It is a huge challenge to have a
controllable interfacial polymerization
in the fabrication process of nanofiltration (NF) membranes. In this
work, a polyphenol interlayer consisting of polyethyleneimine (PEI)/tannic
acid (TA) was simply assembled on the polysulfone (PSf) substrate
to fine-tune the interfacial polymerization process, without additional
changes to the typical NF membrane fabrication procedures. In addition,
three decisive factors in the interfacial polymerization process were
examined, including the diffusion kinetics of fluorescence-labeled
piperazine (FITC-PIP), the spreading behavior of the hexane solution
containing acyl chloride, and the polyamide layer formation on the
porous substrate by in situ Fourier transform infrared (FT-IR) spectroscopy.
The experimental results demonstrate that the diffusion kinetics of
FITC-PIP is greatly reduced, and the spreading behavior of the hexane
solution is also impeded to some extent. Furthermore, in situ FT-IR
spectroscopy demonstrates that by the mitigation of this PEI/TA interlayer,
the interfacial polymerization process is greatly controlled. Moreover,
the as-prepared NF membrane exhibits an increased water permeation
flux of 65 L m
–2
h
–1
(at the operation
pressure of 0.6 MPa), high Na
2
SO
4
rejection
of >99%, and excellent long-term structural stability.