Column Efficiency Research Articles

Resolution limits of size exclusion chromatography columns identified from flow reversal and overcome by recycling liquid chromatography to improve the characterization of manufactured monoclonal antibodies

The flow reversal (FR) technique consists of reversing the flow direction along a chromatographic column. It is used to reveal the origin (such as poor column packing, active sites, or slow absorption/escape kinetics) for the resolution limit of 4.6 mm × 150 mm long columns packed with 1.7 μm 200 Å Bridge-Ethylene-Hybrid (BEHTM) Particles. These columns are used to separate manufactured monoclonal antibodies (mAb, ∼ 150 kDa) from their close impurities (or IdeS fragments, ∼ 100 kDa) by size exclusion chromatography (SEC). FR unambiguously demonstrates that the resolution limit of these SEC columns is primarily due to long-range flow velocity biases covering distances of at least 500 μm across the column diameter. This confirms the existence of center-to-wall flow heterogeneities which cause undesirable tailing for the mAb peak. Because the transverse dispersion coefficient (Dt=1.1 × 10−6 cm2/s) of mAbs across the column diameter is intrinsically low, the bandspreading of the mAb in a single flow direction is in part reversible upon reversing the flow direction. For the very same residence time in the column, the column efficiency is found to increase by +85% relative to that observed under conventional elution mode. The observed peak tailing of the mAb and its sub-units is not caused by active surface sites or by slow absorption/escape from the BEH Particles. Therefore, the most critical mAb impurities (hydrolytic degradation Fab/c and IdeS F(ab′)2 fragments) can only be successfully separated and quantified with acceptable accuracy by adopting alternate pumping recycling liquid chromatography (APRLC). APRLC enables the full baseline separation of the mAb and 100 kDa mAb fragments and partial separation of Fab/c and F(ab′)2 fragments after increasing the number of cycles to ten. It was made possible to accurately measure the relative abundances of the mAb (99.0 ± 0.1%), F(ab′)2 fragment (0.88 ± 0.03%), and Fab/c immunogenic fragment (0.13 ± 0.02%) in less than 45 min for a total mAb sample load of only 5 μg. Still, further improvements are needed to increase the sensitivity of the APRLC method and to reduce the solvent consumption by adopting narrow-bore 2.1 mm i.d. SEC columns.

Preparation and application of a novel imine-linked covalent organic framework@silica composite for reversed-phase and hydrophilic interaction chromatographic separations

The composites of covalent organic frameworks (COFs) and silica gel have been considered to be promising chromatographic separation materials due to the distinct advantages such as large specific surface area, good mechanical strength and high porosity. In the present study, a novel imine-linked COF@silica composite was prepared by in-situ growth of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) and 2,5-dihydroxyterephthalaldehyde (DHTA) monomers on the surface of aminated silica gel (SiO2–NH2). The successful surface-modification of TAPT-DHTA-COF distinctly enhanced the separation selectivity and efficiency of SiO2–NH2. Multiple types of analyte-stationary phase interactions contributed to the selective retention of structurally similar analytes. The designed TAPT-DHTA-COF@SiO2 was observed to effectively separate hydrophobic phenyl ketones, phthalate esters and steroid hormones. Moreover, the polar amino and hydroxyl groups of TAPT-DHTA-COF facilitated the selective determination of hydrophilic nucleosides/bases. The kinetic performance and thermodynamic behavior of TAPT-DHTA-COF@SiO2 column were particularly explored. It was found that column efficiency was mainly affected by the mass transfer resistance, and the retention of nucleosides/bases on the TAPT-DHTA-COF@SiO2 column was temperature dependent. The developed versatile TAPT-DHTA-COF@SiO2 column was finally applied for detecting environmental hormones as well as water-soluble nicotinamide in real samples. In summary, the potential application of TAPT-DHTA-COF@SiO2 composite material for liquid chromatographic separations was first explored and verified. The TAPT-DHTA-COF@SiO2 was proved to be a promising chromatographic separation material.

Fabrication and application of molecularly imprinted polymer doped carbon dots coated silica stationary phase

Facing the difficulties in chromatographic separation of polar compounds, this investigation devotes to developing novel stationary phase. Molecularly imprinted polymers (MIPs) have aroused wide attention, owing to their outstanding selectivity, high stability, and low cost. In this work, a novel stationary phase based on carbon dots (CDs), MIP layer, and silica beads was synthesized to exploit high selectivity of MIPs, excellent physicochemical property of CDs, and outstanding chromatographic performances of silica microspheres simultaneously. The MIP doped CDs coated silica (MIP-CDs/SiO2) stationary phase was systematically characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area measurement, and carbon elemental analysis. Furthermore, the chromatographic performance of the MIP-CDs/SiO2 column was thoroughly assessed by using a wide variety of compounds (including nucleosides, sulfonamides, benzoic acids, and some other antibiotics). Meanwhile, the separation efficiency of the MIP-CDs/SiO2 stationary phase was superior to other kinds of stationary phases (e.g. nonimprinted NIP-CDs/SiO2, MIP/SiO2, and C18–SiO2). The results demonstrated that MIP-CDs/SiO2 column exhibited best performance in terms of chromatographic separation. For all tested compounds, the resolution value was not less than 1.60, and the column efficiency of MIP-CDs/SiO2 for thymidine was 22,740 plates/m. The results further indicate that the MIP-CDs/SiO2 column can combine the good properties of MIP, CDs, with those of silica microbeads. Therefore, the developed MIP-CDs/SiO2 stationary phase can be applied in the separation science and chromatography-based techniques.

Automated Regularized Deconvolution for Eliminating Extra-Column Effects in Fast High-Efficiency Separations.

With the introduction of ultrahigh efficiency columns and fast separations, the need to eliminate peak deformation contributed by the instrument must be effectively solved. Herein, we develop a robust framework to automate deconvolution and minimize its artifacts, such as negative dips, wild noise oscillations, and ringing, by combining regularized deconvolution and Perona-Malik (PM) anisotropic diffusion methods. A asymmetric generalized normal (AGN) function is proposed to model the instrumental response for the first time. With no-column data at various flow rates, the interior point optimization algorithm extracts the parameters describing instrumental distortion. The column-only chromatogram was reconstructed using the Tikhonov regularization technique with minimal instrumental distortion. For illustration, four different chromatography systems are used in fast chiral and achiral separations with 2.1 and 4.6 mm i.d. columns. Ordinary HPLC data can approach highly optimized UHPLC data. Similarly, in fast HPLC-circular dichroism (CD) detection, 8000 plates were gained for a fast chiral separation. Moment analysis of deconvolved peaks confirms correction of the center of mass, variance, skew, and kurtosis. This approach can be easily integrated and used with virtually any separation and detection system to provide enhanced analytical data.

In-situ immobilization of covalent organic frameworks as stationary phase for capillary electrochromatography

A new kind of covalent organic framework (COF) was first utilized as an stationary phase for open-tubular electrochromatography (OT-CEC) by in situ synthesis immobilized method at room temperature. On the basis of our previous work, 4,4′,4″-(1,3,5-Triazine-2,4,6-triyl)trianiline (TZ) and 2,5-bis(2-propyn-1-yloxy)-1,4-benzenedicarboxaldehyde (BPTA) were employed as building blocks for the synthesis of COF TZ-BPTA. The coated capillary and COF TZ-BPTA were characterized by scanning electron microscopy (SEM). Then, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) were also applied to characterize COF TZ-BPTA and the modified column. In SEM, it can be seen that COF TZ-BPTA was the spherical shape and the modified capillary was covered with globular particles equably. The COF TZ-BPTA coated column exhibited good separation resolution and efficiency towards two antiepileptic drugs and other kinds of small organic molecules involving alkylbenzene, sulfonamides, polycyclic aromatic hydrocarbon (PAH), parabens, amino acids and herbicides. The maximum column efficiency was over 2.8 × 105 plates·m−1. In addition, the precisions (RSDs) of the retention times for the alkylbenzenes of intra-day runs (n = 3), inter-day runs (n = 3) and column-to-column runs (n = 3) were all less than 1.70% and separation performance was without obvious change within 100 times run. In addition, the real sample was tested on COF TZ-BPTA coated column. Hence, COF TZ-BPTA showed great potential in the separation domain.

Serendipitous discovery of a regioselective synthesis of novel benzoyloxy substituted phenyl/benzyl-sulfanyl/selenylbisesters, 3-benzoyloxy-3-(phenylsulfanyl)-β-lactams and their antimicrobial evaluation

The regioselective benzoyloxylation process involves stirring a mixture of phenyl/benzyl-sulfanyl/selenylethanoate 1a-c with appropriate oxidant [benzoyl peroxide (BPO) 2a/ m-chloroperbenzoic acid (m-CPBA) 2b /bis(p-methoxybenzoyl peroxide) (BPM-BPO) 2c] under catalysis of hydrated copper acetate in toluene at 60 °C/RT. Regioselective C–H functionalization of esters 1a-c leads to benzoyloxy substituted phenyl/benzyl-sulfanyl/selenylbisesters 3a-g in good to excellent yields (80–95%). Variably substituted trans-3-phenylsulfanyl-β-lactams 4 employed for C3-H functionalization with BPO 2a generates diastereoisomeric mixture of trans- and cis-3-benzoyloxy-3-(phenylsulfanyl)-β-lactams 5 and 6 as major and minor isomers after efficient column chromatographic purification. The structural confirmation was done using IR, 1H NMR, 13C NMR, DEPT-90 NMR spectroscopic analysis and CHNS elemental analysis. In vitro antibacterial and antifungal evaluations on bisesters suggest benzylselenyl-bisester 3c as potent antimicrobial agent. Out of trans- and cis-3-benzoyloxy-β-lactams 5a and 6a, the trans isomer 5a was active against all microbial strains whereas the cis isomer 6a was completely inactive.

Microchip gas chromatography column using magnetic beads coated with polydimethylsiloxane and metal organic frameworks

Micro gas chromatography (μGC) using microfabricated silicon columns has been developed in response to the requirement for portable on-site gas analysis. Although different stationary phases have been developed, repeatable and reliable surface coatings in these rather small microcolumns remains a challenge. Herein, a new stationary phase coating strategy using magnetic beads (MBs) as carriers for micro column is presented. MBs modified with organopolysiloxane (MBs@OV-1) and a metal organic framework (MBs@HKUST-1) are deposited in on-chip microcolumns assisted with a magnetic field with an optimized modification process. MBs@OV-1 column showed a minimum HETP of 0.074 cm (1351 plates/m) of 62 cm/s. Mixtures of volatile organic compounds are successfully separated using MBs carried stationary phase which demonstrates that this technique has good chromatographic column efficiency. This method not only provides a novel coating process, washing and characterization of the stationary phases but also establishes a straightforward strategy for testing new absorbent materials for μGC systems.

Insights into the startup operation of a thermally efficient multi-tube falling-film distillation column

The motivation for this study is to contribute to the implementation of an innovative and thermally efficient distillation concept, which involves integrating a multi-tube type falling-film distillation column with a biphasic thermosyphon. This study concentrated on examining a startup operation with pilot-scale experiments at a feeding capacity of 250 kg h−1; while examining two possible thermal energy transfer arrangements from the steam chamber to the distillation tubes (isothermal and non-isothermal). The dynamic behavior of the startup operation was analyzed, revealing three distinct phases - discontinuous, semi-continuous, and continuous - each characterized by their respective time requirements and energy consumption. Using non-isothermal heating, the multi-tube falling-film distillation column required 11.2 kW for the startup operation, 17% less than isothermal heating. Operating under both heating configurations, the multi-tube falling-film distillation column achieved a 70 vol% ethanol concentration. Multi-tube falling-film distillation requires 51.0% less time and 72.1% less electrical energy during startup operation than traditional tray distillation. The knowledge obtained from this study can improve the efficiency of falling-film distillation columns, ensuring optimal industrial-level operation, and can contribute to the recognition of this recently developed technology in comparison to established conventional tray columns.

NUMERICAL SIMULATION OF A GEAR

To navigate safely, the ship must be manoeuvrable and have good stability. The steering of the ship depends on a number of factors such as: the means of steering used, the geometric shapes of the hull (stern area), the ratios between the main dimensions (LCWL/B and B/T), the number, position and direction of rotation of the engine. and the hydro-meteorological conditions in which they sail (water, air, wind, waves). Every ship, with the exception of barges, must have a robust and safe steering system to ensure manoeuvrability and sea stability. These installations can be: rudder with hydrodynamic profile, installation with adjustable nozzles and other installations approved by the Classification Societies. In this particular study an analysis on a gear pump fitted in the azimuth system of a chemical tanker is being made, using a CFD technology. The main aim is to study the efficiency of this pump by comparing the CFD analysis results with the results in real operational condition. Main parameters focused on are outlet flow, suction column, power and pump efficiency. There are several differences registered in the case of suction column and power, but they are not that high, while parameters outlet flow and pump efficiency are almost identical.

#4431 PREPARATION OF IMIDAZOLE QUATERNARY AMMONIUM SALT MICROSPHERES WITH HIGH BILIRUBIN ADSORPTION PERFORMANCE AND SELF-ANTICOAGULATION ABILITY

Abstract Background and Aims Bilirubin is a crucial toxin in liver metabolism. Increase of bilirubin is one of common manifestations in patients with abnormal liver function, and large accumulation of bilirubin in the blood can lead to more severe hepatic dysfunction and even death. Due to the poor therapy effect and the shortage of available donor organs, the artificial liver support system has been introduced to maintain the liver function and bridge patients to transplantation. Previous studies have found that imidazole quaternary ammonium salts have great potential to adsorb bilirubin. This work is to develop a novel bilirubin adsorption column by simple and general method, and evaluate the removal efficiency, anticoagulant property and biocompatibility of the bilirubin adsorption column. Method Multifunctional microspheres were fabricated by in situ co-polymerization of 1-vinylimidazole and divinylbenzene. Nuclear magnetic resonance (NMR), thermo-gravimetric analysis and X-ray photoelectron spectroscopy (XPS) etc. were performed to characterize the chemical compositions of the microspheres. Meanwhile, hemolysis test, blood routine test and clotting time test etc. were leveraged to evaluate the biocompatibility of the microspheres. Both static adsorption test and dynamic adsorption test were performed in vitro to evaluate adsorption performance. Results A variety of methods had proved successful synthesis of the adsorption performance. The hemolysis ratios of microspheres were less than 5%. Compared with BS330 microspheres and PES microspheres, the activated partial thromboplastin time (APTT) and thrombin time (TT) were longer in this work. Moreover, the microspheres showed a high adsorption clearance. In PBS solution of bilirubin, the adsorbent could decrease bilirubin from 200 mg/L to 45-55 mg/L. Conclusion The results suggested that the multifunctional microspheres can significantly reduce bilirubin concentration without obvious adverse interactions and could exhibit anticoagulation activity.

Chromatography-Free Synthesis of β-Carboline 1-Hydrazides and an Investigation of the Mechanism of Their Bioactivity: The Discovery of β-Carbolines as Promising Antifungal and Antibacterial Candidates.

Agrochemical science prioritizes the discovery and effective synthesis of innovative and promising lead compounds. Herein, we developed an efficient column chromatography-free synthesis for β-carboline 1-hydrazides via a mild CuBr2-catalyzed oxidation and investigated the antifungal and antibacterial activities and mechanisms for these compounds. In our study, compounds 4de (EC50 = 0.23 μg·mL-1) and 4dq (EC50 = 0.11 μg·mL-1) displayed the best efficacy, demonstrating enhancements in inhibitory activity of more than 20-fold against Ggt compared to silthiopham (EC50 = 2.39 μg·mL-1). Additionally, compound 4de (EC50 = 0.21 μg·mL-1) demonstrated outstanding in vitro antifungal activities as well as in vivo curative activities against Fg. According to preliminary mechanistic studies, β-carboline 1-hydrazides led to the accumulation of reactive oxygen species, destruction of cell membranes, and dysregulation of histone acetylation. Furthermore, several substances exhibited antibacterial activity against Psg and Cms by preventing the development of bacterial biofilms.

Applicability of core-shell SiO2 microspheres with a high TiO2 loading as stationary phase for HPLC

BackgroundDue to its high chemical stability, sufficient rigidity and zwitterionic ion exchange properties, TiO2 can be considered as an alternative stationary phase material to SiO2 for high performance liquid chromatography. TiO2 stationary phase is usually prepared by coating TiO2 onto SiO2 support by sol-gel method. However, in the traditional coating method, in order to overcome the rapid hydrolysis rate of tetrabutyl orthotitanate, only a very low concentration of tetrabutyl orthotitanate can be used, resulting in a low loading of TiO2 on the support. ResultsTiO2 core-shell spheres with a good monodispersity were prepared using 0.25 mol L−1 tetrabutyl orthotitanate. The specific surface area, pore volume, pore diameter and TiO2 loading of the TiO2 core-shell spheres were 66 m2 g−1, 0.15 cm3 g−1, 9.8 nm and 57%, respectively. The core-shell spheres were derivatized with n-octadecyltrichlorosilane and then packed into a stainless steel column to test the separation performance for neutral, basic and acidic samples in liquid chromatography. A baseline separation of polyaromatic hydrocarbons was achieved, showing a column efficiency for fluorene of 118075 plates m−1. The prepared stationary phase was also used to separate acidic and basic mixtures, and column efficiencies of 54500 and 25836 plates m−1 were obtained for N,N-dinitroaniline and p-chlorophenol, respectively. The relative standard deviations of the retention times of polyaromatic hydrocarbons for run-to-run, day-to-day and column-to-column repeatability were all below 5.1%. Significance and noveltyThis work demonstrated that TiO2 can be coated in the pores of the shell of SiO2 core-shell spheres with high TiO2 loading using a high concentration of tetrabutyl orthotitanate as the titania source. The experimental results show that the TiO2 coated core-shell spheres can be a good alternative stationary phase for liquid chromatography.

Fluorinated covalent-organic polymers as stationary phase for analysis of organic fluorides by open-tubular capillary electrochromatography.

Fluorinated porous materials, which can provide specific fluorine-fluorine interaction, hold great promise for fluoride analysis. Here, a novel fluorinated covalent-organic polymer was prepared by using 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 2,3,5,6-tetrafluorotelephtal aldehyde as the precursors and introduced as stationary phase for open-tubular capillary electrochromatography. The as-synthesized fluorinated covalent-organic polymer and the modified capillary column were characterized by infrared spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectrometry. Based on strong hydrophobic interaction and fluorine-fluorine interaction provided by fluorinated covalent-organic polymer coating layer, the modified column showed powerful separation selectivity toward hydrophobic compounds, organic fluorides, and fluorinated pesticides. Additionally, the fluorinated covalent-organic polymer with good porosity and regular shape was uniformly and tightly coated on the capillary inner wall. The obtained highest column efficiency could reach up to 1.2 × 105 plates⋅m-1 for fluorophenol. The loading capacity of the modified column can reach 141pmol for trifluorotoluene. Besides, the relative standard deviations of retention times for intraday run (n=5), interday run (n=3), and between columns (n=3) were all less than 2.55%. Significantly, this novel fluorinated material-based stationary phase shows great application potential in fluorides analysis.

Analiza trybu pracy istniejącego desorbera i jego modernizacja z wykorzystaniem dodatkowych urządzeń stykowych

Amine regeneration studies using two devices are presented in this work. In the first apparatus, a problem analysis was carried out in the operation of the desorber, which is used in petrochemical complexes, affecting various parameters of regeneration, such as temperature and pressure at the top and bottom of the column, pressure drop in the columns, rich amine feeding and flow rate, feed temperature, reboiler temperature and stripping pressure. The problems in the existing desorber and modernized the device was studied and an experiment that affects different parameters of regeneration was conducted. The desorber-1 (existing apparatus) and desorber-2 (modernized apparatus) mass-exchange apparatus was selected to serve as experimental regeneration plants. The dimensions of the experimental setup were determined based on the principles of geometric similarity with respect to the dimensions of an industrial regeneration column on a scale of 1:10 and physical similarity (with the same scaling) of gas and liquid flow rates and initial conditions. Thus, during the experiment, the pressure drop in the column increased in the desorber. To solve the problem and to improve the efficiency of the regeneration column, the desorber was upgraded using a Raschig packing. A laboratory stand was also developed for the purpose of conducting an experiment aimed at finding the optimal modes for the parameters of the regeneration column. As a result of the modernization of the desorber, the content of carbon dioxide in lean amine decreased, and there was a 4-fold reduction in column pressure drop. The modernization of the apparatus also led to an increase in the recovery factor.

In situ growth preparation of a new chiral covalent triazine framework core-shell microspheres used for HPLC enantioseparation.

Themanufacturing of chiral covalent triazine framework core-shell microspheres CC-MP CCTF@SiO2 composite is reportedas stationary phase for HPLC enantioseparation. The CC-MP CCTF@SiO2 core-shell microspheres were prepared by immobilizing chiral COF CC-MP CCTF constructed using cyanuric chloride and (S)-2-methylpiperazine on the surface of activated SiO2 through an in-situ growth approach. Various racemates as analytes were separated on the CC-MP CCTF@SiO2-packed column. The experimental results indicate that 19 pairs of enantiomers were well separated on the CC-MP CCTF@SiO2-packed column, including alcohols, phenols, amines, ketones, and organic acids. Among them, there are 17 pairs of enantiomers that can achieve baseline separation with good peak shapes. Their resolution values on this chiral column are between 0.4 and 5.61. The influences of analyte mass, column temperature, and composition of the mobile phase on the resolution of enantiomers were studied. In addition, the chiral resolution ability of CC-MP CCTF@SiO2-packed column was compared with the commercial chiral chromatographic columns (Chiralpak AD-H and Chiralcel OD-H columns) and some CCOF@SiO2 chiral columns (β-CD-COF@SiO2, CTpBD@SiO2, and MDI-β-CD-modified COF@SiO2). The CC-MP CCTF@SiO2-packed column exhibited some unique advantages and can complement these chiral columns in chiral separations. The research results show that the CC-MP CCTF@SiO2 chiral column offered high column efficiency (e.g., 17680 plates m-1 for ethyl mandelate), low column backpressure (5-9 bar), high enantioselectivity, and excellent chiral resolution ability for HPLC enantioseparation with good stability and reproducibility. The relative standard deviations (RSD) (n = 5) of the retention time, and peak areas by repeated separation of ethyl mandelate are 0.23% and 0.67%, respectively. It demonstrates that the CC-MP CCTF@SiO2 core-shell microsphere composite has great potential in enantiomeric separation by HPLC.

Stiffness evaluation of UHPC-filled socket column-foundation joints: Numerical investigation and analytical model

Socket connections are widely used to connect precast columns to the foundation and the initial stiffness of the socket joints is of great significance for seismic design. The connection efficiency of precast socket column has an important influence on its initial stiffness. Therefore, based on the previous experiment research on socket column by authors’ team, a finite element model (FEM) of ultra-high performance concrete (UHPC)-filled socket precast bridge column-foundation joints was established and verified by the local damages, failure mode and hysteresis curves. The key parameters that influencing the initial stiffness of socket joints were studied by numerical analysis, and a simplified calculation formula of initial stiffness was proposed. In addition, based on the theory of elastic foundation beam, an analysis model for predicting the initial stiffness of socket joints considering rotating stiffness of the connection was developed. The theoretical results are verified by the proposed simplified equations and experiments results in the literature. The method presented in this paper can conveniently predict the initial stiffness of RC socket column-foundation joints with reasonable accuracy.

Experimental study to enhance prediction of jet-grout column diameter and efficiency in sand

One of the most significant factors affecting the efficiency of jet-grouting operation is the diameter of the constructed column, depending on soil properties, stress state and operating parameters, including grout pressure (P), grout flow rate (Q), monitor rotational speed (ω) and lifting step (Δs). Increasing treatment efficiency results in a larger diameter with specific energy applied per unit length of the column. In this study, 35 full-scale and small-scale single-fluid jet-grouting elements were constructed in the field and laboratory to investigate the effects of the operating parameters on the diameter and treatment efficiency of the columns constructed in silty sand. Furthermore, measured values and obtained trends were controlled by a comprehensive equation commonly used to predict the diameter of jet-grouting columns. The results indicate that an increase in the time interval per step (Δt) and grout pressure (P), as well as a decrease in the lifting step (Δs), causes a larger column diameter and lower efficiency. However, a decline in rotational speed (ω) improves both diameter and efficiency. Subsequently, the well-known equation has been modified by considering field measurements in this study to predict more-accurate values and trends for both full-scale and small-scale jet-grouting elements.

Simulation and comprehensive study of an optimum process for CO2 capture from flue gas; technical, economic, and environmental analyses

An optimum process with a novel method for improving the thermodynamic efficiency of the conventional post-combustion process based on a mono-ethanolamine (MEA) 30 wt% solvent is presented. The presented process, by preheating the rich solvent stream twice and using lean vapor compression (LVC), causes the solvent regeneration energy (Eregen) to decrease, the exergy efficiency of the desorption column to increase, and the net CO2 emission to diminish. According to the simulation results, the solvent regeneration energy in the base process is 3.47 GJ/tCO2 and has a value of 2.77 GJ/tCO2 in the proposed scheme, which exhibits a 20.17% decrease. The exergy analysis showed that the desorption column contributes the most to the exergy destruction in the post-combustion process. According to the performed analysis, in the proposed scheme, the exergy destruction in the desorption column reduces from 476.67 kW to 257.48 kW, which shows a 45.98% decrease. Under these conditions, the exergy efficiency of the desorption column is improved by 12.2%. Comparing Eregen parameter with that of previous studies demonstrated that the proposed scheme in this paper has significant superiority regarding optimizing the reboiler's energy. Due to the addition of a compressor, heat exchanger, expansion valve, and separator, the annual capital expenditure (CAPEXy) of the proposed scheme is 13.71% higher than the conventional process, which results in a 12.5% increase in the cost of CO2 capture (CostCO2,capture).

Particle Size Regulation of Single-Crystalline Covalent Organic Frameworks for High Performance of Gas Chromatography.

Although polycrystalline covalent organic frameworks (PCOFs) have already shown great potential as stationary phases for chromatography, irregular shape and size distribution of PCOFs make regulation of particle size of PCOFs for high separation performance impossible, which is accessible by the application of single-crystalline COFs (SCOFs). Herein, we showed preparation of three-dimensional SCOF (SCOF-303) bonded capillaries (SCOF-303-capillary) with different particle sizes (about 0.4-1.6 μm) and further investigated gas chromatographic separation ability of these SCOF-303-capillaries for isomers of xylene, dichlorobenzene, and pinene. It was found resolution and column efficiency of SCOF-303-capillaries for isomers decreased with the increase in particle size, mainly resulting from the weaker size-exclusion effect and higher mass transfer resistance of the larger particle size of flexible SCOF-303. The obtained SCOF-303-capillary (particle size of ∼0.4 μm) offered baseline separation of xylene isomers with the high resolution of 2.26-3.52, great efficiency of 7879 plates m-1 for p-xylene, better than PCOF-303-capillary, and commercial DB-5 and HP-FFAP capillary columns as well as many reported capillaries. This work not only shows the great potential of SCOFs for gas chromatography but also provides the theoretical direction for the design of the efficient COF based stationary phase by adjusting the particle sizes.

Experimental design and data prediction by Bayesian statistics for adsorption of tetracycline in a GAC fixed-bed column

In the present work, the efficiency and applicability of fixed-bed columns were evaluated for the adsorption of tetracycline (TC) on granular activated carbon (GAC). An experimental planning by the Box-Benking (BOX) design was evaluated to determine the best operational conditions of the column. It is involving three independent variables: initial concentration of the pollutant (20, 50 and 80 mg.L-1), bed height (1, 2 and 3 cm) and feed flow rate (3, 6 and 10 mL.min−1); and two response factors: the saturation time (tsat) and the maximum adsorption capacity (qmax). To simulate the breakthrough curve six models were applied (Thomas, Yoon-Nelson, Yan, Clark, Gompertz and Log-Gompertz) for the best operational conditions. The parameter estimates and model selection were performed using a Bayesian technique, applying the experimental value of qmax, and five statistical metrics (classical: R2 and R2ajstd; Bayesian: AIC, AICC and BIC). The results showed that all operational adsorption conditions applied obtained 95 % of TC removal and the best ones were: 80 mg.L-1, 6 mL.min−1 and 1 cm, for TC initial concentration, feed flow rate and bed height, respectively, achieving a tsat of 23 min and qmax of 2.08 mg.g−1. The Yan and the Log-Gompertz models were the ones that best predicted the behavior of the breakthrough curve obtained. The Yan model being responsible for elucidating the mechanisms of the column and the Log-Gompertz model useful for the scaleup of the process, being applicable for industrial implementation.