Figure - available via license: CC BY
Content may be subject to copyright.
Figure A1. Coherent scattering length density of the H2O/D2O mixture according to ρ = () 2 D O -0.561+ 6.933×Φ
Source publication
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 rad...
Citations
... Recent reviews discuss the many-fold applications of the GISA(N)S method in detail [37][38][39][40] (we refer here to grazing incidence small angle scattering in general because often x-rays are also employed). The science case of GISANS instruments is supported by but not limited to several recent examples such as: lipid bilayers [41] (be it supported from a substrate or at the air-liquid interface), membranes for fuel cells [42] or reverse osmosis [43], lithium batteries [44], thin skyrmion layers [45], spray deposition of organic solar cells [46], and cellulose fibrils (for sensors) [47]. ...
This manuscript describes a concept of a grazing incidence small-angle neutron scattering (GISANS) instrument for the high brilliance source (HBS). The HBS being a compact pulsed neutron source using a moderate energy proton accelerator which allows for very compact moderators and shielding, and flexible pulse repetition rates. Similar to many other instrument concepts for this source, the lowest proposed HBS pulse frequency of 24 Hz with a relatively large detector distance is the optimal choice for the instrument described here in terms of obtained intensity and Q-range (i.e. scattering vector range). Such a configuration has the added advantage of good Q-resolution, which is important when scattering depths need to be resolved well. This is especially the case for GISANS when the incident angle is close to the critical angle of total reflection. The performance obtained from detailed ray-tracing computer simulations predict a high performance instrument that will be comparable to reflectometers and small angle neutron scattering (SANS) instruments at high-flux reactor sources such as the Forschungsreaktor Munich (FRM-2) and others.
... The resolution problem remains at spallation sources such as the European Spallation Source (ESS) because many SANS instruments are built with short collimation and sample-to-detector distances in order to cover a ISSN 1600-5767 wider wavelength band (Andersen et al., 2020). For very small angle neutron scattering (VSANS), the typically larger structures in the micrometre size range enhance multiple scattering effects at smaller Q values (Pipich et al., 2020). For ultra-smallangle neutron scattering (USANS), the Bonse-Hart technique is applied with considerable slit smearing (Barker et al., 2005;Adams et al., 2019). ...
... Furthermore, we had to introduce a 'fudge factor' = 0.057 cm for methods 2 and 3, which could not be reproduced exactly for other samples. One example from the literature (Pipich et al., 2020) displays the scattering from a reverse osmosis membrane (Fig. 10). This measurement also included very small Q values down to 10 À4 Å À1 using the VSANS instrument KWS3. ...
... The other methods did not agree well enough with method 1 and are not displayed here. An example of small-angle scattering from the RO98 pHt membrane that is used in the desalination of potable water (Pipich et al., 2020). The black circles indicate the calibrated apparent measurement including multiple scattering effects, and the red plus signs represent the data corrected by method 1. ...
This article deals with multiple scattering effects that are important for the method of small-angle neutron scattering (SANS). It considers three channels for the coherent elastic, the incoherent elastic and the incoherent inelastic scattering processes. The first channel contains the desired information on the experiment. Its multiple scattering effects can be desmeared, as shown in the later sections of the article. The other two channels display a nearly constant background as a function of the scattering angle. The incoherent elastic scattering is treated by the theory of Chandrasekhar, allowing for multiple scattering even at large scattering angles. The transfer to a single representative thermalized wavelength by the inelastic scattering-as a simplification-is assumed to happen by a single scattering event. Once the transition to this altered wavelength has happened, further incoherent multiple scattering is considered. The first part of the paper deals with the multiple scattering effects of light water. In the later part of the article, deconvolution algorithms for multiple scattering and instrumental resolution of the elastic coherent signal as implemented in the program MuScatt are described. All of these considerations are interesting for both reactor-based instruments with velocity selectors and time-of-flight SANS instruments and may improve the reliability of the data treatment.
... Therefore, the scattering from membrane and spacer must be subtracted from the total scattering of the cell in order to obtain the scattering from the silica colloids alone for further analysis. A detailed analysis of several RO and NF membranes as well as of a standalone polyamide layer with SANS and Positron-Annihilation Lifetime Spectroscopy (PALS) is found in Ref. [26] and [27], respectively. The permeate flux and electric conductivity was measured in parallel to the SANS experiments. ...
... Reasons of the different heights of the feed channel are (i) the larger thickness of the RO98 membrane (Table A1) and (ii) the applied pressure along the membrane. Information about the producers of the RO membranes can be found in the title of Table A1 and in Ref. [26]. It is obvious that pressure induces with 35% and 40%, the strongest increase in channel height in the middle part of the cell. ...
... We apply here the simplest approach, namely the structure factor of "hard" spheres in Equation colloids achieved after subtraction the scattering from the RO membrane. Systematic studies of TFC membranes are reported in [26,27]. The silica volume fraction from the HS fit is with 8.1 vol% larger than the corresponding values of 5.4 and 5.9 vol% evaluated from Equation (A3) and (A4). ...
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.
... For CV-SANS analysis, samples were fabricated by coating MPL slurry onto silicon wafers and annealing in the same manner, after which the samples were transferred onto Kapton® tape. It should be noted that the sample thickness was set to be 25 μm in order to reduce the influence of multiple scattering, which is considered in CV-SANS analysis [44] . ...
The performance of polymer electrolyte fuel cells depends on the nanostructure of the polymer composites in their components. The microporous layer within the cells, which generally comprises a composite of carbon black and polytetrafluoroethylene (PTFE), is a key component that prevents mass-transport losses in electrochemical reactions of the cells; therefore, we studied the distribution of PTFE within microporous layers using contrast-variation small-angle neutron scattering. By performing annealing above the PTFE melting point, its self-aggregations were reduced, and this effect was explained via the surface energies of PTFE and carbon black. Moreover, fuel cell performance testing demonstrated that better mass-transport properties were achieved when there were fewer PTFE self-aggregations within the microporous layers. Our findings suggest that an optimal PTFE distribution within fuel cell microporous layers can be achieved by engineering the surface energies of carbon black.
... A detailed analysis of several RO and NF membranes as well as of a standalone polyamide layer with SANS and Positron-Annihilation Lifetime Spectroscopy (PALS) is found in Refs. [26,27], respectively. The permeate flux and electric conductivity was measured in parallel to the SANS experiments. ...
... Reasons of the different heights of the feed channel are (i) the larger thickness of the RO98 membrane (Table A1) and (ii) the applied pressure along the membrane. Information about the producers of the RO membranes can be found in the title of Table A1 and in Ref. [26]. It is obvious that pressure induces with 35% and 40%, the strongest increase in channel height in the middle part of the cell. ...
... Reasons of the different heights of the fe channel are (i) the larger thickness of the RO98 membrane (Table A1) and (ii) the appl pressure along the membrane. Information about the producers of the RO membranes c be found in the title of Table A1 and in Ref. [26]. It is obvious that pressure induces w 35% and 40%, the strongest increase in channel height in the middle part of the cell. ...
We introduce a new method for real-time studies of membrane scaling and biofouling on thin film composite membranes (TFC) in reverse osmosis and nanofiltration water treatment using in-situ small-angle neutron scattering (SANS). SANS delivers information on nano and microscopic structures that support the interpretation of relevant engineering parameters such as membrane permeability and water flux. A flow cell high pressure SANS is described, followed by SANS characterization of TFC membranes finding ~ 0.5 μm large cavities and ~ 300 Å diameter large rod-like cavities inside the non-woven polyester and micro-porous polysulfone layer, respectively. In-situ desalination experiments in cross-flow mode at an applied pressure of 6 bars and feed flow velocity of 0.2 cm/s are followed. The scattering cross-section times sample thickness (μt = Σt × DS) derived from the transmission coefficient shows an overall enhancement due to newly formed scattering centers which is accompanied by a reduced membrane permeability measured simultaneously. This observation is supported by enhanced scattering of the membrane due to μm large domains of mass fractal structure. The addition of the protein BSA to the feed after desalination of 30 h effectuates strong enhancement of the permeability accompanied by a about a 50% decline of μm large scattering centers.
Small Angle Neutron Scattering (SANS) is a powerful and novel tool for the study of soft condensed matter, including the microscopic and nanomaterials used for drug discovery and delivery. The sample is exposed to a neutron beam, and neutron scattering occurs, which is studied as a function of the scattering angle to deduce a variety of information about the dynamics and structure of the material. The technique is becoming very popular in biomedical research to investigate the various aspects of structural biology. The low-resolution information on large heterogeneous, solubilized bio-macromolecular complexes in solution is obtained with the use of deuterium labelling and solvent contrast variation. The article reviews the basics of the SANS technique, its applications in drug delivery research, and its current status in biomedical research. The article covers and overviews the precise characterization of biological structures (membranes, vesicles, proteins in solution), mesoporous structures, colloids, and surfactants, as well as cyclodextrin complexes, lipid complexes, polymeric nanoparticles, etc., with the help of neutron scattering. SANS is continuously evolving as a medium for exploring the complex world of biomolecules, providing information regarding the structure, composition, and arrangement of various constituents. With improving modelling software automation in data reduction and the development of new neutron research facilities, SANS can be expected to remain mainstream for biomedical research.
Keywords: Neutron scattering, SANS, nanoparticles, scattering, solid state, macromolecular
High flux nanofiltration (NF) membranes with tunable molecular weight cut-off (MWCO) are desired for energy-efficient separation processes in many industries. The separation mechanism of these membranes involves size sieving and charge-based Donnan exclusion. The precise control over the pore size of NF membranes would produce better solute-solute selectivity. Thus it is essential to know the pore size and its distribution to ideally custom-design them. In this article, the advantages and limitations of various mathematical models of pore size estimation are discussed. The probability density function (PDF) model, which is a simple and efficient model for estimating pore size distribution (PSD) based on the rejection of electroneutral solutes, is discussed in detail, along with the flaws in its usage. The model has been randomly used in the past, which makes it difficult to compare the results obtained in different studies. We have introduced some critical points to be contemplated for the standardization of the model.
We present a short overview about neutron applications in polymer science. After describing some neutron scattering basics such as neutron cross section and structure factors, we describe the major instrumentations that are used. Concerning structural research, we discuss neutron small‐angle scattering (SANS) and grazing incident SANS that because of space limitations stands also for reflectometry. In the realm of dynamics, we focus on quasielastic scattering (QENS) and address time of flight, backscattering, and neutron spin echo instruments. For both structural and dynamic studies, we present typical examples that demonstrate the breadth and width of neutron scattering in the field.
