Monolithic Sorbents Research Articles

Poly(ethylenimine)-Functionalized Monolithic Alumina Honeycomb Adsorbents for CO2 Capture from Air.

The development of practical and effective gas-solid contactors is an important area in the development of CO2 capture technologies. Target CO2 capture applications, such as postcombustion carbon capture and sequestration (CCS) from power plant flue gases or CO2 extraction directly from ambient air (DAC), require high flow rates of gas to be processed at low cost. Extruded monolithic honeycomb structures, such as those employed in the catalytic converters of automobiles, have excellent potential as structured contactors for CO2 adsorption applications because of the low pressure drop imposed on fluid moving through the straight channels of such structures. Here, we report the impregnation of poly(ethylenimine) (PEI), an effective aminopolymer reported commonly for CO2 separation, into extruded monolithic alumina to form structured CO2 sorbents. These structured sorbents are first prepared on a small scale, characterized thoroughly, and compared with powder sorbents with a similar composition. Despite consistent differences observed in the filling of mesopores with PEI between the monolithic and powder sorbents, their performance in CO2 adsorption is similar across a range of PEI contents. A larger monolithic cylinder (1 inch diameter, 4 inch length) is evaluated under conditions closer to those that might be used in large-scale applications and shows a similar performance to the smaller monoliths and powders tested initially. This larger structure is evaluated over five cycles of CO2 adsorption and steam desorption and demonstrates a volumetric capacity of 350 molCO2 m-3monolith and an equilibration time of 350 min under a 0.4 m s(-1) linear flow velocity through the monolith channels using 400 ppm CO2 in N2 as the adsorption gas at 30 °C. This volumetric capacity surpasses that of a similar technology considered previously, which suggested that CO2 could be removed from air at an operating cost as low as $100 per ton.

Preparation of a monolithic sorbent using a response surface methodology

A 17-run Box-Behnken Design (BBD) was introduced to optimize the synthesis conditions of a monolithic sorbent. The effects of the amount of monomer (mL), crosslinker (mL) and porogen (mL) were investigated. The experimental data was fitted to a second - order polynomial equation by multiple regression analysis, which was examined using statistical methods. The adjusted coefficient of determination (R2Adj) in this model was 0.9867. The probability value (p<0.0001) revealed the high significance of the regression model. A mean amount of 5057.4 mg polymer was produced under the following optimized synthesis conditions: 0.51 mL monomer, 2.94 mL crosslinker and 2.84 mL porogen. The actual experimental result was in good agreement with the predicted model value.

Application of silica-based monolith as solid-phase extraction sorbent for extracting toxaphene congeners in soil

A silica monolith was developed as a solid-phase extraction sorbent for the extraction and separation of toxaphene congeners from soil extraction solutions, prior to their measurement by gas chromatography-mass spectroscopy. The silica monolith was characterized by scanning electron microscopy, transmission electron microscopy, N2 adsorption/desorption and Fourier transform infrared spectroscopy. The recovery parameters including type of eluent, eluent volume, flow rate and varying amounts of sorbent were systemically optimized. Our method has a low detection limit, and it was 1.64, 0.76, 1.03 and 2.28 ng/mL for hexachloro, heptachloro, octachloro and nonachloro toxaphene, respectively. The sorbent offered good linearity with coefficient of determination (r 2) >0.99, over a concentration range of 200–1000 ng/mL. The relative recoveries of toxaphene congeners ranged between 96.8 and 105.7 % with relative standard deviations (% RSD) below 5 %. The recoveries of toxaphene congeners were 99.9–104.0 % after using the sorbent five times, showing the excellent stability and reusability of prepared silica monolith sorbent.

Hollow fiber membrane-coated functionalized polymeric ionic liquid capsules for direct analysis of estrogens in milk samples.

Protein removal process is always time-consuming for the analysis of milk samples. In this work, hollow fiber membrane-coated functionalized polymeric ionic liquid (HF-PIL) capsules were synthesized and used as solid-phase microextraction (SPME) sorbent for direct analysis of estrogens in milk samples. The functionalized PIL monolith sorbent was obtained by copolymerization between 1-(3-aminopropyl)-3-(4-vinylbenzyl)imidazolium 4-styrenesulfonate IL monomer and 1,6-di(3-vinylimidazolium) hexane bishexafluorophosphate IL-crosslinking agent. A group of four capsules were installed as SPME device, to determine four kinds of estrogens (estrone, diethylstilbestrol, hexestrol, and 17α-ethynylestradiol) in milk samples, coupled to high performance liquid chromatography. Extraction and desorption conditions were optimized to get satisfactory extraction efficiency. Good linearity was obtained in the range of 5-200 μg L(-1). The limits of detection were 1 μg L(-1) for diethylstilbestrol and 2 μg L(-1) for 17α-ethynylestradiol, estrone, and hexestrol. The present method was applied to analyze the model analytes in different milk samples. Relative recoveries were in the range of 85.5-112%. The HF-PIL SPME capsules showed satisfactory extraction efficiency and high resistance to sample matrix interference.

Monolithic Zn–Co–Ti based sorbents for hot syngas desulfurization

Charge of monolithic Zn–Co–Ti–O based sorbent was manufactured using natural clay as a binder and tested in model hot syngas desulfurization. Fresh and regenerated sorbent was characterized by XRD, SEM–EDX, XPS, mercury porosimetry, and TPRH2. After four cycles of desulfurization (at 540°C) and regeneration (540–650°C), monoliths retained the mechanical integrity and their geometry did not change. Monolithic sorbent captured 5.3gS/100g in the first cycle and 13.8gS/100g in the last one. Concentration of H2S in the treated gas was lowered from 6000ppmv to 3ppmv and the H2S removal efficiency was min. 99.6%. Fresh sorbent contains Zn2Ti3O8 (dominant phase), TiO2 and SiO2, while in the regenerated one always occurs: TiO2 (dominant phase), ZnTiO3, Zn2Ti3O8; SiO2; Zn2SiO4 and ZnAl2O4. Reducibility and the amount of sulfates formed in the used sorbent depend on its position in the bed. After tests, small amounts of free ZnO are present on the surface of the used monoliths. During regeneration the zinc oxide (from Zn–Ti–O mixed oxides) reacts with Al2O3 or SiO2 (clay components), and forms compounds more resistant to deactivation, such as Zn2SiO4 and ZnAl2O4.

Improved microextraction of selected triazines using polymer monoliths modified with carboxylated multi-walled carbon nanotubes

This article reports on the enhancement of the capacity of an acrylate-based monolithic solid sorbent by anchoring carboxylated multi-walled carbon nanotubes (c-MWCNTs) in its pores and on its surface. Monolithic poly(butyl acrylate-co-ethyleneglycol dimethacrylate) [poly(BA-co-EGDMA)] was synthetized inside a fused silica capillary via free-radical polymerization, and an ethanolic dispersion of c-MWCNTs was passed through the capillary. The resulting poly(BA-co-EGDMA-c-MWCNTs) monolith was characterized by scanning electron microscopy to confirm the presence of the c-MWCNTs. The effect of using three different kinds of carbon nanoparticles and the microextraction step were studied using triazine herbicides as model compunds. The use of c-MWCNTs resulted in best performance in terms of extraction enhancement (compared to carboxylated single-walled carbon nanotubes and oxidized single-walled carbon nanohorns). The use of these carbon nanoparticles improved the extraction of triazines in any case when compared to using a bare poly(BA-co-EGDMA) monolith. The triazines were then quantified by gas chromatography with mass spectrometric detection. Detection limits ranged from 0.03 to 0.1 μg·L−1 (except for simazine; 0.6 μg·L−1), and the precision (relative standard deviation) varied between 3.0 and 11.4 %. The reproducibility between units is <14.3 % (expressed as relative standard deviation) which demonstrates the robustness of the method. The method was applied to analyze an unknown sample of orange juice and gave a value of 0.18 μg·L−1 for prometryn. Finally, the analysis of spiked samples of water and orange juices yielded recoveries ranging from 81 to 113 % and 75 to 125 %, respectively.

Specific features of using ultrashort monolithic columns for analysis of biologically active synthetic polymers labeled with radioactive metal isotopes (99mTc, 161Tb, 68Ga)

A fast and efficient method of separation of radioactive metal isotopes (99mTc, 161Tb, 68Ga) and synthetic biologically active water-soluble copolymers of the class of N-vinylamides is developed using HPLC on ultrashort monolithic CIM (Convective Interaction Media) columns at the interface. It is shown that, under conditions of elution in aqueous media, the polymers are not separable by molecular weights and structures, but they are well-separable from metal ions. Radioactivity sorption on monolithic sorbents is insignificant, allowing series of experiments to be expressively performed for an optimization of conditions of radiochemical synthesis and routine analysis of radiopharmaceutical preparations.

Polymer monolith microextraction using poly(butyl methacrylate-co-1,6-hexanediol ethoxylate diacrylate) monolithic sorbent for determination of phenylurea herbicides in water samples

In this study, recently developed 1,6-hexanediol ethoxylate diacrylate (HEDA)-based polymeric monoliths were utilized as sorbents for efficient extraction of phenylurea herbicides (PUHs) from water samples. The HEDA-based monolithic sorbents were prepared in a fused silica capillary (0.7mm i.d., 4.5-cm long) for polymer monolith microextraction (PMME). The experimental parameters of PMME microextraction including sample loading speed, pH of sample solution, composition of elution solvent, and addition of salt were optimized to efficiently extract PUHs from environmental water samples. The extracted PUHs were determined using ultra-high performance liquid chromatography (UHPLC) with UV-photodiode array detection. The extraction recoveries for PUHs-spiked water samples were 91.1–108.1% with relative standard deviations lower than 5%. The linearity range was 0.025–25ngmL−1 for each PUH and the detection limits of PUHs were estimated at 0.006–0.019ngmL−1. In addition, good intra-day/inter-day precision (0.1–8.7%/0.2–8.9%) and accuracy (92.0–108.0%/96.5–105.2%) of the proposed method were obtained. The extraction capacity of the monolith-filled capillary was also determined to be approximately 1μg. Moreover, each monolith-filled capillary could be reused up to 8 times without carry-over. According to the European Union regulations, the allowed permissible limit of any single herbicide in drinking water is 0.1ngmL−1. This permissible level fell in the linear range examined in this study. In addition, the proposed method provided detection limits lower than the allowed permissible level, which demonstrated the feasibility of utilizing the HEDA-based monolithic sorbent to perform PMME for determining contaminants, such as PUHs, in environmental application.

Prospects of monolithic MIL-MOF@poly(NIPAM)HIPE composites as water sorption materials

Monolithic shaping of metal-organic frameworks (MOFs), which are normally received as microcrystalline powder is crucial for possible applications of MOFs. Three members of the MIL-family (MIL-100(Fe), MIL-100(Cr) and MIL-101(Cr)), known as water stable porous coordination polymers, were embedded into a macroporous oil–water (o/w) high internal phase emulsion (HIPE) foam, based on cross-linked poly(N-isopropyl acrylamide) (NIPAM). Pre-polymerization of the HIPE emulsions before adding the MIL-MOF powders was an indispensable step in synthesizing highly porous composites, thus, minimizing pore blocking effects. The larger the pores and the higher the surface area of the MIL the less pronounced were pore blocking effects upon composite formation. These composite materials (MIL@poly(NIPAM)HIPE, in short MIL@NIPAM) could be loaded with up to 92 wt% of the MIL component (followed and verified by powder X-ray diffractometry, infrared spectroscopy and scanning electron microscopy). MIL@NIPAM composites show higher water vapor uptakes in comparison to the native HIPE material so that MIL@NIPAM composites could be used as monolithic water sorbents for heat transformation applications. For MIL-101(Cr)@NIPAM the water uptake of up to 0.4 g/g occurs with the typical S-shaped isotherm in the range of 0.3 < P∙P0−1 < 0.5.

Monolithic capillary columns based on pentaerythritol acrylates for molecular-size-based separations of synthetic polymers.

Monolithic capillary columns based on pentaerythritol triacrylate and pentaerythritol tetraacrylate were synthesized using different compositions of polymerization mixtures and different polymerization conditions. The impact of porogen type and porogen/monomer ratio on the porosity of synthesized monoliths was investigated. Porogen type appears to be the main factor influencing the separating properties of the monolithic sorbent. Using optimal polymerization conditions (porogen type, porogen/monomer ratio, reaction temperature, time etc.) monoliths with a porous structure optimized for polymer separations can be obtained. The monolithic capillary columns containing porous sorbents with optimized porosity are capable of separating 10 to 12 polystyrene standards in one chromatographic run utilizing both size exclusion chromatography and hydrodynamic chromatography separation mechanisms.

Sensitive determination of four camptothecins by solid-phase microextraction-HPLC based on a boronic acid contained polymer monolithic layer

Camptothecin (CPT) and its derivative have been revealed to possess special anti-cancer activity, extraction methods are necessary for trace determination of CPTs in complex samples. In this work, we prepared a high efficient boronic acid-based polymer monolithic layer for microextraction of CPTs. A disposable membrane filter-based extraction device was developed, and boronic acid groups were co-polymerized into a polyporous polymer skeleton and served as the monolithic sorbent. The prepared poly(4-VB-MA-TRIM) showed good stability and great extraction efficiency toward four CPTs. After optimization of extraction conditions, poly(4-VB-MA-TRIM)-based solid-phase microextraction was coupled HPLC for determination of CPTs in biological samples. The method exhibited low limits of detection of 0.05–0.2ngmL−1, which is significantly more sensitive than reported HPLC methods. The method also showed wide linear range (0.1–100 and 0.5–200ngmL−1), good linearity (R2≥0.9981) and good reproducibility (RSD ≤3.76%). The method has been applied in plasma samples, with good selectivity and good recoveries ranging from 85.1 to 104.7%.

Nanostructured ZnO/sepiolite monolithic sorbents for H2S removal

ZnO chemisorbs H2S as ZnS in inert atmospheres and catalyzes H2S to SO2 oxidation in the presence of O2. ZnO nanoparticle dispersion is preserved after extrusion of ZnO/sepiolite composites and favors H2S removal.

Influence of porogen nature on the kinetic and potential efficiencies of divinylbenzene-based monolithic sorbents in gas chromatography

It has been shown that using Poppe curves for characterization of monolithic sorbents makes it possible to optimize conditions for both the synthesis of monoliths intended for high-speed analysis and achievement of the best separation efficiency. The influence of the nature of a porogen on the kinetic efficiency of monolithic sorbents in high-pressure gas chromatography has been considered. It has been found that the nature of the porogen alcohol determines to a considerable extent the structure of the monolith and its kinetic efficiency. The sorbents prepared with the use of octanol-1 and dodecanol-1 have shown the best kinetic characteristics; however, minimal HETP values have been observed for the columns prepared using hexanol-1 as a porogen.

A novel ionic liquid-modified organic-polymer monolith as the sorbent for in-tube solid-phase microextraction of acidic food additives.

A novel ionic liquid-modified organic-polymer monolithic capillary column was prepared and used for in-tube solid-phase microextraction (SPME) of acidic food additives. The primary amino group of 1-aminopropyl-3-methylimidazolium chloride was reacted with the epoxide group of glycidyl methacrylate. The as-prepared new monomer was then copolymerized in situ with acrylamide and N,N'-methylenebisacrylamide in the presence of polyethylene glycol (PEG)-8000 and PEG-10,000 as porogens. The extraction performance of the developed monolithic sorbent was evaluated for benzoic acid, 3-hydroxybenzoic acid, cinnamic acid, 2,4-dichlorophenoxyacetic acid, and 3-(trifluoromethyl)-cinnamic acid. Such a sorbent, bearing hydrophobic and anion-exchange groups, had high extraction efficiency towards the test compounds. The adsorption capacities for the analytes dissolved in water ranged from 0.18 to 1.74 μg cm(-1). Good linear calibration curves (R(2) > 0.99) were obtained, and the limits of detection (S/N = 3) for the analytes were found to be in the range 1.2-13.5 ng mL(-1). The recoveries of five acidic food additives spiked in Coca-Cola beverage samples ranged from 85.4 % to 98.3 %, with RSD less than 6.9 %. The excellent applicability of the ionic liquid (IL)-modified monolithic column was further tested by the determination of benzoic acid content in Sprite samples, further illustrating its good potential for analyzing food additives in complex samples.

Dynamics of carbon dioxide chemisorption by substances based on alkali metal superoxides

Analytical solutions have been obtained for dynamic equations of carbon dioxide chemisorption by sorbents based on potassium and sodium superoxides. The parameters of these equations have been determined for granular and monolithic sorbents used in respiratory protective equipment.

Efficiency of monolithic capillary columns in high-pressure gas chromatography

Monolithic sorbents for gas chromatography obtained in quartz capillaries are analyzed by means of kinetic curves (Poppe plots). The values for the time of a theoretical plate and the maximum number of plates are found to be strongly dependendent on the parameters of monolith synthesis, i.e., the relative amount of a monomer in the initial mixture, the temperature, and the polymerization time. Synthesis conditions are established using the kinetic curves, allowing the preparation of sorbents suitable for both performing high-rate analysis and achieving the most effective separation. It was shown that plotting kinetic curves on the basis of van Deemter curve data requires we allow for the compressibility of mobile phase.

Kinetic efficiency of polar monolithic capillary columns in high-pressure gas chromatography

Poppe plots were used for analysis of kinetic efficiency of monolithic sorbents synthesized in quartz capillaries for utilization in high-pressure gas chromatography. Values of theoretical plate time and maximum number of theoretical plates occurred to depend significantly on synthetic parameters such as relative amount of monomer in the initial polymerization mixture, temperature and polymerization time. Poppe plots let one to find synthesis conditions suitable either for high-speed separations or for maximal efficiency. It is shown that construction of kinetic Poppe curves using potential Van Deemter data demands compressibility of mobile phase to be taken into consideration in the case of gas chromatography. Model mixture of light hydrocarbons C1 to C4 was then used for investigation of influence of carrier gas nature on kinetic efficiency of polymeric monolithic columns. Minimal values of theoretical plate times were found for CO2 and N2O carrier gases.

Monolithic capillary columns based on ethylene glycol dimethacrylate for separation of polymers by molecular mass

Polar monolithic capillary columns for the molecular-mass separation of polystyrene standards are synthesized on the basis of ethylene glycol dimethacrylate. The monolith structure is optimized through variation in the type of porogen because variation in other synthesis parameters (the time and temperature of polymerization, the amount of monomer in the initial feed) is inefficient. The separation of polymers on monolithic sorbents proceeds via a combined exclusion-hydrodynamic mechanism. In terms of a model that allows for contributions of both mechanisms to retention, calibration plots are drawn for the synthesized columns. Monolithic columns with the optimum monolith structure make it possible to use up to 60% of the column free volume for the efficient separation of polymers in a broad molecular-mass range.

Monolithic polymeric sorbents for high-performance chromatography of synthetic polymers

A number of macroporous monolithic materials based on copolymers of butyl methacrylate or lauryl methacrylate with ethylene glycol dimethacrylate is obtained via thermal free-radical polymerization. The effect of polymerization conditions on pore parameters of the synthesized sorbents is studied. Polymer stationary phases obtained for the efficient analysis of synthetic polymers are tested for the separation of a multicomponent mixture containing polystyrene samples of various molecular masses.

Modified hplc method of determination of the valproic acid in biological fluids

Proposed modified HPLC method for determination of valproic acid in biological fluids. Created solid-phase extraction of valproic and heptanoic acids (internal standard, IS) on the cartridges packed hyper cross-linked polystyrene which maintain some tens extractions without losses of efficiency. Carboxylic acids are derivative with 1-(bromoacetyl)pyrene in acetone at presence of triethylamine. Chromatographic separation of derivatives is performed on Chromolith Perfonnance RP-18e columns, which packed unique monolithic sorbent. UV detection at 360 nm. Mobile phase acetonitrile - water (90:10, v/v) plus 1% isopropanol, speed flow 2000 microL/min, pressure 21 bar. Complete chromatographic cycle less than 3 minutes. Yield of IS and valproic acid (extraction plus derivatization) was 101-106%. Sensitivity (limit detection) was near 1 ng for valproic and near 0.6 ng for heptanoic acid during signal/noise ratio = 3.