Adsorption Of Volatile Organic Compounds Research Articles

Efficient Catalytic Elimination of Toxic Volatile Organic Compounds via Advanced Oxidation Process Wet Scrubbing with Bifunctional Cobalt Sulfide/Activated Carbon Catalysts.

Advanced oxidation process (AOP) wet scrubber is a powerful and clean technology for organic pollutant treatment but still presents great challenges in removing the highly toxic and hydrophobic volatile organic compounds (VOCs). Herein, we elaborately designed a bifunctional cobalt sulfide (CoS2)/activated carbon (AC) catalyst to activate peroxymonosulfate (PMS) for efficient toxic VOC removal in an AOP wet scrubber. By combining the excellent VOC adsorption capacity of AC with the highly efficient PMS activation activity of CoS2, CoS2/AC can rapidly capture VOCs from the gas phase to proceed with the SO4•- and HO• radical-induced oxidation reaction. More than 90% of aromatic VOCs were removed over a wide pH range (3-11) with low Co ion leaching (0.19 mg/L). The electron-rich sulfur vacancies and low-valence Co species were the main active sites for PMS activation. SO4•- was mainly responsible for the initial oxidation of VOCs, while HO• and O2 acted in the subsequent ring-opening and mineralization processes of intermediates. No gaseous intermediates from VOC oxidation were detected, and the highly toxic liquid intermediates like benzene were also greatly decreased, thus effectively reducing the health toxicity associated with byproduct emissions. This work provided a comprehensive understanding of the deep oxidation of VOCs via AOP wet scrubber, significantly accelerating its application in environmental remediation.

Micro- and Mesoporous Structural Effects of Beta Zeolites for Volatile Organic Compound Sorption.

To fully exploit pore engineering in the design of more efficient zeolite adsorbents for volatile organic compound (VOC) treatment, the roles of meso- and micropores need to be clarified to provide the theoretical basis and feasible measures. In this work, the three VOC sorption properties of conventional and hierarchical porous beta zeolites were comparatively investigated to study the roles of meso- and micropores. There is a division of functions between micro- and mesopores, with micropores being the main VOC adsorption sites and mesopores greatly enhancing VOC diffusion and adsorbent reusability. On the one hand, micropores should be preserved as much as possible because obtaining mesopores by sacrificing micropores (i.e., alkali treatment) results in 28-60% decreases in adsorption capacities. On the other hand, mesopore introduction is highly desirable, which results in an enhancement of VOC intraparticle diffusion rates by 1.3-2.3 times (at the VOC concentration of 600 ppm) and chlorobenzene adsorption capacity on the 20th cycle increasing from 78% of the initial value to 89 and 93%. The findings may provide valuable information about zeolite-based adsorbents for adsorption removal or recovery of VOCs.

Direct activation and hydrophobic modification of biomass-derived hierarchical porous carbon for toluene adsorption under high humidity

Hierarchical porous starch-based carbon (PSC) with tunable pore structure (surface area 1974 ∼ 2721 m2/g and pore volume 0.80 ∼ 1.74 cm3/g) was prepared through direct activation. Due to its high surface area and large pore volume, PSC shows great potential for volatile organic compounds (VOCs) removal. Water vapor commonly exists along with VOCs and the competitive adsorption between VOCs and water vapor would significantly restrict the VOCs adsorption of PSC under high humidity. To address this issue, hydrophobic porous starch-based carbon composite (PSCC) was also prepared by physically mixing PSC with poly-divinylbenzene (PDVB) for toluene adsorption under high humidity to suppress the influence of water vapor. As relative humidity increased from 0 % to 80 %, the toluene adsorption capacity of PSC-2 decreased by 46 % while PSCC only experienced a decrease of 22 %. PSCC could also maintain its toluene adsorption performance (close to 100 %) after five adsorption–desorption cycles. Theoretical computations were also proved that the addition of PDVB inhibits water vapor adsorption and promotes its desorption, thereby enhancing the toluene adsorption of PSCC under high humidity. This work provides a controllable preparation and facile modification of porous carbon to improve its toluene adsorption under high humidity, offering a great application prospect for VOCs removal.

Melamine Network as a Solution for Significant Enhancement of the Mechanical, Adsorptive, and Surface Properties in a Novel Carbon Nanomaterial-Silica Aerogel Composite.

Silica aerogels exhibit exceptional characteristics such as mesoporosity, light weight, high surface area, and pore volume. Nevertheless, their utilization in industrial settings remains constrained due to their brittleness, moisture sensitivity, and costly synthesis procedure. Several studies have proved that adding nanofillers, such as carbon nanotubes (CNT) or graphene nanoplatelets (GNP), can improve the mechanical strength of the aerogels. The incorporation of nanofillers is often accompanied by agglomeration and pore blockage, which, in turn, deteriorates the surface area, pore volume, and low density. Including flexible melamine foam (MF) as a scaffold for the silica aerogel and nanofiller composite can prevent the restacking of the nanofillers through π-π interaction, hence maintaining the incredible properties of aerogels and improving their mechanical properties. CNT, GNP, and the polymeric silica precursor, polyvinyltrimethoxysilane (PVTMS), were added to a MF, at varying concentrations, to fabricate the MF-aerogel nanocomposites. Surfactant and sonication were utilized to ensure a homogeneous dispersion of the nanofillers in the system. The presence of MF prevented the agglomeration of nanofillers, resulting in lower density and relatively higher surface properties (SBET up to 929 m2·g-1 and pore volume up to 4.34 cc·g-1). Moreover, the MF-supported samples could endure 80% strain without breakage and showed an outstanding compressive strength of up to ∼20 MPa. These aerogel nanocomposites also demonstrated an excellent volatile organic compound (∼2680 mg·g-1) and cationic dye adsorption (∼10 mg·g-1).

3D monolithic composites TiO2/HKUST-1/RGO@melamine foam with improved surface mass transfer for efficient photocatalytic degradation of toluene gas

Currently, photocatalytic technology mostly uses powdered TiO2 catalysts, which are not conducive to recycling, limit the contact between volatile organic compounds (VOCs) and the photocatalyst, and result in lower mass transfer efficiency in gas-solid reactions. Meanwhile, TiO2 catalysts including the electrospun TiO2 nanofibers with hydrophilic surfaces are not favorable for the infiltration and adsorption of non-polar VOCs. To solve these problems, in this work, the monolithic composites TiO2/HKUST-1/RGO@melamine foam (named MRTH) with improved surface mass transfer composed of metal-organic framework (HKUST-1), graphene oxide (GO) and electrospun TiO2 nanofibers was designed. The metal-organic framework HKUST-1 plays a role in promoting the adsorption of toluene, while the reduced graphene oxide (RGO) facilitates the infiltration of non-polar molecules on the surface of the composite and has better electron transport capability. A type II heterojunction between the electrospun TiO2 nanofibers and HKUST-1 formed in the monolithic composites suppresses the recombination of electron-hole pairs and extends their lifespan. Comparing with the bare electrospun TiO2 nanofibers, the MRTH foam composites exhibit a wider light absorption range, hydrophilic and oleophobic properties and a higher separation efficiency of photogenerated carriers. In 90 min of dark adsorption, the removal rate of toluene over MRTH-8 was 52.32 %, while under irradiation by xenon lamp for 150 min, the removal rate over MRTH-8 reached 90.15 %. The amount of monolithic foam composites can also be easily adjusted in the reactor to achieve the best possible removal of the contaminant. The prepared composite materials have been characterized in detail, and the possible mechanisms have also been discussed. The foam composites prepared in this work have high catalytic activity and gas-solid reaction mass transfer efficiency, so they have wide practical application prospects in the field of VOCs abatement.

Shaped binderless high SiO2/Al2O3 ratio Beta/ZSM-5 composites for volatile organic compounds adsorption

Shaped binderless high SiO2/Al2O3 ratio Beta/ZSM-5 composites for volatile organic compounds adsorption

Green synthesis of biomass-derived porous carbon with hierarchical pores and enhanced surface area for superior VOCs adsorption

The release of volatile organic compounds (VOCs) during the production, storage, and transportation of petroleum and its derivatives can be hazardous to human health and lead to secondary pollution. Addressing this challenge, this study introduces a sustainable and low-energy approach for synthesizing high-efficiency porous carbon materials, leveraging the abundant and renewable watermelon rinds as a carbon source. The carbonization and activation processes were optimized to minimize energy consumption while maximizing adsorptive performance. In this research, watermelon rinds were used as a source of carbon production, and melamine phosphate (FR-MP) was employed as a modifying agent. The FR-MP modified porous biomass-derived activated carbon (PWAC) was created by subjecting it to physical milling, carbonization, and activation. This approach not only utilized a waste biomass effectively but also reduced the overall carbon footprint of the production process. An examination of the effects of FR-MP dosage on the pore structure, surface chemical properties, and VOCs adsorption abilities of PWAC revealed that a higher FR-MP dosage resulted in a wider range of pore sizes within PWAC. The incorporation of FR-MP intensified the development of internal porosity and pore expansion in PWAC. Specifically, the optimized PWAC-0.3 exhibited a significant increase in specific surface area (3149 m²/g) and pore volume (1.76 cm³/g), enhancing adsorption capacities for acetone and n-hexane up to 1046 mg/g and 760 mg/g, respectively. Furthermore, the PWAC demonstrated exceptional recyclability, maintaining 97% of its original adsorption capacity after five cycles, underscoring its sustainable and economic viability. The highly advanced hierarchical ultra-meso-macroporous structure of PWAC significantly reduced the diffusion resistance of VOCs, guaranteeing swift mass transfer and desorption of VOCs. Consequently, the developed PWAC represents a novel, cost-effective, and environmentally-friendly approach for VOCs adsorption, aligning with the principles of green chemistry and low-energy consumption. This research not only provides a promising solution for VOCs mitigation but also highlights the potential of waste biomass in producing high-performance carbon materials.

Heteroatom Sr doped MCM-41 molecular sieve for VOC adsorption: Study of the surface functionalization and adsorption performance

Volatile organic compounds (VOCs) are recognized as greater adverse effects on both environment and human health, and adsorption is a simple and effective method. Ordered mesoporous MCM-41 molecular sieve was functionalized with heteroatom Sr to change the pore size and surface property by one-step hydrothermal method and adsorption performance for toluene (C7H8) and formaldehyde (CH2O) was investigated. It is found that Sr doped MCM-41 achieves high static adsorption capacities of 534 mg/g for C7H8 and 388 mg/g for CH2O. The dynamic adsorption of C7H8 follows the Langmuir model over Sr doped and undoped MCM-41 under different process conditions, but the dynamic adsorption capacity is only 21 ∼ 99 mg/g. Sr doped MCM-41 maintains a typical pore structure of MCM-41, with some Sr entering the skeleton to form Sr-O-Si bonds. Sr-M−130 has 857 m2/g of SBET and 0.86 cm3/g of Vtotal, but high hydrothermal temperature (150 °C) causes the sintering of MCM-41 structure. Sr doping decreases surface acidity of MCM-41 and increases surface hydroxyl groups (Si-OH). The kinetic diameter and polarity of the adsorbate cause differences in adsorption performance of Sr doped or undoped MCM-41, meaning that the adsorption behavior of non-polar C7H8 mainly depends on surface area and micropore volume while that of polar CH2O is related to the number of ultra-micropore (<1 nm) and forms chemical adsorption of C = O with Si-OH by hydrogen bonds.

Fluorination modification enhanced the water resistance of Universitetet i Oslo-67 for multiple volatile organic compounds adsorption under high humidity conditions: Mechanism study

The construction of metal–organic frameworks (MOFs) with highly efficient capture for volatile organic compounds (VOCs) adsorption under humid conditions is a significant yet formidable task. Herein, series of fluorinated UiO-67 modified with trifluoroacetic acid (TFA) and 4-fluorobenzoic acid were successfully synthesized for VOCs adsorption under high humidity conditions. Experiments results showed that UiO-67 modified with 4-fluorobenzoic acid (67-F) presented excellent adsorption capacity of 345 mg/g for toluene adsorption and exhibited great water resistance (10.0 vol% H2O, 374 mg/g toluene adsorption capacity). Characterization results indicated that the introduction of 4-fluorobenzoic acid induced the competitive coordination between 4-fluorobenzoic acid and 4,4-biphenyl dicarboxylic acid (BPDC) with Zr4+, causing the formation of abundant defects to provide extra adsorption sites. Meanwhile, the benzene ring in 4-fluorobenzoic acid enhanced the π-π conjugation, causing the further promotion of VOCs adsorption capacity. More importantly, the water resistance mechanism was investigated and elucidated that the introduction of F decreased the surface energy of 67-F and its affinity with water. Meanwhile, the metal complex induced by the fluorinated modification produced an electron-dense pore environment, which greatly improved its chemical and water stability. This work provided a strategy for preparing an adsorbent with high water resistance for real-world VOCs adsorption at high humidity conditions.

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.

Facile synthesis of natural stearic acid modified carbon adsorbent for toluene adsorption under high humidity conditions

The diminished adsorption efficiency of porous carbon for volatile organic compounds (VOCs) in high-humidity conditions poses a critical challenge that limits its widespread application. This study presents a facile method for enhancing the adsorption capacity of coffee grounds activated carbon in high-humidity environments through stearic acid modification. The incorporation of 20 % stearic acid (20 % ST-AC) significantly amplifies the saturated adsorption capacity and penetration duration of porous carbon for toluene under high-humidity conditions. Specifically, the toluene adsorption capacity improves from 230 mg/g to 498 mg/g in an 80 % relative humidity condition. However, increasing the stearic acid doping ratio beyond 20 % has a limited impact on moisture resistance while leading to micropore blockage, resulting in a significant reduction in toluene adsorption capacity. Additionally, 20 % ST-AC demonstrates excellent adsorption recycling performance over five cycles, maintaining 97 % of its original adsorption capacity. This study provides a novel perspective on the preparation of hydrophobic activated carbon, which helps to address the challenge of VOC adsorption in high-humidity flue gas environments.

Anti-competitive adsorption of gaseous benzene on hydrophilic microporous carbon in humid conditions

The adsorption capture of ambient volatile organic compounds (VOCs) is of practical importance for air quality management. Herein, unique anti-competitive adsorption behavior of benzene on a hydrophilic activated carbon (Procarb-900 (P900)) is evidenced in the presence of competing components (e.g., formaldehyde (FA) and/or moisture). Contrary to general expectations, the adsorption capacity of 10 Pa benzene (QB) onto P900 (30 mg) at the 99 % breakthrough level improves from 144.8 to 187 mg g−1 as the relative humidity (RH) increases from 0 to 25 %. Such pattern is maintained at 183.9 mg g−1 even at the relatively high RH of 50 %. Furthermore, QB exhibits a remarkable increase of 56.1 % (to 226.0 mg g−1) in the binary phase (100 ppm benzene plus 50 ppm FA) relative to its single phase (144.8 mg g−1). The kinetic studies confirm the occurrence of anti-competitive adsorption of benzene under humid conditions with the unusual decrease in rate constants at the elevated RHs (i.e., 25 and 50 %). The thermodynamic studies suggest the exothermic nature of benzene adsorption onto P900. The hydrophilicity of P900's outer surface promotes the preferential adsorption of polar FA and water vapor over non-polar benzene, which deforms the activated carbon texture and lowers the pore size distribution (PSD). The narrow PSD enhances benzene uptake in the complex systems due to the confinement effect. Overall, this study offers insights into the unique anti-competitive adsorption of non-polar VOCs (e.g., benzene) on hydrophilic microporous adsorbents in the presence of potential interferences such as polar water vapor and FA. These findings offer a guideline for the practical implementation of adsorption techniques for gaseous VOCs in humid conditions.

Designing activated carbon and porous carbon nanofibers for insight into their differences in adsorption affinity mechanisms of VOCs

The adsorption technology has been considered as an effective and economical strategy to control volatile organic compounds (VOCs) through various types of porous materials. As two potential porous materials, activated carbon and carbon nanofibers were synthesized as VOCs adsorbents. In order to investigate the difference in the adsorption of VOCs between activated carbon and carbon nanofibers, the specific surface area, pore structure and chemical functional groups of VOCs adsorbent were analyzed. In particular, the carbon nanofibers (CNF) activated at 800 ℃ showed an excellent specific surface area (2524 m2·g−1), abundant pores (1.66 mL·g−1), and rich functional groups (N: 8.29 at%). Meanwhile, the carbon nanofibers had a better adsorption performance for acetone (1069.82 mg·g−1) and toluene (427.72 mg·g−1) than activated carbon materials. Furthermore, the theoretical calculations were conducted to reveal the mechanism of favorable adsorption on the CNFs. The theoretical adsorption energies of CNF are −31.9 kJ·mol−1 (acetone) and −67.5 kJ·mol−1 (toluene), respectively, which have more favorable adsorption sites and stronger charge redistribution than activated carbon. This research guided the approach to obtain the porous carbon nanofibers and provided the evidence for CNFs (curved carbon) exhibiting a better adsorption ability to VOCs.

Thermosetting Phenolic Resin-Derived Activated Carbon Fibers for Volatile Organic Compound Adsorption: Electrospinning, Preoxidation, and Carbonization

Thermosetting Phenolic Resin-Derived Activated Carbon Fibers for Volatile Organic Compound Adsorption: Electrospinning, Preoxidation, and Carbonization

A comprehensive review on removal of VOCs from air using fly ash as an adsorbent

Volatile Organic Compounds (VOCs) play a critical role in the atmosphere and are produced from biogenic and anthropogenic sources. These chemicals have serious health consequences for humans. Among many types of industrial waste available, Coal Fly Ash (CFA) are mostly produced by coal- fired power plants with the ability to capture VOCs from the air. The use of an inexpensive, high-performance electrospun nanofiber membrane to filter out airborne impurities. Adsorption is thought to be the best approach out of all of them due to its convenience, ease of usage, and easy-to-understand design. This review article covers the procedure, and environmental effects of employing fly ash for the adsorption of VOCs. The main concerns with fly ash disposal are the need for massive land areas for landfills and the harmful effects and groundwater pollution caused by the accumulation of heavy metals. Additionally, the methods for overcoming the benefits of using fly ash are also examined.

Density functional theory study on the enhanced adsorption mechanism of VOCs by Cu4 cluster decorated UiO-66

Volatile organic compounds (VOCs) are a class of air pollutants that greatly harm human health and the ecological environment, convenient and effective treatment of VOCs has become a challenge. This work proposed a transition metal cluster decorated UiO-66 (a typical type of metal-organic framework) as the effective adsorbent for the purification of VOCs with typical functional groups based on density functional theory (DFT) calculations. The results show that the VOCs adsorption energy on the modified UiO-66 increased significantly, especially for Cu4 cluster-modified UiO-66, and the adsorption energy of trichloroethene is greater than that of the other considered VOCs, which may be induced by halogens or carbon-carbon double bond in trichloroethene. We compared chloromethane, chloroethylene, and ethylene and found that VOCs with carbon-carbon double bond have stronger adsorption energy, increasing with the number of chlorine atoms. The density of states (DOS), Hirshfeld charge analysis, and orbital distribution further confirm the charge distribution in UiO-66 after the decoration of the Cu4 cluster. Cu4 cluster can act as a bridge to promote the formation of chemical bonds between UiO-66 and VOCs molecules. Therefore, Cu4 cluster-modified UiO-66 can be a promising VOCs adsorption material, especially for vinyl chloride molecules.

Effect of pore size distribution of biomass activated carbon adsorbents on the adsorption capacity

AbstractBACKGROUNDIn order to investigate the correlation between the pore size distribution of biomass activated carbon adsorbents (BACAs) and VOCs (volatile organic compounds) adsorption/desorption performance. Four BACAs with same specific surface area but different pore size distribution were prepared under different experimental conditions and processes.RESULTSThe impact of the pore size distribution of BACAs on the adsorption/desorption performance of benzene, toluene and xylene was investigated. The results indicated that the adsorption ability of the prepared BACAs for benzene, toluene and xylene was mostly affected by the pore sizes distributed in the 2.60 ~ 3.25, 2.68 ~ 3.35and 4.20 ~ 4.90 nm ranges, respectively, when the studied BACAs had similar specific surface area (SBET ≈ 1080 m2 g−1). However, the desorption amount of adsorbed benzene molecules mainly relied on the pore structures of BACAs having pore sizes in the 3.95 ~ 4.60 nm range.CONCLUSIONThe pore structures of BACAs distributed in different pore size ranges have various effects on the phenyl VOCs adsorption capacity. Benzene adsorption on the BACAs was mainly affected by the microporous structures. The pore structure with larger pore size was more favorable for the desorption of the adsorbed toluene and xylene molecules compared to the adsorbed benzene molecules. Benzene, toluene and xylene had low residual rates in the studied activated carbon adsorbents attesting to their superior regenerative properties. This work could provide an important reference for the design, preparation, and selection of activated carbon adsorbents for the adsorption capacity of benzene, toluene and xylene. © 2024 Society of Chemical Industry (SCI).

In-situ growth of MIL-101(Fe) onto PET base for high-efficiency adsorption of low concentrations benzene series VOCs and easy recycling

With the proliferation of vehicles in households, people are spending more and more time in their cars, so it is important to ensure the air quality and safety of the car. In this research, environmentally friendly, green PET@PDA@MIL-101(Fe) (PPM) was prepared by in-situ solvothermal growth and acid etching methods, which was categorized by SEM, FTIR, XRD, XPS, and BET. PPM was used to adsorb benzene, toluene, and m-xylene at low concentrations. The maximum amount of adsorption of PET@PDA@MIL-101(Fe) (PPM) for benzene, toluene, and m-xylene was 68.72 mg/g, 91.63 mg/g, and 78.47 mg/g respectively. The adsorption process of PPM is well fitted by the pseudo-first-order kinetic model and Langmuir isothermal adsorption model. Furthermore, PPM exhibited excellent toluene removal performance in simulated vehicles and excellent cycling capability in adsorption-desorption experiments. As a result, PPM can be used to treat and manage toluene volatile organic compounds (VOCs) at low concentrations.

Volatile Organic Compounds (VOCs) in Soil: Transport Mechanisms, Monitoring, and Removal by Biochar-Modified Capping Layer

Volatile organic compounds (VOCs), as a primary pollutant in industrial-contaminated sites or polluted soils, cause severe damage to the soil. Therefore, a comprehensive understanding of the transport of VOCs in soil is imperative to develop effective detection means and removal methods. Among them, biochar possesses potential advantages in the adsorption of VOCs, serving as an effective method for removing VOCs from soil. This review provides an overview of the VOCs within soil, their transport mechanisms, monitoring technology, and removal approach. Firstly, the historical development of the VOC migration mechanism within the capping layer is described in detail. Secondly, the in situ monitoring techniques for VOCs are systematically summarized. Subsequently, one of the effective removal technologies, a capping layer for polluted sites, is simply introduced. Following this, the potential application of a biochar-modified capping layer for the removal of VOCs is comprehensively discussed. Finally, the major challenges in the field and present prospects are outlined. The objective of this study is to furnish researchers with a foundational understanding of VOCs, their relevant information, and their removal approach, inspiring environmental protection and soil pollution control.

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.