Activated Carbon Surface Research Articles

Hydrophobic modification of walnut shell biomass-derived porous carbon for the adsorption of VOCs at high humidity

Volatile organic compounds (VOCs) often contain water vapor in their exhaust emissions, resulting in the deterioration of the adsorption capacity of activated carbon (AC). A hydrophobic walnut shell biomass-derived AC using polytetrafluoroethylene (PTFE) and polydimethylsiloxane-coated SiO2 (PDMS/SiO2) was developed to improve the selectivity of VOCs under high humidity conditions. These modified ACs were systematically characterized, and dynamic adsorption behaviors of VOCs such as toluene, acetone and their mixtures at the relative humidity (RH) between 0 and 90 % were conducted. The results showed that walnut shell biomass-derived AC has large specific surface area (1853 m2/g) and total pore volume (1.27 cm3/g), strong hydrophilicity (water contact angle of 6.3°), abundant oxygen-containing groups (OH, CO, CO) and aromatic rings. The coating of PDMS/SiO2-PTFE reduces the surface area and total pore volume of AC, but it creates a double-layer rough structure on the AC surface and introduces CF and SiOSi hydrophobic groups, which achieves a water contact angle of 152.8° for 25PSP/AC. The Yoon-Nelson model is suitable to describe the dynamic adsorption process of single- toluene or acetone under dry/humid condition but not suitable for their mixtures. At RH 90 %, PDMS/SiO2-PTFE modified AC significantly increases the adsorption capacity of toluene but is not obviously improved for acetone, which is due to the different polarity of toluene and acetone. PDMS/SiO2-PTFE films on AC have good thermal stability before 500 °C and the hydrophobicity does not change after multi-regeneration at 200 °C. Therefore, PDMS/SiO2-PTFE modified AC has shown great potential as adsorbent to remove the toluene from the humid condition.

Ethylenediamine-modified activated carbon photocatalyst with the highest TiO2 attachment/dispersion for improved photodegradation of sulfamethazine

Due to the high pollution caused by several molecules, it is necessary to develop efficient materials to degrade these contaminants. Activated carbons (ACs) are exceptional and versatile adsorbents, and titanium dioxide (TiO2) has remarkable photocatalytic properties. The combination of activated carbon (AC) and TiO2 provides a system capable of simultaneously adsorbing and degrading several emerging contaminants. This study presents a new absorbent/photocatalyst material by modifying the AC with ethylenediamine (ET) and impregnated with TiO2 (AC-ET/TiO2). AC modified with amine groups keeps the TiO2 nanoparticles more bound onto its surface. A study exploring the dispersion onto the surface of unmodified AC revealed that the material lacked stability, releasing TiO2 particles into the solution. The characterization by nitrogen adsorption/desorption isotherms showed a mesoporous material that can have a synergic effect between the adsorption and photocatalysis. The photocatalyst was analyzed by field emission gun scanning electron microscopy (FEG-SEM) and demonstrated the presence of TiO2 dispersed on the surface. The AC-ET/TiO2 exhibited an improved photodegradation of sulfamethazine (SMT), superior to the commercial TiO2 – P25, by removing more than 90% of the SMT in 2 h of UV light irradiation. The reuse of the AC-ET/90TiO2 showed that this material is active after three photoreactions. In conclusion, amino groups insertion into AC is essential for the stability of the TiO2 on the surface. Besides, this material has increased photocatalytic activity with speedy degradation of SMT.

Simulation of the VOC Adsorption Mechanism on Activated Carbon Surface by Nitrogen-Containing Functional Groups

In this paper, the physical adsorption of volatile organic compounds (VOCs) such as methyl chloride (CH3Cl), carbon disulfide (CS2), dimethyl sulfide (C2H6S), and benzene (C6H6) by three models of activated carbon (without a functional group, with a pyridine-containing functional group, and with a pyrrole-containing functional group) was simulated. The surface electrostatic potential (ESP), physical adsorption energy, and non-covalent interaction between activated carbon and VOC molecules were analyzed based on the density functional theory (DFT). The effect mechanism of nitrogen-containing functional groups on VOC adsorption by activated carbon was determined. Our simulations showed that nitrogen-containing functional groups can change the surface ESP and polarity of activated carbon. The pyrrole functional group is conducive to CH3Cl and CS2 adsorption on the activated carbon plane, while the pyridine functional group is relatively small or even unfavorable for CH3Cl and CS2 adsorption on the activated carbon plane. The promotional effect of the pyrrole functional group on the adsorption of C2H6S is more significant than that of the pyridine functional group. The adsorption of C6H6 on activated carbon occurs through parallel-displaced π–π stacking interactions, in which functional groups have little influence on it. The adsorption energy of VOCs on the activated carbon plane is higher than that at the edge, so VOCs are more likely to be adsorbed on the activated carbon plane.

Zinc Chloride as a Catalyst in Hydrothermal Carbonization of Cocoa Pods Husk

In this study, we have successfully synthesized a high surface area of activated carbons (ACs) from cocoa pod husk (CPH) by using a combination of hydrothermal carbonization (HTC) and chemical activation in the presence of ZnCl2 as both of catalyst as well as activating agent. During HTC, the effect of HTC temperature (200 and 225 °C) and ZnCl2 to biomass mass ratio (1:1, 2:1, 3:1) as a catalyst to the characteristics of the obtained hydrochar (HC) and ACs were investigated. The obtained hydrochar (HCs) was then processed by using ZnCl2 chemical activation with a fixed HC to ZnCl2 mass ratio of 1:4 and the mixture was pyrolyzed at 600 °C for 1 h under an inert atmosphere. The results showed that the addition of catalyst during HTC presented different AC morphology, where the carbon samples were decorated with carbon microspheres. An increase of surface area was observed, where the ACs synthesized from catalyzed HC at biomass to ZnCl2 ratio of 1:3 at temperature 200 °C gave a higher surface area of 1954 m2/g compared to that of without catalyst (1165 m2/g). The catalysis effect was more profound at the HTC temperature of 200 °C compared to 225 °C, as reflected in the significant increase of AC surface area. The addition of a catalyst creates ACs with narrow pore distribution compared to that of synthesized in the absence of a catalyst. It was also observed that the ACs from catalyzed hydrochar possessed higher oxygenated functional groups (OFG) than those without catalysts.

Fe (II) Immobilized on Activated Carbon Surface as a Catalyst for elimination of Alizarin Red S at the Presence of Hydrogen Peroxide

Fe (II) Immobilized on Activated Carbon Surface as a Catalyst for elimination of Alizarin Red S at the Presence of Hydrogen Peroxide

Activated-carbon-induced morphological and crystal transformation of α-FeOOH for efficient catalytic removal of hydrogen sulfide from blast furnace gas

The performance of FeOOH for the removal of hydrogen sulfide (H2S) has been widely investigated. However, the harsh conditions of use and the difficulty of regeneration limit its practical application. In this study, FeOOH was loaded on activated carbon (AC) by a hydrothermal method to obtain a series of XF-AC catalysts for the removal of H2S from blast furnace gas (BFG). Among these catalysts, 3F-AC exhibited a high penetrating sulfur capacity of 482.3 mg/g and good regeneration performance. It is noteworthy that the use of AC as the support induced the transformation of α-FeOOH crystals into amorphous FeOOH and affected their morphology, and uniformly dispersed nanoparticles rather than agglomerated acicular crystals appeared on the surface of AC. The presence of amorphous FeOOH modulated the basic sites and surface hydroxyl groups of the catalysts while generating hydroxyl radicals during the reaction, thus improving the adsorption and oxidation of H2S. More importantly, the structural properties (surface area and pore volume) of 3F-AC enhanced the storage capacity of elemental sulfur and reduced the formation of by-products. The cyclic catalytic role of Fe3+/Fe2+ played an important role in the oxidation process. This work provides a simple and effective strategy for the design of BFG desulfurization catalysts.

Adsorption and interaction of CO2 and N2O on NaOH-impregnated activated carbon surface

Adsorption and interaction of CO2 and N2O on NaOH-impregnated activated carbon surface

Harnessing the photocatalytic potential of bismuth ferrite-activated carbon nanocomposite (BFO-AC) for Staphylococcus aureus decontamination under visible light.

In response to the escalating global issue of microbial contamination, this study introduces a breakthrough photocatalyst: bismuth ferrite-activated carbon (BFO-AC) for visible light-driven disinfection, specifically targeting the Gram-positive bacterium Staphylococcus aureus (S. aureus). Employing an ultrasonication method, we synthesized various BFO-AC ratios and subjected them to comprehensive characterization. Remarkably, the bismuth ferrite-activated carbon 1:1.5 ratio (BA 1:1.5) nanocomposite exhibited the narrowest band gap of 1.86 eV. Notably, BA (1:1.5) demonstrated an exceptional BET surface area of 862.99 m2/g, a remarkable improvement compared to pristine BFO with only 27.61 m2/g. Further investigation through FE-SEM unveiled the presence of BFO nanoparticles on the activated carbon surface. Crucially, the photocatalytic efficacy of BA (1:1.5) towards S. aureus reached its zenith, achieving complete inactivation in just 60 min. TEM analysis revealed severe damage and rupture of bacterial cells, affirming the potent disinfection capabilities of BA (1:1.5). This exceptional disinfection efficiency underscores the promising potential of BA (1:1.5) for the treatment of contaminated water sources. Importantly, our results underscore the enhanced photocatalytic performance with an increased content of activated carbon, suggesting a promising avenue for more effective microorganism inactivation.

Friction Evolution of Graphite Bearing Impregnated with Polymer Subjected to Vibration Fretting at High Temperature

To address friction and wear challenges in dry contacts, manufacturers often employ self-lubricating materials. Graphite and its derivatives stand out as particularly suitable due to their exceptional tribological properties. However, under intense friction conditions, graphite can experience a decline in lubricating efficiency due to severe abrasive wear. This abrasive damage results in elevated activated carbon surfaces with increased surface energy, fostering greater adhesion between sliding surfaces. The low friction coefficient of graphite is not an inherent property but rather a consequence of water vapor adsorption by the material. Beyond 150 °C, desorption of the vapor occurs, leading to a transition in the friction coefficient from µ = 0.1 to µ = 0.6. To address this issue, impregnation solutions for self-lubricating materials have been developed, with various compositions tailored to specific objectives. Common types include molybdenum disulfide, soft metals and polymers. In this predominantly experimental study, the impact of polymer impregnation on the evolution of friction force and wear rate in graphite material bearings subjected to a dry fretting contact under severe thermal stresses at 270 °C was investigated. Additionally, the mechanical stresses in the bearings throughout different phases of our tests were analyzed using a numerical model.

Enhancing energy carrier gas storage: Novel MOF-decorated carbons with high affinity toward methane and hydrogen

The low volumetric density of alternative energy sources, like methane and hydrogen, makes their efficient storage challenging. This issue hinders their widespread adoption as clean energy carriers and limits their potential to address the energy crisis and reduce CO2 emissions. To overcome this limitation, a novel hybrid adsorbent was synthesised by incorporating MIL-101(Cr) and pitch-based activated carbon (AC), and its potential for methane and hydrogen adsorption was evaluated through experimental and molecular simulation methods. The adsorption capacity of CH4 and H2 on the MOF-doped ACs was simulated using Grand Canonical Monte Carlo (GCMC). Through the ex-situ method, varying amounts of MIL-101(Cr) were integrated onto the surface of AC, resulting in a nanocomposite with enhanced gas uptake properties. The AC/MIL-101(Cr) nanocomposite with 50 wt% MOF-doping exhibited superior methane loading performance (12.21 mmol.g-1) at room temperature and 35 bar, surpassing MIL-101(Cr) by approximately 20% (10.15 mmol.g-1). In terms of hydrogen adsorption, the AC/MIL-101 composites demonstrated advantageous gas uptake at low pressures (P ≤ 4.5 bar) due to a decrease in pore diameter (2.17 nm to 1.61 nm) and an increase in the number of micropores (60% to 78%). Conversely, at higher pressures, the dominant factor influencing H2 storage was the surface area.

G‐C3N4 Coating Enhanced Cu@AC for Catalytic Wet Air Oxidation of Phenol under Mild Conditions

AbstractA Cu‐based supported catalyst with g‐C3N4 coating (Cu/g‐C3N4@AC) was prepared by facile in‐situ growth over activated carbon surface with urea and Cu(NO3)2, and the catalytic performance for wet air oxidation of phenolic wastewater was investigated. The effects of different reaction conditions (catalyst, temperature, pressure and pH) were examined. The results show that under the catalysis of Cu/g‐C3N4@AC phenol could be completely oxidized at 120 °C and 0.5 MPa O2 with COD removal of 92.6 % (from 4883 mg/L to 361 mg/L). TEM, BET, XRD, FTIR and XPS characterizations showed that g‐C3N4 coating could strengthen the metal surface interaction via the Cu−N−C bonds formation, thus suppressing the aggregation of the active components on the surface and mitigating the catalyst deactivation. Moreover, the interaction between the Cu species and the g‐C3N4 structure facilitates the electron transfer and thus significantly boost up the catalytic activity. These findings help explore efficient catalysts for the wastewater treatment via wet air oxidation under mild conditions.

Persistent free radicals of activated carbon induce highly toxic by-products formation during chlorination

Both activated carbon (AC) and chlorine are commonly used in water treatment processes and thus the exposure of chlorine to AC surface is unavoidable under some circumstances. Therefore, evaluating the effects of AC, particularly the persistent free radicals (PFRs) of AC on the chlorination by-products is critical for drinking water safety. Here, through comparison of the chlorination process of different ACs with similar pore structure but different PFR intensities, it was found that AC with more PFRs generated more unknown by-products with lower relative cell viability (85%). The Fourier transform ion cyclotron resonance- mass spectrometry results showed that the proportions of one-chlorine and nitrogen containing by-products generated by AC with higher PFR intensity were 19.6% and 16.9%, respectively, which were higher than those generated by AC with lower PFR intensity. Furthermore, the polycyclic aromatic compounds and polyphenols with high toxicity were only found in the chlorination products of AC with high PFR intensity. The PFRs of AC could promote the chlorine decay and induce the generation of superoxide radical and chlorine radical, and thus led to the formation of more toxic by-products. This study provides new insights into the risks of water chlorination process and by-product formation in the presence of AC.

Preparation of nitrogen-doped activated carbon used for catalytic oxidation removal of H2S

In this study, nitrogen-doped modified activated carbons were synthesized for H2S removal from Zhuxi activated carbon and 4,4′-bipyridine as raw material and nitrogen source, respectively. The synthesis strategy was hydrothermal treatment and subsequent NH3 annealing, and the formation and conversion patterns of the different N configurations were investigated. When the annealing temperatures were 500 °C and 600 °C, N-5 account for the majority. As the annealing temperature increased, the proportion of N-6 gradually increased. After the temperature increased to 1000 °C, N-5 and N-6 were converted to N-Q to a certain degree, while the amount of nitrogen doping decreased significantly. The sample H160-0.2-800 exhibited excellent H2S removal with a high sulfur capacity of up to 206.89 mg/g, significantly higher than that of the original activated carbon ZX1200 (67.56 mg/g). The reason for this is that the micropores (Vmic = 0.5155 cm3/g) and specific surface area (SBET = 1369.5 m2/g) of the modified activated carbon are more developed than those of the original activated carbon. A high nitrogen content (3.14 wt%) and N-6 configuration proportion (73.56 %) are significant reasons for the excellent adsorption properties. The mechanism of the catalytic oxidation was investigated. The introduction of surface nitrogen-containing functional groups alkalizes the activated carbon surface, enhancing the adsorption and dissociation of H2S and O2 and facilitating the formation of sulfur radicals and elemental sulfur.

Transformation of Al Species on Carbon Surfaces: Effects of Al Species and Carbon Surface Oxygen Groups.

Control of residual Al is critical, owing to its high tendency to accumulate in drinking water distribution systems and its potential risks to human health. Herein, the effects of surface properties of activated carbon (AC) on intercepting different Al species (including monomeric Al and polymeric Al species-Al13) are evaluated. The results showed that Al in the form of monomers was considerably adsorbed by AC; whereas Al in the form of polymeric Al13 was held to a much lower degree by AC, and the effluent Al concentration was even higher than that without AC. By comparing virgin AC and hydrogen thermal treated AC, the surface oxygen functional groups on the AC were proposed to play a critical role in the transformation of Al species. The oxygen functional groups on the AC surface can directly form complexes with monomeric Al, thereby inducing the binding of monomeric Al on the AC surface. However, the AC surface oxygen groups could not bind to polymeric Al13, and the interaction between AC surface oxygen groups and polymeric Al13 partially transforms Al13 into monomeric Al species, which inhibited the self-aggregation of Al13. This study aims to provide new insights into the control of residual Al in water treatment plants to ensure drinking water safety.

Effect of Si Doping and Active Carbon Surface Modifications on the Structure and Electrical Performance of Li4Ti5O12 Anode Material for Lithium-Ion Batteries

Effect of Si Doping and Active Carbon Surface Modifications on the Structure and Electrical Performance of Li4Ti5O12 Anode Material for Lithium-Ion Batteries

Preparation of surface-active carbon dots with fluorocarbon and hydrocarbon hybrid chains via a one-pot solvothermal technique and their characterization and potential applications

Amphiphilic carbon dots (CDs) are new surface-active materials that exhibit several advantages over conventional small surfactants, such as improved stability and reduced toxicity. However, unlike for conventional small surfactants, amphiphilic CDs that simultaneously exhibit excellent surface and interfacial activities have never been achieved. Herein we prepare new amphiphilic CDs with fluorocarbon and hydrocarbon hybrid hydrophobic chains (FH-CDs) using a facile one-pot solvothermal technique. The obtained FH-CDs showed excellent surface and interfacial activities, and reduced the surface tension at critical micelle concentration and the oil-water interfacial tension to 16.7 and 2.2 mN/m, respectively. Comparison with control CDs bearing only non-hybrid hydrophobic chains demonstrated that decorating CDs with fluorocarbon and hydrocarbon hybrid chains contributed to the excellent interfacial activity, while only fluorocarbon chains contributed to good surface activity. The excellent surface and interfacial activities made FH-CDs good emulsifiers for the formation of stable water-in-oil emulsions and for the preparation of relatively uniform polystyrene spheres via emulsion polymerization. Moreover, FH-CD was a good wetting agent, whose aqueous solution could wet numerous different surfaces, including the commonly non-wettable amphiphobic polytetrafluoroethylene.

Nanodisk–like activated carbon-branched polyamine for adsorption and degradation of gaseous formaldehyde

The adsorption potential of activated carbon (AC) is determined to a large extent by an interplay between its surface functional groups and target pollutants like volatile organic compounds (VOCs). Herein, we present a new approach to improve such property through the creation of nanodisk-like material by modifying the surface and morphology of AC with branched polyamine (BPA). The formulated AC-BPA possesses large number of surface functional moieties (e.g., amine, –COOH, –OH, and Cl−) to facilitate physical, chemical, and reactive adsorption to tackle a common air pollutant such as formaldehyde (FA). Despite its reduction in surface area (relative to AC), AC-BPA was demonstrated to have a significantly large potential for reactive adsorption and catalytic oxidation (RACO) against FA with high adsorption capacity (82.3 mg g−1) and partition coefficient (PC = of 0.64 mol kg−1 Pa−1) under dry condition. Interestingly, a noticeable enhancement in its performance is attained by the presence of moisture (e.g., 100 % RH) as evidenced by adsorption capacity of 144.3 mg g−1 (PC of 1.25 mol kg−1 Pa−1). This can be attributed to its rich heteroatom content (e.g., COO− and Cl−), possibly inducing partial ionization of water molecules and generating secondary active sites for FA adsorption. In-situ diffuse reflectance infrared Fourier-transform spectroscopy revealed that AC-BPA catalyzed the chemical transformation of FA into methylol adducts, H2O, and CO2. These findings indicate that FA adsorption is primarily influenced by surface functional groups rather than by surface area. This study is expected to pave the way for designing metal-free high-performance RACO materials against FA under ambient conditions.

REGENERATION OF ACTIVATED CARBON AFTER ADSORPTION OF DYE USING PERACETIC ACID. PART 2: ROLE OF PERACETIC ACID IN THE OXIDATION STEP

This study focuses on investigating how peracetic acids can be used to regenerate activated carbon and remove methylene blue. The research provides valuable insights into the process of regeneration and the effectiveness of peracetic acids in revitalizing the activated carbon surface. By conducting desorption experiments, we observed that approximately 4.5% of the initially adsorbed methylene blue was released into the washing solution, while the majority (95.5%) remained strongly attached to the activated carbon. Through Fourier-transform infrared spectroscopy analysis, it was determined that after undergoing oxidation by peracetic acids, the regenerated carbon surface exhibited the emergence of additional functional groups, such as hydroxyl and carboxyl groups. Liquid phase chromatography analysis confirmed the successful removal of methylene blue from the liquid phase, indicating the high selectivity of the peracetic acids/Co2+ system in treating the adsorbed methylene blue molecules. Furthermore, Brunauer - Emmett-Teller analysis demonstrated that the regenerated carbon retained its surface characteristics and porous structure, with only slight reductions in specific surface area and total pore volume. These findings emphasize the effectiveness of peracetic acids in the regeneration process and its potential to improve the reusability of activated carbon in industrial applications. The study provides valuable insights for further research on the regeneration mechanism and the optimization of regeneration conditions utilizing peracetic acids.

Recent research progress on modified activated carbon from biomass for the treatment of wastewater: A critical review

AbstractWater is one of the most vital substances on the planet that supports and sustains life. One of the most crucial challenges of our time is water. It is a basic need for all living beings. Worldwide, a large amount of wastewater is produced daily from home and industrial sources, creating problems such a water shortage and environmental degradation. Water that has already been utilized is called wastewater. It has been observed that the wastewater released varies in composition according to the kind of industry and the municipal sources. Microorganisms, heavy metals, organic pollutants, pesticides, phthalates, polycyclic aromatic hydrocarbons, emerging contaminants, and potentially dangerous wastes are all present in it. Among the most effective methods for removing these contaminants in recent times is the adsorption phenomenon. The presence of various contaminants in wastewater can be efficiently reduced by the simple, efficient, and affordable process of adsorption. Selection of suitable adsorbent is the crucial technique in this operation of adsorption. A versatile adsorbent is activated carbon (AC). Their maximum surface reactivity, large surface area, and microporous form are what give them their adsorptive capabilities. To enable recovery and filter, eliminate, or change the toxic components from gases and liquid solutions, they are used to purify, decolorize, deodorize, dechlorinate, separate, and concentrate. As a result, a variety of industries are interested in AC for the process of adsorption. This review paper briefs the characteristics of AC and their preparation techniques. It discusses the numerous approaches for modifying the surface of AC with significant adsorption capability. It also emphasizes the usage of AC with the elimination of different toxins found in waste water.

Study on the mechanism of constructing structure defects on surface of activated carbon with carbon black to promote hydrogen production by thermal-decomposition of methane

Hydrogen production from catalytic decomposition of methane is a promising method of hydrogen production that caters to low-carbon energy sources. The low cost and easy regeneration of carbon-based catalysts is more compatible with the concept of sustainability than metal catalysts. The key problem with catalytic decomposition using activated carbon is the rapid deactivation of the activated carbon due to structural changes caused by the production and accumulation of deposited carbon. Carbon black, on the other hand, exhibits slowly increasing catalytic performance in the catalytic decomposition of methane. Therefore, combining the properties of the two, it is proposed to disperse and load the nano conductive carbon black onto the surface of urea-modified activated carbon, so that the activated carbon can also have self-repairing ability at a later stage. It is shown that the combined application of carbon black loading and urea modification enhances the structural properties of the activated carbon by enriching the microporous structure of the activated carbon surface, increasing the disorder of its crystal structure, and altering the content and concentration of oxygen-containing functional groups on the surface. These microstructural changes combined to enhance the overall catalytic activity of the activated carbon, including its late deactivation time and catalytic performance after deactivation.