(381as) Oligo-Ethylene-Glycol Based Thin-Film Composite Nanofiltration Membranes for Effective Separation of Mono-/Di-Valent Anions

Oligo-ethylene-glycol based thin-film composite nanofiltration membranes
for effective separation of mono-/di-valent anions

Dan Ren¹, Xiao-Tian Bi¹,
Tian-Yin Liu^{1 ,2*} and Xiaolin Wang^1*

¹Beijing
Key Laboratory of Membrane Materials and Engineering, Department of Chemical
Engineering, Tsinghua University, Beijing, China

²Barrer
Centre, Department of Chemical Engineering, Imperial College London, South
Kensington Campus, London, SW7 2AZ, UK

*email: *tianyin.liu@imperial.ac.uk *xl-wang@tsinghua.edu.cn

Separation
of monovalent and divalent anions is highly required in water treatment technologies
for recycling concentrated brine resources, upgrading industrial separation
processes and reducing the release of hazardous compounds
into the environment. For the selective separation
of monovalent and divalent anions, the porous organic networks comprising oligo-ethylene-glycol
units were finely tailored with pore structure, ion
affinity and hydrophilicity. Enhanced cation affinity and tailored pore
structures were achieved by using closely-related oligo-ethylene-glycol-containing building blocks, including
1,2-Bis(2-aminoethoxy)ethane
(EDA), 4,7,10-trioxygen-1,13-tridecane diamine (DCA)  and polyethylene glycol diamine (N-PEG).
Thin-film composite (TFC) nanofiltration (NF) membranes were prepared by
interfacial polymerization using the oligo-ethylene-glycol-based amines
with trimesoyl chloride (TMC) on a polyethersulfone
support (PA@DCA, PA@EDA and PA@N-PEG TFC membranes). The sub-nanometer pore size of the PA@DCA film was larger
than the PA@EDA film in 2 angstroms,
and the PA@DCA TFC membrane exhibited a NaCl permeation 3-fold higher than the PA@EDA TFC membrane. Furthermore,
the cation permeances of the oligo-ethylene-glycol-based membranes increased in
the same order of cation affinity based on the valent of ions. These
results indicated a translation of the properties
of the
oligo-ethylene-glycol units to the ion-selective
performances. Enhanced
pure water permeance, faster NaCl permeance and high Na₂SO₄
rejection (more than 99%) were achieved at a reduced degree of cross-linking
and a thinner thickness of the thin film layer. In terms of mono-/di-valent anion
selectivity, the PA@DCA TFC
membrane showed a performance
4-fold higher than the
typically-used commercial
NF membranes, such as DOW NF 270. This strategy
paves the way to microporous organic networks for the fabrication of nanofiltration
membranes.

References

[1] M. A.
Shannon, P. W. Bohn, M. Elimelech, J. G. Georgiadis, B. J. Marinas and A. M.
Mayes, Nature, 2008, 452, 301-310.

[2] O. Shyshov, K. A. Siewerth and M.
von Delius, Chem. Commun., 2018, 54,
4353-4355.

Keywords: Interfacial polymerization; nanofiltration
membranes; oligo-ethylene-glycol; separation
of mono-/di-valent anions.