Activated Carbon Monoliths Research Articles

Valorisation of bamboo stalk waste: eco-friendly synthesis and characterisation of activated carbon monolith

ABSTRACT In contemporary waste management, the escalating volumes of bamboo stalk waste present a pressing environmental challenge, necessitating innovative and sustainable solutions. This research examined the properties of activated carbon monolith (ACM) derived from bamboo stalk (BS) using a facile method. Polystyrene resin and KOH were employed as an eco-binder and activator in the monolith synthesis, respectively. Analytical methods were employed to characterise the mechanical, morphological, elemental, and textual profiles of the monolith obtained. The study's results indicated the creation of a monolith characterised by a rough, amorphous shape firmly secured by the binder. It revealed a BET surface area measuring 265 m2/g and a pore diameter of 2.8 nm. The monolith displayed various irregular void pores, forming a mesoporous morphological network, along with sporadically distributed slivery-white dot-like particles on its heterogeneous surface. EDX analysis also revealed the BS-ACM is largely composed of carbon (77%), potassium (11%), oxygen (8%), and trace amounts of aluminium, gold, iron, and plutonium. The compressive strength test indicated a peak force of 21,536 N before any significant signs of appreciable deformation were observed, with the subsequent estimation of Young's modulus at 8.34 MPa. Beyond advancing bamboo waste valorisation, the research aligns with circular economy principles and sustainable practices, presenting a promising pathway for developing eco-friendly materials and contributing to a more sustainable and resource-efficient future.

Efficient Preparation and Optimization of Activated Carbon Monoliths from Resorcinol-Formaldehyde Resins for CO2 Capture

Activated carbon monoliths with developed porosity, high surface area and excellent adsorption properties were successfully prepared from resorcinol-formaldehyde resins using a physical activation method. The primary objective of this study was to examine the impact of key parameters, namely hexamethylenetetramine content (0.08–0.2 g), pyrolysis heating rate (5–20 °C/min) and activation time (1–7 h), on the final characteristics of the activated carbon in order to identify the optimal operating conditions to achieve the desired properties. All the cured resin samples were pyrolyzed at 900 °C under a nitrogen atmosphere, while the activation process took place in the presence of CO2. The evaluation of the activated carbon materials was based on the CO2 adsorption capacity and BET surface area, micropore area and total pore volume, which were employed as the criteria for selecting the optimal activated carbon. The synthesized porous carbon monoliths exhibited good properties: high BET surface area (900 m2/g), high CO2 adsorption capacity (5.33 mmol/g at 0 °C and 1 bar, 3.8 mmol/g at 25 °C and 1 bar) and good CO2 selectivity for CO2/N2 and CO2/CH4 mixtures. These results were obtained with a pyrolysis heating rate of 5 °C/min and a 3 h activation period.

Monoliths for gas storage manufactured with precision pore engineering using 3D-printed templates

A fast, customizable, and systematic route for producing activated carbon monoliths for gas storage with low interparticle porosity (9 % to 24 %) containing tailored macro channels is disclosed. The production uses a three-dimensional (3D)-printed polymeric lattice, rich in oxygen, as a sacrificial template. Its interstitial voids are filled with a phenolic resin that is carbonized and activated at 1173 K under carbon dioxide (CO2). Sequential pyrolysis occurs via thermal treatment with the 3D-printed lattice removed first, rendering macro channels with the same shape as the template in accurately placed positions. Resulting in adsorbents with interparticle porosities ranging from 10 % to 23 %, calculated from X-ray micro-computed tomography (micro-CT) images. The axial resolution of these macro channels was similar to the SLA printing layer thickness used of 100 µm. Making it the best resolution attained to date in fabricating monoliths via a 3D-printed sacrificial templating method. Breakthrough experiments indicated healthy macro channel connectivity due to the reduced mass transfer zone. Moreover, excellent mechanical integrity was displayed, with a monolith withstanding 900 N before excessive fracturing occurred despite the presence of macro channels. Therefore, this method emphasizes its use for gas storage applications by enabling the adsorbent material to efficiently utilize the volumetric space while allowing a fast rate of adsorption over the entire structure.

Cigarette filter butts-derived activated carbon with free binder electrode design for solid-state supercapacitor application

The aim of this research is to formulate activated carbon monolith from hazardous waste of cigarette filter butts (CFB) for electrode material monolith design in solid-state supercapacitor application. Potassium hydroxide (KOH) was selected for activation. The ratio of CFB to KOH varied in terms of weight between 1:2 and 1:4, thereby obtaining activated cigarette filter carbon (ACFC). The carbon that has been obtained is designed to be solidly in the form of an additive-free monolith. Monolith-activated carbon is physically characterized to examine thermal decomposition profiles (pre-carbonized), structure, composition, morphology, surface area adsorption, and electrochemical measurements. The optimum precursor was marked with high wettability with self-O-doped of 5.44%.in carbon content of 94.56%. Activated carbon electrodes prepared from ACFCs showed an optimum specific capacitance of ~87.17 F g-1, which is a more ecologically responsible method of producing supercapacitors.

Electrochemical Property of Activated Carbon Monolith from Potato for Supercapacitor Electrode

Electrochemical property of activated carbon monolith from potato was studied for possible application in supercapactor electrode. First, potato powder was purchased and used to prepare column shape samples via pressing. Then, they were subjected to two-step pyrolysis to avoid cracking, such as the 1st step at 300 °C at 0.5 °C/min heating rate and the 2nd pyrolysis at 400, 500 or 600 °C under N2 flow in a tube furnace. Next, the samples were cut into 1 mm thickness and then grinded into 0.5 mm, followed by immersing in 6M KOH solution and then the activation at 700 °C under N2 flow. Finally, the electrochemical properties of activated carbon monoliths were evaluated with a three-electrode system by cyclic voltammetry, galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). In addition, two-electrode system was also studied with the samples having highest specific capacitances, being from 400 °C pyrolysis. The samples were characterized by Raman, XRD, XPS and SEM, and specific surface area was also measured. Specific capacitance of 382 F/g was obtained from 400 °C pyrolysis, followed by 321 and 253 F/g from 500 and 600 pyrolysis, respectively.

Highly porous biocarbon monoliths for methane storage

Pollution, resulting from the use of gasoline and diesel fuels, presents an evident concern to environmental health and safety, contributing to greenhouse gases, smog, and a plethora of other hazards to everyday life. A variety of alternative energy sources and technologies are being considered towards the reduction of pollution from the use of fossil fuels, one such being natural gas. The bottleneck of technology for natural gas implementation is the storage and distribution at ambient condition with low-cost media. Activated carbon materials, having been further popularized for their adsorbent properties, have become established as a popular choice for natural gas storage thanks to their high pore volume and surface area and the abundant availability of carbon precursors. Herein, the synthesis of activated carbon monoliths and their application for methane adsorption, as it relates to natural gas storage, is described.

Active carbon monoliths from soft brown coal: A systematic study of their preparation, pore structure modification and characterization

High surface area active carbons in a ‘honeycomb monolith’ (HM) configuration can be prepared directly from soft brown coal by a novel approach. Kneading the coal into a plasticine consistency enables it to be extruded in HM form, then dried, carbonized and activated, retaining its structural integrity throughout these steps. Unlike higher rank coals, soft brown coal, which inherently contains relatively high oxygen functional group concentrations and high moisture contents, develops a strong H-bonding network during kneading. This opens the way to a novel and simpler method of preparing activated carbons in a monolith configuration. A systematic study was therefore conducted to evaluate the potential of these monoliths for being converted into higher value activated carbons by a low-cost process. Carbon honeycomb monoliths HMs from brown coal were modified by carbon dioxide (CO2) activation with a uniform domain size over a wider range of activation conditions (1–3 h, 750–950 °C) and the products were characterized by N2 adsorption (surface area and porosity), SEM, TEM, Raman spectroscopy, XPS and elemental analysis. The optimum conditions for development of porosity, aromaticity and a graphitizing structure were activation at 900 °C for 3 h. Interestingly, higher temperatures did not yield additional benefits. These materials should be useful in applications requiring highly ordered carbon.

CO2 adsorption on carbonaceous materials obtained from forestry and urban waste materials: a comparative study.

The increasing emissions of gaseous pollutants of anthropogenic origin, such as carbon dioxide (CO2), which causes global warming, have raised great interest in developing and improving processes that allow their mitigation. Among them, adsorption on porous materials has been proposed as a sustainable alternative. This work presents a study of CO2 equilibrium adsorption at low temperatures (0, 10, and 20°C) over a wide range of low pressures, on activated carbon derived from Eucalyptus (ES) and Patula pine (PP) forest waste, and carbonaceous material derived from waste tires (WT). The precursors of these materials were previously prepared, and their physicochemical properties were characterized. ES and PP were thermochemically treated with phosphoric acid, and WT was oxidized with nitric acid. Additionally, these materials were used to obtain monoliths using uniaxial compaction techniques and different binding agents, with better results obtained with montmorillonite. A total of six adsorbent solids had their textural and chemical properties characterized and were tested for CO2 adsorption. The highest specific surface area (1405 m2g-1), and micropore properties were found for activated carbon derived from Eucalyptus whose highest adsorption capacity ranged from 2.27mmolg-1 (at 0°C and 100kPa) to 1.60mmolg-1 (at 20°C and 100kPa). The activated carbon monoliths presented the lowest CO2 adsorption capacities; however, the studied materials showed high potential for CO2 capture and storage applications at high pressures. The isosteric heats of adsorption were also estimated for all the materials and ranged from 16 to 45kJmol-1 at very low coverage explained by the energetic heterogeneity and weak repulsive interactions among adsorbed CO2 molecules.

Continuous catalytic esterification using a solid acid activated carbon monolith: Comparison of granular and monolith forms with a commercial catalyst

2-hydroxyisobutyric acid (2-HIBA) is a significant platform chemical for the synthesis of various products and has been produced fermentatively. Recently, the esters of 2-HIBA have gained interest for applications in fragrances and as low-toxic solvents. In this study, solid acid (sulfonated) wood-based activated carbon granular (sGAC) and monolith (sACM) catalysts were employed for the continuous esterification of 2-hydroxyisobuytric acid with ethanol. The effect of reaction conditions, including pressure and feed flow rate (Ql) on ester (ethyl 2-hydroxyisobutyrate) space–time yield (STY), ester yield, and selectivity, were determined. A higher STY of 96 g Lcat-1h−1 (341 g kg cat-1h−1) and selectivity of 76 % was achieved with the sACM compared to the sGAC (87 g Lcat-1h−1, 60 %) at 150 °C, 300 psig, and 3 mL min−1 (18.5–20 min contact time). At optimum pressure (300 psig) and temperature (150 °C for sGAC and sACM; maximum of 120 °C for Amberlyst), and in time-on-stream studies, 2-HIBA turnover frequency and ester selectivity were higher for sGAC and sACM over Amberlyst-15. The solid acid carbon monolith is a promising catalyst for the continuous catalytic upgrading of biobased organic acids.

Synthesis and characterization of activated carbon monolith from African locust bean pods and polystyrene resin

ABSTRACT Activated carbon monoliths (ACMs) are single-piece, three-dimensional (3D) hierarchical porous structures with good permeability, high stability, and swift mass transfer features. Production of activated carbon monoliths from biomass has been identified as promising and sustainable for process development. In this study, ACM was synthesised from African locust bean pods and polystyrene resin. The pods were chemically activated using potassium hydroxide and then carbonised in a locally fabricated auto-thermal biomass-powered reactor for 100 minutes. The activated carbon was then hand-mixed with an organic binder, expanded polystyrene resin, and the product was thermally cured to form the ACM. The ACM was then characterised to determine its properties. Elemental determination revealed the ACM was mostly composed of carbon (63%), potassium (18%), oxygen (4%), and a host of other metals. SEM micrographs showed that the ACM’s surface is composed of irregular or heterogeneous-sized carbon materials firmly held by the resin with well-developed visible micropores. Some of the functional groups inherent in the ACM include hydroxyl, alkene, carbonyl, and alkyne. The ACM has a BET surface area of 237 m2/g, a pore diameter of 2.86 nm, and a Young modulus of 1.064 MPa. The synthesised ACM can be utilised as an adsorbent for pollution control, as a catalyst, and for electrochemical applications.

Synthesis of activated carbon monolith from lignocellulosic material: Evaluation of product quality

Synthesis of activated carbon monolith from lignocellulosic material: Evaluation of product quality

Adsorption Potential of Contaminants with Activated Carbon Monoliths from Dried Fruit Epicarp of Lecythis minor

Lecythis minor is a tree commonly known as Monkey pot tree. Its fruits are composed of urn-shaped epicarps, which are bulky ligneous capsules of slow degradation. Activated carbon monoliths were prepared from this fruit epicarp (bioresidue, the source of lignocellulosic matter) by chemical activation with H3PO4. The activation conditions were optimized using a central composite design, considering parameters of temperature, time, and chemical ratio as variables, and iodine and methylene blue number (IN and MBN), along with yield (Y), as responses. The best conditions for activation were 532°C (T), 1.5 h (t), and 1.5-g H3PO4/1-g raw matter (chemical ratio, CR), with response values of 996 mg I/1-g activated carbon (AC) (IN), 361-mg MB/1-g AC (MBN), and 42% (Y). Likewise, the physicochemical/surface characterization of the activated carbon Lecythis minor (ACLM) allowed establishing that it developed micro- and mesopores (Vmicro=0.72 cm3/g; Vmeso=0.87 cm3/g), as well as ultra-microporosity, a BET surface area of 2,164 m2/g, and a total pore volume of 1.7 cm3/g; also, the removal percentages of the emerging contaminants diclofenac and cephalexin in water were above 96%. It is concluded that fruit epicarp of L. minor is a natural-origin resource to produce AC monoliths, with satisfactory yield, desirable surface development, and high thermal stability, capable of adsorption and removal of pharmaceutical products, and other emergent contaminants from water bodies.

Preparation of activated carbon monolith from waste biomass using solvated polystyrene-based binder

ABSTRACT This study demonstrated the production of activated carbon monoliths from biomass waste (Delonix regia pods) using a facile method. This was achieved using solvated polystyrene as the binder, which has never been achieved in the past, and KOH as the activating agent. The monolith’s pore structures, functional group, morphology, and elemental composition were all investigated. According to the results, the monolith was found to have mesoporous properties, with a surface area of 314.9 m2/g and a pore size of 2.45 nm. Several functional groups, including nitro, carboxyl, and carbonyl groups, were identified, which confirms the potential applications of the monolith. Meanwhile, the KOH activator causes the production of particles with various clusters. The results demonstrated that solvated polystyrene has the ability to function as a binder in monolithic formation and are comparable to those of earlier investigations.

3D printing of powdered activated carbon monoliths: Effect of structuring on physicochemical and mechanical properties and its influence on the adsorption performance

Herein, a methodology for 3D printing of activated carbon powders in monolithic form using direct ink writing and carboxymethylcellulose as binder is reported, along with the effect on their physicochemical and mechanical properties. Monoliths with different wall diameters (0.42, 0.62, and 0.82 mm) and infill percentages (30, 50, and 70%) were designed and manufactured. The monoliths were heat-treated under a nitrogen atmosphere at 400 °C and 600 °C to remove the volatile material from the binder used. The monoliths showed a decrease in dimension of less than 8% from their designed values, attributed to the volatilization of water present in the binder solution in the drying and heat-treatment process. The printed monoliths presented pore distributions similar to those of their powdered counterparts. The isoelectric point of the monoliths increased relative to that of the powdered material and became more basic as the heat treatment temperature increased. The monoliths presented compressive strengths from 0.58 to 3.53 MPa. The analysis of variance of the compressive strength showed that the wall diameter and temperature are the most influential treatment parameters. The printed monoliths exhibited similar CO 2 adsorption capacity (0.37 mol Kg -1 at 10 kPa and 25°C) compared to the powder precursor. Fixed bed tests demonstrated that the 3D printed monoliths enhanced the mass transfer compared to conventionally extruded pelletswith same wall diameter.

Electrical swing adsorption on 3D-printed activated carbon monoliths for CO2 capture from biogas

Direct, resistive or Joule heating of the adsorbent allows for the intensification of Thermal Swing Adsorption processes by reducing process cycle time and reducing heat losses. In this work, an electrically conductive activated carbon monolith was 3D-printed using a potassium silicate binder. The monolith was assessed for biogas upgrading, using Joule heating for regeneration of the monolith. The electrification of the 3D-printed monolith resulted in very rapid and homogenous heating, to 150 °C in less than 30 s at a potential of 8 V. Next, the monolith was subjected to cyclic adsorption-desorption experiments for CO2 capture from a synthetic biogas mixture (30 v% CO2 – 70 v% CH4). The main parameters in ESA, namely voltage, electrification time, purge conditions and an additional rinsing step were investigated by determining the impact on the heating, regeneration efficiency and purity. Increasing the voltage from 4 V to 8 V step is preferred for recovery (82–95%) as well as for energy consumption, as it increases the efficiency (27.1–28.4%). It was also found that using the same amount of purge gas, it is preferred to use a higher purge flow rate for a shorter time (100 Nml/min for 15 s) over a lower purge flow rate for a longer time (50 Nml/min for 30 s). This benefits both recovery (87.3% vs 84.0%) and purity (84.5% vs 83.4%). Lastly, the benefit of adding a rinse step to increase the purity was demonstrated, where having a rinse step prior to electrification allowed to augment the total purity from 58% to 81.2%, while the regeneration of the monolith was as efficient.

Integration of the adsorption and electro-oxidation process using 3D printed activated carbon monoliths for the degradation of pharmaceutical compounds

A three-dimensional electrode reactor (3DER) was developed and evaluated for the degradation of recalcitrant pharmaceutical compounds such as diclofenac (DCF) and acetylsalicylic acid (ASA) from water, using for the first-time activated carbon monoliths (ACm) fabricated by 3D printing as a third electrode in the oxidation process. The degradation and mineralization percentages for the 3DER system were 81% and 74% respectively, which was up to 2.5 times higher than the system without using a third electrode. On the other hand, synergy calculations were performed, obtaining values of up to 35% when the integrated adsorption-oxidation technology was used compared to the degradations obtained by both processes sequentially. Operating parameters such as initial ACm saturation time (60 and 240 min) and applied voltage (0.6 and 0.9 V) were evaluated. Kinetic constants (kapp) were 3.2 times larger when the saturation time was shorter and the voltage higher. In addition, ACm regeneration tests were carried out to evaluate the regeneration of the material during the process, obtaining regenerations of up to 99%. Finally, the energy consumption by order of magnitude (EEO) was calculated for the best operating conditions in the 3DER, obtaining a value of 2.06 kWh/m3, which implies 50% less energy than the system without ACm. Despite the challenges in understanding the integrated processes in adsorption-electrooxidation, this study proposes compact and well-structured structures as an alternative for process optimization in 3DER.

Comparing column dynamics in the liquid and vapor phase adsorption of biobutanol on an activated carbon monolith

Comparing column dynamics in the liquid and vapor phase adsorption of biobutanol on an activated carbon monolith

3D-printed activated carbon for post-combustion CO2 capture

The applicability of 3D-printed activated carbons for their use to CO 2 capture in post-combustion streams and the influence of activation conditions on CO 2 uptake and CO 2 to N 2 selectivity were studied. For two monoliths with the same open cellular foam geometry but low and high burnoff during activation, a series of fixed-bed breakthrough adsorption experiments under typical post-combustion conditions, in a wide range of temperature (313 and 373 K), and partial pressure of CO 2 up to 120 kPa were carried out. It is shown that the higher burnoff during activation of the 3D printed carbon enhances the adsorption capacity of CO 2 and N 2 due to the increased specific surface area with sorption uptakes that can reach 3.17 mol/kg at 313 K and 120 kPa. Nevertheless, the lower burnoff time on monolith 1 leads to higher selectivity of CO 2 over N 2 , up to 18 against 10 on monolith 2, considering a binary interaction to a mixture of CO 2 /N 2 (15/85 vol%) at 313 K. The single and multicomponent adsorption equilibrium is conveniently described through the dual-site Langmuir isotherm model, while the breakthrough curves simulated using a dynamic fixed-bed adsorption linear driving force model. Working capacities for the 3D printed carbon with lower burnoff time lead to the best results, varying of 0.15–1.1 mol/kg for the regeneration temperature 300–390 K. Finally, consecutive adsorption-desorption experiments show excellent stability and regenerability for both 3D printed activated carbon monoliths and the whole study underpins the high potential of these materials for CO 2 capture in post-combustion streams. • Printed activated carbon monoliths were developed as adsorbents for CO 2 capture. • Thermal treatment affects the selectivity of CO 2 over N 2 on the monoliths. • CO 2 working capacity on the monolith M1 is 17% higher than monolith M2. • 3D-printed monoliths show high stability and regenerability over consecutive cycles. • A mathematical model has been developed for process simulation to CO 2 capture.

Ammonia Plasma Treatment of Porous Activated Carbon Monoliths for Enhanced Co2 Capture

Ammonia Plasma Treatment of Porous Activated Carbon Monoliths for Enhanced Co2 Capture

Porous activated carbon monoliths as a novel target material for the production of 99Mo by fission

Porous activated carbon monoliths as a novel target material for the production of 99Mo by fission