Design and test of a reverse osmosis pressure cell for in-situ small-angle neutron scattering studies

Schwahn, D.; Feilbach, Herbert; Starc, Thomas; Pipich, Vitaliy; Kasher, Roni; Oren, Yoram

doi:10.1016/j.desal.2016.11.026

Cited by 8 publications

(4 citation statements)

References 32 publications

(51 reference statements)

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“…These data were measured at KWS3 and KWS1 together covering a Q interval from 10 −4 to 0.2 Å −1 and are corrected for multiple scattering as outlined in Appendix A.2. Similar scattering data over the same Q range were already presented for the XLE membrane in Figure 7 of a previous article [8]. The main differences between the Alfa Laval and Dow Filmtec membranes are, respectively, the overall thickness of 300 µm and 140 µm as well as the nonwoven fabric layers made from polypropylene and polyester fibers.…”

Section: Resultssupporting

confidence: 78%

“…This effort provides a basis of interpretation for our operando RO-SANS desalination experiments including membrane compaction, membrane scaling, and biofouling as well as concentration polarization in the presence of organic molecules in a simulated secondary effluent (SSE) solution [5][6][7] or aqueous silica solution. Some of the very first results of those operando RO-SANS experiments are reported in [8].…”

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confidence: 99%

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Morphology of Thin Film Composite Membranes Explored by Small-Angle Neutron Scattering and Positron-Annihilation Lifetime Spectroscopy

Pipich¹,

Dickmann

Frielinghaus³

et al. 2020

Membranes

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The morphology of thin film composite (TFC) membranes used in reverse osmosis (RO) and nanofiltration (NF) water treatment was explored with small-angle neutron scattering (SANS) and positron-annihilation lifetime spectroscopy (PALS). The combination of both methods allowed the characterization of the bulk porous structure from a few Å to µm in radius. PALS shows pores of 4.5 Å average radius in a surface layer of about 4 µm thickness, which become~40% smaller at the free surface of the membranes. This observation may correlate with the glass state of the involved polymer. Pores of similar size appear in SANS as closely packed pores of~6 Å radius distributed with an average distance of~30 Å. The main effort of SANS was the characterization of the morphology of the porous polysulfone support layer as well as the fibers of the nonwoven fabric layer. Contrast variation using the media H 2 O/D 2 O and supercritical CO 2 and CD 4 identified the polymers of the support layers as well as internal heterogeneities.Keywords: detection of the order of Å to micrometer large pores in RO membranes; fibers of nonwoven fabric support layer; chemistry and internal structures; positron-annihilation lifetime spectroscopy; small-angle neutron scattering using contrast variation Thickness of the polyamide skin layer is in the range 0.1 to 0.3 µm, the porous and nonwoven fabric support layers about 40 µm and 100 to 300 µm, respectively.In this paper, we analyze the morphology of several commercial RO and NF membranes from the perspectives of positron-annihilation lifetime spectroscopy (PALS) and small-angle neutron scattering (SANS). Both methods are non-invasive techniques, which usually do not require special sample treatment. PALS measures pores of a few Å radius in the membrane surface layer over a depth of about 3 µm thickness thereby exploring the attendance of micro pores in the whole polyamide skin layer as well as in the outer part of the polysulfone support layer. Thus, PALS delivers relevant structural information of the PA selective layer, which determines water permeability and salt rejection. Neutrons, on the other hand, penetrate the whole membrane, thus characterizing pores and the fibers of the nonwoven fabric of radii between Å and several µm as well as identifying the polymers of the entire membrane.However, the analysis of asymmetric TFC-RO/NF membranes with SANS is complicated and work-intensive as the scattering is strong and locally not specified. These difficulties were largely resolved by corrections for multiple scattering and by performing contrast variation measurements, which allow for identification and a more detailed morphological characterization of the membrane polymers. Scattering from the PA skin layer of the membrane is almost non-detectable with SANS due to its small thickness in comparison with both supporting layers. Only at large scattering angles analogous to large Q the morphology of the PA layer might become visible when scattering from pores of several Å size are dominating. PALS supports t...

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Section: Resultssupporting

confidence: 78%

mentioning

confidence: 99%

Morphology of Thin Film Composite Membranes Explored by Small-Angle Neutron Scattering and Positron-Annihilation Lifetime Spectroscopy

Pipich¹,

Dickmann

Frielinghaus³

et al. 2020

Membranes

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“…However, the interpretation of the data is difficult as scattering occurs in several parts of the setup. Furthermore, a relationship was found between the decline in permeability and the formation of large particles with fractal structures at the membrane surface [165].…”

Section: Small-angle Scattering Techniquesmentioning

confidence: 93%

A review of in situ real-time monitoring techniques for membrane fouling in the biotechnology, biorefinery and food sectors

Rudolph

Virtanen

Ferrando

et al. 2019

Journal of Membrane Science

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Pressure-driven membrane processes are often used for the separation and purification of organic compounds originating from biomass. However, membrane fouling remains a challenge as these biobased streams have a very complex composition and comprise a high fouling tendency. Conventional, the fouling is monitored based on either a decrease in flux or an increase in pressure over time. Those conventional techniques provide no information on the location, composition or amount of fouling. As fouling is often cumulative, it will be detected as a loss of performance. Once fouling becomes irreversible, it is often not possible to clean the membrane without chemicals and the filtration/separation process has to be stopped eventually. In situ real-time monitoring of membrane fouling could provide dynamic information on the development of fouling, allowing optimization of the process. This paper reviews the state of the art in in situ monitoring techniques that could be applied to membrane processes in the biotechnology, biorefinery and food sectors and briefly reflects on the current awareness of in situ monitoring techniques among experienced industrial users of membrane processes. The physical principles as well as the strengths and weaknesses are addressed, and potentially, promising techniques are identified.

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“…The device for operando SANS experiments is described in Appendix A, further developed than the one we presented in [25]. The principle layout of the membrane cell (RO-MC) is depicted and explained in Figure A1.…”

Section: Instrumentationmentioning

confidence: 99%

Silica Fouling in Reverse Osmosis Systems–Operando Small-Angle Neutron Scattering Studies

et al. 2021

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We present operando small-angle neutron scattering (SANS) experiments on silica fouling at two reverse osmose (RO) membranes under almost realistic conditions of practiced RO desalination technique. To its realization, two cells were designed for pressure fields and tangential feed cross-flows up to 50 bar and 36 L/h, one cell equipped with the membrane and the other one as an empty cell to measure the feed solution in parallel far from the membrane. We studied several aqueous silica dispersions combining the parameters of colloidal radius, volume fraction, and ionic strength. A relevant result is the observation of Bragg diffraction as part of the SANS scattering pattern, representing a crystalline cake layer of simple cubic lattice structure. Other relevant parameters are silica colloidal size and volume fraction far from and above the membrane, as well as the lattice parameter of the silica cake layer, its volume fraction, thickness, and porosity in comparison with the corresponding permeate flux. The experiments show that the formation of cake layer depends to a large extent on colloidal size, ionic strength and cross-flow. Cake layer formation proved to be a reversible process, which could be dissolved at larger cross-flow. Only in one case we observed an irreversible cake layer formation showing the characteristics of an unstable phase transition. We likewise observed enhanced silica concentration and/or cake formation above the membrane, giving indication of a first order liquid–solid phase transformation.

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Design and test of a reverse osmosis pressure cell for in-situ small-angle neutron scattering studies

Cited by 8 publications

References 32 publications

Morphology of Thin Film Composite Membranes Explored by Small-Angle Neutron Scattering and Positron-Annihilation Lifetime Spectroscopy

Morphology of Thin Film Composite Membranes Explored by Small-Angle Neutron Scattering and Positron-Annihilation Lifetime Spectroscopy

A review of in situ real-time monitoring techniques for membrane fouling in the biotechnology, biorefinery and food sectors

Silica Fouling in Reverse Osmosis Systems–Operando Small-Angle Neutron Scattering Studies

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