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Activated carbon produced from bamboo and solid residue by CO2 activation utilized as CO2 adsorbents
Abstract
Bamboo and its solid residue after hydrothermal treatment were converted successfully into porous carbon by physical activation with the CO2 agent. The solid residue exhibits a higher potential to form activated carbon thanks to its very low ash content (almost 0%). The porosity and CO2 uptake of the carbon materials were characterized by the N2 and CO2 adsorption/desorption techniques. The results showed a dominant microporous structure in the carbon derived from both bamboo and solid residue. The highest BET surface area that the carbon material from bamboo could achieve was 976 m² g⁻¹, meanwhile, this value at the carbon prepared from solid residue activated at the same temperature was 1496 m² g⁻¹. The microporosity structure of activated carbon could be stimulated and enhanced at the optimal condition of CO2 activation. The CO2 adsorption capacity of the carbon made from bamboo and the solid residue was also analyzed with good capacity (3.4 mmol g⁻¹) comparing to the 3 reference materials at the same condition of adsorption (293 K, 1 atm).
... Examples include chars from sugarcane bagasse and bamboo gasification, characterized by substantial surface area and pore volume. These chars feature abundant ultra-microporous structures, enhancing their CO 2 adsorption capacity (Khuong et al., 2021;Nguyen et al., 2021a). Studies underscore their proficiency in CO 2 capture, with maximum capacities of 123 mg g -1 (at 25 • C) and 150 mg g -1 (at 20 • C), respectively (Khuong et al., 2021;Nguyen et al., 2021a). ...
... These chars feature abundant ultra-microporous structures, enhancing their CO 2 adsorption capacity (Khuong et al., 2021;Nguyen et al., 2021a). Studies underscore their proficiency in CO 2 capture, with maximum capacities of 123 mg g -1 (at 25 • C) and 150 mg g -1 (at 20 • C), respectively (Khuong et al., 2021;Nguyen et al., 2021a). ...
... Furthermore, the remarkable micro-porosity observed in MNS gasified chars, along with the abundance of oxygen-containing and basic functional groups, and a substantial concentration of K and Ca on the surface, synergistically led Fig. 9. Evolution of CO 2 uptake of MNS gasified chars. (Khuong et al., 2021) CO 2 gasification, 900 o C 150 Coconut husk (Ello et al., 2013) CO 2 gasification, 800 o C 172 246 Whitewood (Shahkarami et al., 2015) CO 2 gasification, 890 o C 63 ...
... Its composition, rich in cellulose and marked by a high calorific value, makes it suitable for energy production. Furthermore, its low ash content signifies a cleaner combustion process, which is beneficial for both the environment and energy yield (NATH;DAS;DAS, 2009;LIU et al., 2018;KHUONG;NGUYEN;TSUBOTA, 2021). ...
... Its composition, rich in cellulose and marked by a high calorific value, makes it suitable for energy production. Furthermore, its low ash content signifies a cleaner combustion process, which is beneficial for both the environment and energy yield (NATH;DAS;DAS, 2009;LIU et al., 2018;KHUONG;NGUYEN;TSUBOTA, 2021). ...
... Its composition, rich in cellulose and marked by a high calorific value, makes it suitable for energy production. Furthermore, its low ash content signifies a cleaner combustion process, which is beneficial for both the environment and energy yield (NATH;DAS;DAS, 2009;LIU et al., 2018;KHUONG;NGUYEN;TSUBOTA, 2021). ...
This study aimed to perform the agricultural zoning of climatic risk for bamboo in Brazil by means of artificial neural networks. It was used climatic data of air temperature (TAIR, ºC) and rainfall (P). The Feed Forward Artificial Neural Network, Multilayer Perceptron (MLP) with backpropagation learning algorithm for multilayers was employed. The agroclimatic zoning allowed the classification of regions by climatic suitability and showed that 71% of the national territory was suitable for bamboo cultivation. The use of the neural network allowed an accurate and fast classification of climate suitability.
... On the other hand, Bamboo-A-900 exhibits improved CO 2 and CH 4 adsorption capacities (8.0 ± 0.3 and 3.4 ± 0.2 mol kg −1 , respectively) compared to Bamboo-700 (3.8 ± 0.1 and 1.4 ± 0.2 mol kg −1 , respectively) and Bamboo-500 (1.9 ± 0.3 and 0.8 ± 0.2 mol kg −1 , respectively) at 1.9 MPa (see Figure 7). This enhancement is linked to the increase in BET surface area from 365 m 2 g −1 to 1220 m 2 g −1 , micropore volume from 0.09 to 0.34 cm 3 g −1 , and mesopore volume from 0.07 to 0.26 cm 3 g −1 as indicated in Table 2, which offers additional adsorption sites for CO 2 molecules [38,94,95]. In addition, the presence of O-functional groups and CaO in Bamboo-A-900 enhances interactions with CO 2 molecules, making these factors particularly effective in the intermediate and high-pressure ranges. ...
... For activated biochars, Bamboo-A-900 shows a CO 2 adsorption capacity of 2.6 ± 0.1 mol kg −1 at 0.1 MPa, which is higher than the 2.0 mol kg −1 reported by Khuong et al. [38] for bamboo biochar activated with CO 2 at 800 • C (see Table 4). This improvement is attributed to the increased surface area and enhanced pore structure resulting from higher activation temperatures, facilitating more effective CO 2 adsorption. ...
Purifying biogas by removing contaminants and carbon dioxide (CO2) to produce biomethane enhances its energy content, making it suitable as fuel and for injection into natural gas grids. Bamboo-derived adsorbents Bamboo-500 (pyrolyzed at 500 °C), Bamboo-700 (pyrolyzed at 700 °C), and Bamboo-A-900 (activated with CO2 at 900 °C) were synthesized and characterized to evaluate their performance for CO2 and CH4 adsorption. Increasing pyrolysis temperature from 500 °C to 700 °C and further CO2 activation at 900 °C enhanced adsorption capacities of CO2 and CH4 due to improved surface area and micropore structure. In this study, the novel Approximate Adsorption Performance Indicator (AAPI) approach is introduced, offering an efficient method for evaluating adsorbent performance, particularly in biogas upgrading. AAPI results suggest Bamboo-500 is suitable for biogas upgrading at very low pressures (<0.12 MPa) with low regeneration energy and acceptable CO2 capacity (1.9 ± 0.2 mol kg⁻¹). However, Bamboo-A-900 excelled at medium and high pressures by its highest CO2 adsorption capacity (8.0 ± 0.3 mol kg⁻¹) promoted by the high surface area (1220 m²g⁻¹) and calcium oxide presence. Finally, Bamboo-A-900 shows promise for enhancing CO2 adsorption and biogas upgrading. Bamboo-derived adsorbents offer a sustainable solution for biogas upgrading, supporting Sustainable Development Goals by promoting clean energy transitions.
... This leads to more available adsorption sites and improved accessibility for both CO 2 and CH 4 [67,68]. This improvement is attributed to the increase in BET surface area from 4 m 2 g −1 to 97 m 2 g −1 and total pore volume from 0.003 to 0.06 cm 3 g −1 , as shown in Table 1, which provides more adsorption sites and an optimal structure for CO 2 capture [67][68][69]. In other words, Cabosse-A-700 exhibits heterogeneous surface properties with bottleneck-shaped pore entrances, largely due to the increase in ash content during activation, from 20.9% in Cabosse-700 to 26% (Table 1) [69]. ...
... This improvement is attributed to the increase in BET surface area from 4 m 2 g −1 to 97 m 2 g −1 and total pore volume from 0.003 to 0.06 cm 3 g −1 , as shown in Table 1, which provides more adsorption sites and an optimal structure for CO 2 capture [67][68][69]. In other words, Cabosse-A-700 exhibits heterogeneous surface properties with bottleneck-shaped pore entrances, largely due to the increase in ash content during activation, from 20.9% in Cabosse-700 to 26% (Table 1) [69]. To optimize the CPH samples for CO 2 capture in biogas upgrading, the focus should be on chemically modifying the samples, particularly by enhancing basic groups (e.g., nitrogen groups) or oxygenated groups such as carboxyl and hydroxyl which improve interactions with CO 2 molecules. ...
The preliminary selection of adsorbents for the separation of a gas mixture based on pure gas adsorption remains a critical challenge; thus, an approximate adsorption performance indicator (AAPI) was proposed for the initial evaluation of the adsorbents to separate the biogas main constituents (carbon dioxide/methane (CO2/CH4)) by studying their pure gas adsorption. Three samples derived from cocoa pod husk (CPH), namely Cabosse-500 (pyrolyzed at 500 °C), Cabosse-700 (pyrolyzed at 700 °C), and Cabosse-A-700 (activated with CO2 at 700 °C), were synthesized, characterized, and evaluated for the pure gases adsorption. This study presents an AAPI evaluation, which takes into account adsorption capacity, approximate selectivity, and heat of adsorption. Adsorption isotherms indicate the ability of the CPH family to selectively capture CO2 over CH4, as they have a high approximate selectivity (>1) thanks to their physical properties. Changing the pyrolysis temperature, activation methods, and varying the pressure can significantly change the choice of the most effective adsorbent; Cabosse-A-700 showed better performance than the other two in the low and high pressure range owing to its presence of micropores and mesopores, which enhances the CO2 adsorption and therefore the AAPI.
... The amount of residual chars is quite significant in the entire process, and without a suitable application, it could lead to environmental pollution, increased gasification costs, and reduced overall system sustainability. However, when considering their use as an adsorbent, the residual char is well-suited, as compared to other activation methods (physical or chemical activation) where the final material typically constitutes only 10-20 % of the initially used material [24,26,27]. The residual chars produced in each run were gathered for subsequent analysis of their textural and surface properties. ...
... Wheat flour [45] KOH activation,700 • C, ratio 3:1 3.48 Bamboo [26] Hydrothermal carbonization at 200 • C, 2.5 h, followed by CO 2 activation, 800 • C, 10 min 3.4 Fig. 10. ...
... These transitions can be observed via thermal analysis [9]. The char produced via pyrolysis can be activated by various methods, including thermal, chemical, and thermochemical activation techniques [10]. Recently, a few studies have reported that porous carbon can be produced from biomass through low-temperature carbonization [11,12]. ...
The growing demand for eco-friendly activated carbon necessitates sustainable production methods. This study investigates the conversion of waste wood into activated carbon using goethite iron ore as an activating agent. A high-temperature rotary furnace was used to activate the carbon at 1373 K. The oxygen released from the iron oxide during the heat treatment reacted with the carbon in the wood, resulting in 49% of activated carbon with BET surface areas between 684 m²/g and 770 m²/g. The activated carbon and char showed type I isotherms with micropore areas between 600 m²/g and 668 m²/g, respectively. Additionally, 92% of the iron in the ore was reduced from ferric to ferrous. The findings demonstrate that goethite iron ore is an effective activating agent for producing wood-based activated carbon while also generating metallic iron as a byproduct. This alternative activation method enhances the sustainability and efficiency of activated carbon production.
... Given these considerations, there is a growing imperative to develop methods that combine the environmental benefits of physical activation with the superior performance characteristics typically associated with chemical activation. Specifically, the challenge lies in utilizing biomass precursors to produce activated carbon with high specific surface area and substantial pore volume through a straightforward and eco-friendly physical activation process [11][12][13]. ...
The porosity of activated carbon is significantly influenced by both the precursor biomass and the activation parameters. Waste sawmill wood (WSW) dust, an abundantly available precursor from the furniture manufacturing , construction, carpentry, and shipbuilding industries, was collected, dried, pulverized, carbonized, and activated using steam and a novel high-pressure CO 2 activation approach. Activation was performed in a tubular furnace at 800°C with a pure CO 2 flow for 90 min at 1 MPa pressure (WSW-A800-CO 2-90 min-1 MPa). Another activated carbon sample was synthesized from the same precursor at atmospheric pressure using steam flow at 700°C for 20 min (WSW-A700-Steam-20 min). XRD and FTIR analyses were conducted to compare the structural information of both samples. Additionally, the thermal characteristics of the samples were determined by measuring their specific heat capacities. N 2 and CO 2 adsorption experiments were performed to investigate the porous properties and CO 2 capture capacities of the synthesized samples. The activated carbon synthesized in a pressurized CO 2 environment produced a BET surface area of 684 m 2 /g, while steam activation achieved a BET surface area of 947 m 2 /g. Interestingly, despite the lower surface area of the CO₂-activated sample, it exhibited a higher CO₂ adsorption capacity (106.29 mg/g at 5°C and 110 kPa) compared to the steam-activated carbon due to its unique pore size distribution. The experimental CO₂ adsorption data were also correlated with Langmuir, Freundlich, and modified Dubinin-Astakhov (D-A) models to elucidate the CO₂ capture parameters, such as isosteric heat of adsorption, activation energy, and Gibbs free energy.
https://authors.elsevier.com/c/1kCE88jVwQ1BeI
... Khuong et al. [30] described the effect of temperature on the sugar production from bamboo. From their result, the authors stated that the maximum yield of sugar could be extracted at around 200 °C. ...
Typically, the hydroxide agents, such as sodium hydroxide and potassium hydroxide, which have corrosive properties, are used in the carbon activation process. In this study, potassium oxalate (K 2 C 2 O 4), a less toxic and non-corrosive activating reagent, was used to synthesize activated carbon from the solid residue after autohydrolysis treatment. The effect of the autohydrolysis treatment and the ratio of the K 2 C 2 O 4 /solid residue are presented in this study. Moreover, the comparison between the activated carbon from bamboo and biochar from the solid residue are also reported. The resulting activated carbon from the solid residue exhibited a high surface area of up to 1432 m 2 ·g-1 and a total pore volume of up to 0.88 cm 3 ·g-1. The autohydrolysis treatment enhanced the microporosity properties compared to those without pretreatment of the activated carbon. The microporosity of the activated carbon from the solid residue was dominated by the pore width at 0.7 nm, which is excellent for CO 2 storage. At 25 °C and 1.013 × 10 5 Pa, the CO 2 captured reached up to 4.1 mmol·g-1. On the other hand, the ratio between K 2 C 2 O 4 and the solid residue has not played a critical role in determining the porosity properties. The ratio of the K 2 C 2 O 4 /solid residue of 2 could help the carbon material reach a highly microporous textural property that produces a high carbon capture capacity. Our finding proved the benefit of using the solid residue from the autohydrolysis treatment as a precursor material and offering a more friendly and sustainable activation carbon process.
... The feature of both materials is that they have a high carbon composition. BAC consists of 82.13 % C [32], while CTP, based on SEM_EDX testing, consists of 63.6 % C. Apart from that, the main reason for using BAC and CTP was that both materials are highly porous [33,34], and there is an aromatic structure [35] influencing the interaction of delocalized π electrons around the aromatic ring [36,37]. ...
... For several years, biomass has received strong attention to synthetize biochars and derived activated carbons, but the research has been mainly focused on adsorption/depollution applications [11][12][13][14][15] or energy storage systems [16][17][18][19][20][21][22] because of their high specific surface areas, adjustable porous structures and the presence of heteroatoms that facilitate ion transfer and diffusion. Only few data can be found in the literature concerning porous carbons for tribological applications. ...
Activated carbons are commonly used for adsorption/depollution applications, but only a few studies are related to their lubricating properties. In order to investigate a new family of friction reducers, the tribological properties of biochars and derived activated carbons obtained from sugar cane bagasse are investigated. Activated carbons are obtained from either a physical (steam water) or chemical (with phosphoric acid) activation process. The tribological tests show that the activated carbons present very low friction coefficients, close to 0.08. The correlation of textural and tribological investigations shows that the specific surface area of the compounds as well as the microporous and mesoporous domain extensions are key parameters to optimize the friction reduction properties of activated carbons. The friction properties of the compounds are improved if the mesoporous domain extension is above 40% of the total porous volume. This study shows that local biomass waste valorization is possible and that sugar cane bagasse-derived activated carbons appear as interesting new friction reduction additives for lubricants.
... Notably, as the activation temperature increased, the activated carbon NO conversion rate first weakened and then increased. The reason is that, at low activation temperatures, activated carbon reacts normally with CO 2 and the carbon atoms are replaced by CO 2 [46], forming a new pore structure, and the NO conversion rate increases accordingly. However, for extremely high activation temperatures, CO 2 reacts excessively with activated carbon, eroding the pore wall, causing the pore structure to collapse, and reducing the NO conversion rate. ...
This study investigates the effects of different combinations of potassium hydroxide (KOH)–nitrogen (N2)/carbon monoxide (CO)/air activation on the low-temperature ammonia (NH3) removal NO performance of coconut shell-activated carbon. KOH–N2-combined activation resulted in expanded pores of activated carbon, while high temperatures caused structural collapse. While increasing the activation temperature induced larger average pore sizes, introducing nitrogen-containing functional groups on the surface positively affected the NO conversion rate. Furthermore, while KOH–CO2-combined activation yielded activated carbon with denser and more ordered pore structures upon increasing activation temperature, a relatively large specific surface area and total pore volume were also observed. Introducing functional groups such as C = C on the surface yielded a higher overall NO conversion rate. Although KOH–air activation resulted in developed porous structures, some pore sizes were blocked, thereby yielding a smaller specific surface area. Nevertheless, introducing nitrogen-containing functional groups contributed to an overall increase in the NO conversion rate. Orthogonal experimental analysis revealed that activation time significantly impacted the physical activation process of KOH-activated carbon, followed by activation temperature, with activation gas minimally affecting the activated carbon structure and NO conversion rate. Notably, the optimal activation conditions included 1-h activated carbon activation in 3 mol/L of KOH, followed by 1-h CO2 activation at 150℃.
... Khuong et al. [30] described the effect of temperature on the sugar production from bamboo. From their result, the authors stated that the maximum yield of sugar could be extracted at around 200 °C. ...
Typically, the hydroxide agents, such as sodium hydroxide and potassium hydroxide, which have corrosive properties, are used in the carbon activation process. In this study, potassium oxalate (K 2 C 2 O 4 ), a less toxic and non-corrosive activating reagent, was used to synthesize activated carbon from the solid residue after autohydrolysis treatment. The effect of the autohydrolysis treatment and the ratio of the K 2 C 2 O 4 /solid residue are presented in this study. Moreover, the comparison between the activated carbon from bamboo and biochar from the solid residue are also reported. The resulting activated carbon from the solid residue exhibited a high surface area of up to 1432 m ² ·g ⁻¹ and a total pore volume of up to 0.88 cm ³ ·g ⁻¹ . The autohydrolysis treatment enhanced the microporosity properties compared to those without pretreatment of the activated carbon. The microporosity of the activated carbon from the solid residue was dominated by the pore width at 0.7 nm, which is excellent for CO 2 storage. At 25 °C and 1.013 × 10 ⁵ Pa, the CO 2 captured reached up to 4.1 mmol·g ⁻¹ . On the other hand, the ratio between K 2 C 2 O 4 and the solid residue has not played a critical role in determining the porosity properties. The ratio of the K 2 C 2 O 4 /solid residue of 2 could help the carbon material reach a highly microporous textural property that produces a high carbon capture capacity. Our finding proved the benefit of using the solid residue from the autohydrolysis treatment as a precursor material and offering a more friendly and sustainable activation carbon process.
... This is attributed to the kinetic diameter of CO 2 molecules, which is a mere 0.33 nm, with micropores being particularly conducive to CO 2 adsorption. 36,37 Given that the M-N-C catalyst shares similarities with carbon material, it can be inferred that increasing the specific surface area and micropores content of the M-N-C catalysts can enhance their CO 2 adsorption capacity, thereby bolstering the catalytic activity of the ECR. ...
While achieving a Faradaic efficiency (FE) over 90% in the electroreduction of CO2 to CO with single transition metal atom anchored on nitrogen-doped carbon (M-N-C) catalyst is indeed notable, the...
... In recent research by Rostamian et al. [36], rice husk was chemically activated using potassium hydroxide to create activated carbon and a large surface area (2201 m 2 /g) covered with a total pore volume of 0.96 cm 3 /g with an excellent sodium adsorption capability with a capacity of 134.2 mg/g was recorded. Khuong et al. [37] used physical activation with CO 2 to create activated carbon using a by-product from bamboo hydrothermal treatment. The resultant substance was well suited for use in carbon capture due to its large specific surface area of 2132 m 2 /g and high capacity for carbon dioxide adsorption. ...
Activated carbon is the preferred adsorbent for gas and water treatment in various industry across the world due to its efficiency, reliability, and accessibility. Recently, in Malaysia, studies are mainly focused on the fabrication of activated carbon from lignocellulosic biomass-based precursors from agricultural waste such as coconut shell, rice husk, and palm kernel shell. Activated carbon fabrication is a two-step process; the precursor will first undergo carbonization, then, activation is carried out either physically or chemically to develop its porous surface for adsorption purposes. The main benefit of activated carbon is the customizable pore structure for different utilization, which can be easily achieved by the chemical activation process. The types and concentration of chemicals used for activation, pre-treatment of precursor, duration of the activation process, and the mass ratio of precursor to chemicals are proven to effectively influence the resulting pore structure. However, the chemicals used in the activation process can be harmful to the environment. Thus, the chemical recovery process is necessary after the activation process. Nonetheless, more in-depth research on producing activated carbon from abundant biomass materials with bio-based chemical agents for activation is needed to achieve an ecological and sustainable manufacturing process.
... Recently, physical activation is preferable for environmental safety reasons. Physical activation is usually conducted by flowing gas such as water vapor, CO2, or N2 while a high temperature is applied Khuong et al., 2021;Rezma et al., 2017). Steam or water vapor is preferable by following the cost and its ability to increase the surface area of the activated carbon Hidayat & Sutrisno, 2016) , which can reach up to 946.5m 2 /g (Widanarto et al., 2022). ...
This research aimed to produce a screen-printed carbon electrode (SPCE) from an activated coconut shell carbon. As a raw material, coconut shell char provides renewability and is abundantly available in the market. Meanwhile, SPCE offers a simple electroanalytical electrode because the working, counter, and reference electrodes are in one piece. The coconut shell carbon was activated by steam at 700 oC for 1h, producing AC700 that was then characterized to ensure the result by following per under carbon as the main component, the phases, crystal structure, surface area, morphology, and elemental content. The result showed that the surface area of AC700 is 816 m2/g, and the surface structure is porous, as identified by SEM images. Impedance analysis followed by data fitting and conductivity calculation found a high conductivity of 8.68 x 10-2 Scm‑1. The produced-SPCE or SPAC700 was modified by ferrocene at various compositions of 10%; 20%; and 30% of mass. The SPAC700-Fc30 provided the best performance for lead analysis with a detection limit of 0.35 mM, a quantitation limit of 1.17 mM, and good reproducibility with a Repeatability Coefficient (RC) of 0.022. SPAC700-Fc30 showed good lead ions detection despite under 10% Cu2+ and 10% Co2+ interferences. The result confirmed the potential use of coconut shell char as the raw material for SPCE production.
... Current CO 2 capture technologies include the chemical absorption methods such as amine scrubbing [3], ionic liquid absorption [4] and solid-based adsorption techniques by amine-, or calcium-based adsorbent materials [5][6][7][8]. Numerous solidbased adsorbents such as carbonaceous materials [9][10][11][12][13][14][15][16][17][18][19][20][21], zeolites [22], ordered mesoporous silica [23], metal-organic rameworks (MOFs) [24,25], nitriying-enriched activated sludge (NAS) [26] and well-designed porous polymers [27][28][29] have been researched or CO 2 capture; however, porous carbons based on agricultural eedstocks have been receiving signicant attention owing to the act that the less corrosiveness, low regeneration cost, high stability and porosity [15,18,[30][31][32][33][34]. ...
... During pyrolysis (300-1100 • C), degradation products generate different kinds of gas, such as CO 2 , CO, CH 4 , NO, H 2 O, and NH 3 , depending on the precursor's source [37]. Sometimes, external sources of media like CO 2 , NH 3 , steam, He, Ar, air, or a mixture of gases (binary mixture) are utilized to activate the carbon surface ( Figure 5) [74][75][76]. Several efforts have been made to increase the pore volume and surface area by utilizing external steam during pyrolysis [77]. ...
Porous carbon is an emerging material for the capture of CO2 from point sources of emissions due to its high structural, mechanical, and chemical stability, along with reusability advantages. Currently, research efforts are mainly focused on high- or medium-pressure adsorption, rather than low-pressure or DAC (direct air capture) conditions. Highly porous and functionalized carbon, containing heteroatoms (N, O, etc.), is synthesized using different activation synthesis routes, such as hard template, soft template, and chemical activation, to achieve high CO2 capture efficiency at various temperatures and pressure ranges. Fundamental pore formation mechanisms with different activation routes have been evaluated and explored. Higher porosity alone can be ineffective without the presence of proper saturated diffusion pathways for CO2 transfer. Therefore, it is imperative to emphasize more rational multi-hierarchical macro-/meso-/micro-/super-/ultra-pore design strategies to achieve a higher utilization efficiency of these pores. Moreover, the present research primarily focuses on powder-based hierarchical porous carbon materials, which may reduce the efficiency of the capture performance when shaping the powder into pellets or fixed-bed shapes for applications considered. Therefore, it is imperative to develop a synthesis strategy for pelletized porous carbon and to explore its mechanistic synthesis route and potential for CO2 capture.
... Yang et al. found relatively closer values of CO 2 uptakes (between 111 and 135 mg/g at 25 °C) with activated biochars prepared from walnut shells via chemical activation with NaNH 2 at 450 °C [48]. In other work [49], physical activation (with CO 2 at 900 °C) of the solid residue from hydrothermal treatment of bamboo led to slightly higher CO 2 uptakes (150 mg/g); this solid was characterized by an S BET of 1316 m 2 /g and a V T of 0.55 cm 3 /g. In contrast, lower values were reported for activated biochars prepared by monoethanolamine impregnation of coconut shells, showing CO 2 adsorption capacities of 36 mg/g [50]. ...
An integral valorization route based on a pyrolysis process has been proposed to find sustainable applications for argan shells focused on the simultaneous production of activated biochar and antioxidant additives from bio-oil. The bio-oil obtained in the pyrolysis process was furtherly upgraded (hydrothermal treatment and extraction process) to obtain antioxidant additives. On the other hand, the biochar obtained in the pyrolysis was used as a feedstock to produce high-quality activated biochar (by physical activation with CO 2 ). The increase in the pyrolysis temperature (350–550 °C) hardly affected the pyrolysis products distribution (biochar yields of 28–34 wt.% and bio-oil yields between 51 and 55 wt.%), but it led to a slight decrease in the content of phenolic monomers extracted from bio-oil (from 63 wt.% at 350 °C to 53 wt.% at 550 °C). When these extracted fractions were blended with biodiesel (<1 wt.%), improvements of up to 300% in biodiesel oxidation stability were attained. The hydrothermal treatment of the bio-oil did not show noteworthy effects either on the production or antioxidant performance of the extracted fractions if compared with the fractions extracted from the raw bio-oil. Regarding the valorization of argan shells biochar, the activated biochar prepared from it showed considerable potential as an adsorbent material for CO 2 (125 mg of CO 2 per g of the activated biochar) or phenols (complete removal of 99.6% in 4 h of contact time). It was characterized by a high BET surface area (up to 1500 m ² /g), a high carbon content (up to 95 wt.%), low ash content (around 2 wt.%), and a pH of around 8.
Carbonization of Manchurian nut shells (MNS) in argon medium at 400‐700°C was studied by electron paramagnetic resonance (EPR) and thermal analysis. Thermal treatment of MNS leads to the formation of radicals stabilized in the solid matrix, the concentration of which decreases with an increase in temperature from 400 to 700°C. Simultaneous increase in EPR signals intensity of paramagnetic species in the structure of carbon materials is observed. Activation of carbonized MNS with CO2 leads to the formation of microporous adsorbent. The texture of adsorbent depends on the concentration of radicals in the carbonization products: radical concentration of 4.2‐4.7×1020 spin/g leads to the formation of material with specific surface area (SBET) of 760‐800 m2/g, total pore volume (Vads) of 0.32‐0.34 cm3/g and micropore volume (Vmicro) of 0.26‐0.27 cm3/g; a decrease in radicals concentration to 0‐4×1018 spin/g also reduces SBET to 670‐700 m2/g, Vads to 0.28 cm3/g and Vmicro to 0.24 cm3/g.
The availability of agricultural land is central to stimulating reserves in sustainable food and crop production amidst accelerating economic sustainability and growth. Therefore, this article aims to investigate the influence of agricultural land (AGL) on food production (FP) and crop production (CP) with the linkage of environmental sustainability (ES) as a moderator from 1990 to 2021 for the economy of China with the autoregressive distributed lag (ARDL) bounds testing estimation model. Our findings showed that the ARDL model estimates the long-term and short-term joint matching relationships between agricultural land and the independent variables in the model, which is a statistically significant outcome. Therefore, in the long term, the food and crop production adjustment for speed to steadiness was huge as it was projected at 1.337%, 53.6%, 133.5%, and 37.4%, respectively, in all the models, which shows that the adjustment for speed of models is a good post-shock association process. We found evidence for a significant and positive relationship between agricultural land and food and crop production in ordinary least square (OLS) estimation, which also ensured the outcomes of the primary model. Furthermore, Toda–Yamamoto Granger causality test estimation found reverse causality between food production (FP) and crop production (CP) and showed evidence of the conservation hypothesis. We found bidirectional causality between food production and agricultural land and between crop production and agricultural land, which shows evidence of the feedback hypothesis. Additionally, the empirical findings of a robustness check with fully modified ordinary least square (FMOLS) and dynamic ordinary least square (DOLS) techniques showed consistency with the investigations of ARDL estimation in the long run, ensuring the validity and strength of the primary outcomes. Overall, the present paper brings fresh knowledge about agricultural land use, and food and crop production to promote environmental sustainability.
The development of carbon-based supercapacitors is pivotal for advancing high energy and power density applications. This review provides a comprehensive analysis of structural regulation and performance enhancement strategies in carbon-based supercapacitors, focusing on electrode material engineering. Key areas explored include pore structure optimization, heteroatom doping, intrinsic defect engineering, and surface/interface modifications. These strategies significantly enhance electrochemical performance through increasing surface area, improving conductivity, facilitating charge transfer, introducing additional pseudocapacitive reactions, and optimizing the density of states at the Fermi level, among other mechanisms. After introducing these fundamental concepts, the review details various preparation methods and their effects on supercapacitor performance, highlighting the interplay between material structure and electrochemical properties. Challenges in scaling advanced fabrication techniques and ensuring the long-term stability of functionalized materials are discussed. Additionally, future research directions are proposed, emphasizing the development of cost-effective, scalable methods and interdisciplinary approaches to design next-generation supercapacitors, thereby meeting the growing demand for efficient and sustainable energy storage solutions.
The review presents data on the nomenclature and production methods of the most intensively investigated classes of nanoporous carbon materials, which are increasingly used in science, medicine, and various fields of economy. The traditional activated carbons, which are produced by conventional biomass and fossil hydrocarbon processing methods, are compared with nanoporous carbon materials obtained using modern synthetic methods. Recommendations are given on the use of template synthesis to obtain carbon materials with a controlled nanoporosity. Self-template synthesis, in which environmentally benign and readily available organic salts can be used as precursors, is considered as a promising avenue of research. This approach markedly reduces the cost of template synthesis of nanoporous carbons and allows for the preparation of carbon materials with specific particle morphology from organometallic precursors. Methods for the preparation of functional materials with ordered architectures of micro- and mesopores are considered, including modern functionalization and doping approaches. A part of the review is devoted to advanced applications of nanoporous carbon materials such as water treatment, energy and hydrogen storage, separation of gas mixtures, development of catalysts and sensors, and solution of other significant problems. The conclusion summarizes the experience of application of various methods for the preparation of nanoporous carbon materials, identifies the most problematic issues of the development and practical use of these materials, and presents the authors' view on further development of this area of materials science.
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Biogas contains significant quantities of undesirable and toxic compounds, such as hydrogen sulfide (H2S), posing severe concerns when used in energy production-related applications. Therefore, biogas needs to be upgraded by removing H2S to increase their bioenergy application attractiveness and lower negative environmental impacts. Commercially available biogas upgradation processes can be expensive for small and medium-scale biogas production plants, such as wastewater treatment facilities via anaerobic digestion process. In addition, an all-inclusive review detailing a comparison of biochar and hydrochar for H2S removal is currently unavailable. Therefore, the current study aimed to critically and systematically review the application of biochar/hydrochar for H2S removal from biogas. To achieve this, the first part of the review critically discussed the production technologies and properties of biochar vs. hydrochar. In addition, exisiting technologies for H2S removal and adsorption mechanisms, namely physical adsorption, reactive adsorption, and chemisorption, responsible for H2S removal with char materials were discussed. Also, the factors, including feedstock type, activation strategies, reaction temperature, moisture content, and other process parameters that could influence the adsorption behaviour are critically summarised. Finally, synergy and trade-offs between char and biogas production sectors and the techno-economic feasibility of using char for the adsorption of H2S are presented. Biochar’s excellent structural properties coupled with alkaline pH and high metal content, facilitate physisorption and chemisorption as pathways for H2S removal. In the case of hydrochar, H2S removal occurs mainly via chemisorption, which can be attributed to well-preserved surface functional groups. Challenges of using biochar/hydrochar as commercial adsorbents for H2S removal from biogas stream were highlighted and perspectives for future research were provided.
Graphical abstract
CO2 concentration in the atmosphere has crossed an unprecedented level of 420 ppm, causing catastrophic events like climate change. Climate change mitigation via carbon capture is crucial for reducing CO2 emissions. Among various CO2 capture technologies, adsorption is considered one of the most efficient and promising techniques. In recent times, substantial research has been conducted on producing cost-effective and efficient adsorbents for CO2 capture via the thermal and chemical treatments of biomass. In this review, we discuss key scientific results to give broad insight into the recent progress in biomass conversion to activated porous carbon (APC). The effects of various chemical and thermal treatments on the textural properties and CO2 adsorption capacity of APC are comprehensively discussed. CO2 adsorption mechanism based on interaction with the surface functionality is thoroughly explained. The economic aspects of APC synthesis and post-combustion CO2 capture using APC are systematically reviewed.
The escalating issues of rising CO2 emissions and radioactive pollution, specifically from isotopes like 232U and 241Am, present critical global environmental challenges. This study utilized bamboo and Japanese cedar as biomass sources for biochar production, aiming to investigate the influence of carbonization temperature on the biochars capacity to adsorb CO2 and radionuclides. The biochars were produced at 500, 600 and 700oC and underwent a comprehensive structural and material property analyses employing electron microscope, gas adsorption isotherms, and spectroscopy methods. Characterization revealed that the biochar samples predominantly consisted of micropores, whereas the Japanese cedar biochars exhibited elevated mesoporous surfaces compared to bamboo-derived biochars, along with the presence of oxygen-containing moieties on their surface. Remarkably, the results indicate a positive correlation between carbonization temperature and adsorption capacity for both CO2 and the radionuclides. Notably, biochars produced at 700 °C exhibited the highest CO2 adsorption capacity of 2.21 mmol g−1. While both bamboo and cedar biochars exhibited comparable adsorption behavior against CO2, Japanese cedar biochars demonstrated superior capacity for adsorbing 232U and 241Am compared to bamboo biochars. JC700 showed the optimum adsorption behavior, achieving 91 and 88% removal of 232U and 241Am at pH 4, respectively. These findings highlight the potential of both bamboo and Japanese cedar biochars as effective adsorbents for mitigating CO2 emissions and radioactive pollution.
Biomass-derived carbon materials are now an essential source of carbon electrodes for high-performance supercapacitors due to their cost-effectiveness and abundant heteroatom self-doping properties. When preparing porous carbon materials from biomass for supercapacitor use, the use of activators can significantly increase the specific surface area of carbon materials, enhance pore structures, introduce more heteroatoms, promote the generation of various functional groups, and play a crucial role in the capacitance performance of biomass-derived carbon materials. However, the role of activators during the activation process has been overlooked in previous work focused on improving supercapacitor capacitance performance. In addition, there is a lack of comprehensive reviews summarizing the role of activators. Therefore, this work classifies the types of activators, discusses their activation mechanisms, operability, economy, and environmental friendliness, and proposes future development directions for activators. The main mixing methods of activators and carbon materials are also demonstrated, highlighting the advantages and disadvantages of each method. This work could provide valuable insights for the development of activators for high-performance supercapacitors.
The exacerbated conventional exploitation of fossil fuels has been one of the main causes of climate and environmental alterations that the planet has seen recently. The performance of transforming highly polluting waste into methanol has crossed borders and become an interesting option in the industrial and scientific context. The purpose of this study was to develop a review of the main environmental challenges and economic assessments involving the methanol purification process. Furthermore, scientific research focuses on innovative technologies and the main economic challenges related to methanol purification processes are described to enhance the overall sustainability of methanol production.
Waste activated carbon (WAC) regeneration is a classic problem of solid-waste treatment and recycling, and an important topic in CO2-emission reduction. However, seldom report dealt with honeycomb WAC. In this work, a two-step method was put forward to regenerate the honeycomb WAC. As a result, iodine value was increased from 163 to 406 mg·g−1, 72% of the fresh value. At the same time, specific surface area was increased from 463.1 to 1288.2 m2·g−1. Moreover, a re-extrusion technology rebuilt the honeycomb structure with good appearance and sufficient mechanical strength (92.65 N). The rebuilt honeycomb removed 298.2 mg·g−1 of toluene, 71.5 mg·g−1 of chlorobenzene, and 1.1 mg·g−1 of methyl mercaptan. Under same conditions, the WAC only removed 138.4 mg·g−1 of toluene, 6.2 mg·g−1 of chlorobenzene, and 0.3 mg·g−1 of methyl mercaptan. Moreover, the regeneration and re-extrusion processes were repeated for eight cycles, showing a good stability. At last, a mesh belt furnace/rotary furnace process was designed to meet industrial demand. These results will help the development of “zero waste” concept in solid-waste recycling and green economy.
In this study three kinds of biomass were investigated: wood biomass (pine), energy crop (Sida hermaphrodita) and agriculture biomass (straw) using the hydrothermal carbonization process (HTC). The HTC process was conducted in a specially designed reactor under the following conditions: 220 °C temperature and 4 h residence time. The solid (hydrochar) and liquid products of hydrothermal conversion were determined in terms of their chemical and physical properties. Futhermore, the basic parameters of the obtained hydrochars were established: ultimate and proximate analyses, higher heating value, mass and energy yield and energy densification ratio. The liquid products were analysed by measuring pH and conductivity, which confirmed their acidic and polar character, and Chemical Oxygen Demand (COD) at very high value indicating that the liquid phase contained a high concentration of organic matter and nutrients. Additionally, the TGA of hydrochar was performed in an air and inert atmosphere to simulate the combustion and pyrolysis process. Moreover, the pyrolysis process of the hydrochars was investigated using Py-GC-MS apparatus. The process was performed to analyze the composition of pyrolysis products from the hydrochars. The samples were pyrolyzed in sequence at 400, 500, and 600 °C with rapid heating and a short residence time. The pyrolysis of the hydrochars resulted in varied organic compounds dependent on the pyrolysis temperature and chemical composition of hydrochars.
The bamboo charcoals (BC) in various range pyrolysis (400–900 °C) were modified by HNO3, and then the samples were tested for water vapor adsorption. The adsorption experiments were conducted follows to Japanese industrial standard JIS A 1470-1-2002. The physical and chemical properties of the samples were studied by scanning electron microscope, Brunauer–Emmett–Teller surface area analysis, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.
The humidity adsorption tests show that the modified BC samples with HNO3 at room temperature (about 22 °C) in pyrolysis temperature (400–500 °C) have a significant enhancement than the control one at lower relative humidity (< 60%). This characteristic is an advantageous application in conservation needs extremely low humidity. Specific surface area and total pore volume are supposed to play an important role for humidity adsorption at high relative humidity (> 60%). Whereas, at low relative humidity, surface functional groups on BC are a dominant factor compared to specific surface area on humidity adsorption.
Activated carbons (ACs) are widely used in different industrial processes as adsorbents for pollutant removal or as catalytic material support. The parameters and methods of activation can vary, and they affect the final characteristics of ACs, e.g., specific surface area, pore size distribution, and surface functional groups. The results of this study show that microporosity and mesoporosity can be modified, variating these parameters. ACs from Northern Finland Region peat have been prepared through physical activation with steam. The process has been evaluated using the design of experiment approach. Different parameters have been considered as factors, including holding time, oven temperature, heating rate, steam flow, nitrogen flow, kiln rotation, and biomass initial mass. Based on these factors, several responses characterizing the porosity and the elemental analysis of ACs have been selected. All the data collected have been processed statistically using the Fractional Factorial Resolution IV design linear model in a screening configuration fitted with a partial least squares regression using MODDE 9.1 by Umetrics Software.
Graphical Abstract
Hydrothermal carbonisation (HTC) is an attractive biomass pre-treatment as it produces a coal-like fuel, can easily process wet biomass and wastes, and lowers the risk of slagging and fouling in pulverised fuel (PF) combustion boilers. One of the major factors in determining the suitability of a fuel as a coal replacement for PF combustion is matching the char reactivity and volatile matter content to that of coals, as these significantly affect heat release and flame stability. The char reactivity of wood and olive cake biocoals and their respective drop tube furnace chars have been studied using thermogravimetric analysis in comparison to other biomass fuels and high-volatile bituminous coal. It was found that HTC reduces the reactivity of biomass, and in the case of HTC of wood pellets the resulting biocoal has a char reactivity similar to that of high-volatile bituminous coal. Proximate analysis, X-ray fluorescence analysis, and textural characterisation were used to show that this effect is caused primarily by removal of catalytic alkali and alkaline earth metals. Subsequent torrefaction of the wood biocoals was performed to tailor their volatile matter content to match that of sub-bituminous and high volatile bituminous coals without major impact on char reactivity.
The cascade use of bamboo as the raw material for high-value products, that is, the production of xylo-oligosaccharide and the preparation of activated carbon for EDLC electrode, was proposed as an economically effective use of bamboo in this study. Xylo-oligosaccharides, such as xylobiose and xylotriose, were successfully produced from bamboo in a water solution by a hot compressed water process. The solid residue of bamboo after the treatment of the hot compressed water was carbonized at 400–800 °C, then activated with KOH. The KOH activation was effective for the preparation of activated carbon having a high BET specific surface area of ca. 2600 m² g⁻¹ from the solid residue. The amount of ash drastically decreased by the hot compressed water treatment, which should be an advantage as the precursor for EDLC electrodes. The capacitance values measured in a 1 M H2SO4 aqueous solution of the activated carbon derived from the solid residue compared well with those from the bamboo.
This study points out the similarities between char from biomass gasification and activated carbon and reviews its successful applications in the field of adsorption. Surface area (SBET) is considered as the standard parameter. Since only few data on biomass gasification char are available in the literature, in this work char residues from different commercial gasification plants were collected and characterized, reporting their SBET values for comparison. The highest values for SBET are associated to dual-stage gasification technologies and are highly affected by the operating temperature.
Coal bed seams have been considered as promising sequestration reservoirs for CO2 disposal to mitigate the green house gas emissions. The CO2 adsorption and desorption attributes of CO2 on dry Malaysian coals (Sarawak, volatile bituminous) were performed using a sorptomat apparatus (ASAP 2010, Micromeritics, USA) and BELSORP-mini II machine (BEL Japan, Inc.) at 273K, 298K and pressure up to 1bar. The CO2 adsorption was favourable at low temperature and dry coal conditions. However, S3 and S4 coals have the highest adsorption capacity by 0.71 and 0.73 mmol/g respectively. According to IUPAC classification of adsorption isotherms, CO2 adsorption isotherm of all coal samples follow type I which most probably describe the adsorption limited to a few molecular layers (micropores). The results of adsorption and desorption isotherm demonstrate a positive hysteresis in all coal samples. The S1 coal and S2 coal have the highest hysteresis between adsorption and desorption isotherm compared to S3 coal and S4 coal. According to hysteresis classifications, the hysteresis during CO2 adsorption and desorption process for all coal samples follows type H3 which describes micropores and mesopores. The evaluation of the equilibrium adsorption data where fitted using by Langmuir, Freundlich, Redlich-Peterson, Koble-Corrigan, Toth and Sips models. Toth model provided the best fit for all adsorption experimental data that predicting all coals having heterogeneous surface properties.
Due to the issue of deforestation and the pressure to avoid use of native forest resources for production of char, there is increasing requirement for the use of renewable materials and development of additional sustainable processes. Bamboo, a biomass that presents the property of fast growth, is an alternative to native or reforested wood. In this work the slow pyrolysis of a woody bamboo (species Dendrocalamus giganteus Munro) was studied, aiming the determination of biochar properties. The process was conducted in a fixed bed reactor at temperatures ranging from 300 to 600 °C and at a 10 °C/min heating rate. The thermal degradation behaviour of bamboo was investigated through thermogravimetric analysis (TGA/DTG). The bamboo biomass and the biochar were characterized by physical-chemical analysis in order to investigate the main changes caused by the pyrolysis process on biochar properties. The surface morphology of bamboo biomass and biochar was determined using scanning electron microscopy (SEM). Additionally, a discussion about the advantages and disadvantages of biochar production by slow pyrolysis is presented, taking into account the applied conventional methods in the process. Results revealed the advantage of pyrolysis process due to simultaneous biochar and bio-oil production. The bamboo biochar presents suitable properties for its use as energy source and for agricultural applications. Its high porosity and carbon content suggest its application as activated carbon after physical or chemical activation.
Bamboo cellulose was prepared by chemical process involving dewaxing, delignification, and mercerization process. Four samples namely, green bamboo fiber (GBF), dewaxed bamboo fiber (DBF), delignified bamboo fiber (DLBF), and cellulose fiber (CF) had been analysed. FTIR and TGA analysis confirmed the removal of hemicellulose and lignin at the end stage of the process. FTIR results reveal that the D-cellulose OH group occurred at 1639 cm−1 region. SEM micrograph showed that mercerization leads to fibrillation and breakage of the fiber into smaller pieces which promote the effective surface area available for contact. Barrer, Joiyner, and Halenda (BJH) method confirmed that the effective surface area of CF is two times larger compared to GBF. CF showed the highest activation energy compared to GBF. It indicates that CF was thermally stable.
Activated carbon was produced from bamboo residues using carbonisation and steam activation in a high temperature reactor. Tests were carried out to study the effects of two processing parameters, namely, activation time (30, 60, 90, 120 and 150 min) and activation temperature (650, 700, 750 and 800°C) on the properties of activated carbon produced. Activated carbon properties were analysed based on iodine number and Brunauer-Emmett Teller (BET) surface area. Increasing activation temperature gave higher iodine values. Optimum conditions for producing activated carbon from bamboo wastes were at activation temperature 800°C and activation time 120 min that resulted in bamboo activated carbon with the highest iodine number of 823 mg g -1 and BET surface area of 719 m 2 g -1. With these parameters, waste bamboo has the potential to be a promising precursor for the production of activated carbon. The characteristics of the activated carbon in this study was comparable with commercial ones.
This study experimentally analyzed the carbon dioxide adsorption capacity of Moso-bamboo- (Phyllostachys edulis-) based porous charcoal. The porous charcoal was prepared at various carbonization temperatures and ground into powders with 60, 100, and 170 meshes, respectively. In order to understand the adsorption characteristics of porous charcoal, its fundamental properties, namely, charcoal yield, ash content, pH value, Brunauer-Emmett-Teller (BET) surface area, iodine number, pore volume, and powder size, were analyzed. The results show that when the carbonization temperature was increased, the charcoal yield decreased and the pH value increased. Moreover, the bamboo carbonized at a temperature of 1000(°)C for 2 h had the highest iodine sorption value and BET surface area. In the experiments, charcoal powders prepared at various carbonization temperatures were used to adsorb 1.854% CO2 for 120 h. The results show that the bamboo charcoal carbonized at 1000(°)C and ground with a 170 mesh had the best adsorption capacity, significantly decreasing the CO2 concentration to 0.836%. At room temperature and atmospheric pressure, the Moso-bamboo-based porous charcoal exhibited much better CO2 adsorption capacity compared to that of commercially available 350-mesh activated carbon.
Waste Entada Rheedii shell (ERS) was used for the preparation of biochar-based adsorbents for CO2 capture at ambient conditions. Three types of adsorbents were prepared by treating ERS with acid, base and neutral condition. The physico-chemical properties of synthesized carbons were derived by X-ray diffraction, N2 adsorption, Fourier-transform infrared spectroscopy, ¹³C-Nuclear magnetic resonance spectroscopy, Laser Raman, Field emission scanning electron microscopy (FESEM), CHNS elemental and thermo gravimetric analysis. Characterization results indicated that the surface area and presence of basic sites in the carbon depended on the nature of pre-treatment of shell. The CO2 adsorption ability of the ERS derived carbons was tested at ambient temperatures. Carbon prepared after acid treatment showed superior CO2 adsorption capacity. The reasons for high CO2 adsorption behavior of the carbons were explained by its characteristics. The adsorption capacity in presence of moisture was also estimated. These carbon adsorbents also exhibited recyclability without any change in its adsorption capacity.
Supported MgO adsorbents were prepared from the calcination of MgCl2·6H2O preloaded on several biomass wastes including sugarcane bagasse, coffee grounds, rice husk, and saw dust. CO2 adsorption behaviors of the adsorbents with different supports and MgO loadings were investigated using a fixed-bed reactor. The modified Avrami fractional kinetic model was adopted to correlate their CO2 uptakes to evaluate the CO2 adsorption kinetic performance. Amongst the prepared MgO adsorbents, the rice husk ash supported sample (MgO-RHA) featured high CO2 adsorption capacity, due to the good textural properties, nano-crystallization of MgO particles, the uniform dispersion of active components and the enriched surface basicity. CO2 uptakes of MgO-RHA increased first and then decreased with the increasing MgO loading. CO2 adsorption kinetic would be hampered by higher MgO contents because of the increased diffusion resistance and decreased MgO utilization. The adsorbent with 20 wt% MgO loading exhibited the highest CO2 uptake of 4.56 mmol CO2/g. Besides, the desired adsorbent presented good working stability with 7.68% loss-in-capacity in 10 repeated cycles. Recycling waste MgCl2·6H2O and biomass residues to synthesize CO2 adsorbents provides remarkable economic and environmental implications, from the prospective of CO2 emission mitigation and waste management.
In this study, lignite based fossil fuel and cotton waste based biofuel were selected as the main components of mixed energy resources due to their similar heating values. The effect of mixing ratio on pyrolysis and oxidation characteristics was investigated by thermal gravimetric analysis (TGA) equipped with Fourier transform infrared (FTIR) spectrometer. Synergy between the fuels was explained by comparing calculated and experimental findings of characteristic temperatures and gas evolution profiles. The results of the TGA and FTIR analyses revealed that cotton waste addition improves thermal decomposition reactivity of low quality lignite under the pyrolysis and combustion conditions. Although no synergy was found between lignite and cotton waste under pyrolysis condition, the best synergistic interaction between fuels was observed in 50% mixing ratio during combustion.
The United Nations (UN) recent report has warned about the excessive CO2 emissions and the necessity of making efforts to keep the increase in temperature below 2 ○C. Current CO2 capture technologies are inadequate in contributing towards reaching that goal, and effective mitigation strategies must be pursued. In this work, we summarized trends in materials development for CO2 adsorption with focus on recent studies. We put adsorbent materials into four main groups of (I) carbon-based materials, (II) silica/alumina/zeolites, (III) porous crystalline solids, and (IV) metal oxides. Trends in computational investigations along with experimental findings are covered to find inform finding of promising candidates in light of practical challenges imposed by process economics.
The carbonaceous by-product of biomass gasification processes is known as char. Although nowadays char is treated as a waste, it could be valorized as cheap precursor for activated carbons (ACs) due to their similarities in terms of physical-chemical properties and mechanism of formation. In particular, this study wants to assess char suitability as substitute/precursor of AC for CO2 adsorption. Five chars were taken from five different commercial biomass gasifiers installed in South-Tyrol (Italy) and characterized through elemental analysis, physisorption analysis, and scanning electron microscopy. CO2 adsorption/desorption capacity of chars were investigated through thermogravimetric analysis and their performances were compared with two commercial ACs selected as reference.
The effects of adsorption temperature (Tads = 50–75–100 °C), CO2 concentration (CO2:N2 = 1:1–1:4), chemical activation (with KOH or ZnCl2), and adsorption cycles were investigated.
The highest uptake (3.7%) was measured for char activated with KOH, at Tads =50 °C and CO2:N2 = 1:1.
During the thermal modification of the wood there is a decreasing gradient of temperature from the surface to its interior, therefore, the most severe chemical modifications occur on the surface. These chemical modifications directly affect the quality and durability of adhesives and coating. Therefore, this study investigated the chemical modification of the surface of thermally-modified teak juvenile wood. Heartwood and sapwood samples were treated at 180 and 200ºC. Chemical analyses were performed by Fourier transform infrared spectroscopy (FTIR) in reflectance mode with a microscope. Spectra showed an increase in cellulose crystallinity and a decrease in relative contents of hydroxyl groups, lignin and extractives - especially quinones, waxes and oils - following thermal modification. Extractive content of the heartwood was relatively higher than that of sapwood. Heartwood was more susceptible to thermal degradation than sapwood.
Slow pyrolysis of bamboo was conducted at 400-600 °C and pyrolysis products were characterized with FTIR, BET, XRD, SEM, EDS and GC to establish a pyrolysis product yield prediction model and biochar formation mechanism. Pyrolysis biochar yield was predicted based on content of cellulose, hemicellulose and lignin in biomass with their carbonization index of 0.20, 0.35 and 0.45. The formation mechanism of porous structure in pyrolysis biochar was established based on its physicochemical property evolution and emission characteristics of pyrolysis gas. The main components (cellulose, hemicellulose and lignin) had different pyrolysis or chemical reaction pathways to biochar. Lignin had higher aromatic structure, which resulted higher biochar yield. It was the main biochar precursor during biomass pyrolysis. Cellulose was likely to improve porous structure of pyrolysis biochar due to its high mass loss percentage. Higher pyrolysis temperatures (600 °C) promoted inter- and intra-molecular condensation reactions and aromaticity in biochar.
Carbonization and post activation of bamboo-cellulose fiber was carried out. The carbonization was performed at 600 °C, 800 °C and 1000 °C in argon atmosphere. Then, they were activated by heating solid mixture of carbonized bamboo and sodium hydroxide (NaOH) at 720 °C in argon atmosphere. The largest specific surface area of the resulting activated carbon (carbonized at 600 °C) was 2366 m²/g with the micropore volume of 0.71 cm³/g and mesopore volume of 0.06 cm³/g. It was found that the carbonization temperature is very important to obtain nanoporous carbon with large specific surface area. The distributions of interlayer spacing were estimated from the power spectra of the TEM images of the carbonized samples. It showed the interlayer spacing of basic structural unit (BSU) decreased from 0.49 nm (BC-0600) through 0.47 nm (BC-0800) to 0.45 nm (BC-1000). The activated carbon was used as the host material of the electrodes of coin type electric double-layer capacitor (EDLC) with organic electrolyte. The observed specific capacitance was 43 F/g (23 F/cm³) for the activated carbon (carbonized at 600 °C), comparable to 44 F/g (22 F/cm³) of commercial activated carbon (MSP). The corresponding values for the activated carbons (carbonized at 800 °C and 1000 °C) were 40 F/g (23 F/cm³) and 17 F/g (12 F/cm³), respectively.
Biomass-based pyrolytic polygeneration system can commercialize all products (liquids, gases, and solids) generated during pyrolysis, while fast pyrolysis, gasification and carbonization, can only singly commercialize liquids, gases, and solids, respectively. To determine the optimum operational parameters for biomass pyrolytic polygeneration while using bamboo waste as the feedstock, the product characteristics were investigated over a temperature range of 250 to 950 degrees C. Meanwhile, details of the evolution of the char structure were analyzed to reveal the pyrolysis mechanism. Results showed that to increase the yield of char, the operational temperature should be at 350 degrees C; however, at this temperature, no inner pores were formed and a low quality char product was produced. Thus, the optimum operating temperature recommended for biomass pyrolytic polygeneration of bamboo waste was set to 550 degrees C. At the optimum temperature, the surface area of the char was 200 m(2)/g, the calorific value of gas was 14 MJ/m(3), and the concentration of phenols in liquid reached the maximum level. A pyrolysis mechanism based on the evolution of the char structure was proposed. First, the ordered organic macrostructure in raw biomass was converted to a network-like structure consisting of a "3D network of benzene rings" during the "initial decomposition stage (< 450 degrees C)", and this was followed by the "first reconstruction stage (450-550 degrees C)" whereby the initial 3D network was converted to a "2D structure of fused rings". Subsequently, with further increases in temperature, a "graphite microcrystalline structure" was formed during the "second condensation stage (> 550 degrees C)". The results of this study are expected to be beneficial for the comprehensive utilization of bamboo waste and provide new insight into the pyrolysis mechanism.
As an emerging class of porous crystalline materials, covalent organic frameworks (COFs) are excellent candidates for various applications. In particular, they can serve as ideal platforms for capturing CO2 to mitigate the dilemma caused by the greenhouse effect. Recent research achievements using COFs for CO2 capture are highlighted. A background overview is provided, consisting of a brief statement on the current CO2 issue, a summary of representative materials utilized for CO2 capture, and an introduction to COFs. Research progresses on: i) experimental CO2 capture using different COFs synthesized based on different covalent bond formations, and ii) computational simulation results of such porous materials on CO2 capture are summarized. Based on these experimental and theoretical studies, careful analyses and discussions in terms of the COF stability, low- and high-pressure CO2 uptake, CO2 selectivity, breakthrough performance, and CO2 capture conditions are provided. Finally, a perspective and conclusion section of COFs for CO2 capture is presented. Recent advancements in the field are highlighted and the strategies and principals involved are discussed.
A facile method for fabricating the superhydrophobic bamboo timber based on an anatase TiO2 film for acid rain protection and flame retardancy is described in the present work. The bamboo timber with the maximal water contact angle of 154 has been prepared by the hydrothermal deposition of anatase TiO2 nanoparticles and further modified with octadecyltrichlorosilane (OTS). The geometric microstructure of anatase TiO2 nanoparticles and chemical composition of the superhydrophobic coating were analyzed by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The wetting behavior of bamboo timber samples was investigated by water contact angle (WCA) measurement. The results indicated that the strong hydrogen bonds were formed between the amorphous TiO2 and the hydroxide radicals of bamboo timber surface, and the strong interaction contributed to the heat stability enhancement of the TiO2/bamboo timber composites. Moreover, diverse performances of superhydrophobic bamboo timber have been evaluated as well. The treated bamboo timber exhibited the outstanding superhydrophobicity, excellent waterproofing durability, acid rain resistance, and flame retardancy, offering a potential opportunity to accelerate the large-scale production of superhydrophobic woody material for new industrial applications.
The isosteric heats of adsorption of the components of a gas mixture are critical variables for design of adsorbers for gas separation. They can be unambiguously defined by the Gibbsian Surface Excess (GSE) model of multicomponent adsorption. These variables can be experimentally measured by multicomponent differential calorimetry (MDC) and directly used to describe nonisothermal behavior of practical adsorbers. There is no need to make simplified assumptions about the nature and size of the adsorbed phase, as required by conventional adsorption thermodynamic models, to define the isosteric heats. Pure gas isosteric heats of adsorption of N-2 and CO2 on a pelletized silicalite sample were measured using a MDC and a data analysis algorithm based on the GSE model. The silicalite sample behaved like a homogeneous adsorbent for weakly polar N-2 adsorption. The presence of polar alumina binder in the silicalite sample introduced significant heterogeneity for more polar CO2 adsorption.
Porous carbons for CO2 capture at low pressures were prepared by KOH activation of rice husk char. Low activation temperature (640–710 °C) and small KOH/char ratio (1:1) favored the increase in low-pressure CO2 uptake. The CO2 uptakes at 0.1 bar (0 °C) reached 2.11 mmol/g, which were probably the highest value ever reported for porous carbons prepared from lignocellulosic biomass. The high CO2 uptakes at low pressures were ascribable to the presence of micropores (<0.7 nm or <1 nm), the narrow micropore size distribution, or the existence of nitrogen. The obtained porous carbons also exhibited a large CO2 uptake at 1 bar (6.24 mmol/g at 0 °C) and good CO2-over-N2 selectivity. No noticeable change in CO2 uptake was observed after five successive runs of adsorption–desorption. The excellent recyclability, high CO2 uptakes, and good selectivity show that high-performance porous carbons for capturing CO2 at low pressures can be prepared by KOH activation of rice husk char.
In this study, bamboo scaffolding was used to produce activated carbon by carbonization at 600 °C and 900 °C with the purge of nitrogen. The 600 °C char was then further modified chemically by acids and alkalis by reflux for 6 hours. The produced chars were then characterized by nitrogen adsorption isotherm, He pyncometry, pH, elemental analysis and Boehm titration. For most of the chemically modified carbons, the micropore surface areas and volumes have increased compared with the 600 °C char, while the mesopore surface areas and volumes slightly decreased, which may have been due to the dissolving of some of the permeated inorganic matter and oxidizing deposited carbon that blocks the pore openings. For the acidic modified carbons, larger amounts of acidic groups were present in the carbons after being activated by phosphoric acid, phosphoric acid further treated with 2 mol·L−1 nitric acid, and calcium hydroxide. Although carbon treated with 2 mol·L−1 and 5 mol·L−1 nitric acid also produced high acidity, the surface areas and pore volumes were relatively low, due to the destruction of pores by nitric acid oxidation. The reduction of porosity may impair the adsorption capacity.
Cost-effective biomass-derived activated carbons with a high CO(2) adsorption capacity are attractive for carbon capture. Bamboo was found to be a suitable precursor for activated carbon preparation through KOH activation. The bamboo size in the range of 10-200 mesh had little effect on CO(2) adsorption, whereas the KOH/C mass ratio and activation temperature had a significant impact on CO(2) adsorption. The bamboo-derived activated carbon had a high adsorption capacity and excellent selectivity for CO(2) , and also the adsorption process was highly reversible. The adsorbed amount of CO(2) on the granular activated carbon was up to 7.0 mmol g(-1) at 273 K and 1 bar, which was higher than almost all carbon materials. The pore characteristics of activated carbons responsible for high CO(2) adsorption were fully investigated. Based on the analysis of narrow micropore size distribution of several activated carbons prepared under different conditions, a more accurate micropore range contributing to CO(2) adsorption was proposed. The volume of micropores in the range of 0.33-0.82 nm had a good linear relationship with CO(2) adsorption at 273 K and 1 bar, and the narrow micropores of about 0.55 nm produced the major contribution, which could be used to evaluate CO(2) adsorption on activated carbons.
The isosteric heats of adsorption of the components of a gas mixture are critical variables for design of adsorbers for gas separation. They can be unambiguously defined by the Gibbsian Surface Excess (GSE) model of multicomponent adsorption. These variables can be experimentally measured by multicomponent differential calorimetry (MDC) and directly used to describe nonisothermal behavior of practical adsorbers. There is no need to make simplified assumptions about the nature and size of the adsorbed phase, as required by conventional adsorption thermodynamic models, to define the isosteric heats. Pure gas isosteric heats of adsorption of N2 and CO2 on a pelletized silicalite sample were measured using a MDC and a data analysis algorithm based on the GSE model. The silicalite sample behaved like a homogeneous adsorbent for weakly polar N2 adsorption. The presence of polar alumina binder in the silicalite sample introduced significant heterogeneity for more polar CO2 adsorption.
This study is focused on improving the reactivity of a CaO sorbent for its use in a reaction-based process for the separation of carbon dioxide (CO2) from flue gas. The separation process consists of cyclical carbonation (of a metal oxide) and calcination (of the metal carbonate formed) reactions to yield concentrated CO2 from flue gas. CaO sorbents synthesized from naturally occurring limestone and dolomite were microporous in nature. Pore filling and pore pluggage of these micropores limited the conversion of CaO in the carbonation reaction to about 45−50% of the stoichiometric limit. A wet precipitation process was tailored to synthesize high-surface-area precipitated calcium carbonate (PCC). The pores of PCC predominantly lie in the mesoporous range (5−20 nm). The CaO sorbent obtained from PCC (PCC-CaO) was less susceptible to pore pluggage and attained over 90% conversion. PCC-CaO was also capable of maintaining its high reactivity (>90%) over two carbonation−calcination cycles.
Activated carbon with high specific surface area and considerable mesopores was prepared from bamboo scraps by phosphoric Activated carbon with high specific surface area and considerable mesopores was prepared from bamboo scraps by phosphoric
acid activation. The effect of activation conditions was studied. Under the conditions of impregnating bamboo with 80% H3PO4 at 80°C for 9 days and activation at 500°C for 4 h, the prepared activated carbon had the highest mesopore volume of 0.67 acid activation. The effect of activation conditions was studied. Under the conditions of impregnating bamboo with 80% H3PO4 at 80°C for 9 days and activation at 500°C for 4 h, the prepared activated carbon had the highest mesopore volume of 0.67
cm3/g, a specific surface area of 1567 m2/g, and the mesopore ratio reached 47.18%. The study on adsorption isotherms of CH4, CO2, N2 and O2 on the activated carbon were carried out at 298 K. The considerable difference in the adsorption capacity between CO2 and the other gases was observed, which would be of interest for the adsorptive separation/purification of gaseous CO2 from its mixtures, especially from mixtures with N2 and/or O2. cm3/g, a specific surface area of 1567 m2/g, and the mesopore ratio reached 47.18%. The study on adsorption isotherms of CH4, CO2, N2 and O2 on the activated carbon were carried out at 298 K. The considerable difference in the adsorption capacity between CO2 and the other gases was observed, which would be of interest for the adsorptive separation/purification of gaseous CO2 from its mixtures, especially from mixtures with N2 and/or O2.
Mesoporous magnesium oxide (MgO) was synthesized using mesoporous carbon CMK-3 obtained from mesoporous SBA-15 as exotemplate. P123 was used as the structure-directing template and rice husk ash (RHA) as the silica source for the synthesis of SBA-15, which was subsequently treated with sucrose and sulphuric acid to obtain mesoporous carbon (CMK-3). X-ray powder diffraction (XRD) results and the type-IV adsorption isotherm with H1 hysteresis obtained by N2 adsorption/desorption study for SBA-15, CMK-3 and mesoporous MgO suggests its resemblance with materials synthesized using conventional silica sources. Mesoporous MgO was subjected for CO2 adsorption study in TGA; adsorption was 8 and 10 wt% at 25 and 100 °C, respectively. Finally, mesoporous MgO is selective to CO2 gas, thermally stable and regenerable. Thus, this study contributes a better route to enhance CO2 gas adsorption and use ecological waste rice husk for the synthesis of such efficient mesoporous materials.
Activated carbons were produced from agricultural waste corncob using a variety of different activation strategies and activators. The BET specific surface area and pore volume of the carbons produced by a two-step KOH activation process were 3012 m2/g and 1.7 cm3/g, respectively. All carbons prepared showed a microporous character, except for that prepared by a one-step phosphorous acid activation which exhibited hysteresis of a mesoporous carbon. The hydrogen adsorption performance of the different carbons was closely investigated. The microporous carbon with the largest BET specific surface area showed H2 adsorption capacities up to 2.0 wt% at 77 K under 1 atm pressure and 0.44 wt% at 298 K at 5 MPa. The adsorption isotherm model based on the Langmuir–Freundlich equation together with Soave–Redlich–Kwong equation of state for determination of the gas phase fugacity provided a satisfactory representation of the high pressure hydrogen data. The parameter representing full coverage of the solid surface from the Langmuir–Freundlich equation is 9.73 mmol/g or 2 wt% at 298 K. The carbon with the largest hydrogen uptake capacity still cannot meet the US DOE target for hydrogen storage of 6 wt%. The isosteric heat of adsorption of carbon was 7 kJ/mol, typical of a physisorption character and in agreement with literature for the hydrogen–carbon interaction.
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