Abstract
Ultrafiltration (UF) is a low-pressure membrane that yields higher permeate flux and saves significant operating costs compared to high-pressure membranes; however, studies addressing the combined improvement of anti-organic and biofouling properties of UF membranes are lacking. This study investigated the fouling resistance and antimicrobial property of a UF membrane via silver phosphate nanoparticle (AgPNP) embedded polyelectrolyte (PE) functionalization. Negatively charged polyacrylic acid (PAA) and positively charged polyallylamine hydrochloride (PAH) were deposited on the membrane using a fluidic layer-by-layer assembly technique. AgPNPs were immobilized within the crosslinked “bilayers” (BL) of PAH/PAA. The effectiveness of AgPNP immobilization was confirmed by microprofile measurements on membrane surfaces using a solid contact Ag micro-ion-selective electrode. Upon stable and uniform BL formation on the membrane surface, the permeate flux was governed by a combined effect of PAH/PAA-derived hydrophilicity and surface/pore coverage by the BLs “tightening” of the membrane. When fouled by a model organic foulant (humic acid), the functionalized membrane exhibited a lower flux decline and a greater flux recovery due to the electrostatic repulsion imparted by PAA when compared to the unmodified membrane. The functionalization rendered antimicrobial property, as indicated by fewer attachments of bacteria that initiate the formation of biofilms leading to biofouling.
Highlights
Membrane fouling may result from an accumulation of filtered organic and inorganic materials and biofilms on the membrane surface and within the pore walls, causing a loss of flux over time.The fouling may be temporary if flux can be recovered by cleaning the surface or backwashing.Otherwise, the membrane would be fouled “irreversibly”
The pH of 3.5 used for the polyelectrolyte complex solutions in this study ensured that free carboxylic acid groups in the polyallylamine hydrochloride (PAH)/polyacrylic acid (PAA) bilayers were available for binding Ag+ [56,70]
Ultrafiltration (UF) membranes were functionalized by immobilizing AgPNPs within polyelectrolyte (PAH/PAA) bilayers, rendering anti-organic fouling and antimicrobial properties membranes were on functionalized by surfaces immobilizing
Summary
Membrane fouling may result from an accumulation of filtered organic and inorganic materials and biofilms on the membrane surface and within the pore walls, causing a loss of flux over time.The fouling may be temporary if flux can be recovered by cleaning the surface or backwashing.Otherwise, the membrane would be fouled “irreversibly”. Membrane fouling may result from an accumulation of filtered organic and inorganic materials and biofilms on the membrane surface and within the pore walls, causing a loss of flux over time. The fouling may be temporary if flux can be recovered by cleaning the surface or backwashing. Considerable attention has been given to surface modification of membranes to tackle the issue of fouling [1,2,3,4,5,6,7]. Considering how the membrane surface serves as an “active layer” in the filtration process, the choice by researchers to explore surface modifications to achieve antifouling membranes has become apparent.
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