Tuning the excess charge and inverting the salt rejection hierarchy of polyelectrolyte multilayer membranes

Kamp, Johannes; Emonds, Stephan; Seidenfaden, Markus; Papenheim, Patrick; Kryschewski, Maira; Rubner, Jens; Weßling, Matthias

doi:10.1016/j.memsci.2021.119636

Cited by 24 publications

(15 citation statements)

References 54 publications

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“…The salt rejection was decreased by 9%, consistent with the ltration experiments. Fluctuations in water permeability and salt rejection were previously recorded for polyelectrolyte multilayers and can be ascribed only to the thin NF layer 39 . NF layer stability will be tested for longer times in the future and can be further improved by, e.g., cross-linking.…”

Section: The Mmcnf Membrane Achieved High Pfoa Removal In Several Ltr...mentioning

confidence: 88%

“…Positively charged PDADMAC (1 g/L in 0.5 M NaCl solution) and negatively charged PSS (1 g/L in 0.5 M NaCl solution) were used to prepare a polyelectrolyte nano ltration thin active layer on the mixed matrix ultra ltration support layer. PDADMAC and PSS were selected for the preparation of the NF active layer as they are strong polyelectrolytes, stable in a wide pH range, and proven to be the appropriate pair for nano ltration active layer preparation 41 . The NF layer was fabricated on the top of UF support layers (UF0, UF6, UF8) through the deposition of six PDADMAC and PSS bilayers, thus forming the MMCNF with a negative surface charge.…”

Section: Fabrication Of Negatively Charged Six-bilayer Mmcnfmentioning

confidence: 99%

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Efficient PFOA removal from drinking water by a dual-functional mixed-matrix-composite nanofiltration membrane

Nir

Chaudhary

Sela-Adler

et al. 2023

Preprint

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Drinking-water contamination by per- and polyfluorinated alkyl substances (PFAS) is a global concern. Nanofiltration is a promising PFAS removal technology due to its scalability and cost-effectiveness. However, nanofiltration cannot typically reduce PFAS concentrations below current drinking-water recommendations. To enhance PFAS removal, we developed mixed-matrix-composite nanofiltration (MMCNF) membranes - an active nanofiltration layer on porous adsorptive support that synergetically combines filtration and adsorption. We synthesized MMCNF membranes comprising thin polyelectrolyte multilayer films deposited on thick (~400 µm) polyethersulfone supports incorporating β-cyclodextrin microparticles. These membranes achieved near complete removal (>99.9%) of model PFAS (perfluorooctanoic acid) for significantly longer filtration times compared to a control membrane without β-cyclodextrin, but otherwise identical. The spent MMCNF membrane was regenerated using ethanol, showing consistent performances in three filtration cycles. Perfluorooctanoic acid was concentrated 38-fold in the ethanol eluent. Further concentration by evaporation is straightforward and can enable eluent recycling and effective PFAS destruction.

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Section: The Mmcnf Membrane Achieved High Pfoa Removal In Several Ltr...mentioning

confidence: 88%

Section: Fabrication Of Negatively Charged Six-bilayer Mmcnfmentioning

confidence: 99%

Efficient PFOA removal from drinking water by a dual-functional mixed-matrix-composite nanofiltration membrane

Nir

Chaudhary

Sela-Adler

et al. 2023

Preprint

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“…However, all of the above non-PA membranes prepared by coating or cross-linking methods showed a relatively low water permeance (0.9–6.4 L m –2 h –1 bar –1 ), weakening their competitiveness for practical applications. By contrast, very large differences in water permeance and rejection performance for OMPs and salts existed among the PEM membranes obtained via the layer-by-layer (LbL) deposition technique. ,,,,, The membrane characteristics including pore size and surface charge are highly adjustable by varying the type of polyelectrolytes used and the number of assembled layers, which makes the PEM membranes promising in removing OMPs and other contaminants of concern or achieving a certain solute–solute selectivity. − …”

Section: Effects and Mechanisms Of Membrane Development Workmentioning

confidence: 99%

Boosting the Performance of Nanofiltration Membranes in Removing Organic Micropollutants: Trade-Off Effect, Strategy Evaluation, and Prospective Development

Liu

Wang

Zhou

et al. 2022

Environ. Sci. Technol.

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In view of the high risks brought about by organic micropollutants (OMPs), nanofiltration (NF) processes have been playing a vital role in advanced water and wastewater treatment, owing to the high membrane performance in rejection of OMPs, permeation of water, and passage of mineral salts. Though numerous studies have been devoted to evaluating and technically enhancing membrane performance in removing various OMPs, the trade-off effect between water permeance and water/OMP selectivity for state-of-the-art membranes remains far from being understood. Knowledge of this effect is significant for comparing and guiding membrane development works toward cost-efficient OMP removal. In this work, we comprehensively assessed the performance of 88 NF membranes, commercialized or newly developed, based on their water permeance and OMP rejection data published in the literature. The effectiveness and underlying mechanisms of various modification methods in tailoring properties and in turn performance of the mainstream polyamide (PA) thin-film composite (TFC) membranes were quantitatively analyzed. The trade-off effect was demonstrated by the abundant data from both experimental measurements and machine learning-based prediction. On this basis, the advancement of novel membranes was benchmarked by the performance upper-bound revealed by commercial membranes and lab-made PA membranes. We also assessed the potentials of current NF membranes in selectively separating OMPs from inorganic salts and identified the future research perspectives to achieve further enhancement in OMP removal and salt/OMP selectivity of NF membranes.

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“…Due to their more open pore structure compared to reverse osmosis (RO) membranes, nanofiltration (NF) membranes have been used in various applications that require selective separation between solutes, such as water softening, groundwater purification, and concentration of products in certain industries. − More recently, with a growing demand for more challenging separations that require precise selectivity (e.g., lithium recovery from salt-lake brines), NF membranes have become a leading candidate to pursue such selectivity. − Relying on steric hindrance, Donnan (charge) exclusion, and other molecular mechanisms, − NF membranes of different materials and fabrication approaches were proposed to create selectivity toward different solutes. ,, Although success has been abundantly reported, − the selectivity of most NF membranes is relatively limited, unspecific, and, for comparison, a few orders of magnitude lower than the selectivity of ion-selective biological channels. − …”

Section: Introductionmentioning

confidence: 99%

The Adverse Effect of Concentration Polarization on Ion–Ion Selectivity in Nanofiltration

Peer-Haim

Shefer

Singh

et al. 2023

Environ. Sci. Technol. Lett.

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While the detrimental effect of concentration polarization (CP) on water flux and solute rejection in pressure-driven membrane processes has been extensively explored, the impact of CP on the selectivity between solutes in these processes has been somewhat overlooked. Considering the growing interest in solute–solute selectivity, in this study, we explored the effect of CP on ion–ion selectivity in nanofiltration (NF) membranes. We first show and discuss the “reversed” observed rejection trend of monovalent cations in NF, which is opposite to the trend of the ions’ hydrated size and mobility in solution. Next, we apply the film theory using three independent approaches to evaluate the extent of CP in the boundary layer adjacent to the membrane surface, from which the real rejection of the ions can be calculated. Our calculated real rejections of monovalent cations, which were in higher correspondence with the ions’ hydration properties and mobility in solution, suggest that CP played a major role in the “reversed” selectivity observed. Last, we demonstrate how CP adversely affects the commonly pursued monovalent–divalent ion separation in NF. Overall, our results highlight the necessity to rigorously account for CP in future studies on NF and suggest minimizing CP as a primary step to improve the selectivity between solutes.

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Tuning the excess charge and inverting the salt rejection hierarchy of polyelectrolyte multilayer membranes

Cited by 24 publications

References 54 publications

Efficient PFOA removal from drinking water by a dual-functional mixed-matrix-composite nanofiltration membrane

Efficient PFOA removal from drinking water by a dual-functional mixed-matrix-composite nanofiltration membrane

Boosting the Performance of Nanofiltration Membranes in Removing Organic Micropollutants: Trade-Off Effect, Strategy Evaluation, and Prospective Development

The Adverse Effect of Concentration Polarization on Ion–Ion Selectivity in Nanofiltration

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