Fabrication of Biomass-Derived Carbon Aerogels with High Adsorption of Oils and Organic Solvents: Effect of Hydrothermal and Post-Pyrolysis Processes.
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ABSTRACT: 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.
Project description:The synthesis of magnetic iron-carbon composites (Fe/C) from waste avocado seeds via hydrothermal carbonization (HTC) has been demonstrated for the first time. These materials are shown to be effective in adsorption and catalytic applications, with performances comparable to or higher than materials produced through conventional processing routes. Avocado seeds have been processed in high-temperature water (230 °C) at elevated pressure (30 bar at room temperature) in the presence of iron nitrate and iron sulfate, in a process mimicking natural coalification. Characterization of the synthesized material has been carried out by X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectrometry (ICP-OES), Fourier-transform infrared spectroscopy (FT-IR), magnetometry, and through surface area measurements. The supported iron particles are observed to be predominately magnetite, with an oxidized hematite surface region. The presence of iron catalyzes the formation of an extended, ordered polymeric structure in the avocado seed-derived carbon. The magnetic Fe/C has been demonstrated as an adsorbent for environmental wastewater treatment using methylene blue and indigo carmine. Kinetic analysis suggests that the adsorbates are chemisorbed, with the positive surface charge of Fe/C being preferential for indigo carmine adsorption (49 mg g-1). Additionally, Fe/C has been evaluated as a heterogeneous catalyst for the hydroalkoxylation of phenylacetylene with ethylene glycol to 2-benzyl-1,3-dioxolane. Product yields of 45% are obtained, with 100% regioselectivity to the formed isomer. The solid catalyst has the advantages of being prepared from a waste material and of easy removal after reaction via magnetic separation. These developments provide opportunities to produce carbon-based materials for a variety of high-value applications, potentially also including energy storage and biopharmaceuticals, from a wide range of lignocellulosic biomass feedstocks.
Project description:Graphene metamaterials with a radial-like structure and negative Poisson's ratio (NPR) were assembled using a unique centripetal freezing technique. Driven by the centripetal temperature gradient, ice crystals were grown toward the center of an aqueous graphene dispersion and form a radially arranged skeleton. A reentrant structure was formed at the diagonal of the monolith as the ice crystals sublimate. The obtained centripetal graphene metamaterial (CGM) was endowed with NPR response. CGM maintained NPR under 50% compression, which reached a minimum (-0.18) at 10% strain. After 50 compressive cycles at 50% strain, CGM retained approximately 96% of the original compressive strength. The radial channels endowed CGM with fast absorption kinetics, and the NPR response effectively accommodated the damage caused by volume shrinkage during repeated adsorption-regeneration cycles. This strategy is an effective method for achieving NPR response and improving the mechanical properties of porous materials.
Project description:Current aquatic chemical testing guidelines recognise that solvents can potentially interfere with the organism or environmental conditions of aquatic ecotoxicity tests and therefore recommend concentration limits for their use. These recommendations are based on evidence of adverse solvent effects in apical level tests. The growing importance of sub-apical and chronic endpoints in future test strategies, however, suggests the limits may need re-assessment. To address this concern, microarrays were used to determine the effects of organic solvents, dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), upon the transcriptome of zebrafish (Danio rerio) embryos. Embryos were exposed for 48 h to 0.025 and 0.1 ml/L DMF or DMSO. Effects on survival and development after 24 and 48 h were assessed microscopically with no effects on mortality or morphology. However, analysis of 48-h embryonic RNA revealed large numbers of differentially expressed genes for both solvent at both concentrations. The enrichment of differentially expressed genes was found for metabolic, development and other key biological processes, some of which could be linked to observed morphological effects at higher solvent concentrations. These findings emphasise the need to remove or lower as far as possible, the concentrations of solvent carriers in ecotoxicology tests.
Project description:The rapid advancement of jujube industry has produced a large amount of jujube biomass waste, requiring the development of new methods for utilization of jujube resources. Herein, medium-temperature pyrolysis is employed to produce carbon materials from jujube waste in an oxygen-free environment. Ten types of jujube biochar (JB) are prepared by modifying different pyrolysis parameters, followed by physical activation. The physicochemical properties of JB are systematically characterized, and the adsorption characteristics of JB for NO3- and NH4+ are evaluated via batch adsorption experiments. Furthermore, the pyrolysis and adsorption mechanisms are discussed. The results indicate that the C content, pH, and specific surface area of JB increase with an increase in the pyrolysis temperature from 300 °C to 700 °C, whereas the O and N contents, yield, zeta potential, and total functional groups of JB decrease gradually. The pyrolysis temperature more significantly effects the biochar properties than pyrolysis time. JB affords the highest adsorption capacity for NO3- (21.17 mg·g-1) and NH4+ (30.57 mg·g-1) at 600 °C in 2 h. The Langmuir and pseudo-second-order models suitably describe the isothermal and kinetic adsorption processes, respectively. The NO3- and NH4+ adsorption mechanisms of JB may include surface adsorption, intraparticle diffusion, electrostatic interaction, and ion exchange. In addition, π-π interaction and surface complexation may also be involved in NH4+ adsorption. The pyrolysis mechanism comprises the combination of hemicellulose, cellulose, and lignin decomposition involving three stages. This study is expected to provide a theoretical and practical basis for the efficient utilization of jujube biomass to develop eco-friendly biochar and nitrogenous wastewater pollution prevention.
Project description:Catalyst regeneration is economically attractive, and it saves resources. Thus, it is important to determine the influence of catalyst regeneration on the chemical composition of upgraded oil. The catalyst was regenerated several times, and the regenerated catalyst was reloaded in the reactor to proceed with the next run. The composition of the derived upgraded pyrolysis oils in relation to catalyst regeneration was determined. The results revealed that the catalyst cracking abilities decreased with an increased number of reaction cycles. The opposite trends of the organic fraction and water yields indicated that the deoxygenation process occurred via H2O production. A decrease in the CO and CO2 yields revealed that the deoxygenation in catalytic pyrolysis with a catalyst mixture occurred via decarbonylation, decarboxylation, and dehydration mechanisms. The chemical formula of bio-oil changed from CH0.17O0.91 for a noncatalytic experiment to CH0.14O0.66 for a catalytic pyrolysis experiment after five reaction cycles, which indicated that the oxygen in the bio-oil decreased at the expense of hydrogen. The high heating value (HHV) of bio-oils decreased as the number of reaction cycles increased, albeit the minimum value of 22.41 wt % in the 6th reaction cycle was still higher than the value for the noncatalytic experiment. Compared to the HHVs of diesel fuel and gasoline petrol, the values of the produced bio-oil with catalyst mixtures were still low. The catalyst regained 94% of the surface area for the fresh catalyst, which indicated that the regeneration procedure was effective.
Project description:Cerium-based MOFs (Ce-MOFs) are regarded as attractive porous materials showing various structures, excellent thermal and chemical stability, tunable porous properties, and simple synthetic methods that are useful for wastewater treatment applications. Hence, in the present work, we synthesized a series of Ce-MOFs through a fast and green synthetic method at room temperature using water as a green solvent. Four different solvents including ethanol, chloroform, acetone, and methanol were used in the solvent-exchange process to engineer the properties of prepared Ce-MOFs. The influence of different exchange solvents on the crystalline structure, porous structure, thermal stability, and surface morphology of Ce-MOFs was studied systematically. It was found that exchange solvents can significantly affect the chemical and physical properties of prepared Ce-MOFs. Using ethanol as an exchange solvent results in the production of highly crystalline MOF that has the highest surface area (843 m2/g) and pore volume (0.7518 cm3/g) compared to other prepared Ce-MOFs. The dye adsorption experiments revealed that the activated sample by acetone (Ce-MOF-4) exhibited the highest adsorption capacities toward both anionic (270.27 mg/g for Congo Red (CR)) and cationic (227.27 mg/g for Malachite Green (MG)) dyes. This MOF adsorbs both organic dyes via different mechanisms including hydrogen bonding, pore-filling, π-π stacking, coordination, and electrostatic interactions. Moreover, it exhibited good structural stability in acidic solution, neutral solution, and during consecutive adsorption-desorption cycles, confirming its potential to be applied as a stable adsorbent for simultaneous removal of cationic and anionic organic dyes from water.
Project description:This paper reports the optimization of a two-step atmospheric pressure plasma process to modify the surface properties of a polyurethane (PU) foam and, specifically, to prepare a superhydrophobic/superoleophilic absorbent for the removal of oils and nonpolar organic solvents from water. In particular, in the first step, an oxygen-containing dielectric barrier discharge (DBD) is used to induce the etching/nanotexturing of the foam surfaces; in the second step, an ethylene-containing DBD enables uniform overcoating with a low-surface-energy hydrocarbon polymer film. The combination of surface nanostructuring and low surface energy ultimately leads to simultaneous superhydrophobic and superoleophilic wetting properties. X-ray photoelectron spectroscopy, scanning electron microscopy and water contact angle measurements are used for the characterization of the samples. The plasma-treated PU foam selectively absorbs various kinds of hydrocarbon-based liquids (i.e., hydrocarbon solvents, mineral oils, motor oil, diesel and gasoline) up to 23 times its own weight, while it completely repels water. These absorption performances are maintained even after 50 absorption/desorption cycles and after immersion in hot water as well as acidic, basic and salt aqueous solutions. The plasma-treated foam can remove mineral oil while floating on the surface of mineral oil/water mixtures with a separation efficiency greater than 99%, which remains unaltered after 20 separation cycles.
Project description:A shift to a bioeconomy development model has been evolving, conducting the scientific community to investigate new ways of producing chemicals, materials and fuels from renewable resources, i.e., biomass. Specifically, technologies that provide high performance and maximal use of biomass feedstocks into commodities with reduced environmental impact have been highly pursued. A key example comprises the extraction and/or dissolution of polysaccharides, one of the most abundant fractions of biomass, which still need to be improved regarding these processes' efficiency and selectivity parameters. In this context, the use of alternative solvents and the application of less energy-intensive processes in the extraction of polysaccharides might play an important role to reach higher efficiency and sustainability in biomass valorization. This review debates the latest achievements in sustainable processes for the extraction of polysaccharides from a myriad of biomass resources, including lignocellulosic materials and food residues. Particularly, the ability of ionic liquids (ILs) and deep eutectic solvents (DESs) to dissolve and extract the most abundant polysaccharides from natural sources, namely cellulose, chitin, starch, hemicelluloses and pectins, is scrutinized and the efficiencies between solvents are compared. The interaction mechanisms between solvent and polysaccharide are described, paving the way for the design of selective extraction processes. A detailed discussion of the work developed for each polysaccharide as well as the innovation degree and the development stage of dissolution and extraction technologies is presented. Their advantages and disadvantages are also identified, and possible synergies by integrating microwave- and ultrasound-assisted extraction (MAE and UAE) or a combination of both (UMAE) are briefly described. Overall, this review provides key information towards the design of more efficient, selective and sustainable extraction and dissolution processes of polysaccharides from biomass.
Project description:The effect of post-treatment upon the H₂O adsorption performance of biomass-based carbons was studied under post-combustion CO₂ capture conditions. Oxygen surface functionalities were partially replaced through heat treatment, acid washing, and wet impregnation with amines. The surface chemistry of the final carbon is strongly affected by the type of post-treatment: acid treatment introduces a greater amount of oxygen whereas it is substantially reduced after thermal treatment. The porous texture of the carbons is also influenced by post-treatment: the wider pore volume is somewhat reduced, while narrow microporosity remains unaltered only after acid treatment. Despite heat treatment leading to a reduction in the number of oxygen surface groups, water vapor adsorption was enhanced in the higher pressure range. On the other hand acid treatment and wet impregnation with amines reduce the total water vapor uptake thus being more suitable for post-combustion CO₂ capture applications.