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Abstract: Pilot-scale experiments were carried out on a nanofiltration (NF)–seawater reverse osmosis (SWRO) integrated membrane system (IMS) to evaluate scaling potential on NF and SWRO membrane surface using a kind of loosen NF membrane and costal seawater. The effect of NF permeate recovery (R NF ) increasing on the occurrence of scaling in the NF and SWRO module was investigated in term of concentration polarization modulus (CP) of scalant ions, Stiff and Davis Stability Index (S&DSI), as well as Supersaturation Index (SI) of CaCO3 and CaSO4. The results show that the salt rejection by the loosen NF module is only about 10%, while the rejection of SO4 2− is higher than 95%; S&DSI is always less than zero, indicating that CaCO3 scaling could not form on the NF membrane surface when R NF was less than 35%. is much higher than ; and at R NF of higher than 30%, SI of CaSO4 on NF membrane surface increased gradually higher than 1.0, which indicated that CaSO4 scale is more apt to form on the NF membrane surface than CaCO3 at that NF permeate recovery. This scaling sequence in the loose NF module was different from that in traditional SWRO desalination processes. [Copyright &y& Elsevier]

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]

A novel nanofiltration (NF) membrane is developed via polyethyleneimine (PEI) deposition on a hydrolyzed polyacrylonitrile (PAN) substrate enhanced by an electric field and chemical cross-linking to achieve improved desalting properties. Compared to the PEI static-deposition process, dramatic increase in salt rejection and substantial reductions of deposition time and PEI concentration are achieved for the membranes prepared by electro-deposition. What's more, the resulting membrane exhibited both stable flux and salt rejection in filtrating seawater for a relatively long term due to a significant membrane stability attributed to the electro-deposition. Desalting properties in terms of salt rejection and flux were found to be strongly affected by both hydrolysis and electro-deposition conditions. Under the optimal fabricating conditions, the resulting NF membrane exhibited a high flux of 24 L/m 2 h, excellent MgCl 2 rejection of ∼92% and low NaCl rejection of ∼39% when filtrating 2000 mg/L salt solution at 0.5 MPa. Under filtration of raw seawater at 1.8 MPa, the resulting membrane exhibited a high flux of 30.2 L/m 2 h and a significant improvement in seawater softening efficiency compared to various commercial NF membranes, which is attributed to its excellent separation efficiency between divalent and univalent ions. The current investigation demonstrated that polyelectrolyte NF membranes fabricated by electro-deposition and cross-linking led to excellent separation performance and satisfactory stability and durability that can be used in seawater softening for a relatively long time. [ABSTRACT FROM AUTHOR]

Abstract: Dynamic layer-by-layer (LBL) self-assembly technology was used to prepare as few as three to five bilayers of poly(diallyl-dimethylammonium chloride) (PDADMAC) and poly(styrene sulfonate) (PSS) on negatively charged polysulfone (PS) ultrafiltration (UF) membranes of 50kDa MWCO and compared with those of the static assembly membranes. The prepared dynamic assembly (PDADMAC/PSS)4 nanofiltration (NF) membrane showed a permeation flux of 60Lm−2 h−1 at 1.0MPa, much higher than that of the commercial DL membrane (GE Osmonics, USA), but with a rejection of about 90% of SO4 2− which is relatively less than that of the DL membrane. The rejection performance showed that the dynamic–static assembly was more effective than others. Using dynamic–static assembly preparation, the rejection of (PDADMAC/PSS)3 membrane was about 90%, while the flux was about 55Lm−2 h−1 at 1.0MPa. The surface morphology of the prepared LBL membranes were characterized by SEM and AFM, and no defect was found. The surface morphology of the membrane prepared by dynamic–static assembly was almost the same as the commercial membranes. The analysis of filtration resistance indicated that the deposition of the first and second bilayer was crucial during the whole preparation process. [Copyright &y& Elsevier]

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]

Solvent resistant nanofiltration (SRNF) membranes are highly demanded in processing organic solutions especially those contain large molecules with molecular weight between 200 to 2000 Da, yet they have some drawbacks such as relatively poor solvent resistance and low solvent permeance. The current work presented an innovative class of amino-functionalized graphene quantum dots (aGQDs) embedded thin film nanocomposites (TFN) for SRNF membranes which were prepared via interfacial polymerization (IP) and subsequent steps (chemical imidization, crosslinking, and solvent activation). The prepared membranes enabled covalent interactions not only between the IP skin layer and the substrate, but also between the IP layer and the embedded aGQDs. The ethanol permeance and surface porosity increased by 44% and 69%, respectively, with the embedment of aGQDs under the optimal conditions, while the Rhodamine B (RDB, 479 Da) rejection maintained essentially stable above 99%. Furthermore, our novel membranes exhibited excellent long-term stability, with a rejection of over 99% for Rose Bengal (RB, 1017 Da) during the continuous filtration of 100 mg L−1 RB/ N , N -dimethyl formamide (DMF) solution at room temperature for more than 768 h. They also exhibited good organic solvent resistance and high-temperature tolerance in both DMF and NMP solvents, with a RDB rejection of over 99% and an ethanol permeance of about 38 L m−2 h−1 MPa−1 after being immersed in DMF at 80 oC for 248 h, and a RDB rejection of over 99% and an ethanol permeance of about 41 L m−2 h−1 MPa−1 after being immersed in NMP at 80 oC for 232 h. The results demonstrated that the aGQDs-embedded TFN OSN membrane has vast potential in SRNF applications. Image 1 • (PI-aGQDs/PI) XA membrane was prepared via IP, imidization, crosslinking, activation. • The (PI-aGQDs/PI) XA SRNF membrane owns a wholly covalent bonding chemical structure. • aGQDs improve greatly the surface morphology and performance of the SRNF membrane. • The SRNF membranes kept >99% RB rejection in filtration of DMF at 25 oC for 30 days. • The SRNF membranes kept good solvent resistance in DMF and NMP at 80 oC for 10 days. [ABSTRACT FROM AUTHOR]