Development of antifouling ultrafiltration PES membranes for concentration of hemicellulose

Abstract

A new approach for one‐stage facile membrane modification during non‐solvent induced phase separation (NIPS)‐process is proposed. The novelty of this study is that cheap and commercially available anionic high molecular polyacrylamide‐based flocculant (AHMPF) is applied for the first time as an additive to coagulation bath (CB). The series of polyethersulfone membranes were prepared using 0.05–0.3 wt% AHMPF aqueous solution as CB at different temperatures (25–50°C) via NIPS. The effect of AHMPF concentration on the structure, composition and hydrophilicity of membranes was investigated. The separation and antifouling performance were evaluated during filtration of bovine serum albumin (BSA) solution and thermomechanical pulp mills process water (ThMP) in order to concentrate hemicellulose. The successful immobilization of AHMPF into the structure of membranes selective layer (not bottom layer) was confirmed by FTIR spectroscopy. It was established that despite the similar rejection of hemicellulose (88.8–93%) and lignin (20–21.4), modified membranes demonstrate 3–8 times higher flux and 2 times higher FRR (43.8% for reference membrane and 86.5% for modified one) in ThMP ultrafiltration. The developed membrane was found to be highly efficient in hemicellulose concentration and purification in pulp industry.

Development of Antifouling Polysulfone Membranes by Synergistic Modification with Two Different Additives in Casting Solution and Coagulation Bath: Synperonic F108 and Polyacrylic Acid

“…Membrane pure water flux (PWF, L m −2 h −1 ) was determined as a permeate volume passed through the unit of membrane area in the unit of time [ 11 , 19 , 20 , 21 , 22 ]. The ultrafiltration studies were described in detail in [ 17 ].…”

“…The ultrafiltration experimental setup used for the filtration of a recirculating batch of ThMP process water in crossflow mode is described in detail in [ 21 , 22 ].…”

“…Determination of conductivity of ThMP process water feed and permeate solutions as well as content of hemicellulose, lignin, total solids, and ash in samples before and after ThMP process water ultrafiltration was described previously [ 21 , 22 ].…”

“…Another cheap and easy to perform one-step method to increase membrane surface hydrophilicity and to introduce charged groups to the membrane selective layer is to use a polyelectrolyte as an additive in the coagulation bath upon membrane preparation by non-solvent-induced phase separation (NIPS) [ 19 , 20 , 21 , 22 ]. It was shown that an introduction of polyelectrolytes (copolymers of acrylamide and 2-acryloxyethyltrimethylammonium chloride [ 19 , 21 ], copolymers of acrylamide and sodium acrylate [ 20 , 22 ], polyacrylic acid (PAA) [ 23 ], and polyethyleneimine (PEI) [ 24 ]) into the coagulation bath leads to the immobilization of macromolecules in the selective layer because of the interlacing of chains of membrane-forming polymers and polyelectrolytes during membrane formation by NIPS. This occurs due to the diffusion of polyelectrolyte macromolecules inside the nascent polymer membrane.…”

“…This occurs due to the diffusion of polyelectrolyte macromolecules inside the nascent polymer membrane. It was found that the immobilization of polyelectrolytes may significantly improve membrane antifouling performance due to the presence of hydrophilic groups, which are also capable of ionization, in the structure of the membrane selective layer [ 19 , 20 , 21 , 22 , 23 , 24 ]. The polyelectrolyte addition to the coagulation bath was revealed to influence the kinetics of phase separation, due to the rise of coagulant viscosity, which results in a delayed demixing mechanism of the phase inversion, which is confirmed by a significant increase in membrane formation time [ 19 , 20 , 21 , 22 ].…”