Mechanistic Insights of a Thermoresponsive Interface for Fouling Control of Thin-Film Composite Nanofiltration Membranes

Abstract

In spite of extensive research, fouling is still the main challenge for nanofiltration membranes, generating an extra transport resistance and requiring a larger operational pressure in practical applications. We fabricated a highly antifouling nanofiltration membrane by grafting poly(N-isopropylacrylamide) (PNIPAM) chains on a bromine-containing polyamide layer. The resulting membrane was found to have a double permeance compared to the pristine membrane, while the rejection of multivalent ions remained the same. In addition, PNIPAM chains yielded a better deposition resistance and adhesion resistance, thereby mitigating the increase of fouling and promoting the recovery of flux during the filtration and traditional cleaning stages, respectively. Moreover, PNIPAM chains shrank when the water temperature was above the lower critical solution temperature (LCST), indicating the formation of a buffer layer between the membrane and pollutants. The buffer layer would eliminate the membrane−foulant interaction energy, thus further enhancing the detachment of pollutants. This simple and efficient cleaning method could act as an enhanced cleaning procedure to remove irreversible fouling. This provides new insights into the fabrication of enhanced antifouling membranes using smart responsive polymer chains.

Trade-off between Endocrine-Disrupting Compound Removal and Water Permeance of the Polyamide Nanofiltration Membrane: Phenomenon and Molecular Insights

“…A thicker layer could potentially encapsulate more carboxyl groups within the network or inside the pores . Despite a reduced surface density of carboxyl groups, the increase in generated amide groups and buried carboxyl groups, due to the synergistic effect of the growing cross-linking degree and PA thickness, contributes to the enhancement in membrane hydrophilicity. , Meanwhile, all of the membranes exhibited a negative charge over a wide range of pH due to the dissociation of the carboxyl groups (Figure S8), and the fluctuations from TFC1 to TFC6 could be also attributed to the growth in cross-links and thickness. As a result, we yielded a series of TFC membranes with thicker, more cross-linked and hydrophilic properties by increasing amine monomer concentration.…”

Flexible covalent organic framework membranes with linear aliphatic amines for enhanced organic solvent nanofiltration

“…This suggests that COF membranes possess strong resistance against the BSA foulant, which could be due to the increased hydrophilicity, negative zeta potential, and the presence of abundant secondary amine (–NH) groups, resulting in a buffered hydrated layer on the COF surface that resists protein adsorption. 63…”

“…This suggests that COF membranes possess strong resistance against the BSA foulant, which could be due to the increased hydrophilicity, negative zeta potential, and the presence of abundant secondary amine (-NH) groups, resulting in a buffered hydrated layer on the COF surface that resists protein adsorption. 63 To ensure applicability in industrial and real-eld settings, the mechanical properties of thin lm COF membranes are crucial. AFM-based nanoindentation experiments have been successfully used to assess the nanomechanical properties of various materials, including graphene, 2D boron nitride, molybdenum sulde, etc.…”

Advanced stimuli-responsive membranes for smart separation

“…Likewise, Xu et al modified a polyamide nanofiltration membrane by grafting PNIPAM chains onto the polyamide layer to improve its antifouling performance. 231 The grafted PNIPAM chains not only acted as a robust buffer layer between pollutants and the membrane surface but also offered the shrinking-stretching effect, eliminating the membrane-foulant interaction and helping to detach pollutants from the membrane (Fig. 13a-c).…”