Development Of Nanofiltration Membranes Research Articles

Data-driven future for nanofiltration: Escaping linearity

Compared with traditional membrane separation methods such as distillation and chromatography, nanofiltration (NF) affords decreased waste generation and energy consumption. Despite the multiple advantages of NF and materials available for NF membranes, the industrial applicability of this process requires improvement. To address these challenges, we propose four important pillars for the future of membrane materials and process development. These four pillars are digitalization, structure–property analysis, miniaturization, and automation. We fill gaps in the development of NF membranes and processes by fostering the most promising contemporary technologies, e.g., the integration of process analytical technologies and the development of a parallel artificial nanofiltration permeability assay (PANPA) or large online databases. Moreover, we propose the extensive use of density functional theory-aided structure–property relationship methods to understand solute transport process at a molecular level. Realizing an inverse design would allow researchers and industrial scientists to develop custom membranes for specific applications using optimized properties.

Dependable Performance of Thin Film Composite Nanofiltration Membrane Tailored by Capsaicin-Derived Self-Polymer.

To address trade-off and membrane-fouling challenges during the development of nanofiltration membranes, a thin-film composite membrane was prepared on the basis of interfacial polymerization regulated by adjusting the capsaicin-derived self-polymer poly N-(2-hydroxy-5-(methylthio) benzyl) acrylamide (PHMTBA) on the polysulfone substrate in this study. Through the self-polymerization of the monomer HMTBA with varied contents, microwave-assisted technology was employed to develop a variety of PHMTBAs. It was discovered that PHMTBA is involved in the interfacial polymerization process. Piperazine and PHMTBA competed for the reaction with trimesoyl chloride, resulting in a flatter and looser membrane surface. The PHMTBA-modified membrane presented a typical double-layer structure: a thicker support layer and a thinner active layer. The addition of PHMTBA to membranes improved their hydrophilicity and negative charge density. As a result, the PHMTBA-modified membrane showed dependable separation performance (water flux of 159.5 L m−2 h−1 and rejection of 99.02% for Na2SO4) as well as enhanced anti-fouling properties (flux recovery ratio of more than 100% with bovine serum albumin-fouling and antibacterial efficiency of 93.7% against Escherichia coli). The performance of the prepared membranes was superior to that of most other modified TFC NF membranes previously reported in the literature. This work presents the application potential of capsaicin derivatives in water treatment and desalination processes.

Bridging the gap between lab-scale and commercial dimensions of hollow fiber nanofiltration membranes

The development of nanofiltration membranes with hollow fiber geometry is a relatively young field of research in membrane science with only limited, but quickly growing, availability on a commercial scale. These membranes offer promising properties for application in water treatment such as high fouling resistance and low cost compared to Reverse Osmosis membranes. Major differences are found in dimension and operating conditions of hollow fiber nanofiltration membranes used in academia and on an industrial scale. To allow for adequate comparison and prediction of membrane performance, the effect of fiber dimension and operating conditions on process performance needs to be properly understood. A systematic experimental study on MgSO4 retention by hollow fiber nanofiltration membranes was performed to investigate the effect of fiber length and operational conditions on membrane performance. A significant drop in the retention of MgSO4 was observed for 1.5 m long fibers in flux ranges of 20 LMH when reducing crossflow velocity to 0.1 m/s. Transport models were used to describe and predict this behavior. We show that the commonly used mass transport models under predict this decrease in retention. Using different theoretical transport models for the hollow fiber feed phase and reducing dimensional resolution from 2D to 1D and 0D allows for the identification of limitations of the commonly applied analytical mass transfer correlations. To accommodate for this discrepancy found between experimental results and model predictions, a correction factor was derived using the 2D model to specifically account for deviations of these correlations at high permeate recovery values. Our newly developed model makes it possible to accurately predict full scale membrane performance solely based on measured done on small scale membranes, an important precondition for the further development of dense hollow fiber based membranes and processes.

Porous Zr-Based Metal-Organic Frameworks (Zr-MOFs)-Incorporated Thin-Film Nanocomposite Membrane toward Enhanced Desalination Performance.

Four different thin-film nanocomposite (TFN) membranes were prepared by adding different concentrations of porous Zr-metal-organic frameworks (MOFs) (UiO-66 and UiO-66-NH2) to piperazine aqueous solution (aqueous phase) or 1,3,5-benzenetricarbonyl trichloride-n-hexane solution (organic phase) by interfacial polymerization. The main purpose is to study the specific effects of different addition methods and addition amounts of nanoparticles on the structure and performance of the TFN membranes by interfacial polymerization. All four TFN membranes exhibited a higher water permeability while maintaining high salt rejection compared to thin-film composite membrane. On the one hand, the TFN membranes behave differently, which are prepared by adding the same kind of nanoparticles to the aqueous phase or organic phase, respectively. The TFN membrane prepared by adding 0.2 w/v% UiO-66 to the organic phase had a high water flux of 87.86 L m-2 h-1, compared to 46.31 L m-2 h-1 of the membrane prepared by adding 0.3 w/v% UiO-66 in the aqueous phase. This is due to the fact that UiO-66 greatly slows the interfacial polymerization rate when UiO-66 is added to the organic phase, resulting in a thinner and wider-aperture polyamide thin-film layer, reducing the water transmission resistance during filtration. Therefore, it is more economical by adding nanoparticles to organic phase than aqueous phase under the same filtering effect. On the other hand, different nanoparticles can also cause differences in performance and structure of the TFN membranes even in the same preparation manner. TFN membrane with UiO-66-NH2 in the aqueous phase has higher water permeance than the one with UiO-66 in the aqueous phase, owing to the good hydrophilicity of the amino group, which improves the water dispersibility of UiO-66-NH2 so that the TFN membrane is more uniform. In addition, UiO-66-NH2 slows down the process of interface polymerization, making the membrane more porous. The monomers in the aqueous phase and organic phase can be adsorbed in the pores of Zr-MOFs, which makes the interfacial polymerization occur both in the pores and on the surface of the pores. Thus, the compatibility between the polyamide and MOFs was enhanced and less defects were formed in the thin-film layer, resulting in a high salt rejection even when the concentration of Zr-MOFs increased. This is the first time to explain that polyamide membrane has not obvious salt rejection attenuation with increasing porous material content using pore adsorption reaction monomer principle. Also, the Zr-MOFs-based TFN membrane exhibited good heat resistance and antifouling property. This work shows that porous Zr-MOFs nanomaterials have significant advantages in the development of nanofiltration membranes with high water flux and rejection.

Development of nanofiltration membrane with high salt selectivity and performance stability using polyelectrolyte multilayers

A selective nanofiltration membrane was engineered layer-by-layer (LBL) from polydiallyldimethylammonium chloride (PDADMAC) and polysodium-4-styrenesulfoate (PSS) polyelectrolytes. Thickness for 5 bilayers of PDADMAC/PSS was 321.00±11nm and showed 73.87±7% rejection of MgSO4, 22.52±2% rejection of NaCl and satisfactory flux of 12.33L.m−2.h−1 at 5bar. Formation of PDADMAC/PSS multilayers using 1.5M of supporting electrolyte produced nanofiltration membrane with the best NaCl/MgSO4 selectivity of 2.97. In addition, the stability of polyelectrolyte multilayers was evaluated through membrane back-flushing. Modified membrane using polyelectrolyte solutions of moderate ionic strength (by adding 1.5M NaCl) displayed the best performance stability in which the MgSO4 retention capability reduced for only 4%.

Nanofiltration membrane bioreactor for removing pharmaceutical compounds

The application of a nanofiltration membrane bioreactor (NF-MBR) has been investigated for the treatment of two pharmaceutical compounds (cyclophosphamide and ciprofloxacine). A new type of ceramic nanofiltration (NF) membrane has been employed for the filtration of acclimated activated sludge artificially doped by these antibiotics. The performance of the NF-MBR was monitored during approximately 4 months, in order to evaluate the long term operational stability of the system and the potential effect of the high sludge retention time on antibiotics degradation. The hypothesis of this study lies in the development of NF membrane and its cut-off support in order to (i) retain micropollutants and (ii) increase micropollutant concentration in the bioreactor. The two antibiotics are weakly degraded even with acclimated sludge, and only a small fraction of these compounds was retained when the fouling of the membrane increased. COD, total suspended solids (TSS) and colour were effectively removed. No unclogging operation was necessary (4 months of operation without chemical cleaning). The biodegradability, retention and adsorption mechanisms have been also studied.

Positively charged nanofiltration membrane based on cardo poly(arylene ether sulfone) with pendant tertiary amine groups

The goal of the present work is the development of nanofiltration membranes by the phase inversion technique using a newly developed polymer, cardo poly(arylene ether sulfone) with pendant tertiary amine groups (PES-TA). The obtained membranes were characterised in terms of their water flux, salt and basic dye rejections, the cross-sectional and surface morphologies, surface charge characteristic, and chlorine tolerance. A typical membrane (M-40) exhibited moderate rejection to salts (36.6% to NaCl, 63.3% to MgCl 2 and 70.2% to FeCl 3), but high rejection to basic dyes (>98%). Zeta potential measurements indicated that the PES-TA membranes were positively charged below pH 10.7. The M-40 membrane showed excellent chlorine tolerance. After exposure to an aqueous NaOCl solution (active chlorine concentration ≥1000 ppm) for 20 days, the rejection of membrane was not changed. In addition, the obtained membrane showed efficient separation of basic dyes in the presence of NaCl salt.