Textile Wastewater Treatment By Bioinspired Antimicrobial Nanofiltration Membranes

            Surface
functionalization with advanced nanomaterials offers tailored control and
targeted design of surface properties optimal for separations. Such
modifications endow materials with improved or new separation qualities such as
high hydrophilicity, excellent selectivity and permeability, and enriched
antimicrobial activity. In this study [1], we develop two strategies (two-step
deposition and co-deposition) that use mussel-inspired polydopamine
(PDA) to strongly immobilize copper nanoparticles (CuNPs) onto a porous polymeric membrane. Through bridged
surface cavities from ultrafiltration (UF) to loose nanofiltration (NF), these
membranes display promising potential for the separation, recycle, and reuse of
dye/salt mixtures as resources rather than as environmentally harmful waste. To
confirm the optimization of membrane surface properties, a series of materials characterizations
was executed: SEM, EDS analysis, AFM, water contact
angle, and zeta potential measurements. The results indicate an overall high
performance of surface properties with a homogeneous nanoparticle distribution,
low roughness, favorable hydrophilicity, and relatively neutral charge.
Co-deposition of PDA and CuNPs was verified as a
facile and time-saving process that expedited a higher
CuNP loading compared to the traditional two-step
strategy, as confirmed by SEM and AFM images. The integration of polyethylenimine (PEI)-modified CuNPs
with high density of positive charges was shown to play an important role in
fine-tuning the hydrophilicity and compatibility with PDA and in largely
neutralizing the negative charge of PDA, thus promoting an outstanding salt
permeation (82% Na₂SO₄, 98% NaCl). In addition, CuNP/PDA-modified membranes performed an ultra-high
rejection (>99.0%) of three types of textile dyes (600-800 Da),
demonstrating a superior NF separation performance. Furthermore, the
functionalized membranes display a distinct bactericidal activity with a pronounced
reduction of 93.7% in the number of live Escherichia
coli (E. coli) bacteria. This
study highlights a fast, facile co-deposition strategy to assemble a
multifunctional separation coating onto UF support, which renders a vast
potential for textile wastewater treatment.

Reference:

[1]  
Zhu, J., Uliana, A., Wang, J., Yuan, S., Li, J., Tian,
M., Simoens, K., Volodin, A., Lin, J., Bernaerts, K., Zhang, Y., & Van der
Bruggen, B. (2016). Elevated salt transport of antimicrobial loose
nanofiltration membranes enabled by copper nanoparticles via fast bioinspired
deposition. Journal of Materials
Chemistry A, 4(34), 13211-13222.