Zirconiumv (IV)-carboxylate metal–organic framework (MOF) UiO-66 nanoparticles were successfully synthesized and incorporated in the polyamide (PA) selective layer to fabricate novel thin-film nanocomposite (TFN) membranes. Compared to unmodified pure polyamide thin-film composite (TFC) membranes, the incorporation of UiO-66 nanoparticles significantly changes the membrane morphology and chemistry, leading to an improvement of intrinsic separation properties due to the molecular sieving and superhydrophilic nature of UiO-66 particles. The best performing TFN-U2 (0.1 wt % particle loading) membrane not only shows a 52% increase of water permeability but also maintains salt rejection levels (∼95%) similar to the benchmark. The effects of UiO-66 loading on the forward osmosis (FO) performance were also investigated. Incorporation of 0.1 wt % UiO-66 produced a maximum water flux increase of 40% and 25% over the TFC control under PRO and FO modes, when 1 M NaCl was used as the draw solution against deionized w...

Thin-Film Nanocomposite (TFN) Membranes Incorporated with Super-Hydrophilic Metal–Organic Framework (MOF) UiO-66: Toward Enhancement of Water Flux and Salt Rejection

Tailor-made thin film nanocomposite membrane incorporated with graphene oxide using novel interfacial polymerization technique for enhanced water separation

A rational manipulation of the surface structures and properties of thin-film composite membranes is important to optimize their separation performance and service durability. In this study, a facile strategy is reported for fabricating electroneutral loose nanofiltration membranes based on the rapid co-deposition of biomimetic adhesive polydopamine and poly(ethylene imine) (PEI) by using CuSO4/H2O2 as a trigger. Through this strategy, the surface properties and the filtration performance of the membranes can be easily tailored by the addition of PEI and CuSO4/H2O2, as well as tuning the deposition time. UV, XPS, SEM, AFM, zeta potential, water contact angle and nanofiltration measurements were used to investigate membrane performance. Surface characterization revealed that overall enhanced surface properties including low roughness, favourable hydrophilicity, and relatively neutral charge can be achieved after the addition of PEI. The optimum membranes, with 1 h co-deposition of PDA and PEI, show an ultrahigh water permeability (26.2 L m−2 h−1 bar−1), distinguished rejection for both negatively and positively charged dyes and a high permeation of divalent salts (>90%). Furthermore, the optimum membranes also show excellent operational stability in long-term nanofiltration operations in alkaline solution. This study provides an efficient and facile approach to tailor the membrane properties and structure for loose nanofiltration membranes.

High flux electroneutral loose nanofiltration membranes based on rapid deposition of polydopamine/polyethyleneimine

Fabrication and characterization of thin-film composite (TFC) nanofiltration membranes incorporated with cellulose nanocrystals (CNCs) for enhanced desalination performance and dye removal

The demand for thin-film composite nanofiltration membranes bearing unprecedented water permeance and desirable salt rejection is ever increasing in desalination. Conventional interfacial polymerization usually generates a thick (∼100 nm) skin layer on hydrophobic substrate having low-porosity, leading to limited water permeance. Herein, we engineered a highly porous and superhydrophilic composite substrate to modulate the interfacial polymerization and generate an ultrathin polyamide skin layer, even below 10 nm. The composite substrate was constructed by depositing covalent organic framework nanosheets (CONs) on a microfiltration membrane via vacuum-assistant assembly. Owing to the highly porous structure and superhydrophilic nature of CONs, the composite substrate favored a high storage capacity and uniform distribution of the amine monomers. We manipulated the monomer storage capacity of the substrate by varying the loading content of CONs and demonstrated that higher amino monomer concentration could accelerate the self-sealing and self-termination of the interfacial polymerization, thus generating a thinner skin layer from ∼70 nm to sub-10 nm. Moreover, the highly porous structure of CONs imparted little additional water transport resistance. The sub-10 nm film composite membrane exhibited a superior water permeance of 535.5 L m−2 h−1 MPa−1 with a high rejection of 94.3% for Na2SO4, which was about 2–8 times higher than that of state-of-the-art nanofiltration membranes with comparable rejection.

Covalent organic framework-modulated interfacial polymerization for ultrathin desalination membranes

Thin film nanocomposite (TFN) membranes containing 0.05 or 0.10 w/v% surface-functionalized titanate nanotubes (TNTs) in a polyamide selective layer were synthesized via interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC) monomers. Nanomaterials were dispersed into the monomer solution using two different approaches. In the first one, the functionalized TNTs were dispersed into the amine aqueous solution, while in the second approach the same nanomaterials were dispersed in TMC organic solution. The TFN membranes were characterized and compared with a control thin film composite (TFC) membrane to investigate the effect of nanofiller loadings and the fabrication approach on membrane properties. Results showed that introducing nanofillers into the organic phase was more effective to synthesize a TFN membrane of greater separation performance as the use of a rubber roller to remove aqueous solution from the substrate surface could cause the loss of a significant amount of nanofillers, which further affected the polyamide layer integrity. It was also found that the incorporation of a high nanofiller loading tended to interfere with interfacial polymerization and weaken the bonds between monomer blocks, resulting in poor polyamide–nanotube integrity. Compared to the TFC membrane, the TFN membrane made of 2% PIP and 0.15% TMC with 0.5% nanofiller incorporation could achieve greater water flux (7.5 vs. 5.4 L m−2 h−1 bar−1) and Na2SO4 rejection (96.4% vs. 86%) while exhibiting higher resistance against fouling by protein and dye.

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A practical approach to synthesize polyamide thin film nanocomposite (TFN) membranes with improved separation properties for water/wastewater treatment

D Emazadah

Papers

A practical approach to synthesize polyamide thin film nanocomposite (TFN) membranes with improved separation properties for water/wastewater treatment