Application of nanofiltration pretreatment to remove divalent ions for economical seawater reverse osmosis desalination

Park, Min‐Ho; Park, Jong Kwan; Lee, Eunkyung; Khim, Jong Seong; Cho, Jaeweon

doi:10.1080/19443994.2015.1111807

Cited by 19 publications

(10 citation statements)

References 22 publications

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“…10, and indicate that the system benefits from raising the pressure since the marginal increase in permeate produced surpasses the marginal increase in applied pressure. Recently, similar trends of decreasing e with increasing RR in seawater NF have also been observed empirically by Park and coworkers [9].…”

Section: Module Energy Consumptionsupporting

confidence: 84%

“…The review cites evidence that NF desalination pretreatment not only improves desalination feeds by reducing scaling, but also allows seawater reverse osmosis (SWRO) to run at lower pressures and potentially achieve higher recoveries [8]. In search of the optimal conditions for NF/SWRO desalination, Park et al followed with their study on NF pretreatment and its effect on SWRO recovery under different conditions, and concluded that the NF/SWRO configuration featured an improvement in the quality of recovered water, especially at high recoveries [9].…”

Section: Introductionmentioning

confidence: 99%

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Design and Modeling of Novel Low-Pressure Nanofiltration Hollow Fiber Modules for Water Softening and Desalination Pretreatment

Labban¹

2018

Preprint

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Given its high surface area to volume ratio and desirable mass transfer characteristics, the hollow fibermodule configuration has been central to the development of RO and UF technologies over the past fivedecades. Recent studies have demonstrated the development of a novel class of low-pressure nanofiltration(NF) hollow fiber membranes with great promise for scale-up implementation. Further progress on large-scaledeployment, however, has been restrained by the lack of an accurate predictive model, to guide module designand operation. Earlier models targeting hollow fiber modules are only suitable for RO or UF. In this work,we propose a new modeling approach suitable for NF based on the implementation of mass and momentumbalances, coupled with a validated membrane transport model based on the extended Nernst-Planck equationto predict module performance at the system-level. Modeling results are validated with respect to syntheticseawater experiments reported in an earlier work. A preliminary module design is proposed, and parametricstudies are employed to investigate the effect of varying key system parameters and elucidate the tradeoffsavailable during design. The model has significant implications for low-pressure nanofiltration, as well ashollow fiber NF module design and operation.

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Section: Module Energy Consumptionsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Design and Modeling of Novel Low-Pressure Nanofiltration Hollow Fiber Modules for Water Softening and Desalination Pretreatment

Labban¹

2018

Preprint

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“…Being negatively charged under these feed conditions, the membrane rejects SO 2− 4 more than Ca +2 by virtue of the resulting electrical interactions, in spite of sulfate's lower Stokes radius and higher diffusivity compared to calcium. An analysis similar to ours could help elucidate the trends observed in other publications for NF rejection on feeds featuring multi-ionic solutions, which becomes increasingly important for NF applications in softening and desalination [59,60].…”

Section: Modeling Artificial Seawatermentioning

confidence: 84%

Fundamentals of low-pressure nanofiltration: Membrane characterization, modeling, and understanding the multi-ionic interactions in water softening

Labban

Liu

Chong

et al. 2017

Journal of Membrane Science

147

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Recently, a novel class of low-pressure nanofiltration (NF) hollow fiber membranes, particularly suited for water softening and desalination pretreatment have been fabricated in-house using layer-by-layer (LbL) deposition with chemical crosslinking. These membranes can operate at exceedingly low pressures (2 bar), while maintaining relatively high rejections of multivalent ions. In spite of their great potential, our understanding as to what makes them superior has been limited, demanding further investigation before any large-scale implementation can be realized. In this study, the Donnan-Steric Pore Model with dielectric exclusion (DSPM-DE) is applied for the first time to these membranes to describe the membrane separation performance, and to explain the observed rejection trends, including negative rejection, and their underlying multi-ionic interactions. Experiments were conducted on a spectrum of feed chemistries, ranging from uncharged solutes to single salts, salt mixtures, and artificial seawater to characterize the membrane and accurately predict its performance. Modeling results were validated with experiments, and then used to elucidate the working principles that underlie the low-pressure softening process. An approach based on sensitivity analysis shows that the membrane pore dielectric constant, followed by the pore size, are primarily responsible for the selectively high rejections of the NF membranes to multivalent ions. Surprisingly, the softening process is found to be less sensitive to changes in membrane charge density. Our findings demonstrate that the unique ability of these membranes to exclusively separate multivalent ions from the solution, while allowing monovalent ions to permeate, is key to making this low-pressure softening process realizable.

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“…This may justify the fact that these salts are better rejected than NaCl. This rejection sequence is very well suited with earlier works on NF membranes that achieved very high rejection of divalent anions with a minimal rejection of monovalent ions and NF targets [ 48 , 49 , 50 , 51 ].…”

Section: Resultsmentioning

confidence: 87%

Nanofiltration Process for Enhanced Treatment of RO Brine Discharge

Ali

2021

Membranes

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Brine discharge of reverse osmosis (RO) desalination plants represents a challenge for both inland and coastal desalination plants. Zero-liquid discharge (ZLD) can be accomplished by using additional stages of RO, which can recycle that brine water, but the key challenge is the high concentration of divalent salts. These divalent salts (especially calcium and magnesium salts) forms a scaling layer on the RO membrane surfaces and hence shorten the life-time of the membranes. In this study, the nanofiltration (NF) procedure was used to remove divalent ions from the brine discharge to minimize the load on additional stages of RO membranes. One of the most critical considerations influencing the selection of an effective NF is the water type, which is expected here by calculation of some hydrochemical parameters (major ions, hypothetical soluble salts (electrolyte), and saturation indices). NF experiments were undertaken on a lab-scale using a low-pressure hand-made system of 4–7 bar. Synthetic single salts solutions and two real brine water discharge (brackish (BWRO) and seawater (SWRO) desalination plants) were used as a feed solution for NF system. The chemical characteristics of the RO-feed, RO-brine, NF-permeate, and NF-reject in were investigated. Electrolyte concentrations and saturation indices were determined based on the concentration of the major ions and the NETPATH software package, respectively. Calculations reveal that the brine concentrate samples contained mostly MgSO4 and MgCl2 soluble salts. The results show that 79–89% of the total dissolved salts (TDS) and 96–98% of the total hardness (TH) were retained using the NF process. The salt rejection of the NF membrane follows the order of CaSO4, Na2SO4, MgSO4, MgCl2, and NaCl with a percent of 97.4, 97.3, 95.2, 93.4, and 79%, respectively.

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Application of nanofiltration pretreatment to remove divalent ions for economical seawater reverse osmosis desalination

Cited by 19 publications

References 22 publications

Design and Modeling of Novel Low-Pressure Nanofiltration Hollow Fiber Modules for Water Softening and Desalination Pretreatment

Design and Modeling of Novel Low-Pressure Nanofiltration Hollow Fiber Modules for Water Softening and Desalination Pretreatment

Fundamentals of low-pressure nanofiltration: Membrane characterization, modeling, and understanding the multi-ionic interactions in water softening

Nanofiltration Process for Enhanced Treatment of RO Brine Discharge

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