Energy barriers to anion transport in polyelectrolyte multilayer nanofiltration membranes: Role of intra-pore diffusion

Sigurdardóttir, Sigyn Björk; DuChanois, Ryan M.; Epsztein, Razi; Pinelo, Manuel; Elimelech, Menachem

doi:10.1016/j.memsci.2020.117921

Cited by 68 publications

(45 citation statements)

References 65 publications

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“…Ion transport through subnanometer pores is composed of two sequential steps: partitioning into the pore and intrapore diffusion ( 47 ). Hence, the overall energy barrier for ion transport should be contributed from both steps.…”

Section: Resultsmentioning

confidence: 99%

“…2C ), respectively. During intrapore diffusion of the dehydrated ions, ions hop between equilibrium positions (i.e., sites of favorable interactions with the pore wall) ( 47 ). Since cations and anions have different interactions with the functional groups in the membrane, the energy barriers experienced by cations and anions during the intrapore diffusion are different.…”

Section: Resultsmentioning

confidence: 99%

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Intrapore energy barriers govern ion transport and selectivity of desalination membranes

et al. 2020

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State-of-the-art desalination membranes exhibit high water-salt selectivity, but their ability to discriminate between ions is limited. Elucidating the fundamental mechanisms underlying ion transport and selectivity in subnanometer pores is therefore imperative for the development of ion-selective membranes. Here, we compare the overall energy barrier for salt transport and energy barriers for individual ion transport, showing that cations and anions traverse the membrane pore in an independent manner. Supported by density functional theory simulations, we demonstrate that electrostatic interactions between permeating counterion and fixed charges on the membrane substantially hinder intrapore diffusion. Furthermore, using quartz crystal microbalance, we break down the contributions of partitioning at the pore mouth and intrapore diffusion to the overall energy barrier for salt transport. Overall, our results indicate that intrapore diffusion governs salt transport through subnanometer pores due to ion-pore wall interactions, providing the scientific base for the design of membranes with high ion-ion selectivity.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Intrapore energy barriers govern ion transport and selectivity of desalination membranes

et al. 2020

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“…This is because the electrostatic repulsion forces exerted by attached divalent ions (Ca 2+ and Mg 2+ ) to the functional groups on the surfaces of the membrane is lower when feedwater contains dilute level of Ca 2+ ions. The only resistance that affected the molecular transport of calcium is the energy barrier of the intrapore diffusion [ 39 , 44 ], resulting from the cations’ interaction with the negatively charged internal pore walls. When the ion concentration becomes higher (especially Ca 2+ ), more divalent ions attach to the membrane surface and cover a significant portion of the membrane surface [ 36 ] while providing enough repulsive force on the cations in solution.…”

Section: Resultsmentioning

confidence: 99%

“…Two major mechanisms can explain the anion diffusion through the polyamide membranes. The first one is anion transfer by pairing with the permeable cations to maintain the ion charge balance of the permeate [ 39 , 44 , 47 ]. The second mechanism is the separate permeation of anion due to the governing force of membrane potential exerted due to the fast permeation of monovalent cations with lower resistance to diffuse [ 50 , 51 ].…”

Section: Resultsmentioning

confidence: 99%

Evaluation of Performance of Existing RO Drinking Water Stations in the North Central Province, Sri Lanka

Indika

Wei

et al. 2021

Membranes

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Reverse osmosis (RO) drinking water stations have been introduced to provide safe drinking water for areas with prevailing chronic kidney disease with unknown (CKDu) etiology in the dry zone of Sri Lanka. In this investigation, RO drinking water stations established by community-based organizations (CBO) in the North Central Province (NCP) were examined. Water samples were collected from source, permeate, and concentrate in each station to determine water quality and performance. Furthermore, the operators of the systems were interviewed to evaluate operational and maintenance practices to identify major issues related to the RO systems. Results show that the majority (>93%) of RO systems had higher salt rejection rates (>92%), while water recovery varied from 19.4% to 64%. The removal efficiencies of hardness and alkalinity were averaged at 95.8% and 86.6%, respectively. Most dominant ions such as Ca2+, Mg2+, K+, Na+, Ba2+, Sr2+ Cl−, F−, and SO42− showed higher rejections at averaged values of 93.5%, 97.4%, 86.6%, 90.8%, 95.4%, 96.3%, 95.7%, 96.6%, and 99.0%, respectively. Low recovery rates, lower fluoride levels in product water, and membrane fouling were the main challenges. Lack of knowledge and training were the major issues that could shorten the lifespan of RO systems.

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“…This model has been reviewed and improved a number of times, including taking into account the dielectric constant [37], hindrance effect [38,39], and even concentration polarization [40]. Especially in the case of a membrane exhibiting a negative affinity in contact with water or any other solvent, the solute particles' transport through the active layer of the NF membrane is affected by the intra-pore diffusion effect [41].…”

Section: Introductionmentioning

confidence: 99%

Euler’s Numerical Method for Ions Rejection Reassessment of a Defect-Free Synthesized Nanofiltration Membrane with Ultrathin Titania Film as the Selective Layer

et al. 2021

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Titanium (Ti) nanoparticles (NPs) were successfully seeded on the platform of a polyacrylonitrile (PAN) ultrafiltration (UF) membrane previously coated with bio-glue (a co-deposition of dopamine hydrochloric bicarbonate buffer having undergone pyrocatechol deprotonation). The tools in vogue, especially field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and atomic force microscopy (AFM), have made it possible to fully characterize the structure of the new organic-inorganic nanofiltration (NF) membrane, namely NF_PAN_Ti. A soft computing model has been applied to make commonplace the complex and implicit extended Nernst–Planck equations that govern the transport of ions through NF membranes. Euler’s numerical method was applied with a small step-size and the results obtained were very interesting. The filtration velocity approach of GUEROUT-ELFORD-FERRY helped to estimate the average pore size of NF_PAN_Ti to rp = 0.538 nm. A six-day test carried out on NF_PAN_Ti demonstrated its long-term stability and showed a steady-rejection rate of 89.3% of MgCl2 salt and permeate flux of 56 L·m−2·h−1. The Euler’ numerical method corroborated perfectly the experimental findings since the relative error was found to be very low at 0.33% for Cl−and 0.09% for Mg2+ (RE << 0.1). These practical prediction tools may henceforth help in the choice and calibration of next-generation NF membranes’ synthesis.

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Energy barriers to anion transport in polyelectrolyte multilayer nanofiltration membranes: Role of intra-pore diffusion

Cited by 68 publications

References 65 publications

Intrapore energy barriers govern ion transport and selectivity of desalination membranes

Intrapore energy barriers govern ion transport and selectivity of desalination membranes

Evaluation of Performance of Existing RO Drinking Water Stations in the North Central Province, Sri Lanka

Euler’s Numerical Method for Ions Rejection Reassessment of a Defect-Free Synthesized Nanofiltration Membrane with Ultrathin Titania Film as the Selective Layer

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