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Novel microspheres (CPs) composited by rigid and flexible polymers are synthesized and embedded in the supporting membranes to enhance both the skin–substrate adhesion and compaction resistance of the thin‐film composite (TFC) nanofiltration membranes. The CPs are in situ formed in the casting solution after the rigid poly(p‐phenylene terephthamide...
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... the reason was that the PMIA which was composed of the CPs was partially dissolved during the diluting operation of the casting solution at the pre-preparation of the TEM samples. Furthermore, the FTIR spectra of the supporting membranes with different PPTA blending ratio are shown in Figure 3. The peak at the 1648 cm −1 was the characteristic adsorption of the amide. ...
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Citations
... It is well-known that the adhesion property between all the layers, including the sub-layer, the interlayer and the skin layer, is of key importance in determining the stable performance of TFC and TFN membranes. Therefore, backward-flush operation is usually conducted to evaluate the property [63,64]. Hence, the PE@PDA-TA-TFC SRNF membrane was amounted upside down in a filtration set-up, and subsequently, filtration with distilled water was done for about 45 min under a pressure of 11 bar, in which the support side was under applying the fixed pressure and the permeate was collected form the skin side. ...
Solvent resistant nanofiltration (SRNF) is now a powerful tool for addressing environmental issues. Hence, we report the fabrication of a thin film composite (TFC) membrane comprised of a novel HDPE support, a polydopamine (PDA)/Tannic acid-Fe(III) interlayer and a polyamide (PA) skin layer. In this respect, high density polyethylene(HDPE)-polystyrene(PS)-styrene-ethylene-butylene-styrene(SEBS) blends were formed with different compositions by mixing via a Brabender machine and making films by using a hot press instrument. Next, a solvent extraction technique was employed for extracting the dispersed phase and making the HDPE membranes. The support membrane with optimum properties was coated with a PDA interlayer. A tannic acid-Fe(III) interlayer was also formed on the as-prepared PDA layer so that the hydrophilicity of the support surface was enhanced to form a defect-free PA layer. The modified support was utilized for the fabrication of the PA top layer by using m-phenylene diamine (MPD) and trimesoyl chloride (TMC) monomers. The prepared TFC membrane provided a significant dye rejection ability (99.9% Direct Yellow, 99.7% Methyl Green, 99.2% Rhodamine B, and 96.1% Methyl Orange), extraordinary solvent resistance ability in harsh solvents, and good methanol (MeOH) Flux (2.25 L/m².h.bar) in SRNF applications. The skin-substrate adhesion strength of the top layer was also evaluated by a back-ward flush operation. It was demonstrated that the interlayer and the skin layer had an excellent adhesion with the support membrane.
A trade‐off behavior is noteworthy between protein rejection and pure water flux (PWF) for ultrafiltration membranes; it is recommendable to increase flux without reducing selectivity. The poly (meta‐phenylene isophthalamide) (PMIA) ultrafiltration membrane was modified via incorporating 1,3,5‐benzene tricarboxylic chloride (TMC) to optimize the performance for the first time. Molecular dynamics (MD) simulation was applied to probe the mechanism of the effects of the concentrations of cosolvent LiCl and addition TMC on the dissolving process. It was turned out that a suitable concentration of TMC in the dope solution markedly enhanced the PWF (from 276.22 to 566.20 m⁻² h⁻¹ bar⁻¹) with an increasing bovine serum albumin rejection (from 92.05% to 94.64%). Besides, the optimized membrane also possesses excellent anti‐fouling and mechanical performance. These improvements can be due to the crosslinking between PMIA and TMC and enlarged average pore diameter. This work broadens the application of PMIA and TMC in ultrafiltration and provides a novel methodology for PMIA modification.
The fragility and brittleness of glassy poly(ionic liquid)s (PILs) hinders the processing of ultrathin PILs membranes. This work is reported the interfacial polymerization of PILs, which enables the first preparation of defect‐free PIL nanomembranes for high flux separation of lithium (Li+, 3.8 Å) and magnesium (Mg2+, 4.3 Å) ions mixture. Aqueous solution of an amine‐functionalized PIL is brought in contact with trimesoyl chloride (TMC) hexane solution. The “amine ≈ acyl chloride” condensation reaction occurs at the “water ≈ hexane” interface to form ≈50 nm thin PILNH2‐TMC nanomembranes consisting of water‐stable nanoaggregates (≈20 nm in size). Water permeance of the PIL nanomembrane is 3 times as high as the state‐of‐the‐art polyamide nanofiltration membranes, while its MgCl2 rejection is as high as 95%. Both the structures and separation performance of PIL nanomembranes are stable versus operation time and pressure. This work opens a new avenue to process fragile PILs, such as into functional nanomembranes for ion separation. An interfacial polymerization method is exploited to circumvent the brittleness and fragility of functional poly(ionic liquids) (PIL) for the first time, allowing for the facile preparation of ≈50 nm thick PIL nanomembranes exhibiting stable microstructures and 3 times improved ion separation performance.
To address the internal concentration polarization (ICP) effect and membrane fouling problems of forward osmosis technology in pressure retarded osmosis (PRO) mode, another highly selective polyamide (PA) layer was introduced on the other side of the single-skinned forward osmosis (FO) membrane. Recently, a new symmetrical nanofiber support layer has shown excellent performance. For better proof, the nanofiber support layer and the phase inversion support layer were prepared separately in this study, respectively, and two double-skinned FO membranes were obtained via interfacial polymerization. By comparing various surface physicochemical properties of the nanofiber support layer and the phase inversion support layer, it can be seen that the double-skinned PA layer formed on the surface of the nanofiber support layer had better performance. The nanofiber double-skinned FO membrane showed water flux of 19.99 LMH when using 2 M NaCl and DI water as the draw and feed solution, much higher than that of the phase inversion double-skinned FO membrane. Furthermore, the anti-fouling performance of the nanofiber double-skinned FO membrane was also better than that of the phase inversion double-skinned FO membrane. This study pointed out a new direction for a double-skinned FO membrane with high permeability selectivity and provided a promising method for anti-membrane fouling.
The separation of the rare and precious metal rubidium is still a challenge to hydrometallurgy and material science. A novel ammonium molybdophosphate (AMP)/polysulfone (PSf) mixed matrix membrane for rubidium adsorption and separation was prepared successfully by NIPs method via immobilizing AMP into the PSf porous membrane. FTIR, XRD, SEM tests indicate that AMP is embedded into the PSf matrix, and its crystalline structure remains intact. WCA tests show that the membrane surfaces are more and more hydrophilicity with the AMP blending content increasing. The fluxes increase approximately linearly from 210.2 to 370.2 L m⁻² h⁻¹ with the AMP content while the bovine serum albu rejections decrease from 97.8% to 88.5%. The Rb⁺ adsorption capacities of the membranes studied as a function of contact time, pH, Rb⁺ concentration, temperature, presence of various interference ions, and the Rb⁺ capacity is up to 98.4 mg g⁻¹ at the optimal adsorption conditions. The Rb⁺ adsorption on the AMP/PSf porous membrane complies with Langmuir adsorption isotherms and pseudo‐second‐order kinetic model. Finally, the reusability in Rb⁺ adsorption of the AMP/PSf porous membrane is investigated, and the recovery rate can still be maintained above 95% after five adsorption–desorption recycles.
Membrane-based separation processes such as reverse osmosis (RO), forward osmosis (FO), and nanofiltration (NF), are the key technologies for the desalination of brackish and seawater . Along these lines, the thin-film composite (TFC) membranes, prepared via interfacial polymerization (IP), are the predominant choice of the separator; nonetheless, the progress with the optimization of their performance has been fairly slow. This slow progress has been mainly associated with the large number of the parameters influencing IP and the need to control thin-film properties at a miniature length scale–where the trade-off between transport rate and selectivity defines the separation performance. Despite the continuous efforts and progresses made, the role of interfacial, physicochemical, and structural properties of the supports layer on the selective layer fabrication and overally the TFC membranes performance is not a well-attended topic. In this short perspective, we outline the efforts and directions that have been explored and provide insights into this aspect of membrane fabrication. We highlight the significance of selective layer-support layer connectivity on the properties of TFC membranes. Given the challenges associated with separation efficiency, insights on how to adjust the transport properties of TFC membranes are critical to the design, fabrication, and development of future water purification processes.
Thin‐film composite (TFC) membranes comprised of a polyamide (PA) selective layer upon a porous substrate dominate the forward osmosis (FO) membrane market. However, further improvement of perm‐selectivity still remains a great challenge. Herein, a polyethyleneimine (PEI) interlayer is intentionally designed prior to interfacial polymerization (IP) to tailor the PA layer, which thus improves the separation performance. The PEI interlayer not only improves the substrate hydrophilicity for adsorbing more diamine monomer and controlling its release rate, but also participates in IP reaction by crosslinking with acyl chloride (TMC). Furthermore, it can decrease the electronegativity of the substrate for decreasing reverse salt diffusion. Consequently, a denser, thinner and smoother PA layer is formed due to the uniform distribution, controllable release of diamine monomer and the extra crosslinking between PEI and TMC. Furthermore, the PA layer becomes more hydrophilic with PEI involvement. As a result, the asprepared TFC membrane exhibits a favorable water flux of 16.1 L m−2 h−1 and an extremely low reverse salt flux (1.25 g m−2 h−1). Meanwhile, it achieves an excellent perm‐selectivity with a ratio of water to salt permeability coefficient of 8.25 bar−1. Moreover, it exhibits an outstanding antifouling capacity. The work sheds light on fabricating high perm‐selective membranes for desalination. A high‐performance polyamide composite membrane is developed by introducing a polyethyleneimine interlayer on the substrate to tailor the polyamide layer. Additionally, an ultrathin and defect‐free polyamide layer is achieved due to the uniform distribution and controllable release of amine monomer as well as the extra crosslinking between PEI and TMC. The PEI‐mediated polyamide composite membrane exhibits excellent perm‐selectivity in forward osmosis.
