Search

Thin film nanocomposite (TFN) organic solvent nanofiltration (OSN) membrane with improved separation performance was fabricated via interfacial polymerization reaction between amine-functionalized graphene quantum dots (af-GQDs) doped aqueous monomer solution of m -phenylenediamine (MPD) and n -hexane solution containing trimesoyl chloride (TMC) monomer. We emphasize the employment of extra-low content for both af-GQDs and MPD, so that we could maximize the function of these nanomaterials and eliminate their aggregation at the same time. The af-GQDs nanomaterials could regulate the interfacial polymerization process and could be strongly anchored in the polyamide film via covalent bonding, hence could prevent their loss while providing more channels for faster solvent penetration. As a result, the optimized OSN membrane, TFN-50, shows a super-smooth surface, with a surface roughness as low as 4.3 ± 0.2 nm, and excellent pure solvent permeances which reach 135.8, 112.7, and 69.8 L m−2 h−1 MPa−1 for methanol, DMF and ethanol, respectively, as well as a very high Rhodamine B (RDB, 479 Da) rejection of up to 99.2%, and an ethanol permeance of 61.4 L m−2 h−1 MPa−1. Furthermore, the TFN-50 OSN membrane still shows excellent filtration performance after being submerged in DMF for 336 h or continuous crossflow filtration with Rose bengal (RB, 1017 Da)/DMF solution for 136 h, demonstrating its excellent solvent resistance. [Display omitted] • TFN OSN membrane incorporated with af-GQDs nanomaterials is prepared via interfacial polymerization method. • Ultra-low content for af-GQDs and MPD is used in the aqueous phase during the interfacial polymerization process. • Af-GQDs effectively manipulate the interfacial polymerization process and help to form a selectivity layer with ultra-smooth surface. • Higher solvent permeance and excellent dye rejection performance are achieved with the aid of af-GQDs. • The af-GQDs doped OSN membrane has excellent durability performance in harsh strong polar solvents. [ABSTRACT FROM AUTHOR]

The separation performance of current organic solvent nanofiltration (OSN) membranes are still not satisfied. In this work, an ultra-thin TpHz covalent organic frameworks (COFs) interlayer was in situ constructed in advance on polyimide substrate, then an ultra-thin polyamide separation layer incorporated with amino-functionalized graphene quantum dots (af-GQDs) was constructed via interfacial polymerization (IP). A high performance interlayered thin-film nanocomposite (iTFN) OSN membrane with integrally covalent bonding structure, ultra-thin and ultra-smooth surface was obtained after post crosslinking and activation. The effect of ultra-low concentrations for the polyamide reaction monomers, the COFs monomer Tp and the doped af-GQDs nanoparticle reveals that they could help to form a very thin (7–8 nm in thickness) and defect-free skin layer with very smooth surface (about 2.7 nm in roughness). The iTFN OSN membrane shows excellent solvent permeance and solute selectivity, with an ethanol permeance reaching 97.6 L m−2 h−1 MPa−1 and an RDB rejection higher than 99%. After a 180 h long-term filtration with 100 mg L−1 RB/DMF solution, it remained an RB rejection of higher than 99%, demonstrating its superior resistance to strong polar solvent. Our work paves a unique way for the fabrication of novel OSN membrane with both in situ constructed nanomaterials interlayer and nanomaterials incorporated in skin layer. [Display omitted] • Integrally covalent iTFN OSN membrane has COFs interlayer and af-GQDs incorporated. • Ultra-thin TpHz COFs layer constructed in situ with ultra-low content of Tp and Hz. • Ultra-thin polyamide skin formed using ultra-low content for MPD, TMC and af-GQDs. • Ethanol permeance reaches 97.6 L m−2 h−1 MPa−1 with RDB rejection of above 99%. • The integrally covalent iTFN OSN membrane achieves superior solvent resistance. [ABSTRACT FROM AUTHOR]

We successfully fabricated a kind of novel sandwich-like thin-film nanocomposite (TFN) polyamide (PA) membranes via interfacial polymerization (IP) method on polyimide (PI) support surface which was modified by a layer of nanosized amine-modified zeolitic imidazolate framework - 8 (mZIF-8) nanoparticles for organic solvent nanofiltration (OSN). Uniform distribution of the nanoparticles was obtained via directly immersing the PI support membrane in aqueous mZIF-8 suspension prior to the IP. A post-IP cross-linking procedure was conducted to enhance further the solvent resistance of the fabricated TFN OSN membranes. Ultra-smooth (average surface roughness of 13.7 nm) and ultra-thin (average thickness of about 33 nm) skin layer was achieved, together with high Rhodamine B (RDB, 479 Da) rejection (99.1%) and reasonable ethanol permeance (~28 L m−2 h−1 MPa−1), as well as nearly unchanged RDB rejection after being submerged in DMF at high temperature (80 °C) for 120 h, indicating their very good resistance in very harsh strong polar solvent circumstance and the promising aspect of their industrial application. • The OSN membrane was fabricated with covalent bonding between layers. • The mZIF-8 interlayer helped to form an ultra-smooth and ultra-thin skin layer. • OSN membrane permeance was effectively increased without sacrificing rejection. • The OSN membrane kept super stability in DMF at 80 °C for 120 h. [ABSTRACT FROM AUTHOR]

• Smooth (R a less than 2 nm) surface of the GQDs-interlayered membrane was achieved. • The 25 nm-thick skin layers of the GQDs-interlayered membranes. • The GQDs-PEI interlayer covalent bonded between substrate and skin layer. • The prepared membrane maintained stable performance in DMF for 45 days at 80 °C. Novel thin film nanocomposite (TFN) organic solvent nanofiltration (OSN) membranes with sandwich-like structure were developed via interfacial polymerization (IP) using both low concentration m-phenylenediamine (MPD) and trimesoyl chloride (TMC), on graphene quantum dots (GQDs)-polyethyleneimine (PEI) modified polyimide substrate surface, and followed by post-IP crosslinking and solvent activation. Such GQDs-interlayered OSN membranes have exhibited a remarkable reduced thickness (about 25 nm) and an ultra-low average surface roughness (less than 2 nm) of their IP skin layers, respectively. Both material features are rarely reported in literature. Meanwhile, our GQDs-interlayered OSN membranes have shown an increased Rhodamine B (479 Da) rejection (from 87.4% to 98.7%) and an increased ethanol permeance (from 33.5 to 40.3 L m−2 h−1 MPa−1) compared with the pristine OSN membrane. Superior solvent resistance was demonstrated after long immersion in pure N , N -dimethylformamide (DMF) at room temperature for 81 days, and at 80 °C for 45 days, and after a long-term consecutively filtration with Rose Bengal (1017 Da) DMF solution at 25 °C for 5 days, without scarifying solute rejection. Antifouling properties during the long-term filtration were also indicated. This paper presents a novel GQDs-interlayered strategy in developing high-performance TFN membranes for OSN application. [ABSTRACT FROM AUTHOR]