Search

Macroporous substrates have great potential in the development of high performance thin film composite forward osmosis (TFC FO) membranes. This paper reports on the preparation of TFC FO membrane via support-free interfacial polymerization (SFIP) technology on a macroporous substrate. SFIP technology can effectively break the bottleneck of conventional interfacial polymerization (IP) technology, which makes it difficult to form a complete polyamide (PA) film on the macroporous substrate. Briefly, the complete PA film is formed at the free water-organic phase interface and then attached to the macroporous substrate by vacuum filtration. The monomer concentration and filtration pressure were adjusted to form the optimal SFIP-PA film. Meanwhile, we chose a macroporous polyvinylidene fluoride (PVDF) microfiltration substrate and screened the pore size to reduce the structural parameters and then the internal concentration polarization, which caused the improvement of water flux. The performance of SFIP-PVDF membranes was investigated and discussed. Under the AL-FS mode with DI water and 1.0 M NaCl solution as the feed solution and draw solution, respectively, the SFIP-PVDF membrane, which used a macroporous PVDF substrate with a pore size of 0.45 μm exhibited a water flux (20 L/m2·h) and a reverse salt flux (2.5 g/m2·h). Besides, the membrane showed good stability in the 72 h test. The specific salt flux (J s /J w) of SFIP-PVDF membranes was much lower than that of IP-PVDF membranes prepared via IP technology, which were incomplete and defective, suggesting that SFIP technology was superior to IP technology. This work effectively exploits the potential of macroporous substrates for the development of high performance TFC FO membranes and provides an insight into the high performance FO membrane design. [Display omitted] • Support-free interfacial polymerization (SFIP) technology was proposed to prepare FO membranes on macroporous substrates. • Macroporous substrates with a pore size of 0.45 μm had high porosity and low tortuosity. • Low ICP, high water flux, and low reverse salt flux were exhibited. • SFIP technology was superior to IP technology on macroporous substrates. [ABSTRACT FROM AUTHOR]

Novel acyl chloride monomer 5-(1-pyrrolidinyl)-1,3-benzenedicarbonyl dichloride (PIPC) featuring a rigid pyrrolidinyl group was proposed as an organic phase monomer to fabricate reverse osmosis (RO) membranes possessing exceptional water permeability and NaCl rejection via a two-step interfacial polymerization method. First, m -phenylenediamine (MPD) in the aqueous phase solution polymerized with PIPC in the first organic phase solution to form the much looser polyamide. After that the remaining MPD continued to diffuse to polymerize with trimesoyl chloride in the second organic phase solution to form the denser polyamide. The pyrrolidinyl group had steric hindrance effects and formed hydrogen bond with MPD, leading to decreasing the thickness significantly and increasing surface roughness of the separating layer. When the PIPC amount was 0.08 wt%, the PIPC-based RO membrane displayed optimal permselectivity with water flux increasing by 84.20 % compared to the original RO membrane (from 20.38 L·m−2·h−1 to 37.54 L·m−2·h−1) whereas retaining high NaCl rejection with 98.59 %. The PIPC-based RO membrane exhibited steady water flux and NaCl rejection within 120 h of filtration, as well as improved antifouling performance. Thus, preparation of the highly permeable RO membrane could be rationally achieved by the novel acyl chloride monomer with a rigid pyrrolidinyl group. [Display omitted] • The novel monomer PIPC was used to prepare RO membrane by a two-step IP method. • PIPC influenced the diffusion rate of MPD via hydrogen bonds and steric hindrance. • The PIPC-based membrane presented rougher surface and thinner PA layer. • Permeability of PIPC-based membrane was obviously enhanced without losing NaCl rejection. [ABSTRACT FROM AUTHOR]

Polyamide/polyethylene thin film composite (PA/PE-TFC) NF membranes were prepared from reverse-phase interface polymerization (RIP) for improved Mg(II)/Li(I) separation. RIP processes between 1,3,5-benzenetricarbonyl chloride (TMC) in bottom organic phase and piperazine (PIP) in upper aqueous phase were developed to form continuous and intact surface PA separation layers on PE porous substrates thinner than traditional polysulfone (PSF) based substrates. After activation with isopropyl alcohol (IPA), PA/PE-TFC-IPA NF membranes were formed, whose NF performance could be tuned by adjusting the preparation conditions. When TMC concentration was kept at 0.15 % w/v, RIP with low PIP concentration (0.025 wt%) yield PA/PE-TFC-IPA NF membranes with negatively charged surfaces, high Na 2 SO 4 rejection rate (95 % ± 3 %) and water permeance (13–19 L·m−2·h−1·bar−1). RIP with high PIP concentration (0.3 wt%) formed PA/PE-TFC-IPA NF membranes with less negative surfaces, high MgCl 2 rejection rate (94.3 ± 0.7 %), low water permeance (4.8 ± 0.3 L·m−2·h−1·bar−1), and high Mg(II)/Li(I) separation coefficient S Li/Mg (18 ± 1) for 1000 ppm LiCl and MgCl 2 mixed solution. PA/PE-TFC-IPA NF membranes also showed good long-term stability and improved anti-fouling performance for positively charged pollutants, bearing high potential for applications in the lithium extraction processes. Polyamide/polyethylene thin film composite NF membranes (PA/PE-TFC-IPA) with superior NF performance for Mg(II)/Li(I) separation had been prepared by using thinner and lower cost PE porous substrates to replace the thicker and more expensive PSF substrates, coupled with reverse phase interface polymerization and isopropanyl alcohol activation strategies. [Display omitted] • PE based PA TFC NF membranes showed superior Mg(II)/Li(I) separation. • Reverse phase IP (RIP) led to NF surfaces with less negative charge. • NF performance could be tuned by RIP reaction conditions. • Anti-fouling property controlled mainly by the surface charges. • Activation by isopropanol could survive long term testing. [ABSTRACT FROM AUTHOR]

In this study, a kind of thin film composite (TFC) membrane with two-dimensional (2D) covalent organic frameworks (COFs) as interlayer, termed as iTFC, which has integrally covalent bonding structure, ultra-thin and ultra-smooth surface, as well as high separation performance was fabricated via interfacial polymerization (IP) and subsequent chemical cross-linking and solvent activation for organic solvent nanofiltration (OSN). The COFs interlayer was in situ constructed using 1,3,5-triformylphloroglucinol (Tp) and hydrazine (Hz) on polyimide (PI) substrate prior to the IP. The optimization of the membrane fabrication process shows that very low concentration for both the COFs aqueous monomer Hz and the IP aqueous monomer m-phenylenediamine (MPD) was conducive to the formation of very smooth (roughness of 2.4 nm), very thin and defect-free cortex, thus improving the organic solvent permeation while remaining the dye rejection. Under optimal conditions, the prepared iTFC OSN membrane has an ethanol permeance of 63.4 L m−2 h−1 MPa−1, a Rhodamine B (RDB) rejection of greater than 99 %, and a molecular weight cut-off (MWCO) of as low as 380 Da. In addition, after filtration of 100 mg L−1 RB/DMF solution for 408 h, the optimized iTFC OSN membrane remained Rose Bengal (RB) rejection above 97 %, which proves its excellent solvent resistance performance. [Display omitted] • Ultra-low content Tp and Hz monomers are used for in situ construction of ultra-thin TpHz COFs interlayer. • Ultra-low content MPD, TMC monomer are used during the interfacial polymerization process. • Integrally covalent bonding forms between the adjacent layers of substrate, COFs interlayer and skin layer. • The iTFC OSN membrane achieves a much higher ethanol permeance of 63 L m−2 h−1 MPa−1 and 99 % high RDB rejection. • The integrally covalent bonding TFN OSN membrane achieves superior solvent resistance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Wetting-induced reversible superlyophobic membranes were fabricated. • A novel method of direct surface decoration during phase inversion was proposed. • The membrane could efficiently separate W/O and O/W emulsions in alternation. • The membrane exhibited excellent durability and recyclability. Super-wettable membranes have been extensively investigated due to their prospective applications in oily wastewater remediation. However, it is still a big challenge to develop super-wettable membranes via a facile and rationally designed method. In this work, we proposed a novel strategy to develop wetting-induced superlyophobic polyacrylonitrile (PAN) membranes with reversible wettability via in situ cross-linking polymerization and surface immobilization of nanoparticles during phase inversion process. The resulting membranes exhibited super-amphilic property in air, and were capable of converting their wetting behavior from underwater superoleophobicity to underoil superhydrophobicity with excellent dynamic stability. The membranes also displayed outstanding separation capability toward various surfactant-stabilized emulsions with separation efficiencies exceeding 99.2% under gravity. Moreover, the membranes could be regenerated with high performance preserved using a facile rinsing-and-drying method, and could be repeatedly applied to separate surfactant-stabilized emulsions. This work has made progress in the fabrication of super-amphiphilic membranes with superior separating performance through a facile method, providing great potential in practical application for oily wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • TFC polyamide-polyarylate OSN membrane prepared via IP reaction with non-planar rigid twisted structure monomer. • Non-planar rigid twisted monomer effectively manipulates the interfacial polymerization process. • The separation performance of the prepared OSN membrane with PIM structure is remarkably enhanced. • High permeability of ethyl acetate, DMF and methanol and greater than 99% RDB rejection was achieved. • Superior solvent resistance was maintained after immersion in DMF at 80 °C for 63 d. Organic solvent nanofiltration (OSN) has become an emerging green and efficient technique for the separation and purification of organic solvents. The key of the industrial application of this technique is OSN membrane. Till now, current OSN membranes still have relatively low solvent permeance due to the high hydraulic resistance of the dense structure of the OSN barrier layer. Herein, a thin-film composite (TFC) polyamide-polyarylate OSN membrane containing polymers of intrinsic microporosity (PIMs) structure was successfully prepared via interfacial polymerization (IP) using a kind of hydrophilic monomer with rigid twisted structure as aqueous co-monomer together with m -phenylenediamine (MPD). The added co-monomer remarkably enhanced the perm-selectivity of the prepared OSN membrane, with an increase of more than 1.5 times for ethanol permeance, while maintaining the rejection of rhodamine B (RDB, 479 Da) above 99% under the optimal conditions. Moreover, the prepared OSN membrane has a much high permeance to polar solvents, e.g., 110.5, 112.6 and 95.8 L m−2h−1 MPa−1, for ethyl acetate, methanol and DMF, respectively. The most exciting aspect of the prepared OSN membrane is its superior solvent resistance in strong polar organic solvent. It maintained an essentially unchanged solute rejection during 63 d immersion in DMF at 80 °C, and during 120 h continuous cross-flow filtration of the RB-DMF solution at room temperature, which is superior over most of the state-of-the-art literature works, indicating its broad application prospects for separation and purification of polar organic solvent systems. [ABSTRACT FROM AUTHOR]

Divalent metal nitrates were pre-loaded on polysulfone support to modulate the interfacial polymerization between piperazine (PIP) and trimesoyl chloride (TMC). It is found that the nano-porosity and nano-morphology of thus formed thin film composite polyamide (TFC-PA) nano-filtration (NF) membranes as well as their filtration performance could be effectively tuned by the type and concentration of the divalent metal salts, especially the divalent cations used. Main group cations, such as Mg (II) and Ca (II), increased the water flux of the NF membranes by increasing their surface nano-scale nodular arrays without altering the pore sizes and rejections of the membranes, while transitional metal cations such as Zn (II), Cu (II) and Co (II) increased the water flux of the NF membranes not only by the formation of high surface area nano-scale Turing type crisscrossed ridge networks, but also by the increase of their nano-pore sizes due to their coordination with the >NH groups of the PIP. The prepared NF membranes pore sizes adjustable from 0.54 Å to 0.90 Å could be developed to have varied selectivity and rejections among inorganic salts and organic dyes. [Display omitted] • Nano-porosity of NF membranes could be tuned in the IP processes. • Retention selectivity of TFC-PA NF membranes could also be tuned. • Divalent transitional metal cations increased both pore size and surface area. • Divalent main group metal cations increased water flux without changing selectivity. • Anions Cl- may act as a ligand to impeach the action of divalent transitional cations. [ABSTRACT FROM AUTHOR]

Super-wetting membranes have recently attracted widespread attention for their promising application in oil/water separation. Generally, the preparation procedures of the super-wetting membranes are quite arduous, and it remains challenging to design a reasonable fabrication method. In this work, we present a facile method to prepare polyvinylidene fluoride (PVDF) based super-wetting membranes from direct immobilization of nanoparticles by in-situ polymerization and ionic cross-linking during phase inversion. The as-prepared membranes exhibited excellent amphiphilic properties, and had switchable wettability between super-oleophobic underwater and super-hydrophobic under oil. The modified PVDF membranes with such switchable wettability had high separating performance towards both surfactant-stabilized water-in-oil and oil-in-water emulsions under gravity and exhibited good durability and recyclability. This research not only provides a simple preparation method of amphiphilic super-wetting membranes, but also the unique performance of the membrane in water treatment. [Display omitted] • Amphiphilic super-wetting membranes was successfully fabricated. • A novel in situ surface decoration during phase inversion method was adopted. • The wettability of membrane could be reversibly switched. • The membrane could effectively separate emulsions under gravity. • The membrane demonstrated excellent durability and recyclability. [ABSTRACT FROM AUTHOR]