Enhanced performance of expanded bed chromatography on rigid superporous adsorbent matrix

Rigid spherical macroporous adsorbent beads with surface hydroxyl groups were prepared by cross-linking of cellulose. These beads had diameter in the range 100-200 microm and a mean pore size of about 3 microm with about 60% pore volume. The matrix (bulk density approximately 1600 kg m(-3)) could be expanded into a stable bed and used for protein chromatography. Chromatographic runs were performed on a 10 mm diameter column under non-retaining and retaining conditions on the prepared matrix (called Celbeads) and performance of the runs was measured in terms of the height equivalent to a theoretical plate (HETP). The HETP curves in both packed and expanded bed modes followed profiles typical of macroporous adsorbents, i.e. increasing and levelling with velocity. Unimpaired performance of the matrix at increasing flow-rates permitted expanded bed elution of adsorbed solutes without loss of efficiency in terms of purification factor and product concentration. As a model system, Celbeads was used to purify lactate dehydrogenase from porcine muscle homogenate by dye-affinity chromatography. The prepared matrix provided about 100 theoretical plates per meter for the enzyme system at a linear flow velocity of 1.27 cm x min(-1) in an expanded bed elution mode, and gave enzyme yields of 100% with a purification factor of 31 using an optimized procedure. The adsorbent could be cleaned in place with 5 M urea and used repeatedly without loss of performance.     

Optimization of synthesis procedures for structured PSA adsorbents

Structured adsorbents in the form of supported thin zeolite films may represent a competitive alternative to traditional zeolite adsorbents in form of beads or pellets used in PSA processes, due to the reduction of mass- and heat-transfer limitations typical of packed beds. Thin NaX films were grown by hydrothermal treatment using a clear solution on cordierite monoliths. Films grown by a multiple synthesis procedure were dense and uniform with a very small amount of sediments adjacent to the film, which may be an advantage in PSA applications. The CO₂ adsorption capacity and the pressure drop for the supported films were compared to those of a packed NaX bed. Although the adsorption capacity of the column filled with the structured adsorbents was 67 times lower than when the column was filled with zeolite beads, the pressure drop was 100 times lower for the structured adsorbent. The adsorption capacity can be increased by increasing the film thickness or the cell density of the monoliths without increasing the pressure drop significantly, indicating the potential advantage of structured adsorbents in PSA processes. Further investigations are needed in order to prove this hypothesis.     

Benzene and toluene adsorption at low concentration on activated carbon fibres

The present study analyses the preparation of activated carbon fibres (ACFs) by the so-called “physical” activation method with steam or carbon dioxide and their application for benzene and toluene adsorption at low concentration (200 ppmv). ACFs have been scarcely studied for the adsorption of these pollutants at low concentration in gaseous phase, despite their interesting features regarding adsorption kinetics, bed pressure drop, possibility of conformation and others. Our results have shown that the preparation method used is suitable to produce ACFs with high adsorption capacities for benzene and toluene at the low concentration used. The fibre morphology of the ACFs does not enhance their performance, which results to be similar to other non-fibrous activated carbons such as granular, pellets and powders. Such good performance of the ACFs, leading to benzene and toluene adsorption capacities as large as 31 g benzene/100 g ACF or 53 g toluene/100 g ACF, can be explained due to their large volume of narrow micropores (<0.7 nm) developed upon activation and their low content in surface oxygen groups. Our results have also shown very good agreement between the adsorption results derived from dynamic adsorption experiments and from adsorption isotherms. As the relative pressure of the organic compound increases the corresponding fraction of narrow micropore volumes filled by benzene and toluene increases. For a given low and comparable relative pressure, toluene always occupies a larger fraction of narrow micropores than benzene.     

Effects of Glass Beads Packing on SF6 Abatement by Packed Bed Plasma

Plasma Chemistry and Plasma Processing - This article investigated the effects of SF6 degradation by packed bed DBD (PBDBD) with packing material of glass beads (diameter of 4&nbsp;mm). The...     

pH shifting effect on anionic dye removal by surfactant-modified sugar beet pulp: Modeling of column studies

pH shifting effect on the adsorption of anionic RBB dye was tested by using untreated and CTAB-treated SBP as adsorbent in both batch and continuous systems. Characterization of the sorbents revealed the effects of surface modification. Enhanced binding sites and more porous surface structure resulted in improved adsorption capability. Flow rate and initial RBB concentration effects were tested in packed bed column. Optimum pH value of the adsorption, which was determined as 2.0 in the batch studies with untreated SBP, shifted to 8.0 with 20 g/L CTAB treated SBP. Experimental data in column studies showed the decreasing capacity with increasing flow rate and enhanced performance with increasing inlet RBB concentration for both sorbents. Maximum capacities of the columns were found as 36.9 and 2.6 mg/g with dried SBP at pH 2.0 and 8.0, respectively, at a maximum inlet RBB concentration of 500 mg/L and a minimum flow rate of 0.8 mL/min. The highest capacity value at pH 8.0 was found as 140.0 mg/g under the same operating conditions, which reveals positive effect of the treatment on adsorptive performance. Langmuir isotherm was found to be most convenient model for the all equilibrium cases in the column. Moreover, Thomas model accurately predicted the breakthrough curves of each system. This is the first study reporting the modeling data of an anionic dye adsorption in a packed bed column by using modified SBP.     

IgG adsorption on a new protein A adsorbent based on macroporous hydrophilic polymers: II. Pressure–flow curves and optimization for capture

Pressure–flow curves are obtained for a new protein A adsorbent matrix based on macroporous hydrophilic polymer beads with average diameter of 57 μm and a narrow particle size distribution. Experimental data are obtained in a 1 cm diameter laboratory column and in preparative scale columns with diameters of 20, 30, and 45 cm. The results are consistent with a model that assumes a linear relationship between bed compression and relative flow velocity. Surprisingly, the packing compressibility is essentially independent of column diameter for the preparative columns. As a result, after accounting for the variation in extraparticle porosity caused by compression, the column pressure drop is accurately predictable using the Carman–Kozeny equation. A model is also developed to predict productivity for IgG capture as a function of operating conditions based on dynamic binding capacity data presented in Part I of this work. For typical conditions, the model predicts maximum productivity at low residence times, between 1 and 1.5 min, when the dynamic binding capacity is at about 70–80% of the maximum. Combining the two models for column pressure and for dynamic binding capacity allows the design of preparative scale columns that maximize productivity while meeting specified pressure constraints.     

Evaluation of interlaminar fracture toughness and dynamic mechanical properties of nano TiO2 coated flax fibre epoxy composites

In this study, fibre modification technique is performed by coating nano titanium dioxide (TiO₂) particles on flax fibres. The fibre surface is treated with silane coupling agents and coated with nanoparticles at weight percentage 0.2, 0.4, 0.6 and 0.8% to develop chemical bonding at the fibre matrix interface. The improved interface is evaluated by performing Mode I, Mode II interlaminar fracture toughness (ILFT), and Dynamic mechanical analysis (DMA). The results indicate that the fibre modified composites with 0.4 wt % and 0.6 wt % coating shows 37% and 24% improvement in Mode I and Mode II ILFT values respectively. The storage modulus from the DMA analysis also exhibits improvement for the fibre modified composites. SEM analysis explains the changes in the fracture mechanism. FTIR analysis provides the details on the fibre coating by nanoparticles.     

Lab on a chip packing of submicron particles for high performance EOF pumping

The packing of submicrometer sized silica beads inside a microchannel was enabled by a novel method which avoids the complication and limitations of generating a frit using conventional approaches and the restriction of flow using a submicrometer sized weir. A micrometer sized weir and two short columns of 5 μm and 800 nm silica beads packed in succession behind the weir together functioned as a high pressure frit to allow the construction of a primary packed bed of 390 nm silica beads. This packed bed microchannel was tested as an EOF pump, wherein it exhibited superior performance with regards to pressure tolerance, i.e., sustaining good flow rate under extremely high back pressure, and maximal pressure generation. Under a modest applied electric field strength of 150 V/cm, the flow rate against a back pressure of 1200 psi (～8.3 MPa) was 40 nL/min, and the maximal pressure reached 1470 psi (～10 MPa). This work has demonstrated that it is possible to create a high performance packed bed microchannel EOF pump using nanometer sized silica beads, as long as proper care is taken during the packing process to minimize the undesirable mixing of two different sized particles at the boundaries between particle segments and to maximize the packing density throughout the entire packed bed.     

Experimental studies on performance augmentation of single hole cored brick sensible heat storage system using turbulence inducers

This article presents experimental analysis on performance augmentation of a single hole cored brick regenerator using turbulence inducers. Experiments were carried out for different velocities with air as the working fluid for both charging and discharging processes of a 455 mm long aluminum regenerator with inner and outer diameters of 26 mm and 40 mm, respectively. Two numbers of turbulence inducers of 1.5 mm diameter and 13 mm long were placed in ten different combinations and the results were compared with the trials wherein no inducers were used. The mean temperature of the cored brick, exit temperature during discharge, ratio of heat transfer rate to pressure drop, and exergetic efficiencies are the characteristics that were used to study the performance of the regenerator. Placement of inducers increased the mean temperature of the regenerator and the ratio of heat transfer rate to pressure drop by about 15% and a maximum of 40%, respectively, during charging. The exit air temperature during discharge exhibited maximum improvement of 18%. Increased exergetic efficiencies of more than 10% and 5% were estimated for charging and discharging, respectively. It was also observed that the addition of inducers does not necessarily result in an increased performance, and some of the combinations in fact deteriorated the performance of the regenerator.

     

Pressure drop in CIM disk monolithic columns

Pressure drop analysis in commercial CIM disk monolithic columns is presented. Experimental measurements of pressure drop are compared to hydrodynamic models usually employed for prediction of pressure drop in packed beds, e.g. free surface model and capillary model applying hydraulic radius concept. However, the comparison between pressure drop in monolith and adequate packed bed give unexpected results. Pressure drop in a CIM disk monolithic column is approximately 50% lower than in an adequate packed bed of spheres having the same hydraulic radius as CIM disk monolith; meaning they both have the same porosity and the same specific surface area. This phenomenon seems to be a consequence of the monolithic porous structure which is quite different in terms of the pore size distribution and parallel pore nonuniformity compared to the one in conventional packed beds. The number of self-similar levels for the CIM monoliths was estimated to be between 1.03 and 2.75.     

Simulation of ordered packed beds in chromatography

A computer simulation of chromatographic dispersion in an ordered packed bed of spheres is conducted utilizing a detailed fluid flow profile provided by the Lattice Boltzmann technique. The ordered configurations of simple cubic, body-centered cubic, and face-centered cubic are employed in these simulations. It is found that zone broadening is less for the fcc structure than the sc and bcc structures and less than a random packed bed analyzed in a previous study in the low flow velocity region used for experimental chromatography. The factors which contribute to the performance of the ordered pack beds are analyzed in detail and found to be dependent both on the nearest surface to surface distance and on the distribution of velocities found in the various packing geometries. The pressure drops of the four configurations are compared and contrasted with the pressure drop from monolithic columns.     

Stage-frit: A straightforward sub-2 μm nano-liquid chromatography column fabrication for proteomic analysis

In this work we demonstrated a facile method for the fabrication of C18 coordination polymer gel in a capillary, called stage-frit, which was efficiently applied to pack sub-2 μm C18 beads into the capillary by a high pressure bomb for the online separation of proteolytic peptides. The back pressure of the column with 10 cm × 75 μm i.d. is regularly lower than 170 bar at a flow rate of 300 nl/min, which could be operated on a common nanoLC system instead of nanoUPLC system due to the good permeability, low back pressure and high mechanical stress of the frit that will totally reduce the cost for the purchase of instrument. The stage-frit allows long-term continuous flow of the solvent and no significant beads loss or pressure instability was observed during the period. The repeatability of retention time for fifteen BSA tryptic peaks was found to be less than 1.08% (RSD) in six time nanoLC-ESI-MS/MS experiments. The average full width at half maximum (FWHM) of peptide peaks is 5.87 s. The sub-2 μm stage-frit nanoLC column showed better sensitivity than the commercial available for large scale proteomic analysis of total tissue proteins from human spleen. The number of identified peptides is approximately 0.4-fold and 0.2-fold higher than that obtained by utilizing commercial columns packed with 3 μm and 1.8 μm C18 materials, respectively. In the field of analytical chemistry, particularly the use of nanoLC systems, stage-frit nanoLC column offers a great potential for the separation of complex mixtures.     

Preparation of alginate coated chitosan hydrogel beads by thermosensitive internal gelation technique

Chitosan hydrogel beads were successfully prepared by the method of thermosensitive internal gelation technique. The prepared beads were spherical, smooth-surfaced and non-aggregated with a diameter of 1.7–2.1 mm. The diameters of beads can be controlled and have a correlation with the initial drop size, the concentration of CaCl₂, alginate and the time of solidification. The bead is comprised of three parts, which are chitosan/glycerophosphate (CS/GP) hydrogel core, chitosan-alginate (CS/SA) gel layer in the middle and calcium-alginate gelatin capsules in outer layer. Swelling studies indicate that the beads can be stable in simulated gastric fluid. But the beads shrink sharply when removed to simulated intestinal fluid. Drug release behavior showed that release of ornidazole in the beads is much slower than in the CS/GP hydrogel.     

Oxygen production using La0.6Sr0.4Co0.2Fe0.8O3−α (LSCF) perovskite hollow fibre membrane modules

A phase-inversion/sintering technique has been employed in the production of La_0.6Sr_0.4Co_0.2Fe_0.8O_3−α (LSCF) hollow fibre membranes, a bundle of which has then been placed in a high-temperature furnace for production of high purity oxygen from air at temperatures between 980 °C and 1060 °C. By applying a vacuum in the hollow fibre lumens, a product stream containing oxygen purity of 97.15% has been obtained. The downstream vacuum degree higher than 99 kPa shows negligible effect on the oxygen production rate. Studies on long-term operation suggest that the LSCF hollow fibre membranes are less stable for the oxygen production due to the segregation of the constituent membrane elements and the formation of new phases on the outer membrane surfaces. The effect of the operating cycle on the retrogression of membrane performance is much larger than that of duration used in a single cycle.     

Sorption–Chromatographic Determination of Aniline, 4-Chloroaniline, and 2,5-Dichloroaniline in Air

Conditions were found for the chemisorption preconcentration of aniline, 4-chloroaniline, and 2,5-dichloroaniline from air using tubes packed with silica gel with immobilized 4-chloro-5,7-dinitrobenzofurazan and for the subsequent HPLC determination with diode-array detection. The maximum analyte recoveries (98, 90, and 75% for aniline, 4-chloroaniline, and 2,5-dichloroaniline, respectively) were achieved at a 2-cm thickness of the adsorbent layer (silica gel with a grain size of 0.1–0.3 mm impregnated with 3 wt % 4-chloro-5,7-dinitrobenzofurazan), an aspiration rate of 0.6–0.8 L/min, and an aspirated air volume of 10 L. Taking into account a tenfold preconcentration of analytes after the desorption, the detection limit for aniline is equal to 0.0007 mg/m³.     

Capture of CO<Subscript>2</Subscript> from flue gas by vacuum pressure swing adsorption using activated carbon beads

Vacuum pressure swing adsorption (VPSA) for CO₂ capture has attracted much research effort with the development of the novel CO₂ adsorbent materials. In this work, a new adsorbent, that is, pitch-based activated carbon bead (AC bead), was used to capture CO₂ by VPSA process from flue gas. Adsorption equilibrium and kinetics data had been reported in a previous work. Fixed-bed breakthrough experiments were carried out in order to evaluate the effect of feed flowrate, composition as well as the operating pressure and temperature in the adsorption process. A four-step Skarstrom-type cycle, including co-current pressurization with feed stream, feed, counter-current blowdown, and counter-current purge with N₂ was employed for CO₂ capture to evaluate the performance of AC beads for CO₂ capture with the feed compositions from 15–50% CO₂ balanced with N₂. Various operating conditions such as total feed flowrate, feed composition, feed pressure, temperature and vacuum pressure were studied experimentally. The simulation of the VPSA unit taking into account mass balance, Ergun relation for pressure drop and energy balance was performed in the gPROMS using a bi-LDF approximation for mass transfer and Virial equation for equilibrium. The simulation and experimental results were in good agreement. Furthermore, two-stage VPSA process was adopted and high CO₂ purity and recovery were obtained for post-combustion CO₂ capture using AC beads.     

On the determination of crystallinity and cellulose content in plant fibres

A comparative study of cellulose crystallinity based on the sample crystallinity and the cellulose content in plant fibres was performed for samples of different origin. Strong acid hydrolysis was found superior to agricultural fibre analysis and comprehensive plant fibre analysis for a consistent determination of the cellulose content. Crystallinity determinations were based on X-ray powder diffraction methods using side-loaded samples in reflection (Bragg-Brentano) mode. Rietveld refinements based on the recently published crystal structure of cellulose Iβ followed by integration of the crystalline and amorphous (background) parts were performed. This was shown to be straightforward to use and in many ways advantageous to traditional crystallinity determinations using the Segal or the Ruland–Vonk methods. The determined cellulose crystallinities were 90–100 g/100 g cellulose in plant-based fibres and 60–70 g/100 g cellulose in wood based fibres. These findings are significant in relation to strong fibre composites and bio-ethanol production.     

Effect of strain rate on the dynamic tensile behaviour of UHMWPE fibre laminates

Ultra-high molecular weight polyethylene (UHMWPE) fibre has great potential for strengthening structures against impact or blast loads. A quantitative characterization of the mechanical properties of UHMWPE fibres at varying strain rates is necessary to achieve reliable structural design. Quasi-static and high-speed tensile tests were performed to investigate the unidirectional tensile properties of UHMWPE fibre laminates over a wide range of strain rates from 0.0013 to 163.78 s⁻¹. Quasi-static tensile tests of UHMWPE fibre laminates were conducted at thicknesses ranging from 1.76 mm to 5.19 mm. Weibull analysis was conducted to investigate the scatter of the test data. The failure mechanism and modes of the UHMWPE fibre laminates observed during the test are discussed. The test results indicate that the mechanical properties of the UHMWPE fibre laminate are not sensitive to thickness, whereas the strength and the modulus of elasticity increase with strain rate. It is concluded that the distinct failure modes at low and high strain rates partially contribute to the tensile strength of the UHMWPE fibre laminates. A series of empirical formulae for the dynamic increase factor (DIF) of the material strength and modulus of elasticity are also derived for better representation of the effect of strain rate on the mechanical properties of UHMWPE fibre laminates.     

A co-templated approach to hierarchically mesoporous–macroporous bioactive glasses (MMBG) scaffolds for bone tissue regeneration

In this paper, one kind of well-ordered hierarchical mesoporous–macroporous bioactive glasses (MMBG) scaffolds with large pore size of 60–120 μm and mesoporous phase in inner-wall has synthesized successfully. This method used stem core of corn as macroporous template and P123 as mesoporous template. The final samples have replicated the structure of the macroporous plant templates precisely. Since the aperture and pore structure of different plants are variable, it provides a possible way for the synthesis of materials with various aperture holes and pore structure. The organizational structure of final sample is benefit to transport and storage guest molecule, making these hierarchical porous materials have more superior performance and application in the field of macromolecules separation, bone tissue regeneration, and drug delivery, etc. The in vitro tests indicated hierarchical MMBG scaffolds have well capacity for inducing the HA growth. They have the potential to satisfy the demands of bone tissue engineering regeneration.     

Removal of endocrine‐disrupting compounds from water using macroporous molecularly imprinted cryogels in a moving‐bed reactor

Highly efficient removal of endocrine‐disrupting compounds (EDCs) such as 17β‐estradiol (E2), 4‐nonylphenol (NP) and atrazine from water was achieved using a novel macroporous adsorption medium. The medium consisted of a macroporous poly(vinyl alcohol) (PVA) cryogel with molecularly imprinted polymer (MIP) particles embedded in it. The MIP was prepared using E2, NP and atrazine as templates. The macroporous composite molecularly imprinted cryogels were formed inside the open‐ended protective shells, known as Kaldnes carriers. These adsorbents (defined as Macroporous Gel Particles, MGPs) were evaluated on the removal of E2, NP and atrazine from water using different column configurations, namely column filled with the MGPs (packed‐bed column) and in moving‐bed reactors (defined here as moving‐bed MGPs reactor). Complete binding (> 99%) of E2 from a spiked aqueous solution (1 mg/L) was achieved using E2‐MIP/MGPs in a moving‐bed MGPs reactor at the retention time in the reactor of 4 min, while only 77% was bound to the nonimprinted medium (NIP/MGPs). Similar results were also obtained for the adsorption medium imprinted with atrazine. All contaminants studied (E2, atrazine and NP) were effectively removed from water at low (environmentally relevant) concentrations by the respective adsorption medium.