Improved Separation Performance Research Articles

Experimental and numerical study of the characteristics of the forced oscillation in a pulsation fluidized bed (PFB) for coal separation

Pulsation fluidized bed (PFB) has indisputable advantages for the dry coal beneficiation process. Due to the interaction mechanism between pulsation gas flow and particles is not clear, the regulation of the parameters is still based on empirical method. In this study, the oscillation characteristics of PFB in relation to pressure fluctuations and bubbles motion were studied by both lab experiments and CFD-DEM simulation. Power Spectral Density (PSD) results indicated that dominant frequency of pressure fluctuations was the same as the pulsation frequency of gas flow. In addition, double peaks were clearly formed when the pulsation frequency was set close to the bed natural frequency (about 3.49 Hz). Furthermore, Bubble growth was limited at a moderate frequency (3.49 Hz), but continued to increase at a higher frequency (5.24 Hz). Lab separation experiment also proved that, the pulsation frequency in the middle ranges (especially close to the natural frequency) can significantly improve separation performance.

Non-covalently-functionalized CNTs incorporating poly(vinyl alcohol) mixed matrix membranes for pervaporation separation of water-isopropanol mixtures

Poly(vinyl alcohol) (PVA) / modified carbon nanotubes (CNTs) mixed matrix membranes (MMMs) were prepared to study the pervaporation (PV) dehydration of aqueous azeotrope isopropanol mixture. CNTs were modified by wrapping different amount (5–14 wt%) of poly(styrenesulfonate) (PSSA) and poly(vinylpyrrolidone) (PVP) on CNT respectively. ATR, XRD, FESEM, TGA and tensile tests were used to characterize the modified carbon nanotubes and the membranes. For carbon nanotubes wrapped lower amount of poly(styrenesulfonate), the pervaporation results showed that the separation factor remarkably increased and the flux slightly decreased by increasing the content of the modified nanotubes from 0 to 3 wt%, while a reverse trend was observed with further incorporation of the nanotubes up to 5 wt%. Interestingly, increasing poly(styrenesulfonate) density around nanotubes’ sidewalls led to non-ideal effects such as interchain coiling of poly(styrenesulfonate) and formation of rigidified coiled-coil aggregations, so the best PV results were achieved at lower wrapping of poly(styrenesulfonate). However, wrapping nanotubes by poly(vinylpyrrolidone) resulted in fabrication of nanocomposites without evidence of defects or agglomerations and enhanced thermal and mechanical properties. Among all prepared membranes, the best PSI (303) was obtained by embedding 4 wt% of poly(vinylpyrrolidone)-wrapped-nanotubes into poly (vinyl alcohol) that could be attributed to good compatibility and interactions between the fillers and the matrix. Hydrogen bonding between carbonyl groups of poly(vinylpyrrolidone) and hydroxyl groups of poly(vinyl alcohol), formation of hydrophilic channels and helical wrapping of poly(vinylpyrrolidone) chains instead of interchain coiling were responsible for the observed improvement in separation performance of the membranes containing PVP-wrapped-CNTs.

A nanofiltration membrane fabricated on a surfactant activated substrate with improved separation performance and acid resistance

Uniformly dispersed and enhanced amounts of PEI molecules attract drag by SDS exhibit a high crosslinking degree and smooth surface morphology.

Adversarial Unsupervised Domain Adaptation for Harmonic-Percussive Source Separation

This letter addresses the problem of domain adaptation for the task of music source separation. Using datasets from two different domains, we compare the performance of a deep learning-based harmonic-percussive source separation model under different training scenarios, including supervised joint training using data from both domains and pre-training in one domain with fine-tuning in another. We propose an adversarial unsupervised domain adaptation approach suitable for the case where no labelled data (ground-truth source signals) from a target domain is available. By leveraging unlabelled data (only mixtures) from this domain, experiments show that our framework can improve separation performance on the new domain without losing any considerable performance on the original domain. The letter also introduces the Tap & Fiddle dataset, a dataset containing recordings of Scandinavian fiddle tunes along with isolated tracks for “foot-tapping” and “violin”.

Robust siloxane/graphene oxide thin film membranes: Siloxane size adjustment for improved separation performance and flux recovery

Siloxane/graphene oxide (GO) nanocomposites were synthesized by hydrolysis and condensation of tetraethyl orthosilicate in the presence of GO nanosheets through a sol-gel process. The influence of synthesis parameters on the properties of the siloxane/GO samples was studied and their structural, morphological and physicochemical characteristics were compared using various techniques. Polyether sulfone-supported GO and siloxane/GO thin film membranes were prepared using a pressure-assisted self-assembly method using a dead-end cell, and their separation performance and antifouling ability were evaluated. Siloxane/GOs appeared to have higher interlayer spacing, higher zeta potential and thus higher dispersion stability in aqueous media compared to GO. This gave rise to slower and more uniform sedimentation of the siloxane/GOs during the filtration process and formation of thin film membranes possessing denser and smoother morphology. The porosity, mean pore radius, water contact angle and pure water flux of the prepared membranes were compared. The separation performance of the prepared membranes to remove methylene blue (MB) and penicillin G-procaine (PG-P) from water was evaluated as a function of used GO solution concentration. The antifouling ability of membranes was studied by determining reversible fouling (Rr), irreversible fouling (Rir) resistances and flux recovery ratio (FRR). The siloxane/GO thin film membranes containing larger siloxane network exhibited the highest rejection percentage for MB (∼99%) and PG-P (∼88%), which were about 40% and 90% higher than that achieved for GO thin film membranes, while the water flux remained as high as 78.1 l·m−2h−1. Furthermore, these membranes exhibited the highest chlorine resistance, stability under ultrasonication, FRR (89%) and Rr (57%) values, implying higher chemical and mechanical stability, flux recovery capacity and antifouling ability.

Experimental study on the design of light phase outlets for a novel axial oil-water separator

Oil-water separation plays a serious role in oil exploitation to reduce the production cost. Centrifugal separation is one of the feasible methods due to its large capacity, high separation efficiency and low maintenance cost. Besides, the centrifugal separation equipment can be divided into tangential inlet separators and axial inlet separators. The ones with tangential inlet have received a large number of investigation on structure optimization but some shortcomings limit the further improvement of separation performance. In this paper, an axial separator with multiple-stage separation was introduced and investigated experimentally with water flow rate range from 3 to 7 m3/h and inlet oil fraction below 10%. Additionally, the schedule for Light Phase Outlets (LPOs) was studied experimentally and theoretically to ensure high separation efficiency and low split ratio. The results show that the multiple stage separator can keep high separation performance that the oil concentration in HPO is below 200 ppm while the split ratio ranged from 0.2 to 0.45 within experimental conditions. Besides, the reasonable schedule can lead an obvious drop in split ratio with high separation performance. Additionally, based on the analysis of flow field characteristic, the LPOs positioned in the two sides of the oil core can ensure the discharge of oil droplets in high swirl flow field and the LPO located downstream has better potential to separate small size droplets.

Triple-layered thin film nanocomposite membrane toward enhanced forward osmosis performance

Forward osmosis (FO) has attracted enormous research interests as a prospective low-energy membrane-separation technology in many potential applications such as desalination, wastewater treatment and agricultural irrigation. The novel thin film nanocomposite (TFN) FO membranes have demonstrated great improvement in separation performance and antifouling capacities. As an intermediate layer, carbon nanotubes (CNTs) could control the interfacial polymerization (IP) process to obtain an ultrathin and dense polyamide (PA) selective layer. Silver phosphate loaded acidified graphitic carbon nitride (aCN/AP) exhibited excellent nanofiller properties, including excellent aqueous dispersity, confined mass transfer, and outstanding bacteriostasis. In view of this, we fabricated TFN FO membranes with CNT as interlayer and aCN/AP as nanofillers into PA layer. Improved hydrophilic and enhanced negatively surface charges were obtained with the incorporation of aCN/AP. The optimal TFN-aCN/AP membrane possessed a higher water flux of 67.0 L m−2 h−1 accompanied with a reverse salt flux lower than 3.0 g m−2 h−1 by using 1 M NaCl as draw solution. Besides, the TFN-aCN/AP membrane showed excellent antibacterial property against both gram-negative E.coli and gram-positive S.aureus with a sterilization rate of 99.0% and 92.0%, respectively. This work provides a new strategy to fabricate novel TFN FO membranes with high permselectivity and excellent antibacterial capacities.

Activated potassium ions as CO2 carriers for PEBAX-5513/KBF4 composite membranes

This study showed that potassium tetrafluoroborate (KBF4) could be used as a carrier to facilitate the transport of CO2. A polymer electrolyte membrane was prepared by incorporating KBF4 into poly (ether-block-amide) (PEBAX-5513) with a flexible PE group. The prepared PEBAX-5513/KBF4 electrolyte membrane exhibited CO2 separation performance that was improved by nine times compared to pure PEBAX-5513 and by about seven times compared to a PVP/KF electrolyte membrane. The membrane exhibited a selectivity of 27.9. This improved separation performance increased the transport of CO2 owing to the reversible interaction of the dissociated potassium ions with CO2 molecules. The dissociation of potassium ions upon thermal treatment of the material was confirmed by Fourier transform Raman spectroscopy, and the selective layer in which the separation mechanism was generated was confirmed by scanning electron microscopy.

Enhanced pervaporation performance of zeolite membranes treated by atmospheric-pressure plasma

Zeolite membranes are widely used for the dehydration of alcohol via pervaporation. This paper presents a post-synthesis atmospheric-pressure plasma jet (APPJ) treatment aimed at enhancing the water/ethanol separation factor for FER, MOR, and FER-MOR hybrid zeolite membranes. APPJ treatment was shown to increase the separation factor of the three membranes as follows: FER (93 to 377), MOR (141 to 286), and FER-MOR (178 to 315). Pure FER zeolite and MOR membranes increased the water flux slightly. APPJ treatment was shown to reduce crystallinity and air permeability, which suggests a partial elimination of pinholes at grain boundaries in the zeolite membranes and may partially explain the improvement in water/ethanol separation performance. The hydrophilic surface of the APPJ-treated samples may also contribute to the improved separation performance. Note that the proposed APPJ treatment scheme is also applicable to other types of zeolite membrane for alcohol dehydration.

Hydrogels in Electrophoresis: Applications and Advances.

A hydrogel is a solid form of polymer network absorbed in a substantial amount of aqueous solution. In electrophoresis, hydrogels play versatile roles including as support media, sieving matrixes, affinity scaffolds, and compositions of molecularly imprinting polymers. Recently, the study of hydrogels has been advancing with unprecedented speed, and the application of hydrogels in separation science has brought new opportunities and possible breakthroughs. A good understanding about the roles and effects of the material is essential for hydrogel applications. This review summarizes the hydrogels that has been described in various modes of electrophoretic separations, including isoelectric focusing gel electrophoresis (IEFGE), isotachophoresis (ITP), gel electrophoresis and affinity gel electrophoresis (AGE). As microchip electrophoresis (ME) is one of the future trends in electrophoresis, thought provoking studies related to hydrogels in ME are also introduced. Novel hydrogels and methods that improve separation performance, facilitate the experimental operation process, allow for rapid analysis, and promote the integration to microfluidic devices are highlighted.

MOF Nanosheet-Based Mixed Matrix Membranes with Metal-Organic Coordination Interfacial Interaction for Gas Separation.

In the mixed matrix membrane (MMM), the interface between the filler and the polymer matrix will directly affect the gas separation performance of the membranes. Reasonable interfacial design in MMMs is thus important and necessary. In this work, metal-organic coordination interaction is used to construct the interface in metal-organic framework (MOF) nanosheet-based polyimide MMMs where ultrathin Co-benzenedicarboxylate MOF nanosheets (CBMNs) with a thickness less than 5 nm and a lateral size more than 5 μm are synthesized as fillers and a carboxyl-functionalized polyimide (6FDA-durene-DABA) is used as a polymer matrix. Because of the high aspect ratio (>1000) of CBMNs, abundant metal-organic coordination bonds are formed between Co2+ in CBMNs and the -COOH group in 6FDA-durene-DABA. As a result, the 6FDA-durene-DABA/CBMN MMMs exhibit improved separation performance for the CO2/CH4 and H2/CH4 gas pairs with H2/CH4 and CO2/CH4 selectivities up to 42.0 ± 4.0 and 33.6 ± 3.0, respectively. The enhanced interfacial interaction leads to the comprehensive separation performance of CO2/CH4 and H2/CH4 gas pairs approaching or surpassing the 2008 Robeson upper bound. In addition, the CO2 plasticization pressure of the MMMs is significantly enhanced up to ∼20 bar, which is 2 times that of the pure 6FDA-durene-DABA membrane. When separating a mixed gas of CO2/CH4, the selectivity of CO2/CH4 remains stable at around 23 and the CO2 permeability keeps around 400 barrer during the long-term test.

Study on the flow field and improved separation performance of a three-stage cone water-only cyclone

In this study, computational fluid dynamics (CFD) numerical simulations were applied to comparatively evaluate the flow field of a three-stage cone water-only cyclone (TWOC) with that of a single-stage cone water-only cyclone (SWOC). The reliability of numerical simulations was validated using particle image velocimetry (PIV) technology. According to the analyses of the influences of the flow field characteristics on the separation process, the reasons for the improved separation performance of the TWOC were reasonably explained. The differences in the flow fields inside of the two cyclones only exist in their cone components. In the TWOC cone, the tangential velocity and the axial velocity are both smaller than those of the SWOC, the near-wall fluid is disturbed and two secondary eddies are formed. The secondary eddies increase the looseness of the coal particles and prompt the radial separation of the coal particles. In the TWOC, low-ash coal particles below the theoretical separation density (δ50) are sufficiently separated into the overflow products throughout the downward motion. Most of the coal particles reaching the cone bottom are high-ash coal particles above δ50 that are basically discharged through the underflow pipe. Even if some coal particles are forced into the internal spiral flow, these particles will be re-separated by the secondary eddy.

Engineered Nanomaterials for Sustainable Oil Separation and Recovery

AbstractIn this review, we focus on engineered nanomaterials (NMs) offering economic and environmental sustainability in oil extraction. We introduce underlying issues in oil recovery and separation and discuss fundamental physical and chemical interactions in typical oil‐water‐solid systems that guide the design of NMs. In recovery, the NMs change rock wettability, permeability, or sweep fluid properties to attain optimal resource use and minimal environmental impact. Applied NMs include nanosurfactants, silica core‐shell structures, nano‐encapsulated acids, and nanofluids. While for separation, the NMs use mechanisms of adsorption, filtration, or dispersion to improve separation performance in industrial or aquatic oil spill settings. The NMs include iron oxide nanoparticles, graphene Joule‐heating sponges, superhydrophilic poly(vinylidene fluoride) membranes, and amphiphilic Janus silicon dioxide nanoparticles. Albeit the NMs exhibit impressive performance in sustainable oil extraction, a technological gap remains between the lab‐scale demonstrations and practical field deployment. We conclude with a perspective on bridging this gap.

Anti-fouling polyethersulfone nanofiltration membranes aided by amine-functionalized boron nitride nanosheets with improved separation performance

Nowadays, the implementation of a desirable membrane with high permeation and rejection properties in liquid and gas separation processes has become a competitive necessity in water purification and desalination. In this field, nanostructured membranes have enticed many researchers and industrialists to use them. Herein, an amine-functionalized boron nitride (BN) embedded microporous polyethersulfone (AFBN-PES) membrane was fabricated to examine the anti-fouling properties and separation performance of mixed matrix membranes (MMMs). Also, fouling parameters such as intrinsic resistance (Rm), pore resistance (Rp), cake resistance (Rc), and total resistance (Rt) were investigated, and a significant improvement in the anti-fouling characteristics of the fabricated MMMs was detected. Surprisingly, water permeation across AFBN-PES membrane increased two-fold compared to the bare PES, while its BSA and Reactive Blue 19 dye rejection capability remained over 99 %. Faster solvent-nonsolvent exchange during the preparation of polymeric membrane owing to the presence of AFBN nanosheets enhanced the hydrophilicity, changed the mean pore size, and decreased the surface roughness beyond the creation of larger microvoids in the sub-layer of MMMs.

Modification of PES ultrafiltration membranes by cationic polyelectrolyte Praestol 859: Characterization, performance and application for purification of hemicellulose

Novel approach for membrane modification to improve separation performance and antifouling stability was proposed. It involves using of 0.1–0.3wt.% aqueous solutions of Praestol 859 (cationic polyelectrolyte based on copolymer of acrylamide and 2-acryloxyethyltrimethylammonium chloride) as coagulants upon membrane preparation via non-solvent induced phase separation. It was shown that the addition of small amounts (0.1–0.3wt.%) of Praestol 859 into the coagulation bath leads to an increase in membrane pure water flux from 51 up to 68Lm−2h−1 without decreasing membrane retention. Contact angle for modified membranes decreased from 64° down to 55°. Immobilization of Praestol 859 on the surface of a selective membrane layer was confirmed by FTIR spectroscopy. It was found that the addition of Praestol 859 into the coagulation bath suppressed the macrovoid formation in the membranes supporting layer due to the decrease of “solvent-non-solvent” exchange rate which is attributed to the significant increase of viscosity of the coagulation bath. The separation performance of modified membranes for fractionation of thermomechanical pulp mill process water, for concentration and purification of hemicellulose for further processing was studied. It was found that membrane modification by Praestol 859 leads to 2–6 times increase of flux, increase of fouling recovery ratio and improvement of cleaning efficiency without decreasing membrane rejection with regard to hemicelluloses (91.5–93%) and lignin (21–22%) as reference components.

Single-walled carbon nanotubes grafted with dextran as additive to improve separation performance of polymer membranes

Permeability and selectivity are two important parameters for evaluating membrane separation performance. In this work, the functionalized single-walled carbon nanotubes (DexDTM-g-SCNT) is fabricated by non-covalent interaction using dextran-based macro-chain transfer agent, and used as an additive to blend with polyethersulfone to prepare ultrafiltration membranes via a non-solvent induced phase separation technique. DexDTM-g-SCNT modified membrane has excellent anti-fouling properties, good permeability, and excellent separation performance. Typically, the hydrophilicity of the modified membrane is significantly improved, when the content of additive is 3 wt%. The modified membrane shows high pure water flux of up to 223.3 L m−2h−1, and high rejection ratio for bovine serum albumin, and congo red of 98.5 and 98.8%, respectively. The strategy has great potential for practical applications in water purification and other separation fields.

Mechanistic Insights into the Role of Polydopamine Interlayer toward Improved Separation Performance of Polyamide Nanofiltration Membranes.

Interlayered thin-film nanocomposite membranes (TFNi) are an emerging type of membranes with great potential to overcome the permeability-selectivity upper bound of conventional thin-film composite (TFC) nanofiltration and reverse osmosis membranes. However, the exact roles of the interlayer and the corresponding mechanisms leading to enhanced separation performance of TFNi membranes remain poorly understood. This study reports a polydopamine (PDA)-intercalated TFNi nanofiltration membrane (PA-PSF2, PDA coating time of 2 h) that possessed nearly an order of magnitude higher water permeance (14.8 ± 0.4 Lm-2 h-1 bar-1) than the control TFC membrane (PA-PFS0, 2.4 ± 0.5 Lm-2 h-1 bar-1). The TFNi membrane further showed enhanced rejection toward a wide range of inorganic salts and small organic molecules (including antibiotics and endocrine disruptors). Detailed mechanistic investigation reveals that the membrane separation performance was enhanced due to both the direct "gutter" effect of the PDA interlayer and its indirect effects resulting from enhanced polyamide formation on the PDA-coated substrate, with the "gutter" effect playing a more dominant role. This study provides a mechanistic and comprehensive framework for the future development of TFNi membranes.

Improvement in separation performance of PEI-based nanofiltration membranes by using L-cysteine functionalized POSS-TiO2 composite nanoparticles for removal of heavy metal ion

L-cysteine as an amino acid was used for the modification of glycidyl POSS in the synthesis of L-cysteine functionalized POSS, including carboxyl, hydroxyl, and diamine groups. Then, the synthesized nanoparticles were applied to fabrication of L-cysteine POSS-TiO2 composite nanoparticles. NF membranes were prepared from the incorporation of different concentrations of the synthesized composite nanoparticles into the polyether-imide (PEI) as the membrane matrix. The prepared membranes were characterized by Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM) and atomic force microscope (AFM). Moreover, the separation performance of the NF membranes was examined by pure water flux (PWF) and the separation of Na2SO4, Pb(NO3)2, Cr(NO3)2 and Cu(NO3)2 aqueous solutions. The results showed the increase of pure water flux due to present hydrophilic groups on the membrane surface. The highest pure water flux obtained was 22.03 L/m2h in 1 wt% of nanoparticles. Furthermore, the rejection of Na2SO4 and Pb(NO3)2, CrSO4, and Cu(NO3)2 improved to 78%, 64%, 67% and 66% that increased 11%, 33%, and 22%, and 39% compared with the pristine PEI membrane, respectively. Finally, the best FRR% (81%) was obtained for 0.1 wt% of the composite nanoparticles (M3).

Defect free hollow fiber reverse osmosis membranes by combining layer-by-layer and interfacial polymerization

Hollow fibre RO membranes would be desired for many applications, but are notoriously difficult to fabricate. Here we demonstrate that combining layer-by-layer and interfacial polymerization (IP) allows straightforeward production of defect-free hollow fiber RO membranes. A polyelectrolyte multilayer (PEM) is used to fill the pores of a support membrane, to provide a controlled and smooth surface that can nevertheless act as an IP monomer reservoir. This approach is first demonstrated on a model surface, with IP layers being successfully applied on both poly(diallyldimethylammonium chloride) (PDADMAC)/poly(4-styrene sulfonate) (PSS) and poly(ethyleneimine) (PEI)/PSS PEMs. On plain hollow fiber support membranes, IP coating was found to have a success rate as low as 40%. However, by application of a PEM interlayer the success rate increases to 72% for PDADMAC/PSS and 90% for PEI/PSS. Also the separation performance of the successfully prepared IP membranes was significantly better when a PEM interlayer was applied, with higher NaCl retentions (from 94% to 97%), and better removal of organic micro-pollutants (from 96% to 98%), with just a small decrease in permeability (from 0.9 L/m2hbar to 0.7 L/m2hbar). Combining layer-by-layer and IP approaches can thus lead to the fabrication of defect free RO membranes with improved separation performance.

Tailoring the separation performance and antifouling property of polyethersulfone based NF membrane by incorporating hydrophilic CuO nanoparticles

CuO/PES composite membranes were fabricated through phase inversion method, focusing on fouling reduction and improving separation performance. Copper oxide nanoparticles were used as filler additive in the membrane structure. The effect of the embedded CuO nanoparticles on the morphology was studied by considering SEM, SOM and 3D surface images. Flux recovery ratio (FRR%), water contact angle, water content, mechanical tensile strength, porosity and mean pore size, salt rejection and water flux were investigated to evaluate the performance of fabricated membranes. The SOM images showed a uniform surface for the modified membranes. SEM images showed a finger-like structure for the modified membranes. Results also denoted an increment in porosity and mean pore size of membrane at low concentration of CuO NPs, whereas the opposite trend was found at higher concentration of nanoparticles. Utilizing CuO NPs enhanced the membrane tensile strength obviously PWF significantly was improved by applying CuO NPs in membrane matrix. Highest PWF (42.63 L/m2h) was observed for PES-0.05wt% CuO blended membrane, whereas it was 10.41 (L/ m2h) for pristine ones. Salt rejection also measured 82% for virgin membrane and 63-90% for modified membranes. Moreover, FRR% were measured (~77% to ~93%), while the pristine membrane showed ~63% FRR%.