Abstract
In this study, a triblock copolymer was used as additive to fabricate new dual layer hollow fiber membranes with a hydrophilic active inner surface in order to improve their fouling resistance. The polymeric components of the solutions for membrane fabrication were poly(ether sulfone), poly(N-vinyl pyrrolidone), and the triblock copolymer. The additive consists of three blocks: a middle hydrophobic poly(ether sulfone) block and two outer hydrophilic alkyl poly(ethylene glycol) blocks. By varying the additive concentration in the solutions, it was possible to fabricate dual layer hollow fiber membranes that are characterized by a hydrophilic inner layer, a pure water permeance of over 1800 L/(m2 bar h) and a molecular weight cut-off of 100 kDa similar to commercial membranes. Contact angle and composition determination by XPS measurements revealed the hydrophilic character of the membranes, which improved with increasing additive concentration. Rheological, dynamic light scattering, transmission, and cloud point experiments elucidated the molecular interaction, precipitation, and spinning behavior of the solutions. The low-molecular weight additive reduces the solution viscosity and thus the average relaxation time. On the contrary, slow processes appear with increasing additive concentration in the scattering data. Furthermore, phase separation occurred at a lower non-solvent concentration and the precipitation time increased with increasing additive content. These effects revealed a coupling mechanism of the triblock copolymer with poly(N-vinyl pyrrolidone) in solution. The chosen process parameters as well as the additive solutions provide an easy and inexpensive way to create an antifouling protection layer in situ with established recipes of poly(ether sulfone) hollow fiber membranes. Therefore, the membranes are promising candidates for fast integration in the membrane industry.
Highlights
Ultrafiltration membranes, based on poly(ether sulfone) (PESU), are commonly used and well established in the water filtration industry
Membranes 2020, 10, 143 pyrrolidone) (PVP) or poly(ethylene glycol) (PEG) of high molecular weight, the pore diameter and the permeance of the membrane can be adjusted in a way that PESU is applicable in a wide range from gas separation to liquid filtration [1,2]
The chemical cleaning leads to the second drawback of PESU, which is its sensitivity to halogens [3]
Summary
Ultrafiltration membranes, based on poly(ether sulfone) (PESU), are commonly used and well established in the water filtration industry. If the necessity of chemical cleaning can be reduced due to better fouling resistance, the membrane’s lifetime can profit as well Knowing these challenges, one can go to chemically more stable polymers like poly(vinylidene fluoride), poly(phenylene sulfone) or poly(tetrafluoro ethylene), which has been conducted by various groups [5,6,7,8]. One can go to chemically more stable polymers like poly(vinylidene fluoride), poly(phenylene sulfone) or poly(tetrafluoro ethylene), which has been conducted by various groups [5,6,7,8] These materials suffer from other drawbacks like low permeance and difficult processability, or even higher hydrophobicity and lower surface energy. Most recent research articles have been devoted to biomimetic, mussel-inspired surface engineering on polymeric membranes [15]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call