Impregnated Silica Gel Research Articles

Preparation and Testing of Polyethylenimine-Impregnated Silica Gel for CO2 Capture.

This work studied the low-temperature sorption of carbon dioxide on impregnated silica gel. An impregnating agent was used polyethyleneimine. The content of the impregnating agent in the silica gel matrix was 33.4 wt.%. Material properties such as the Brunauer-Emmett-Teller (BET) surface area, pore distribution, total pore volume, and thermal stability of the impregnated material were determined for the sample. During the measurement of the adsorption-desorption cycles, the loss of the impregnating agent in the material matrix was also determined. Due to the decrease in the content of polyethyleneimine, the sorption capacity of the adsorbent for CO2 also decreased. It was found that after the 20th adsorption-desorption cycle, the content of the impregnating agent in the adsorbent dropped by 3.15 wt.%, and, as a result, the adsorption capacity for CO2 dropped to almost half.

Simultaneous impregnation and microencapsulation of CaCl2 using silica gel and methyl cellulose for thermal energy storage applications

Thermal energy storage utilizing the adsorption of moisture from air is a promising energy storage technology due to its high energy density and minimum heat losses. Salt hydrates and salt hydrate composites, such as calcium chloride (CaCl2) and CaCl2-based composites, have shown favourable energy storage properties in this area of research. However, these materials have shown issues with stability due to swelling and deliquescence. In this work, CaCl2 was stabilized using three methods: impregnation into silica gel, encapsulation in methyl cellulose, and both impregnation and encapsulation stabilization techniques used simultaneously. Therefore, three CaCl2-based composites were synthesized. For the first composite, silica gel was impregnated with CaCl2. For the second composite, CaCl2 was encapsulated by methyl cellulose. For the third composite, silica gel was impregnated with CaCl2 and the CaCl2 was encapsulated with methyl cellulose. These samples were structurally characterized using scanning electron microscopy as well as Brunauer-Emmett-Teller (BET) to determine surface area, pore size distribution and nitrogen adsorption isotherms at 77 K. Water vapour adsorption isotherms were also determined at 25 °C for different relative humidities by dynamic vapor sorption (DVS). Similarly, LiCl-based composites were also synthesized and examined in this work, but issues of deliquescence, swelling, and agglomeration made the materials impractical to work with. To determine the prepared materials’ thermal energy storage performance, 2–6 g of each sample was tested in a lab-scale apparatus. This process uses the exothermic adsorption of moisture from ambient air in an open thermal energy storage system. The CaCl2 impregnated silica gel that was encapsulated in methyl cellulose showed reasonably high stability and energy storage performance after 3 hydration and dehydration cycles with minimum agglomeration. An energy storage density of 241 kWh/m3 (0.87 GJ/m3) and specific energy of 630 Wh/kg (2268 kJ/kg) was achieved with this material for 90% inlet relative humidity after a regeneration at 90 °C.

Development and Validation of a Rapid Analytical Method for Polybrominated Diphenyl Ethers in House Dust

In this study, a rapid analytical method was developed and validated for the determination of polybrominated diphenyl ethers PBDEs in house dust samples. The dust sample was solvent extracted by using a focused ultrasonic processor with reduced extraction time (total 30 min/sample) and solvent volume (about 30 mL/sample). The crude extract was purified by passing through a self-packed multilayer column containing 44% sulfuric acid impregnated silica gel, Florisil, and anhydrous sodium sulfate. PBDEs were eluted from the clean-up column by a mixture of dichloromethane in hexane (1:3,…). PBDEs (41 mono- to deca-BDE congeners) were analyzed by using gas chromatography/mass spectrometry (GC/MS) with negative chemical ionization (NCI) and selected ion monitoring (SIM) mode. The analytical method was validated by using procedural blank, matrix-spike, and standard reference material (SRM) samples. Recoveries of PBDEs in spiked samples ranged from 65% to 120%. Analytical results of the SRM 2585 (Organic Contaminants in House Dust, National Institute of Standards and Technology, USA) indicate method accuracy with ratios of measured to certified values of almost compounds ranging from 76% to 110%. All the experiments were conducted in duplicate, showing acceptable repeatability (RSD < 15%). This method can be applied for simultaneous determination of mono- to deca-BDE congeners in dust samples at ppb to ppm levels with several advantages such as simple, rapid, accurate, cost-effective, and reducing amounts of chemicals and solvents.

Quantification of synthetic-based drilling mud olefins in crude oil and oiled sediment by liquid column silver nitrate and gas chromatography

Synthetic-based drilling muds (SBMs) are complex mixtures of man-made fluids used during the drilling of oil and gas wells. SBM-derived chemicals can enter the environment through failed wells and routine or poor disposal practices, where they can persist and thereby warrant measurement. SBMs are commonly formulated with linear and methyl branched α- and internal-olefins mostly in the C14 to C20 carbon range, which are not native to crude oils. Thus, SBM-derived olefins can provide a basis to recognize the impact of these drilling wastes in the environment. However, the presence of abundant native hydrocarbons in oils and sediments can hinder the detection of trace level SBM-derived olefins by conventional organic sample preparation and analytical methods. Silver ion chromatography using silver nitrate (AgNO3) impregnated silica gel can serve to physically separate olefins from saturated aliphatic hydrocarbons native in crude oils, which can subsequently be analyzed and measured by conventional one-dimensional gas chromatography-flame ionization detection (GC-FID). In this study, SBM-derived olefins are measured in crude oils from the Deepwater Horizon oil spill and in their laboratory mixtures to a detection limit of approximately 5000 µg/g (0.5 wt%). In oiled sediment, SBM-derived olefins were reliably detected at concentrations as low as 1 µg/g-dry. An application of this method is demonstrated through analysis of crude oils and oil-contaminated seafloor sediment from the Taylor Energy oil spill site in the northern Gulf of Mexico where SBM was historically used and discharged.

Silica gel impregnated with deep eutectic solvent-based matrix solid-phase dispersion followed by high-performance liquid chromatography for extraction and detection of triazine herbicides in brown sugar.

A novel method was developed to determine six triazine herbicides from brown sugar samples using matrix solid-phase dispersion (MSPD) based on silica gel impregnated with deep eutectic solvent (DES) followed by high-performance liquid chromatography with photodiode array detector (HPLC/PDA). Several factors involved in the MSPD procedure such as DES type, DES content in impregnated silica gel, adsorbent-to-sample mass ratio, type and volume of washing solvent, type and volume of eluent, and grinding time were screened using single-factor experiments and then optimized using Box-Behnken design to accomplish the highest recoveries. The above method demonstrated a good linear range (20-1000μgkg-1) with a determination coefficient exceeding 0.9962, low limits of determination (1.59-3.77μgkg-1), acceptable limits of quantifications, and acceptable spiking recoveries (95.0-101.7%) for six triazines under optimized conditions. The proposed MSPD-HPLC/PDA method is a convenient, effective, and sensitive method for rapidly isolating and quantifying six triazines from brown sugar.

Determination of brominated flame retardants including polybrominated diphenyl ethers, pentabromoethylbenzene, hexabromobiphenyl, and decabromodiphenyl ethane in sediment samples: Validation of a rapid and efficient clean-up method and application to a sediment core from Lake Biwa, Japan

The development of rapid and efficient analytical method for the determination of legacy and current-use brominated flame retardants (BFRs) has been performed due to environmental concern related to these pollutants. In the present study, we used an automated clean-up device equipped with pre-packed micro-column sets (containing sulfuric acid impregnated silica gel and silver-modified alumina) to develop an effective purification method for polybrominated diphenyl ethers (PBDEs), pentabromoethylbenzene, hexabromobiphenyl, and decabromodiphenyl ethane (DBDPE) in sediment extracts. Matrix-spiked sediments (n = 6) and the Standard Reference Material® 1944 samples (n = 6) were tested. Our method showed acceptable accuracy, repeatability, and sensitivity for almost all the target compounds with reduced processing time, labor requirement, and solvent amounts as compared to conventional clean-up method (e.g., sulfuric acid treatment and self-packed chromatographic columns). The validated method was applied to sediment core samples (n = 16) collected in 2019 from Lake Biwa, the largest lake in Japan. PBDEs were detected in sediment samples of 0–13 cm depth (dated between 1990 and 2019) at relatively low concentrations (median 5.7; range 2.6–9.4 ng/g dry weight). PBDE profiles were dominated by BDE-209, which accounted for 91 ± 10% of total PBDEs. Among other BFRs, only DBDPE was found in sediment layers of 0–9 cm depth (deposited between 2005 and 2019). DBDPE concentrations ranged from 0.43 to 1.6 (median 0.71) ng/g and showed increasing trend toward shallower depths.

Extraction chromatographic separation of thorium by silica gel impregnated with cyanex 923

Solvent impregnated silica gel material was prepared for thorium recovery from its aqueous nitrate solutions using the neutral phosphine oxide extractant, cyanex-923 in toluene. This was achieved by adsorption of the extractant onto the solid phase in three steps. The obtained adsorbent was characterized by means of Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). The relevant factors of extraction such as influence of acid concentration, flow rate and impregnated cyanex 923 amount were optimized by equilibrium column experiments. The results revealed that thorium loaded on 0.5 g cyanex-silica achieved with about 99.6% efficiency. Selective elution of the loaded thorium was carried out in two steps using both sulfuric and hydrochloric acids after volume optimization. Based on the obtained optimum factors, validation of the studied impregnated solid phase occurred on three certified granite samples where the practical applicability was then examined upon two geological samples bearing Th(IV) collected from Abu Zeneima mineralization, South-Western Sinai.

Mercury in samples of gas mixtures – a review of mercury sampling and determination methods

The determination of the composition of gas mixtures, especially those analytes which exist, for example, as contaminants for the main components of the gas mixture, very often requires the concentration of the analyte so that it can be quantified. The analysis of gaseous environmental samples, including air and air samples at workplaces, is difficult, which results from: the need to work with samples with an extensive matrix and heterogeneous distribution of pollutants, the stability of the analyte and the presence of interfering substances (interferents) in the sample. On the other hand, the analysis of trace components of gaseous fuels is difficult due to the need to collect a suitably concentrated sample so that these components can be quantified. This article provides an overview and analysis of the methods used for the collection and determination of mercury in gas mixtures. Currently, there are standardized mercury collection and determination methodologies dedicated to matrices such as air, workplace air, waste gases or natural gas. These are both manual and fully automated methods. Most of the methods described in the literature on the subject consist of two stages, i.e. the stage of collecting a sample for a solid or liquid sorbent and the stage of desorption and determination of the mercury content in the collected sample using methods dedicated to the analysis of this element. The most frequently used methods for collecting mercury samples in gas mixtures are: the gold amalgamation method and the sorption methods on powder sorbents (such as activated carbon, hopcalite, impregnated silica gel), glass fibers, impregnated cellulose filters and liquid sorbents (such as e.g. acids). The methods of sample desorption are varied and depend on the material on which the analyte has been absorbed and the selected mercury determination method. Three methods are mainly used to analyze samples for mercury content, i.e. the cold vapor atomic absorption spectrometry method (CV-AAS), the cold vapor fluorescence atomic spectrometry method (CV-AFS) and the inductively coupled plasma mass spectrometry method (ICP-MS). However, it should be kept in mind that although the methods available and used for the analysis of mercury content in gas are standardized, they are not resistant to the presence of hydrocarbons and hydrogen sulphide in the tested samples. These are the compounds that are most often mentioned as substances interfering in the determination of mercury in gases using the above-mentioned methods.

Retardation of some drugs in thin-layer chromatographic systems with impregnated silica gel plates with hen's egg white and bovine serum albumin

The influence of impregnation the chromatographic plate adsorbent layer, silica, with hen's egg white albumin (OVA) or bovine serum albumin (BSA) on the retention of some popular medicines (paracetamol, aminophenazone, theophylline, caffeine, acetanilide, ciprofloxacin, tramadol, acetylsalicylic acid, acebutolol) is investigated. The effect of composition and buffer pH of the mobile phase on solute separation selectivity is also studied. The chromatographic systems with and without above mentioned albumins and their influence on investigated drug retention are compared. In general, it has been turned out that retention of tested medicines in systems with the sorbent impregnated with albumin significantly increase relative to those with non-impregnated.

Synthesis and characterization of amine-impregnated silica gel for potential carbon dioxide (CO2) absorption

The rising of CO2 concentration in atmosphere become global concern due to its effect to the global warming. One potentially economical for CO2 capture is through adsorption using solid sorbents. Silica gel has potential to adsorb carbon dioxide with modification of silica gel with amine groups which provide specific adsorption sides for carbon dioxide adsorption. Therefore, a study of impregnated silica gel with amine for carbon dioxide adsorption was done. A series of characterization was made between raw silica and impregnated silica with amine. Based on the results from Iodine Test Analysis and DSC characterization, it can be stated that the modification of Raw Desiccant Silica Gel (DSG) which had been modified with Aminopropyltrimethoxysilane (APMS), 95% had the highest possibilities of percentage to absorb CO2 from the environment with iodine value of 2736.85 mg/g that indicate the porosity and surface area of the adsorbent is higher. Amine 1A consist of 17.84 % of carbon, 5.41 % of hydrogen and 6.44 % of nitrogen. For FTIR result, Amine 1A has Si-O-Si stretching, C-C stretching, N-C stretching and C-N stretching due to the impregnation of amine to the raw silica gel. From DSC analysis, the higher the peak shows that water molecule bound to Amine 1A evaporated at a higher temperature of 92.4°C shows the highest porosity and have highest possibility as adsorbent for CO2 adsorption.

VAPOR-PHASE SYNTHESIS OF LACTIDE FROM ETHYL LACTATE OVER TiO2/SiO2 CATALYST

The lactide is monomer for production of polylac- tide – biodegradable polymer that use as an ecological packagingmaterial. In an industry the two-stage lactide synthesis is applied. At first, lactic acid condenses into the oligomer using Sn-octanoate catalyst, then oligo- mer depolymerizes to lactide. The drawbacks of this liquid-phase method are a significant amount of by- products — dimers and trimers of lactic acid and low lactide yield.Now a direct vapor-phase condensation of lactic acid and its esters to lactide is considered as alternative to the industrial process. One-stage lactide obtaining and use of solid catalysts are advantages of such method. In this work, the vapor-phase transfor- mation of ethyl lactate over supported TiO2/SiO2 and TiO2/Al2O3 oxides in nitrogen flow at 200–300 °С
 was studied. The oxide samples were obtained by impregnating silica gel and γ -alumina with an approp- riate amount of titanium tetrabutoxide solution in iso- propanol, then dried at 80 oC, and finally calcined at 500 oC in air for 4 h. The catalysts were characterized by BET method, X-ray diffraction and UV-Vis diffuse reflectance spectroscopy. Catalytic experi- ments were carried out in a steel flow reactor at 200
 –270 °С and atmospheric pressure. The load on a ca-talyst was varied in the interval of 8.2–36.4 mmol ethyllactate/(gcat⋅ h) that corresponds gas hourly space velo- city of the mixture of ethyl lactate and nitrogen of 1230–1490 h–1. It was shown that TiO2/SiO2 with5 wt.% content of titanium dioxide provides 48 % conversion of ethyl lactate with selectivity and pro- ductivity towards lactide 74 % and 7.0 mmol/(gcat⋅ h)at 270 °C, respectively. It was found thatTiO2/SiO2 is more efficiently for lactide producing (STY = 6.2 mmol/(gcat⋅ h) compared to TiO2/Al2O3catalyst (STY =1.8 mmol/(gcat⋅ h). It was shown that spent TiO2/ SiO2 catalyst fully restores activity after regenerati- on in air at 500 °С for 2 h. The two-stage scheme of ethyl lactate condensation with the participation of coordina- tion-unsaturated titanium ions is discussed.

Identification and Quantification of Germacrene D from the Extracts of Zanthoxylum ovalifolium Leaves by AgNO3-TLC Densitometric Method

Germacrene D an important sesquiterpenoid has been extracted from leaves of Zanthoxylum ovalifoilum and high performance thin-layer chromatographic method has been developed for its simultaneous identification and determination. The compound was extracted by cold extraction and separated and identified on a AgNO3 impregnated silica gel 60 F254 HPTLC plates with dichloromethane:acetone (9.8:0.2 v/v) as mobile phase. The quantification of geremcare D was carried out by densitometry scanning performed at λ = 254 nm by reflectance scanning. This facilitated a well-resolved band for the compound with a Rf value of 0.46 ± 0.01. Linear regression concentration analysis data for mean calibration plots showed good linear relationship in the range of 1000-10000 ng/mL, with a correlation coefficient, slope and intercept of 0.9985 ± 0.0004, 21.62 ± 0.435 and 3308.87 ± 10.24, respectively. The minimum amount of germacrene D that could be authentically detected (LOD) and quantified (LOQ) were determined and found to be 212.07 and 521.23 ng/spot, respectively. The method was validated by considering the parameters linearity, precision, accuracy, specificity and robustness wherein, it is evident from the results that the proposed method was simple, safe and reliable.

Retention behavior of metal ions on tri-n-butyl phosphate and tri-n-butyl amine-impregnated silica gel G layers: Quantitative separation of lead from other metal ions and synthetic alloys

The retention behavior of 40 metal ions has been studied on tri-n-butyl phosphate (TBP) and tri-n-butylamine (TBA)-impregnated silica gel G layers in aqueous acid solutions including the complexing acids and butanol-nitric acid mixtures in varying ratios as mobile phases. The mechanism of migration is explained in terms of solubility of the metal salt, adsorption, complex formation, and precipitation of the ions in the network of the adsorbent. The effect of pk1 of the complexing acids used as the mobile phase and also of the metal complexes formed on the RF values of metal ions is discussed. The effect of the mobile phase composition on the migration behavior of these ions has also been studied. Twenty percent TBP-and TBA-impregnated silica gel G layers are found the most suitable for the separation of metal ions. The quantitative separation of lead from other metal ions and synthetic alloys such as architectural bronze and leaded bronze has been carried out.

A tantalum(v) oxide impregnated silica gel surface: application as a promising adsorbent for simultaneous heavy metal preconcentration

This article reports on an investigation into the ability of SiO2–Ta2O5 as a new sorbent for simultaneous preconcentration of Cd(ii), Co(ii), Cr(iii), Cu(ii), Fe(iii), Mn(ii), Ni(ii) and Pb(ii) ions from water by the column method and the parameters involved in this process.

Improved heat insulation and mechanical properties of silica aerogel/glass fiber composite by impregnating silica gel

In this paper, a kind of silica gel was applied to improve the mechanical properties of silica aerogel/glass fiber composite without compromising its thermal conductivity. The composite was prepared by acid-base catalyzed tetraethylorthosilicate sol-gel followed by supercritical CO2 drying, in which the silica gel was impregnated. The effects of the silica gel on the thermal conductivity and strength of the composite were investigated. The results indicated that the composite possessed not only ultra-low thermal conductivity of 0.0179 W·(m·K)−1, but also excellent mechanical strain and low bulk density of 0.246 g/cm3, and was dust-free. It was demonstrated that the impregnated silica gel filled in the gap between the glass fibers and anchored the silica aerogel on the glass fiber tightly via the –Si-O-Si- network, which not only prevented the heat transfer but also trapped and protected the silica aerogel from collapsing. This new approach shed light on solving the big issue of the silica aerogel in practical application due to its brittle and dust-drop.

Rapid Production of trans‐Cyclooctenes in Continuous Flow

AbstractA new method for rapid larger‐scale production of trans‐cyclooctenes (TCOs) in continuous flow was developed: Up to 2.2 g/h of specific TCOs can be produced by using this procedure. This method utilizes the classical photoisomerization of cis‐cyclooctenes (CCOs) for the synthesis of TCOs but substitutes the conventionally used silver nitrate impregnated silica gel column for a liquid−liquid extraction module. In addition, this method provides the possibility of external addition of a substrate to scale up and speed up the production of TCOs because the concentration of the CCO is kept constant. This method was applied for the synthesis of several commonly used TCOs.

Unconventional TLC systems in lipophilicity determination: A review

ABSTRACTThis review focuses on four unusual thin-layer chromatography (TLC) approaches for the determination of lipophilicity: (1) the use of medium-polar stationary phases: CN, NH2, and DIOL instead of RP plates, together with water-based mobile phase; (2) the use of silica gel in a typical normal-phase manner and treating extrapolated retention indices as the “reversed lipophilicity”; (3) the use of oil impregnated silica gel in the reversed-phase manner; and (4) the use of salting-out mobile phases. The chromatographic indices obtained in these systems are numerously reported as well correlated with lipophilicity and they are an interesting alternative to classical RP systems approaches.

Sorption behavior of metal ions on thiourea-impregnated silica gel G and alumina stationary phases in aqueous HCl and acetone—HCl media: Quantitative separation of Pb2+ and Hg2+ from other metal ions

The sorption behavior of a number of metal ions was investigated on thiourea-impregnated silica gel G and alumina layers with aqueous HCl and acetone—HCl mobile phases. The mobility of the metal ions was examined under varying experimental conditions of mobile phase pH, effect of concentration of thiourea as the impregnant, and also the effect of solvent composition in acetone—HCl mixtures. The migration of metal ions depends on the solubility of metal salt, adsorption and precipitation of the ions in the network of the adsorbent. On impregnated silica gel G layers, for many ions, maximum adsorption occurs at pH 2 and above. 0.1 m and 0.2 m thiourea-impregnated alumina layers were found the most suitable for metal ion separations. For some metal ions, comparative study was made with thiourea and urea as the impregnant. Quantitative separations of Pb2+ and Hg2+ from some other metal ions and synthetic alloys were also carried out.

Wet impregnation of a commercial low cost silica using DETA for a fast post-combustion CO2 capture process

This work presents an economic and simple method to manufacture low cost, but effective adsorbents for CO2 capture through impregnating DETA to a low cost, porous silica gel. The results have demonstrated that the low cost silica gel impregnated by low molecular-weight amine is stable and work very well at a temperature up to 130°C. The developed adsorbent has a fast adsorption kinetics and can be regenerated at a low temperature. This will significantly reduce the energy used to desorb CO2, therefore the energy penalty. The effect of amine loading on the textural properties, thermal stability, and CO2 capture performance of the impregnated silica gel is also reported in this paper. 10% amine loading gives the best porosity, stability and the highest adsorption capacity.

Spectrometric determination of iron and copper in vegetable oils after separation with Schiff base impregnated silica gel column: A simple approach for eliminating the high organic matrix

SummaryA simple solid‐phase extraction method has been described for the separation of Fe(III) and Cu(II) from liquid vegetable oils using N,N′‐bis(4‐methoxy salicylidene) ethylenediamine impregnated silica gel and the determination of these ions. The experimental parameters that affect the separation/preconcentration of ions were investigated by batch and column methods prior to the determination by flame atomic absorption spectrometry. Fe(III) and Cu(II) ions in 20.0 g portion of oil samples can be quantitatively sorbed and then eluted completely with 5.0 mL of 2.0 mol L−1 HNO3. Limits of detection were calculated as 22.8 and 13.9 μg kg−1 for Fe(III) and Cu(II), respectively. The repetition of the suggested method was checked by finding relative standard deviation for five repeated analyses, which was 1.5% for Fe(III) and 0.1% for Cu(II). Applicability of the method was controlled with spiked and unspiked sunflower, corn, canola, olive, soya and hazelnut oils.