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Journal articleLi Y, Klosowski MM, McGilvery CM, et al., 2017,
Probing flow activity in polyamide layer of reverse osmosis membrane with nanoparticle tracers, JOURNAL OF MEMBRANE SCIENCE, Vol: 534, Pages: 9-17, ISSN: 0376-7388
We investigate the flow activity of the nanostructured polyamide layer in reverse osmosis (RO) membrane, using gold nanoparticle (NP) tracers of 1–40 nm diameter. Following a detailed structural examination of a commercial SW30RH membrane selected for this study, NP solutions were infiltrated from either the polyamide front or the polysulfone support side. The permeate was then analyzed spectroscopically while the entrapment of NPs within the membrane was mapped by high resolution electron microscopy. Results show that back-filtered NPs exhibited a fractionated distribution according to size: 1 nm nanoparticles permeate across the polyamide-polysulfone interface reaching the interior of the polyamide corrugations, while the larger ones (>10 nm) are retained within the polysulfone and gradually arrested at approximately 100 nm below the polyamide-polysulfone interface. Intermediate-sized 5 nm nanoparticles reached the undulating folds just below the polyamide layer. Permeation pathways across polyamide layer appear to exclude all tracers above 1 nm, which become selectively distributed across the polyamide layer: positively charged NPs label the outer surface of the polyamide film (expected to be carboxylate-rich), while negatively charged particles are uniformly distributed within the layer. Diafiltration measurements quantify the transient kinetics of NP retention and permeation. Overall, our results establish the flow activity of the polyamide nodular surface and provide estimates for the dimensions of permeation pathways.
Conference paperValentino L, Matsumoto M, Dichtel W, et al., 2017,
Covalent organic frameworks as novel membrane materials, 253rd National Meeting of the American-Chemical-Society (ACS) on Advanced Materials, Technologies, Systems, and Processes, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
PatentGaffney P, Livingston A, Chen R, et al., 2017,
Defined Monomer Sequence Polymers, WO/2017/042583
Processes of preparing defined monomer sequence polymers are disclosed, in which a backbone portion of the polymer is first prepared by performing one or more sequential monomeric coupling reactions with intervening membrane diafiltration purification/isolation steps, followed by a step of decorating the backbone portion with one or more side chains at predetermined positions along its length. The process represents an improvement on prior art techniques, which impose limitations on the size of the side chains that may be present. Defined monomer sequence polymers that are obtainable by the processes are also disclosed.
Conference paperSong Q, Liu TY, Jelfs KE, et al., 2017,
Advanced Microporous Membranes for Molecular Separations, British Zeolite Association 40th Annual Meeting
Journal articleLivingston A, Baker R, 2017,
Membranes from academia to industry, Nature Materials, Vol: 16, Pages: 280-282, ISSN: 1476-1122
Journal articlePeeva LG, Da Silva Burgal J, Heckenast Z, et al., 2016,
Continuous consecutive reactions with inter-reaction solvent exchange by membrane separation, Angewandte Chemie International Edition, Vol: 55, Pages: 13576-13579, ISSN: 1433-7851
Pharmaceutical production typically involves multiple reaction steps with separations between successive reactions. Two processes which complicate the transition from batch to continuous operation in multistep synthesis are solvent exchange (especially high‐boiling‐ to low‐boiling‐point solvent), and catalyst separation. Demonstrated here is membrane separation as an enabling platform for undertaking these processes during continuous operation. Two consecutive reactions are performed in different solvents, with catalyst separation and inter‐reaction solvent exchange achieved by continuous flow membrane units. A Heck coupling reaction is performed in N,N‐dimethylformamide (DMF) in a continuous membrane reactor which retains the catalyst. The Heck reaction product undergoes solvent exchange in a counter‐current membrane system where DMF is continuously replaced by ethanol. After exchange the product dissolved in ethanol passes through a column packed with an iron catalyst, and undergoes reduction (>99 % yield).
Journal articleYeo BJL, Goh S, Livingston AG, et al., 2016,
Controlling biofilm development in the extractive membrane bioreactor, SEPARATION SCIENCE AND TECHNOLOGY, Vol: 52, Pages: 113-121, ISSN: 0149-6395
Journal articleBurgal JDS, Peeva L, Livingston A, 2016,
Negligible ageing in poly(ether-ether-ketone) membranes widens application range for solvent processing, JOURNAL OF MEMBRANE SCIENCE, Vol: 525, Pages: 48-56, ISSN: 0376-7388
Journal articleShi B, Marchetti P, Peshev D, et al., 2016,
Will ultra-high permeance membranes lead to ultra-efficient processes? Challenges for molecular separations in liquid systems, JOURNAL OF MEMBRANE SCIENCE, Vol: 525, Pages: 35-47, ISSN: 0376-7388
Journal articleMazlan NM, Marchetti P, Maples HA, et al., 2016,
Organic fouling behaviour of structurally and chemically different forward osmosis membranes – A study of cellulose triacetate and thin film composite membranes, Journal of Membrane Science, Vol: 520, Pages: 247-261, ISSN: 0376-7388
The HTI cellulose triacetate (CTA) and novel thin film composite (TFC) membranes are used to study the multifaceted interactions involved in the fouling and cleaning of forward osmosis (FO) membranes, using calcium alginate as a model foulant. Results show that fouling on the TFC membrane was more significant compared to CTA, arising from a variety of factors associated with surface chemistry, membrane morphology and structural properties. Interestingly, it was observed that in FO mode, membrane surface properties dominated over fouling layer properties in determining fouling behaviour, with some surface properties (e.g. surface roughness) having a greater effect on fouling than others (e.g. surface hydrophilicity). In pressure retarded osmosis (PRO) mode, structural properties of the support played a more dominant role whereby fouling mechanism was specific to the foulant size and aggregation as well as the support pore size relative to the foulant. Whilst pore clogging was observed in the TFC membrane due to its highly asymmetric and porous support structure, fouling occurred as a surface phenomenon on the CTA membrane support layer. Besides pore clogging, the severe fouling observed on the TFC membrane in PRO mode was due to a high specific mass of foulant adsorbed in its porous support. It was observed that a trade-off between enhanced membrane performance and fouling mitigation is apparent in these membranes, with both membranes providing improvement in one aspect at the expense of the other. Hence, significant developments in their surface and structural properties are needed to achieve high anti-fouling properties without compromising flux performance. Measured fouling densities on the studied surfaces suggest that there is not a strong correlation between foulant-membrane interaction and fouling density. Cleaning results suggest that physical cleaning was more efficient on the CTA membrane compared to the TFC membrane. Further, they implied that despite diff
Journal articleKlosowski MM, McGilvery CM, Li Y, et al., 2016,
Micro-to nano-scale characterisation of polyamide structures of the SW30HR RO membrane using advanced electron microscopy and stain tracers, Journal of Membrane Science, Vol: 520, Pages: 465-476, ISSN: 1873-3123
The development of new reverse osmosis (RO) membranes with enhanced performance would benefit from a detailed knowledge of the membrane structures which participate in the filtration process. Here, we examined the hierarchical structures of the polyamide (PA) active layer of the SW30HR RO membrane. Scanning electron microscopy combined with focused ion beam milling (FIB-SEM) was used to obtain the 3-D reconstructions of membrane morphology with 5 nm cross-sectional resolution (comparable with the resolution of low magnification TEM imaging in 2D) and 30 nm slice thickness. The complex folding of the PA layer was examined in 3 dimensions, enabling the quantification of key structural properties of the PA layer, including the local thickness, volume, surface area and their derivatives. The PA layer was found to exhibit a much higher and convoluted surface area than that estimated via atomic force microscopy (AFM). Cross-sectional scanning transmission electron microscopy (STEM) was used to observe the distribution of a tracer stain under various conditions. The behaviour of stain in dry and wet PA indicated that the permeation pathways have a dynamic nature and are activated by water. High resolution STEM imaging of the stained PA nano-films revealed the presence of <1 nm pore-like structures with a size compatible with free volume estimations by positron annihilation lifetime spectroscopy (PALS). This study presents a comprehensive map of the active PA layer across different length scales (from micro- to sub-nanometre) and mechanistic insight into their role in the permeation process.
Journal articleKim JF, Gaffney PRJ, Valtcheva IB, et al., 2016,
Organic Solvent Nanofiltration (OSN): A New Technology Platform for Liquid-Phase Oligonucleotide Synthesis (LPOS), Organic Process Research and Development, Vol: 20, Pages: 1439-1452, ISSN: 1083-6160
Organic solvent nanofiltration (OSN) technology is a membrane process for molecular separation in harsh organic media. However, despite having well-documented potential applications, development hurdles have hindered the widespread uptake of OSN technology. One of the most promising areas of application is as an iterative synthesis platform, for instance for oligonucleotides or peptides, where a thorough purification step is required after each synthesis cycle, preferably in the same working solvent. In this work, we report a process development study for liquid-phase oligonucleotide synthesis (LPOS) using OSN technology. Oligonucleotide (oligo) based drugs are being advanced as a new generation of therapeutics functioning at the protein expression level. Currently, over 100 oligo based drugs are undergoing clinical trials, suggesting that it will soon be necessary to produce oligos at a scale of metric tons per year. However, there are as yet no synthesis platforms that can manufacture oligos at >10 kg batch scale. With the process developed here, we have successfully carried out eight iterative cycles of chain extension and synthesized 5-mer and 9-mer 2′-O-methyl oligoribonucleotide phosphorothioates, all in liquid phase media. This paper discusses the key challenges, both anticipated and unexpected, faced during development of this process and suggests solutions to reduce the development period. An economic analysis has been carried out, highlighting the potential competitiveness of the LPOS-OSN process and the necessity for a solvent recovery unit.
Journal articleJimenez-Solomon M, Song Q, Jelfs K, et al., 2016,
Polymer nanofilms with enhanced microporosity by interfacial polymerization, Nature Materials, Vol: 15, Pages: 760-767, ISSN: 1476-4660
Highly permeable and selective membranes are desirable for energy-efficient gas and liquid separations.Microporous organic polymers have attracted significant attention in this respect owing to their highporosity, permeability, and molecular selectivity. However, it remains challenging to fabricate selectivepolymer membranes with controlled microporosity which are stable in solvents. Here we report a newapproach to designing crosslinked, rigid polymer nanofilms with enhanced microporosity bymanipulating the molecular structure. Ultra-thin polyarylate nanofilms with thickness down to 20 nmwere formed in-situ by interfacial polymerisation. Enhanced microporosity and higher interconnectivityof intermolecular network voids, as rationalised by molecular simulations, are achieved by utilisingcontorted monomers for the interfacial polymerisation. Composite membranes comprising polyarylatenanofilms with enhanced microporosity fabricated in-situ on crosslinked polyimide ultrafiltrationmembranes show outstanding separation performance in organic solvents, with up to two orders ofmagnitude higher solvent permeance than membranes fabricated with nanofilms made from noncontortedplanar monomers.
Journal articleSchaepertoens M, Didaskalou C, Kim JF, et al., 2016,
Solvent recycle with imperfect membranes: A semi-continuous workaround for diafiltration, Journal of Membrane Science, Vol: 514, Pages: 646-658, ISSN: 1873-3123
For separation of a two-component mixture, a three-stage organic solvent nanofiltration (OSN) process is presented which comprises of a two-stage membrane cascade for separation with a third membrane stage added for integrated solvent recovery, i.e. solvent recycling. The two-stage cascade allows for increased separation selectivity whilst the integrated solvent recovery stage mitigates the otherwise large solvent consumption of the purification. This work explores the effect of washing the solvent recovery unit at intervals in order to attain high product purities with imperfect solvent recovery membranes possessing less than 100% rejection of the impurity. This operation attains a purity of 98.7% through semi-continuous operation with two washes of the solvent recovery stage, even when imperfect membranes are used in a closed-loop set-up. This contrasts favourably with the 83.0% maximum purity achievable in a similar set-up with a single continuous run. The process achieves slightly lower (−0.7%) yield of around 98.2% compared to a continuously operated process without solvent recovery but consumes approx. 85% less solvent (theoretical analysis suggests up to 96% reduction is possible). 9 different membranes, both commercial (GMT, Novamem, SolSep) and in-house fabricated, are screened and tested on a separation challenge associated with the synthesis of macrocycles – amongst the membrane materials are polyimide (PI), polybenzimidazole (PBI) and, polyetheretherketone (PEEK).
Journal articleDa Silva Burgal J, Peeva L, Livingston AG, 2016,
Towards improved membrane production: using low-toxicity solvents for the preparation of PEEK nanofiltration membranes, Green Chemistry, Vol: 18, ISSN: 1744-1560
In this work it is shown that PEEK membranes are “green” from the production point of view when compared with commercial polyimide (PI) based organic solvent nanofiltration (OSN) membranes. Green metrics (E-factor and solvent intensity) and waste cost were used in order to assess the environmental burden of PEEK membranes: the solvent intensity of PEEK membranes is 8.3 vs. 35–224 for PI based membranes, and the waste cost for PEEK membranes is 46 £ kg−1 of polymer vs. 1019 £ kg−1 of polymer (bench scale) and 189 £ kg−1 of polymer (industrial scale) for PI based membranes. Scaling-up of PEEK membranes to spiral-wound modules was successfully achieved with permeances between 0.26 L h−1 m−2 bar−1 and 0.47 L h−1 m−2 bar−1 for THF, and molecular weight cut-offs (MWCO) of ∼300 g mol−1. As a final assessment, the solvent intensity and environmental burden associated with permeating a THF flow of 100 L h−1 using PEEK membranes was also assessed. The results showed a waste cost of 1.4 £ m−2 of membrane, significantly lower than PI based membranes.
Journal articleShi B, Peshev D, Marchetti P, et al., 2016,
Multi-scale modelling of OSN batch concentration with spiral-wound membrane modules using OSN Designer, Chemical Engineering Research & Design, Vol: 109, Pages: 385-396, ISSN: 1744-3563
Three commercial spiral-wound membrane modules of different sizes, from 1.8″ × 12″ to 4.0″ × 40″, are used to concentrate a solution of sucrose octaacetate in ethyl acetate under different operating conditions. A mathematical model to describe the batch concentration process is developed, based on a combination of the classical solution diffusion membrane transport model and the film theory, to account for the mass transfer effects. The model was implemented using the “OSN Designer” software tool. The membrane transport model parameters as well as all parameters in the pressure drop and mass transfer correlations for the spiral-wound modules were obtained from regression on a limited number of experimental data at steady state conditions. Excellent agreement was found between the experimental and multi-scale modelling performance data under various operating conditions. The results illustrate that the performance of a large scale batch concentration process with spiral-wound membrane modules can be predicted based on laboratory crossflow flat sheet test data when the fluid dynamics and mass transfer characteristics in the module, and the necessary channel geometry are known. In addition, the effects of concentration polarisation, pressure drop through feed and permeate channels, and thermodynamic non-ideality of the solution at large scale batch concentration are also investigated.
Journal articleCampbell J, Burgal JDS, Szekely G, et al., 2016,
Hybrid polymer/MOF membranes for Organic Solvent Nanofiltration (OSN): chemical modification and the quest for perfection, Journal of Membrane Science, Vol: 503, Pages: 166-176, ISSN: 1873-3123
One of the main challenges in the field of Organic Solvent Nanofiltration (OSN) is to improve the selectivity of membranes, allowing the separation of closely related solutes. This objective might be achieved by constructing membranes with uniform porous structures. Hybrid Polymer/Metal Organic Framework (MOF) membranes were prepared by in-situ growth (ISG) of HKUST-1 within the pores of polyimide membranes. To improve the performances of ISG membranes, chemical modification was performed. Aryl carboxylic acid moieties were introduced to polyimide P84 ultrafiltration membranes allowing coordination of the HKUST-1 directly on to the polymer. Chemically modified ISG membranes outperformed non-modified ISG membranes in both solute retentions and permeance. Retentions of polystyrene solute in acetone were used to calculate theoretical pore size distributions for each of the membranes tested. It was found that the chemically modified ISG membrane had he narrowest calculated pore size distribution.
Conference paperJimenez-Solomon MF, Song Q, Jelfs KE, et al., 2016,
Polymer nanofilms with enhanced microporosity by interfacial polymerisation for molecular separations
Conference paperMarchetti P, Shi B, Peshev D, et al., 2016,
Membrane performance characterization and process prediction in OSN: Challenges, achievements and perspective, Pages: 104-105
Book chapterAdi VSK, Cook M, Peeva LG, et al., 2016,
Optimization of OSN Membrane Cascades for Separating Organic Mixtures, Editors: Kravanja, Bogataj, Publisher: ELSEVIER SCIENCE BV, Pages: 379-384
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