Effect of Temperature Exposition of Casting Solution on Properties of Polysulfone Hollow Fiber Membranes

Abstract

It was shown for the first time that the conditions of thermal treatment of the casting solution significantly affect the morphology and transport properties of porous, flat, and hollow fiber polysulfone (PSf) membranes. It is ascertained that the main solution components that are subjected to thermo-oxidative destruction are the pore-forming agent polyethylene glycol (PEG) and solvent N-methyl-2-pyrrolidone (NMP). It is proved that hydroxyl groups of PEG actively react in the process of the casting solution thermo-oxidative destruction. It is shown that despite the chemical conversion taking place in the casting solution, their stability towards coagulation virtually does not change. The differences in the membrane morphology associated with the increase of thermal treatment time at 120 °C are not connected to the thermodynamic properties of the casting solutions, but with the kinetics of the phase separation. It is revealed that the change of morphology and transport properties of membranes is connected with the increase of the casting solution viscosity. The rise of solution viscosity resulted in the slowdown of the phase separation and formation of a more densely packed membrane structure with less pronounced macropores. It is determined experimentally that with the increase of casting solution thermal treatment time, the membrane selective layer thickness increases. This leads to the decrease of gas permeance and the rise of the He/CO2 selectivity for flat and hollow fiber membranes. In the case of hollow fibers, the fall of gas permeance is also connected with the appearance of the sponge-like layer at the outer surface of membranes. The increase of selectivity and decline of permeance indicates the reduction of selective layer pore size and its densification, which agrees well with the calculation results of the average membrane density. The results obtained are relevant to any polymeric casting solution containing NMP and/or PEG and treated at temperatures above 60 °C.

Fouling Analysis on Polysulfone/Peg400/ZnO Membrane during Textile Wastewater Treatment

“…When the PSf concentration was reduced to 18 wt.%, the permeate flux increased up to 2 times (from 25 to 54 L.m -2 .h -1 ). By lowering the PSf concentration, the lower viscosity allowed the formation of larger membrane pores, which reduced the membrane resistance and enhanced the mass transfer (Ariono et al, 2017, Borisov et al, 2019. The stability of permeate flux in each UF membrane was observed based on normalized flux, i.e., the ratio between the flux at a certain time to the initial flux (J/Jo) (Figure 3b).…”

Express Method of Preparation of Hollow Fiber Membrane Samples for Spinning Solution Optimization: Polysulfone as Example

“…However, with an increase in the wall thickness in these membranes, the layer with finger-shaped pores was replaced by a dense support layer with spongy pores. In addition, the wall thickness increased with an increase in the viscosity of the solution [18].…”

“…This may be explained either by the formation of a spongy structure in the walls of PSf HF membranes PSf-20, PSf-24, PSf-PEG400-20, PSf-PEGG400-24, or by the formation of thick walls due to the high viscosity of the casting solutions, as in the case of the PSF-PVP-20 and PSf-PVP-24 membranes. crease in the viscosity of the solution [18].…”

“…The latest review of 2020 contains research on the development of casting methods of HF membranes that are safe for humans and the environment [11] Polysulfone (PSf) is one of the most common polymers for the manufacture of HF membranes for micro-, ultrafiltration, gas separation, and membrane contactors [12][13][14]. In scientific works on the formation of HF membranes from this polymer, the influence of the molecular weight and concentration of the matrix polymer, the solvent used, the type of pore-forming agent, its molecular weight and concentration, the nature and composition of the coagulant on their transport and separation properties has been studied in detail [15][16][17][18].…”

Impact of Ionic Liquid Structure and Loading on Gas Sorption and Permeation for ZIF-8-Based Composites and Mixed Matrix Membranes

“…The PSf membrane remained stable until reaching its decomposition temperature of 749 K (Table 2) [59]. The membranes abruptly started to decompose, reaching below 90wt.% of initial mass sample at 773 K. Similarly, the 10wt.% ZIF-8 (PSf) membrane showed signs of decay sooner, with an intermediate decomposition of less than 5wt.% at 473 K, which is potentially related to moisture in the membrane.…”