Separation Media Research Articles

Chiral covalent organic framework core-shell composite CTpBD@SiO2 used as stationary phase for HPLC enantioseparation.

The fascinating framework structures and unique properties of chiral covalent organic frameworks (COFs) make them promising candidates as novel separation medium for high-performance liquid chromatography (HPLC). However, the irregular morphology, inhomogeneous particle size, and low density of conventional COF particles will lead to a low column efficiency, undesirable chromatographic peak shape, and high column backpressure of such COF-packed columns. In this work, a chiral COF CTpBD was synthesized by the Schiff base reaction between benzidine (BD) and chiral organic monomer CTp obtained through the reaction of 1,3,5-triformylphoroglucinol (Tp) and (+)-diacetyl-L-tartaric anhydride ((+)-Ac-L-Ta). The chiral COF CTpBD was immobilized on the surface of amino functionalized silica (SiO2-NH2) by an in situ growth approach to prepare the chiral COF core-shell microsphere composite CTpBD@SiO2, which was used as a novel chiral stationary phase (CSP) for HPLC enantioseparation. Various kinds of racemates were separated on the CTpBD@SiO2-packed column with a low column backpressure (8-11bar). Some effects such as the analyte mass and column temperature on the HPLC enantioseparation have been studied in detail. The fabricated CTpBD@SiO2-packed column exhibited high column efficiency (e.g., 16,800 plates m-1 for atenolol), high enantioselectivity, and good reproducibility toward various racemates. The highest resolution value, retention factor, and separation factor reach to 2.11, 2.85, and 3.73, respectively. The relative standard deviations (RSD) of peak area, peak height, half-peak width, and retention time of atenolol were all below 3.0%.

Simultaneously achieving high-effective oil-water separation and filter media regeneration by facile and highly hydrophobic sand coating

Efficient oil-water separation, including of emulsified oil separation, is one of the problems restricting the green development of the petrochemical industry. Herein, highly hydrophobic sand was fabricated in one-step, followed by an investigation of adsorption capacity for various oils of hexane, petroleum ether, diesel, tetrachloroethylene and tetrachloromethane. The modified sand (MS) filter bed was subsequently set up to investigate the oil separation efficiency for oil-water mixtures, emulsions and actual petroleum refinery wastewater, respectively. Moreover, the capture process of the oil droplet by the MS was observed by a high-speed camera system, and the oil removal mechanism was explored. The removal feasibility of the oil adhered to the MS in a hydrocyclone was also investigated. The oil could be quickly adsorbed by the MS, and the adsorption capacity was positively correlated with oil density. A high flux of 14,436 L·m−2·h−1 and a considerable separation efficiency of 99% were obtained when the MS was applied for oil-water mixture separation. Additionally, the highest separation efficiency of various emulsions was up to 99.3%. Regrading actual petroleum refinery wastewater, the oil removal efficiency of the MS reached 90% rather than 57.8% of raw sand. The oil droplets in the wastewater were efficiently separated by the MS based on the mechanism of adsorption and coalescence. Additionally, the oil adhered on the MS could be removed, and the oil concentration decreased from 17.6% to 5.2%, which was ascribed to the MS spinning in a hydrocyclone. A novel oil-water separation method of hydrocyclone-intensified filtration by facile and highly hydrophobic sand coating was proposed, and simultaneously the filter media can be effectively regenerated. It is believed that this work might provide a low cost, recyclable and efficient strategy for oil removal, which shows high promise for industrial oily wastewater treatment.

Surfactant-Free Aqueous Fabrication of Macroporous Silicone Monoliths for Flexible Thermal Insulation

Abstract Hydrophobic silicone macroporous materials prepared in an aqueous solution by the sol–gel method have been considered for various applications such as separation media, heat insulators, and liquid nitrogen adsorbents. In the conventional preparation process, surfactants are used to suppress phase separation to obtain a uniform bulk material. However, a large amount of solvent and time is required to remove them before drying, which hinders industrial-scale synthesis. By copolymerizing tetra-, tri-, and bifunctional organosilicon alkoxides in an aqueous acetic acid–urea solution, flexible macroporous silicone monoliths were successfully obtained. The marshmallow-like monoliths recovered their original shape even after 80% uniaxial compression and significant bending and water repellency. The thermal conductivity of those materials was ∼0.035 W m−1 K−1 and did not increase even under 60% uniaxial compression. This characteristic property can be used for thermal insulation on surfaces with various shapes and in confined spaces under harsh conditions.

Development of silicone-coated hydrophobic deep eutectic solvent-based membranes for pervaporation of biobutanol

Hydrophobic Deep Eutectic Solvents (HDES) are considered a relatively novel class of solvents, which show perfect features to incorporate them in pervaporation membranes. Composite HDES membranes offer a separation media, which shows a faster molecular diffusion than polymeric membranes, combining the best properties of liquid and polymer membranes, such a high selectivity with high burst pressure and durability.In this work, the separation of acetone–butanol–ethanol mixtures (ABE) from aqueous solutions, is carried out by pervaporation using membranes prepared with HDES lidocaine-thymol (Lidol) and CH3(CH2)8COOH-Thymol (Decadol), coated with two polydimethylsiloxane (PDMS) flat sheet membranes.The composite membranes showed improved results for the butanol/water selectivity compared to the single PDMS layer membrane used as a control. The total flux of butanol obtained with the Lidol-based membrane was 2.93 × 10−3 [kg m−2 hr−1]. The total flux of water was 1.22 × 10−4 [kg m−2 hr−1], showing a selectivity value for butanol/water of 1932, while the control membrane had a selectivity value of 6.The results obtained with the composite membranes exhibited a higher and more stable performance in separating butanol from the ABE solution. The improvement in the selectivity can be explained by the synergic effect of the PDMS coating with the HDES layer.

Genealogy of Discourse in Agitative Messages from Agus Harimurti Yudhoyono's Press Conference Regarding the Issue of the Democratic Party Coup

Language has power and knowledge. Through language, interpersonal communication between humans can bring about changes in attitudes, perceptions and behavior of society. The important role in human interpersonal communication, especially in political communication, leads to findings that are expected to produce thoughts independently. In the discourse text of Agus Harimurti Yudhoyono (AHY) 's speech, during a press conference regarding the news about the coup issue within the Democratic Party. Text discourse that is read articulatively in public, with a target orientation of the speech delivery process aimed at the government reaches its own anti-climax. By using Faucault genealogy discourse methodology, AHY's speech text discourse study presents its own understanding in society. The data found by reviewing the use of diction in text sentences, use of references, substitutions, ellipsis and conjunctive. brings a number of accurate information and explanations as a whole, that the contribution of language and the presence of communication in responding to and seeing the overall context of the news becomes a separate medium for studying the dynamic contexts of language in an integrated manner.

The Recovery and Concentration of Spodumene Using Dense Media Separation

In coming years, global lithium production is expected to increase as the result of widespread electric vehicle adoption. To meet the expected increase in demand, lithium must be sourced from both brine and hard-rock deposits. Heavy liquid separation (HLS) and dense media separation (DMS) tests were conducted on the pegmatites from Hidden Lake, NWT, Canada to demonstrate the potential role of this technology in the concentration of spodumene (LiAlSi2O6) from hard-rock sources. A continuously operated DMS circuit test, conducted on +840 µm material, produced a concentrate grading 6.11% Li2O with ~50% lithium recovery. The circuit rejected 50% of the original mass to tailings, with only 8% lithium losses. Sensitivity analysis showed that minor changes (+/−0.05) in the DMS-specific gravity cut point resulted in significant changes to the mass rejected and to the concentrate grade produced; this may limit the feasibility and operability of the downstream grinding and flotation circuits. The results demonstrate the potential for DMS in the concentration of spodumene from the Hidden Lake pegmatites, and by extension, the potential for DMS in the concentration of spodumene from other hard-rock occurrences.

Nanostructured Multiphase Condensation of Complex Coacervates in Polymerization-Induced Electrostatic Self-Assembly.

We present the nanostructured multiphase condensation of complex coacervates in the dynamic evolving aqueous medium of liquid-liquid phase separation driven polymerization-induced electrostatic self-assembly (LLPS-PIESA). We show that the parent droplets evolve into nanostructured coacervate-in-coacervate multiphase condensates with diverse morphologies, such as dandelions, worms, lamellae, vesicles, and vesicle polymers, upon the kinetically dictated recruitment of anionic free chains, cationic growing chains, and nascent clusters from the dynamic evolving aqueous medium of LLPS-PIESA, under the interplay of electrostatic and arginine-like salt bridge interactions.

Removal of trace DNA toxic compounds using a Poly(deep eutectic solvent)@Biomass based on multi-physical interactions

DNA toxic compounds (DNA-T-Cs), even in trace amounts, seriously threaten human health and must be completely eliminated. However, the currently used separation media face great challenges in removing trace DNA-T-Cs. Based on the functional advantages of deep eutectic solvents (DESs) and the natural features of biomass (BioM), a series of Poly(DES)@BioMs functioning as adsorbents were prepared for the removal of aromatic/hetero-atomic DNA-T-Cs at the ppm level. After optimisation of experimental conditions, the removal efficiency for DNA-T-Cs ranged from 92.4% to 96.0% with an initial concentration of 20.0 ppm, a temperature of 30 °C, duration of 30 min, and pH of 7.0. The removal processes between the DNA-T-Cs and Poly(DES)@BioMs are well described in the Temkin equilibrium and second-order kinetic adsorption models, and the desorption processes are well shown in the Korsmeryer–Peppas equilibrium and zero-order kinetic models. Molecular simulations revealed that the removal interactions include hydrogen bonding, π–π stacking, and hydrophobic/hydrophilic effects. The removal efficiency for the DNA-T-Cs at 8.0 ppm in industrial sewage ranged from 69.7% to 102%, while the removal efficiency for the DNA-T-Cs standing alone at 20.0 ppm in a methyl violet drug solution was 95.4%, confirming that the Poly(DES)@BioMs effectively removed trace DNA-T-Cs in field samples.

Occurrence of Escherichia coli and Salmonella species in Some Livestock (Poultry) Feeds in Mando, Kaduna, Nigeria

The study aimed at assessing the proximate composition, isolation, characterization of some Enterobacteriaceae from two (2) brands of poultry feeds marketed in Mando, Kaduna, Nigeria. A total of sixteen (16) samples of two (2) different poultry feeds (starter and finisher) from four (4) poultry farms in mando were collected and subjected to proximate and microbiological analysis. The proximate analysis was carried out using standard techniques and procedures. All the feed samples were cultured on separate media which include Eosin methylene blue (EMB), nutrient Agar (NA) and Salmonella-Shigella Agar (SSA) media using standard procedures. The antibiogram of the selected antibiotics was evaluated against the test isolates. The result of proximate analysis of the starter and finisher feeds indicated that the Dry matter of starter feed had the highest percentage composition of 95.02% and crude fiber of the finisher feed had the lowest composition of 3.78%. The highest number of bacterial load was recorded to be 10.0×104 CFU/g for the feed sample A (starter feed) and 12.0x104CFU/g was recorded for the feed sample B (finisher feed) which had the highest number of bacterial load recorded among the two (2) different poultry feeds analyzed. The bacteria isolates were identified as Salmonella species and Escherichia coli. Total viable count (TVC) of Salmonella species and E. coli in the feed samples (starter and finisher) ranges from 3.0×104CFU/g to 12.0×104CFU/g. Both organisms (Salmonella species, E. coli) were found as 37.5% and 25% of the analyzed feeds (Broiler starter and broiler finisher) samples, respectively. There was no level of significant (p>0.05) difference between the level of contamination of Salmonella species and E. coli in the two different feeds analyzed, as p=0.06 and p=0.13 for Salmonella species, and E. coli respectively. Sample A and B (Starter and Finisher) feeds had the highest number of Salmonella species occurrence with six ( 6) positive samples while E. coli was recorded in four (4) samples of A and B (Starter and Finisher) feeds. The result of the antibiogram indicated that ciprofloxacin (30 µg), Gentamycin (30µg), Perfloxacin (30µg) and Tarvid (30µg) was effective against Salmonella species and Escherichia coli. The significant of spread of the species of the Enterobacteriaceae in livestock feeds requires the need for effective quality assurance and control, good hygiene practices in production and proper handling of the poultry feeds.

Harvesting freshwater microalgae with natural polymer flocculants

This study revealed the differences in harvesting performance and potential mechanisms of four natural flocculants - Chitosan, Tanfloc, Cationic starch, Moringa oleifera - on microalgae cells and explored the potential of four flocculants for harvesting microalgae. Influence of dosage, culture pH, cell density and algal organic matter (AOM) on harvesting using four flocculants were compared. The effects of the flocculants on cell viability and the reusability of separated medium were also investigated. The results demonstrated that the optimal dosages of Chitosan/Tanfloc/Cationic starch for harvesting Chlorella vulgaris and Scenedesmus obliquus were much lower than Moringa oleifera. Chitosan/Tanfloc/Cationic starch and Moringa oleifera improved microalgae harvesting through electrostatic binding and bridging, respectively. The harvesting of other flocculants were affected by culture pH except for Moringa oleifera. Nevertheless, as biomass concentration increased from ~0.3 g L−1 to ~1.5 g L−1, the optimal dosage of Moringa oleifera increased significantly, which was about 20–100 times than other flocculants. AOM could interfere all harvesting processes to varying degrees. Moreover, the flocs formed from Chitosan/Tanfloc/Cationic starch were smaller but more compacted compared to Moringa oleifera, thus possessing a better dewatering functionality. The harvesting process of four flocculants did not affect cell viability or lead to the loss of cell extractions including lipid, carbohydrates and protein. In addition to Chitosan, the medium separated from the other flocculants after harvesting could be recycled for next cultivation, reducing costs of microalgae cultivation. Amongst four natural flocculants, Tanfloc displayed >98% high harvesting efficiency with low dosages (30 mg L−1 for Chlorella vulgaris and 20 mg L−1 for Scenedesmus obliquus). It could effectively harvest microalgae in a wide pH range (pH 4.0–9.0) and showed a good dewatering potential. More importantly, the lowest harvesting cost of the four flocculants facilitates its application for large-scale harvesting. We therefore recommend Tanfloc for microalgae harvesting of the four flocculants.

Modulation of Topological Structures and Adsorption Properties of Copper-Tricarboxylate Frameworks Enabled by the Effect of the Functional Group and Its Position

To push forward the structural development and fully explore the potential utility, it is highly desired but challenging to regulate in a controllable manner the structures and properties of MOFs. In this work, we reported the structural and functional modulation of Cu(II)-tricarboxylate frameworks by employing a strategy of engineering the functionalities and their positions. Two pairs of unsymmetrical biaryl tricarboxylate ligands modified with a methyl group and a pyridinic-N atom at distinct positions were logically designed and synthesized, and their corresponding Cu(II)-based MOFs were solvothermally constructed. Diffraction analyses revealed that the variation of functionalities and their positions furnished three different types of topological structures, which we ascribed to the steric effect exerted by the methyl group and the chelating effect involving the pyridinic-N atom. Furthermore, gas adsorption studies showed that three of them are potential candidates as solid separation media for acetylene (C2H2) purification, with the separation potential tailorable by altering functionalities and their locations. At 106.7 kPa and 298 K, the C2H2 uptake capacity varies from 64.1 to 132.4 cm3 (STP) g-1, while the adsorption selectivities of C2H2 over its coexisting components of CO2 and CH4 fall in the ranges of 3.28-4.60 and 14.1-21.9, respectively.

Surface Chirality Influences Molecular Rotation upon Desorption.

Chiral surfaces offer great potential as a medium for enantioselective synthesis or separation, yet their dynamic enantiospecific interactions with adsorbates are not well understood. Here, the influence of chiral surfaces on the molecular rotations of desorbing molecules is investigated. Formic acid desorption from Cu{531} and Cu{110} serve as model systems for desorption processes of an achiral adsorbate from a chiral and an achiral surface. Our first-principles molecular dynamics study reveals a much larger and more directed angular momentum for molecules desorbing from the chiral surface and a clear preference for one sense of rotation. This result provides new insight into desorption and adsorption processes and propensities on chiral surfaces.

Graphene Oxide as a Pb(II) Separation Medium: Has Part of the Story Been Overlooked?

A key problem associated with the design of graphene oxide (GO) materials and their tuning for nanoscale separations is how specific functional groups influence the competitive adsorption of solvated ions and water at liquid/graphene interfaces. Computation accompanied by experiment shows that OH and COOH exert an influence on water adsorption properties stronger than that of O and H functional groups. The COO– anions, following COOH deprotonation, stabilize Pb(II) through strong electrostatic interactions. This suggests that, among the functional groups under study, COOH offers the best Pb(II) adsorption capacity and the ability to regenerate the sorbent through a pH swing. In line with computation, striking experimental observations revealed that a substantial increase in Pb(II) adsorption occurs with increasing pH. Our findings provide a systematic framework for controlled design and implementation of regenerable C-based sorbents used in separations and desalination.

Photobioreactors as potential tools for environmentally friendly and sustainable buildings

Global warming is a critical risk for the balance of nature, and its effects are increasing due to gases like CO2. One approach for CO2 capture is bringing together microalgae and buildings in esthetic bio-facade systems for obtaining environmentally friendly benefits. The aim of this study is to investigate the microalgae photobioreactors (PBR) as a potential bio-facade unit. Bio-facade concept focused on the multiple uses of water and nutrients, as well as CO2 capture, to highlight the sustainability and practicality. Chlorella vulgaris is selected as a model microalga due to its low doubling time and high biomass productivity. Experiments covered the dilutions of microalga medium (10%, 20%, 40%, 80%), recycling the cell separated medium and addition of CO2-enriched air (5% and 10%) focusing on their effects on various key factors like biomass and photosynthetic activity. PBR integrated laboratory scale house unit has also been constructed lastly. According to the preliminary results, up to 80% dilution, up to three cycles of medium and 5% CO2-enriched environment provided the high level of activity for bio-facade system. Interior air quality, changing of temperature and amounts of CO2–O2 with increasing of the biomass were investigated in PBR integrated laboratory scale house unit which depended on the outcomes of preliminary experiments (20% dilution and 5% CO2-enriched air). The results of unit showed the positive effects of the microalga integration with regards to its capability as a biofilter and a biocurtain for the sustainability.

First protein affinity application of Cu2+-bound pure inorganic nanoflowers

Today, a new kind of materials is introduced to separation media day by day to increase the efficiency of the separation processes, and multiple-petalled nanostructured materials are one of them. In this study, new pure inorganic copper phosphate nanoflowers (pCP-NFs) were synthesized, and some environmental conditions affecting on binding mechanism with human serum albumin were evaluated via changing medium pH, temperature, initial human serum albumin (HSA) amount and salt concentrations. Before experimental studies, pCP-NFs were subjected to some characterization tests such as scanning electron microscopy, energy-dispersive X-ray, X-ray diffraction and Fourier transform infrared spectroscopy. Besides a lot of valuable instrumental data, some obtained experimental ones as follows: after Cu2+ ions attachment to pCP-NFs as ligand, maximum HSA adsorption capacity of obtained Cu2+-pCP-NFs was found as 225.7 mg/g with an initial concentration of 1.5 mg/mL at pH 7 and 25 °C. Langmuir and Freundlich adsorption equations were evaluated for determination of appropriate adsorption model in interaction, and Langmuir model found as the fittest one with a R2 of 0.9949 was also reviewed to determine Gibbs free energy between HSA and Cu2+-pCP-NFs interaction.

Recent (2018-2020) development in capillary electrophoresis.

Development of new capillary electrophoresis (CE) methodology and instrumentation, as well as application of CE to solve new problems, remains an active research area because of the attractive features of CE compared to other separation techniques. In this review, we focus on the representative works about sample preconcentration, separation media or capillary coating development, detector construction, and multidimensional separation in CE, which are judiciously selected from the papers published in 2018–2020.

Porous Ionic Liquids: Structure, Stability, and Gas Absorption Mechanisms

AbstractPorous ionic liquids prepared from phosphonium‐based ionic liquids and metal‐organic frameworks (MOFs) are fluid in large ranges of temperature including ambient. It is shown that the ion pairs are too voluminous to enter the pores of the MOF, so the porous liquids remain several months as suspensions with permanent free volume, capable of absorbing large quantities of gases. The increase in gas absorption, when compared with the pure ionic liquids, is proportional to the amount of porous solid in suspension. Structural features of the MOFs and of the ionic liquids are maintained in the suspensions. Thermodynamic analysis and molecular simulations show that the driving force for gas absorption by the porous ionic liquids is energetic as well as structural being controlled by gas‐solid affinity or by the porous liquid free volume. The enthalpy of gas absorption allows easy regeneration of the porous liquid in all cases. The dissolved gases fluidify the porous ionic liquids, different gases having distinct effects on mass transport. The molecular mechanisms that explain the stability of the suspensions and their capacity for gas absorption are identified and point toward easy design rules that will enable numerous applications of these innovative materials as reaction or separation media.

Advanced Methods for Modifying the Properties of Separation Media and Mineral Components for More Efficient Separation of Diamond-Bearing Raw Materials

The results of this study proof the effectiveness of combining physical and electrochemical methods to intensify the processing of diamond-bearing ores as shown by:–recovering more diamonds thanks to the synergistic effects of making the diamond crystal surface more hydrophobic in grease recovery and froth flotation;–complete recovery of abnormally luminescent crystals thanks to modifying the spectral and kinetic properties of such crystals in separation by X-ray fluorescence;–lesser use of ferrosilicon thanks to its greater resistance to corrosion induced by interfacing with corrosive water systems.

Purification of black alkali liquor by microchannel filtration to promote energy savings and consumption reduction in lye cleaning systems

Traditionally, multistage plate-frame filtration or centrifugal treatment methods are used to remove fiber from black alkali liquor with high viscosity and high fiber impurity content. However, these methods are limited by the long processes and high consumption of energy and materials. Therefore, in this paper, a new microchannel (deep) filtration process and device were proposed and used to replace the original “three-step” separation process (i.e., metal plate-frame filtration, first-stage polypropylene filtration and second-stage polypropylene filtration) and device. Separation media with different particle sizes were used to carry out online separation experiments. Results showed that an effective separation could be realized by using the combined multiparticle media with a length-diameter ratio of <30. Specifically, the average separation efficiency was higher than 90%. The workload was reduced by 66%. The floor area was decreased by 52%. The energy consumption was reduced by 64%. The material consumption was nearly zero. It is hoped that this study can not only benefit energy savings and cleaner production in the viscose fiber industry but also serve as a useful guide for other chemical industries.

Performance evaluation of silica microspheres functionalized by different amine-ligands for hydrophilic interaction chromatography

In this work, for the first time five amine-ligands including mono-amine, di-amine, tri-amine, secondary and tertiary amine, were functionalized on mesoporous micro-silicas and developed as stationary phases for hydrophilic interaction liquid chromatography (HILIC). The investigations about the retention mechanisms, effects of different chromatographic conditions and stability were systematically conducted. Three kinds of polar and hydrophilic compounds (saccharides, sulfonamides, nucleosides and nucleobases) were selected as probe molecules to evaluate their separation performances. Among the five stationary phases, only aminopropyl-bonded silica has already gained wide developments and applications. Whereas, there are no related researches about the other four to be utilized as separation media. By a series of chromatographic evaluations, the results revealed the other four mesoporous micro-silica materials functionalized with di-amine, tri-amine, secondary and tertiary amine, had great potential to be explored as novel stationary phases of HILIC. Particularly, the two stationary phases functionalized with di-amine and tri-amine exhibited outstanding separation and retention abilities. This work offered some insights on the understanding of retention in HILIC mode and provided us possibility to explore other amine-based HILIC stationary phases.