Evidencing the chemical degradation of a hydrophilised PES ultrafiltration membrane despite protein fouling

Abstract

Hydrophilisation of polyethersulfone (PES) based membrane is often achieved by addition of polyvinylpyrrolidone (PVP) leading to a physical blend of the two polymers. This paper shows that the most commonly used membrane for UF in dairy industry is a PES/PVP based one. Nevertheless if hydrophilisation limits the organic fouling, PVP is also the Achilles heel of these membranes. It is particularly true when membranes are exposed to hypochlorite as it is the case for cleaning/disinfection steps. Evidencing the disappearance of PVP from a pristine PES/PVP membrane can be easily achieved by FTIR-ATR analyses. But when one wants to study the ageing of a membrane used in UF it gets more complicated: regardless of the cleaning efficiency the membrane always remains fouled by some proteins. As both PVP and proteins own chemical bounds leading to absorption at the same wavenumber in FTIR-ATR, it thereby prevents the easy highlighting of the PVP degradation. The aim of this paper is to propose a simple treatment of raw FTIR-ATR spectra to dissociate these two contributions, allowing consequently the study of the degradation of a fouled membrane. Then the procedure is applied to a real case study on a spiral membrane. 2 1. Highlights Ͳ Ͳ Ğ|ŝĚĞŶĐŝŶŐ W^ͬWsW ŵĞŵďƌĂŶĞ ĚĞŐƌĂĚĂƚŝŽŶ ďLJ &d/Z ĚĞƐƉŝƚĞƐ ƉƌĞƐĞŶĐĞ ŽĨ ƉƌŽƚĞŝŶ ĨŽƵůŝŶŐ Ͳ Ͳ Ͳ ŵĞƚŚŽĚŽůŽŐLJ ŽĨ ƚƌĞĂƚŵĞŶƚ ŽĨ &d/Z ƐƉĞĐƚƌĂ ƚŽ ƌĞ|ĞĂů ŵĞŵďƌĂŶĞ ĚĞŐƌĂĚĂƚŝŽŶ ĚƵĞ ƚŽ EĂKů Ͳ Ͳ Ͳ ĂƉƉůŝĐĂƚŝŽŶ ƚŽ ŵĂƉƉŝŶŐ ŽĨ WsW ĚĞŐƌĂĚĂƚŝŽŶ ĚƵĞ ƚŽ EĂKů ŝŶ Ă ƐƉŝƌĂů ŵĞŵďƌĂŶĞ Ͳ Ͳ Ͳ ĂƉƉůŝĐĂƚŝŽŶ ƚŽ ŵĂƉƉŝŶŐ ŽĨ W^ ĚĞŐƌĂĚĂƚŝŽŶ ĚƵĞ ƚŽ EĂKů ŝŶ Ă ƐƉŝƌĂů ŵĞŵďƌĂŶĞ

Influence of PVP content on degradation of PES/PVP membranes: Insights from characterization of membranes with controlled composition

“…Since no cation was detected along with chlorine it was concluded that chlorine was most probably covalently bonded to the membrane backbone and not adsorbed in a salt form (i.e. Cl -together with a charge-balancing cation) [10,23]. Such an observation was in good agreement with further investigations carried out by Hanafi et al who used XPS to show the existence of C-Cl bonds on aged membranes while no chlorine was observed on pristine membrane surfaces [14].…”

“…In more drastic ageing conditions dislodgement of PVP from the membrane matrix has even been reported [3,10,13,15,20].…”

“…At the industrial scale, cleaning-in-place/disinfection steps 4 using various chemicals in cascade are then performed periodically so as to mitigate fouling and restore membrane performance. Sodium hypochlorite is one of the most widely-used disinfecting/cleaning agents owing to its high efficiency and low cost [8][9][10]. However, it is well known that sodium hypochlorite has a strong impact on membranes properties such as structure [2,11,12], surface charge [2,13,14] and chemical composition [3,10,13,15], which directly impacts their filtration performance and their mechanical strength as well [3,15,16].…”

“…Several studies pointed out the occurrence of a PES-chain scission mechanism [2,3,10,13,14,21,22]. For PES (MW = 30,000 g mol -1 ) dense films containing small amounts of polyetherethersulfone (PEES), PES-chain scissions were observed after long term ageing (8 months) in 28,500 ppm total free chlorine (TFC) NaOCl solutions at pH 9 and 12 [23,24].…”

Fabrication of Polyethersulfone Membranes Using Nanocarbon as Additive

“…Recently, membrane mechanism has been widely utilized for water and wastewater treatment [2,3], gas separation [4], food and beverage processing [5], and in the pharmaceutical industry for enzyme and protein concentration [6], Membrane technology offers better control of the treatment rate and product quality, thereby making it very attractive for replacing conventional separation technology, when applicable. In industrial applications, manufacturers select membranes that have good mechanical properties, high permeability, and selectivity, and that are capable of being applied at high temperatures, with resistance to extreme chemical solutions, and low fouling tendency.…”