Hydrophilic Dual Layer Hollow Fiber Membranes for Ultrafiltration

Abstract

<jats:p>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.</jats:p>

Open-Celled Foams of Polyethersulfone/Poly(N-vinylpyrrolidone) Blends for Ultrafiltration Applications

“…PESU is widely used for membranes as it provides high thermal stability due to its high glass transition temperature, good chemical stability due to the presence of sulfonyl groups and ether linkages, and favorable structural stability due to the presence of two aromatic groups in the repeating unit [ 32 ]. PESU membranes are also preferred for ultrafiltration applications due to their capability to deliver reliable retention values and high porosity [ 33 ]. Some researchers used poly( N -vinylpyrrolidone) (PVP) as a water-soluble ‘pore-opener’ along with poly(arylsulfones) to produce ultrafiltration membranes from solutions in organic solvent [ 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ].…”

“…PESU membranes are also preferred for ultrafiltration applications due to their capability to deliver reliable retention values and high porosity [ 33 ]. Some researchers used poly( N -vinylpyrrolidone) (PVP) as a water-soluble ‘pore-opener’ along with poly(arylsulfones) to produce ultrafiltration membranes from solutions in organic solvent [ 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ]. Therefore, due to the proven application of PESU and PVP in ultrafiltration membranes, we use blends of PESU and PVP in this work.…”

“…As PVP is soluble in a variety of commonly available compounds such as water and aqueous solutions of sodium hypochlorite (NaOCl), a permeable selective layer could be created through the dissolution of PVP. NaOCl is selected due to its proven suitability for post-processing of PESU/PVP membranes [ 33 , 35 , 39 ]. The outer surface in batch foams commonly contains cracks that occur due to the expansion of the sample during foaming.…”

Formation of Hydrogels Based on a Copolymer of N-Vinyl-2-pyrrolidone and Glycidyl Methacrylate in the Presence of the Reaction Product of 1,3-Dimethylmidazolium Dimethylphosphate and Elemental Sulfur

“…Poly( N -vinyl-2-pyrrolidone) is one of the water-soluble polymers promising for the creation of adhesive compositions [ 1 ], wastewater treatment systems [ 2 , 3 ] and drug delivery [ 4 , 5 , 6 ]. Poly( N -vinyl-2-pyrrolidone) is also used to impart hydrophilic properties to fibers [ 7 , 8 ], as a modifier and pore-forming agent in the preparation of membranes [ 8 , 9 , 10 , 11 ], as well as for the formation of nanoparticles [ 12 , 13 ] and hydrogels [ 14 ]. Although poly( N -vinyl-2-pyrrolidone)-based hydrogels are promising for the inclusion of drugs and water treatment [ 6 ], the chemical inertia of N -vinyl-2-pyrrolidone residues [ 5 , 6 ] creates impediments for crosslinking chains in one stage under mild conditions.…”

Dual Layer Hollow Fiber Membranes with Functionalized Separation Layer for Improved Hydrophilicity

“…Die hydrophilen Anteile der Additive, bestehend aus monofunktionalen Polyalkylenoxiden mit je 80 Ethylenoxideinheiten, umrahmen den hydrophoben Block, der dem Matrixpolymer PESU entspricht und für eine Verankerung der hydrophilen Enden in die Membranstruktur sorgt. Die so funktionalisierten Membranen werden in dieser Arbeit 15 eingehend hinsichtlich ihrer Morphologie, Hydrophilie und Ultrafiltrationsleistung untersucht, um anschließend die vielversprechendste Membran zu selektieren.…”