane formation mechanism were explained by Saljoughi and coworkers [21-24]. NMP (solvent) is hydrophilic and Brij ® S100 is amphiphilic (i.e.…”

“…The formation of this micelle decreases the interaction between polymer chains [16]. Both phenomena result in instantaneous demixing in the coagulant bath [22-24]. As a result of the fact the growth of skin layer is reduced and formation of finger-like pores in the support is improved.…”

“…%) and because of the importance of viscosity effects, delayed demixing is preferred over instantaneous demixing. So higher concentrations of Brij ® S100 can lead to the suppression of macrovoids and formation of denser structures [24]. Hence, it can be concluded that addition of hydrophilic additives such as Brij ® S100 to the casting solution has a dual effect on the membrane morphology.…”

"SYNERGISTIC ABILITY OF PSf AND PVDF TO DEVELOP HIGH-PERFORMANCE PSf/PVDF COATED MEMBRANE FOR WATER TREATMENT"

“…This is not surprising in consideration by the phase inversion kinetics. [38][39] Stirring process of the casting solution is a mixing process, where nuclei of a polymer-poor phase continue to grow with the continuation of the NH4Cl distribution between PSf and PVDF particles. Thus, the rate of the additive distribution affects the membrane structure.…”