Graphene Quantum Dots-Doped Thin Film Nanocomposite Polyimide Membranes with Enhanced Solvent Resistance for Solvent-Resistant Nanofiltration

Abstract

The core of the organic solvent nanofiltration (OSN) technology is solvent-resistant nanofiltration (SRNF) membranes. Till now, relative poor performance of solvent resistance is still the bottleneck of industrial application of SRNF membranes. This work reports a novel polyimide (PI)-based thin-film nanocomposite (TFN) membrane which was embedded with graphene quantum dots (GQDs) and showed an improved solvent resistance for OSN application. This kind of SRNF membrane, termed (PI-GQDs/PI)XA, was synthesized via serial processes of interfacial polymerization (IP), imidization, cross-linking, and solvent activation. The IP process was performed between an aqueous m-phenylenediamine solution doped with GQDs, having an average size of 1.9 nm, and an 1,2,4,5-benzenetetracarboxylic acyl chloride n-hexane solution on the PI substrate surface. The prepared (PI-GQDs-50/PI)X SRNF membranes without organic solvent activation achieved an ethanol permeance of nearly 50% higher than those of the GQD-free membranes under the same preparation conditions, while no compromise of the dye rejection was observed. Further, after the solvent activation using N,N-dimethylformamide (DMF) at 80 °C for 30 min, the ethanol permeance achieved about an 8-folds increment, from 2.84 to 22.6 L m–2 h–1 MPa–1. Interestingly, the rejection of rhodamine B also increased from 97.8 to 98.6%. A long-term permeation test of more than 100 h using rose bengal (RB, 1017 Da)/DMF solution at room temperature demonstrated that the synthesized (PI-GQDs-50/PI)XA membranes could maintain the DMF permeance and the RB rejection as high as 18.3 L m–2 h–1 MPa–1 and 99.9%, respectively. Moreover, the immersion test of the prepared (PI-GQDs-50/PI)XA SRNF membranes in both DMF and ethanol at room temperature for about one year also demonstrated the long-term organic solvent stability, indicating their good potential for OSN application.

Synergistic Effects of Carbon Dots and Palladium Nanoparticles Enhance the Sonocatalytic Performance for Rhodamine B Degradation in the Absence of Light

“…Also, the presence of the free amine-terminated polymer is indicated by the new N–H peak appearance at 3335 cm –1 for CD-CONH and at 3412 and 3336 cm –1 for BTC-CONH. 39 Similarly, the Pd NPs anchored onto the amide N–H (CD-CONH) are indicated by the shift in the stretching frequency from 1630 to 1588 cm –1 ( Figure 1 a). Also, it is further evidenced by the peak shift of the free NH 2 peak from 3335 to 3400 cm –1 .…”

Graphene‐Based Advanced Membrane Applications in Organic Solvent Nanofiltration

“…Reproduced with permission. [ 287 ] Copyright 2019, American Chemical Society. h) Proposed reaction mechanism of amino‐functionalized graphene quantum dots (aGQDs).…”

“…[ 284 ] The effective utilization of GQDs as advanced materials for OSN applications have been rapidly investigated in terms of their promising separation performance in water treatment processes. [ 285,286 ] In a study conducted by Li et al., [ 287 ] a nanocomposite membrane was developed through the IP process between the PI support and the organic solution (polyamic acid that was doped with a specified loading of GQD). It was observed that after the cross‐linking process (with the use of HDA), the active layer could not be clearly identified from the cross‐sectional images of the membranes (Figure 14f,g), although the cross‐linking process occurs on individual layers (i.e., the support and active layer).…”

Interfacially Polymerized Thin‐Film Composite Membranes for Organic Solvent Nanofiltration

“…Their work provides a good reference to prepare an ultrathin nanofilm with ultrafast solvent permeance. Similarly, other hydrophilic nanomaterials have also been demonstrated to effectively achieve an ultrafast solvent permeance, including graphene quantum dots (GQDs), [ 55,98,100 ] graphene oxide (GO), [ 99 ] etc. Li et al.…”