Preparation Of Carbon Aerogels Research Articles

Preparation of carbon aerogel from waste newspaper for adsorption of antidiabetic drug residue from aqueous system

In this study, the waste newspaper was utilized to prepare carbon aerogel (CA) for adsorptive removal of Metformin hydrochloride (MH) (antidiabetic drug residues) from the aqueous system. The prepared CA was characterized using Field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) analyser. The MH adsorption was carried out using two types of water, one was laboratory-prepared distilled water and another was real river water. Although, optimum removal around 87 % was observed at pH 3, the removal efficiency at about 63 % estimated at neutral pH. In river water experiment, slightly lower rate of adsorption about 59 % was noticed. Nearly 61 % removal was found for 120 min and then no significant adsorption was found. The pseudo-second-order kinetics and Freundlich isotherm models presented a good interpretation of the adsorption experiment data. Physio-sorption was the primary mechanism of the MH adsorption was confirmed by Temkin and D-R isotherms studies. Regeneration studies demonstrated the removal stability of CA around 32 % until five cycles. An adsorption mechanism was also proposed for the removal of metformin hydrochloride using carbon aerogel.

Popcorn-inspired preparation of carbon aerogel with nano-walls for electromagnetic shielding and thermal insulation

In this study, we devised a green and straightforward approach for fabricating carbon aerogels by heating dextrin, drawing inspiration from the popping mechanism of popcorn. The structure and morphology of the samples were intricately regulated through precise adjustments in the temperature and duration of the heat-treatment process, resulting in the formation of a carbon aerogel comprising nano-walls. Upon carbonisation at 2100 °C, the resultant carbon aerogel exhibited an exceptionally low density of approximately 0.029 g cm−3. Notably, the aerogel demonstrated excellent electromagnetic shielding performance, reaching a shielding effectiveness of approximately 57 dB and an impressive specific shielding effectiveness of 1965 dB cm3 g−1 with a thickness of 5 mm across the entire X band. Additionally, it displayed an ultra-low thermal conductivity of approximately 0.016 W m−1 K−1 and good thermal stability. These characteristics position carbon aerogels as promising materials with vast application potential in electromagnetic shielding and thermal insulation.

Asam Gelugur-based Carbon Aerogels for Highly Recyclable Oil Adsorption

Rapid development of the oil industries and improper oil management caused a huge amount of oil pollutant released into the water environment. Oil pollutant is toxic and may harm aquatic biodiversity. The present work highlights the facile preparation of carbon aerogels based from Asam Gelugur (CA@Ga) for oil remediation from aqueous. Analysis on the structure of CA@Ga using Fourier Transform Infrared Spectroscopy (FTIR), Energy Dispersive X-ray (EDX) and Scanning Electron Microscopy (SEM), confirmed the successful preparation of CA@Ga through hydrothermal carbonization. The main parameters affecting the adsorption of oil such as the sorption time, pH and mass of sorbent were screened and oil adsorption studies revealed that the optimum conditions were at contact time of 3 minutes, pH of solution at 7 and the adsorbent mass of 2 g with the highest adsorption capacity of 0.82 + 0.01 g/g. CA@Ga displayed a good stability towards thermal treatment and exhibited good adsorption ability towards several types of oil. Recyclability study depicts that CA@Ga could be regenerated by simple physical treatments and retained a high sorption after 10 cycles with adsorption capacity of 0.80 + 0.01 g/g. Therefore, the prepared CA@Ga has potential in application of oil recovery and environmental protection.

Preparation of Carbon Aerogels from Polymer-Cross-Linked Xerogel Powders without Supercritical Fluid Drying and Their Application in Highly Selective CO2 Adsorption

Preparation of Carbon Aerogels from Polymer-Cross-Linked Xerogel Powders without Supercritical Fluid Drying and Their Application in Highly Selective CO₂ Adsorption

A scalable molecular-templating strategy toward well-defined microporous carbon aerogels for efficient water treatment and electrocatalysis

Carbon aerogels have attracted increasing research interest in a wide range of potential applications owing to their unique structural features, yet the scalable preparation of carbon aerogels configured by nanoporous carbon skeletons with high surface area and precise pore structure is a great challenge. Herein, we report a molecular-scale interface engineering concept for high-throughput and scalable production of well-defined microporous carbon aerogels (MPCAs) based on simple and fast polycondensation (<8 s) of dialdehyde with silsesquioxane. Benefiting from the unique organic/inorganic hybrid molecule structure, the silsesquioxane favours the formation of molecular-scale silica templates with uniform carbon source/template interface. The resulting MPCAs exhibit 3D interconnected macroporous framework combined with well-defined micropore skeleton and large surface area. These intriguing features render MPCAs superb pore accessibility and utilization, and thus they demonstrate great promise as adsorbent materials for rapid removal (<10 s) of organic micropollutants with high uptake, and as electrocatalyst supports for incorporation of metal-nitrogen-carbon species with excellent activities.

Preparation of mesoporous carbon aerogels via ambient pressure drying using a self-sacrificing melamine-formaldehyde template

In order to overcome the pore collapse phenomenon during the ambient pressure drying and subsequent carbonization processes, we propose herein a new strategy of preparing mesoporous carbon aerogel (MeCA) based on a sol–gel polymerization method coupling with two key steps of introducing the self-sacrificing melamine-formaldehyde template (MF) and carefully adjusting the heating rate of the carbonization. The solid-state MF substituting the liquid-state solvent in the pores of organic wet gel effectively alleviates the capillary pressure, preventing the mesopores from collapse during ambient pressure drying, and then decomposes into gases slowly during the modified carbonization process. As a result, the obtained MeCA with the slimmest skeleton demonstrates a pore volume of 0.82 cm3 g−1, a surface area of 534 m2 g−1 and a well-retained mesoporous structure with a pore size of 11 nm. This value of the mesopore size, to our knowledge, is the smallest one of the ever reported MeCAs prepared by ambient pressure drying. We believe that this approach may open the doors for the preparation of carbon aerogels with desired nanostructure for numerous applications.

Facile Preparation of Carbon Aerogels with Different Drying Methods

Carbon aerogels were prepared through a polycondensation of phloroglucinol, resorcinol and formaldehyde with sodium carbonate as the catalyst under different drying methods. The drying methods were room temperature drying, vacuum drying and freeze drying. The effects of different drying methods on the porous structure of carbon aerogels were studied systematically. The texture and pore structure were investigated under scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and a surface-area analyzer. The results show that the freeze-drying method was good for the specific surface area of carbon aerogels, up to 843 m2 g–1.

Preparation of carbon aerogels from TEMPO-oxidized cellulose nanofibers for organic solvents absorption

In this study, ultralight and hydrophobic carbon aerogels were prepared from 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-oxidized cellulose nanofibers (TOCN) for the removal of organic solvents.

Fabrication of Biomass-Derived Carbon Aerogels with High Adsorption of Oils and Organic Solvents: Effect of Hydrothermal and Post-Pyrolysis Processes.

Biomass is the most plentiful and well-utilized renewable carbon resource on the earth. Direct conversion of biomass to carbon aerogel provides a promising approach to develop adsorbent materials. In the present work, the effect of presence of water during hydrothermal treatment and holding temperature during post-pyrolysis process have been investigated for the preparation of carbon aerogels (CAs) using eggplant as raw material. The results showed that the addition of water during hydrothermal treatment was advantageous for the preparation of CA samples with higher surface area and stronger hydrophobicity, resulting in superior adsorption capacities of CAs for both oil and organic solvents compared with that fabricated without the presence of water. The optimized carbon aerogel possessed higher specific surface of 249 m2·g−1 and exhibited excellent hydrophobicity with a water contact angle of 133°. The adsorption capacities of carbon aerogel for oils and organic solvents could reach 35–45 times its own weight. In addition, the adsorbed oil and organic solvents could be recovered by distillation, and the regenerated carbon aerogels samples exhibited the stable performance and outstanding reusability. Therefore, the carbon aerogel has great potential in application of oil recovery and environmental protection.

Pore size-controlled carbon aerogels for EDLC electrodes in organic electrolytes

Pore size-controlled carbon aerogels (CA_X) are prepared from two starting materials: resorcinol and formaldehyde. Carbon aerogels with different pore sizes are successfully obtained by simply varying the polymerization time (X) in the polycondensation of resorcinol and formaldehyde. Pore sizes of the carbon aerogels monotonically increase with increasing polymerization time. The pore size of the carbon aerogel plays an important role in determining its electrochemical behavior (i.e., specific capacitance in EDLC) especially at high current density. A sufficiently large pore size in a carbon aerogel is required for easy transport of electrolyte ions, and these types of carbon aerogels provide excellent electrochemical performance as an EDLC electrode. CA_20, which was polymerized for the longest time, have the largest pore size and the largest pore volume. CA_20 exhibit the highest specific capacitance due to facile electrolyte ion transport. As a result, design of carbon aerogels with a sufficiently large pore size while maintaining a high specific surface area is very important for developing carbon aerogels for use in EDLC electrodes. In addition, we propose a schematic reaction pathway for the preparation of carbon aerogels in ambient conditions from resorcinol and formaldehyde using a base catalyst based on the characterization results.

Preparation of carbon aerogels at room temperature using acetonitrile as solvent

Carbon aerogels were synthesized at room temperature by a sol–gel polymerization route using resorcinol and formaldehyde as precursors, acetonitrile as solvent and hydrochloric acid as catalyst, followed by CO 2 supercritical drying and carbonization. FT-IR, SEM, XRD and nitrogen adsorption were used to characterize the microstructure of the aerogels. Results showed that the carbon aerogels are graphite-like amorphous materials with nano-skeleton networks formed by nanoparticles around 40–70 nm in diameter, whose specific surface area is up to 1300 m 2 g −1 and lowest density about 0.050 g/cm 3 . The heat of condensation and the catalytic action of hydrochloric acid made it possible to form gels at room temperature. The high surface area and low density of the as-prepared carbon aerogels were ascribed to a strong interaction between acetonitrile and –OH groups by hydrogen bonding. [New Carbon Materials 2012, 27(6): 462–468]

Preparation of carbon aerogel by ambient pressure drying and its application in lithium/sulfur battery

Formaldehyde, resorcinol, and sodium acetate were used to synthesize the carbon aerogels by ambient pressure drying. The effect of the ratio of resorcinol and sodium acetate for carbon aerogels was researched by scanning electron microscope and Brunauer-Emmett-Teller characterizations. Then the carbon aerogels were applied in synthesizing sulfur/carbon aerogel composites through a melting method, the specific capacity and cycle performance of lithium/sulfur batteries that adopted the prepared composites as cathodes were measured by galvanostatic discharge–charge. X-ray diffraction, conductivity measurement, cyclic voltammetry, and electrochemical impedance spectra tests were also carried out to help explain the electrochemical performance. Finally, the carbon aerogel with the best properties was chosen for the comparative study of replacement of water by acetone as solvent in the preparation of carbon aerogels. According to our study, the carbon aerogel prepared by ambient pressure drying with high electrical conductivity, controllable pore structure, and high specific surface area was proposed to be used for lithium/sulfur batteries, and the key factors to the performance of carbon aerogel/sulfur composites were discussed.

5-hydroxymethylfurfural as a potential monomer for the preparation of carbon aerogel

To explore a potential of 5-hydroxymethylfurfural (HMF) in the preparation of carbon aerogels, phloroglucinol–HMF–furfural (PHF) and phloroglucinol–HMF (PH) alcogels were synthesized. It was found in PHF carbon aerogels that the addition of HMF led to a change in their surface chemical properties, i.e., the favorable formation of surface C–O and O=C–O groups. When phloroglucinol and HMF were used as a carbon monomer, PH alcogels were formed at room temperature within tens of minutes. The resulting PH carbon aerogels showed a surface area of 975–1290 m2 g−1, a pore size distribution centered at about 30 nm, and a pore volume of 1.35–1.86 cm3 g−1. As a result of varying several preparation variables, their surface chemical properties were different in accordance with PHF samples. Additionally, a cyclic voltammetry test was conducted, resulting in the fact that the gravimetric capacitance of PHF and PH carbon aerogels showed strong dependence on their chemical characteristics. It was consequently revealed that, due to the peculiar structure of HMF, the preferential formation of C–O linkages through intermolecular dehydration occurs along with unreacted phenolic hydroxyl species of phloroglucinol at the surface, thus yielding a higher gravimetric capacitance.

Preparation of carbon aerogels with different pore structures and their fixed bed adsorption properties for dye removal

Controlled porosity carbon aerogels are prepared by a sol–gel polymerization method and the prepared materials are used as fixed bed adsorbents for dye removal. The influences of operating conditions and preparation factors on the adsorption of C. I. Reactive Red 2, as a model compound, from aqueous solution were investigated. Many column parameters were estimated at different stages and the Bed-Depth-Service-Time model was used to analyze the experimental data. The results showed that the adsorption bed capacity increased with increasing bed height, decreasing liquid flow rate and decreasing initial dye concentration. Moreover, the work indicated that the adsorption ability of the carbon aerogel could be controlled by adjusting the molar ratio of resorcinol to surfactant and carbonization conditions. In addition, the adsorption capacity could be improved when the carbon aerogel was activated by CO2. The reasons for the difference in adsorption ability could be related to the different pore structure characteristics of various samples.

Preparation of carbon aerogel supported platinum catalysts for the selective hydrogenation of cinnamaldehyde

The selective hydrogenation of cinnamaldehyde is investigated using platinum catalysts supported on carbon aerogels with different textural and chemical properties. Despite the large amount of oxygenated surface groups introduced after the oxidation step, the original porosity of the carbon aerogels is maintained. The oxidation treatments performed on the materials are found to strongly influence the surface chemistry which in turn affects the Pt dispersion, yielding larger metal particles after the chemical modifications and the H2 pre-treatment. The presence of mesopores and the increase of the acidic character in the carbon aerogels lead to a higher catalytic activity and selectivity towards cinnamyl alcohol when compared with that obtained for the untreated materials. A thermal treatment at 973K is found to favor the hydrogenation of the olefinic bond when using carbon aerogels, due to the remaining oxygenated surface groups, at variance with other previously reported carbon supports (xerogels and nanotubes).

Ionic liquid templated preparation of carbon aerogels based on resorcinol–formaldehyde: properties and catalytic performance

A series of carbon aerogels were prepared with or without using ionic liquids as templates. By varying the structures and contents of ionic liquids, carbon aerogels with different pore size distributions could be obtained. The effect of the ionic liquids on the properties of the final carbon aerogels was explored and the catalytic performance of the carbon aerogels in the selective oxidation of tetralin was studied.

Shrinkage and pore structure in preparation of carbon aerogels

To aim at thermal insulator applications, the shrinkage and the pore structure of resorcinol–formaldehyde (RF) aerogels and carbon aerogels were investigated during the supercritical drying and the carbonization process. The water (W) molar ratio has small effects on the surface area or the particle size, but has significant effects on the density of the aerogel. Higher W/R ratio leads to lower density and larger pore size, and leads to less shrinkage during the carbonization process. The molar ratio of catalyst sodium carbonate (C) has significant effects on the shrinkage, pore size, and particle size of the aerogel. Lower R/C ratio leads to smaller particle size and smaller pore size, and thus induces more shrinkage both in the supercritical drying and in the carbonization, the obtained CA is much denser. The R/C ratio should be higher than 300 to prevent excessive shrinkage. In order to synthesize carbon aerogels combining with small shrinkage, low density (less than 0.1 g/cm3), and small pore size (less than 150 nm) for thermal insulators, the preferred W/R ratio is between 90 and 100, and the preferred R/C ratio is between 300 and 600.

Preparation of carbon aerogel in ambient conditions for electrical double-layer capacitor

Carbon aerogels were prepared by polycondensation of resorcinol with formaldehyde using sodium carbonate as a catalyst in ambient conditions, and they were used as an electrode of electrical double-layer capacitor. The effect of resorcinol to catalyst ratio ( R/ C ratio) on volume shrinkage, BET surface area, and electrochemical property of carbon aerogels was investigated by changing R/ C ratio from 50 to 2000. In order to minimize volume shrinkage, solvent exchange was performed with acetone at 50 °C for 1 day. Volume shrinkage was <2% after 2-day gelation in the absence of CO 2 supercritical drying. BET surface area was strongly dependent on R/ C ratio. Carbon aerogel prepared at R/ C ratio of 500 showed the highest BET surface area (706 m 2/g) with average pore diameter of 10.9 nm. Electrochemical property of carbon aerogels as an electrode of electrical double-layer capacitor was investigated by cyclic voltammetry measurement. Specific capacitance of carbon aerogel prepared at R/ C ratio of 500 was found to be 81 F/g in 1 M H 2SO 4 electrolyte at the scan rate of 10 mV/s.

Preparation of carbon aerogels from 5-methylresorcinol–formaldehyde gels

The systematics of the preparation of low density carbon aerogels from 5-methylresorcinol–formaldehyde (MR/F) organic aerogels dried in CO 2 under supercritical conditions is reported. The synthesis of organic aerogels involves a doubly catalysed process: at first, in basic medium using a sodium carbonate catalyst and second, in acidic medium. The aquagels were obtained at room temperature within an hour. The carbonization of the organic aerogel to get a carbon aerogel was carried out at 973 K and 1273 K in the flow of dry nitrogen. Carbon aerogels with a density of 0.13 g/cm 3 and specific surfaces of over 500 m 2/g were obtained. The optimization of the ratio of the components was carried out in order to achieve minimum shrinkage of the organic aerogel after drying. Regarding to the pore size distribution, it was found that the porosity of obtained the materials obtained could be easily tailored by changing the synthesis conditions. Thus, the conditions for obtaining materials with a preferential micro- or mesoporous structure were determined.

Requirements of organic gels for a successful ambient pressure drying preparation of carbon aerogels

In this paper, we investigated the requirements of organic gels for a successful ambient pressure drying by analyzing the role of the strength, the pore size and the surfactant of organic gels in decreasing the drying shrinkage of organic aerogels. Experimental results showed the effect of the decrease of the surface tension, resulting from the surfactant, on the drying shrinkage was very small and negligible. The drying shrinkage depended strongly on the strength and the pore size. Subsequently, the respective role of the strength and the pore size was evaluated. It can be found that the strength plays a greater role than the pore size.