Superhydrophilic Thin-Film
Composite Forward Osmosis
Membranes for Organic Fouling Control: Fouling Behavior and Antifouling
Mechanisms
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Abstract
This study investigates the fouling behavior and fouling
resistance
of superhydrophilic thin-film composite forward osmosis membranes
functionalized with surface-tailored nanoparticles. Fouling experiments
in both forward osmosis and reverse osmosis modes are performed with
three model organic foulants: alginate, bovine serum albumin, and
Suwannee river natural organic matter. A solution comprising monovalent
and divalent salts is employed to simulate the solution chemistry
of typical wastewater effluents. Reduced fouling is consistently observed
for the superhydrophilic membranes compared to control thin-film composite
polyamide membranes, in both reverse and forward osmosis modes. The
fouling resistance and cleaning efficiency of the functionalized membranes
is particularly outstanding in forward osmosis mode where the driving
force for water flux is an osmotic pressure difference. To understand
the mechanism of fouling, the intermolecular interactions between
the foulants and the membrane surface are analyzed by direct force
measurement using atomic force microscopy. Lower adhesion forces are
observed for the superhydrophilic membranes compared to the control
thin-film composite polyamide membranes. The magnitude and distribution
of adhesion forces for the different membrane surfaces suggest that
the antifouling properties of the superhydrophilic membranes originate
from the barrier provided by the tightly bound hydration layer at
their surface, as well as from the neutralization of the native carboxyl
groups of thin-film composite polyamide membranes