Membrane desalination technologies have gained attention as an effective, cost-
efficient, and environmentally friendly approach to providing alternative freshwater
sources. Graphene oxide (GO), due to its unique properties, is considered a
promising candidate for the fabrication of Nanofiltration membranes. However, a
key challenge in utilizing these membranes lies in achieving an optimal balance
between pure water permeability, salt rejection efficiency and stability in aqueous
environments.
In this study, Graphene oxide nanosheets were synthesized using a modified
Hummers’ method and were further modified with melanin nanoparticles (MNPs)
to enhance permeability and salt rejection performance. Additionally, a
polyethersulfone (PES) substrate was prepared using the phase inversion method.
Subsequently, a polydopamine (PDA) coating was applied to the membrane surface
at pH 8.5 to improve membrane stability in aqueous environments through
hydrogen bonding interactions between the substrate and GO. The effect of
different PDA coating durations on membrane performance and stability was
investigated. Finally, GO-melanin nanocomposite was deposited onto the modified
substrate via pressure-assisted filtration.
To confirm the synthesis of GO nanosheets, XRD, FTIR, Raman, Zeta potential and
SEM analyses were performed. Moreover, the structure and morphology of the
synthesized membranes were characterized using SEM, AFM, and FTIR. Also, the
membranes were evaluated through various tests, including porosity and average
pore size measurement, contact angle analysis, pure water flux and salt rejection
efficiency for Na₂SO₄ and NaCl. The results demonstrated that water permeability
increased from 6.07 L.m⁻².h⁻¹ in unmodified GO membranes to 8.64 L.m⁻².h⁻¹ in
GO membranes modified with melanin, highlighting the positive impact of melanin
in enhancing hydrophilicity and membrane performance. Additionally, the salt
rejection rates for Na₂SO₄ and NaCl increased from 64.11% and 29.0