Adsorption Of VOCs Research Articles

Study on the synergy effect of MnOx and support on catalytic ozonation of toluene.

MnOx has received widespread attention in low-temperature catalytic oxidation of VOCs, however, the synergy effect of MnOx and support on the VOCs catalytic ozonation were rarely studied. In this study, five different MnOx/X (X: MCM-41, 13X, ZSM-5, HY, USY) were synthesized and found their support greatly affect the catalytic oxidation activity. MnOx/MCM-41 presents the largest specific surface area, pore volume and unique surface morphology, and thereby provides more sites for MnOx loading and VOCs adsorption. Moreover, MnOx/MCM-41 presents a high proportion of Mn3+, which helps to enhance the ion exchange capability, and thus promotes the regeneration of oxygen vacancies. Furthermore, a part of Mn was proved to be introduced into the MCM-41 lattice, which can promote the electron transfer between the active components and the support, and thereby effectively improve the surface electronic properties of the catalyst. The toluene catalytic experiments showed that MnOx/MCM-41 exhibited the best catalytic activity, presenting complete degradation of O3 and VOCs at room temperature. In addition, 5wt%MnOx/MCM-41 exhibited better catalytic activity than other loading, and its higher surface oxygen species endowed it with strong water resistance and stability. In-situ DRIFTs indicated that toluene was initially oxidized into benzyl alcohol during the adsorption process, and then decomposed to intermediate products (benzaldehyde, phenolate, etc.) during the catalytic ozonation process, and finally oxidized to carbon dioxide. In conclusion, the supply of loading sites and the improvement of interfacial electron transfer are the manifestations of the synergy between the support and MnOx, leading to the promotion of the catalytic ozonation of VOCs.

Volatile-Mediated Induced and Passively Acquired Resistance in Sagebrush (Artemisia tridentata)

Plants produce a diversity of secondary metabolites including volatile organic compounds. Some species show discrete variation in these volatile compounds such that individuals within a population can be grouped into distinct chemotypes. A few studies reported that volatile-mediated induced resistance is more effective between plants belonging to the same chemotype and that chemotypes are heritable. The authors concluded that the ability of plants to differentially respond to cues from related individuals that share the same chemotype is a form of kin recognition. These studies assumed plants were actively responding but did not test the mechanism of resistance. A similar result was possible through the passive adsorption and reemission of repellent or toxic VOCs by plants exposed to damage-induced plant volatiles (DIPVs). Here we conducted exposure experiments with five chemotypes of sagebrush in growth chambers; undamaged receiver plants were exposed to either filtered air or DIPVs from mechanically wounded branches. Receiver plants exposed to DIPVs experienced less herbivore damage, which was correlated with increased expression of genes involved in plant defense as well as increased emission of repellent VOCs. Plants belonging to two of the five chemotypes exhibited stronger resistance when exposed to DIPVs from plants of the same chemotypes compared to when DIPVs were from plants of a different chemotype. Moreover, some plants passively absorbed DIPVs and reemitted them, potentially conferring associational resistance. These findings support previous work demonstrating that sagebrush plants actively responded to alarm cues and that the strength of their response was dependent on the chemotypes of the plants involved. This study provides further support for kin recognition in plants but also identified volatile-mediated associational resistance as a passively acquired additional defense mechanism in sagebrush.

A facile pore size controlling strategy to construct rigid/flexible silica aerogels for super heat insulation and VOCs adsorption

Silica aerogels have fascinating prospects in the field of energy-saving and environmental purification, however, it is crucial to accurately control the pore structure of aerogel so as to achieve its super heat-insulation and adsorption performance. In this work, two pore size controllable methods were proposed to construct rigid/flexible silica aerogels with an extensive range of pore size by controlling the binding modes among the gel network using methyltriethoxysilane (MTES) as silica source. With the decrease of aerogel pore size from 20.8 µm to 82 nm, the visible light transmittance of wet gel increases from 0.1 % to 34 %. Correspondingly, the thermal conductivity decreases from 0.0567 W/(m·K) to 0.0383 W/(m·K) and then increases to 0.0410 W/(m·K), maintaining a low thermal conductivity in general and showing an excellent thermal insulation and heat preservation performance. In addition, the saturation adsorption capacity of volatile organic compounds (VOCs) such as dichloromethane, dimethylformamide and hexane increases with the increase of pore size of aerogel. The proposed pore size control strategy and the relationship between the pore structure and macroscopic performance of silica aerogels are very helpful for fabricating tailored rigid/flexible silica aerogels suitable for specialized applications.

The Adsorption of VOCs by Honeycomb Ceramics Loaded with Molecular Sieves

In order to improve the adsorption performance of molecular sieve honeycomb ceramics for VOCs, the author proposes a research method for the adsorption performance of VOCs based on the honeycomb ceramics loaded with molecular sieves. The method prepared cordierite honeycomb ceramic-supported HY, Na Y, USY, ZSM-5-300, and ZSM-5-360 monolithic adsorption materials by the coating method. Using toluene, ethyl acetate, isopropanol, and acetone as adsorbates, the adsorption properties of single-component and mixed-component organic compounds on the supported molecular sieve honeycomb ceramics were investigated. The result shows ZSM-5-300 has the largest adsorption capacity for the four adsorbates, which are toluene 68.0 mg/g, ethyl acetate 118.7 mg/g, isopropanol 70.9 mg/g, and acetone 72.5 mg/g. The test results show that ZSM-5-300 molecular sieve has high saturated adsorption capacity and is an ideal VOCs adsorption material.

Effect of non-thermal plasma in the activation and regeneration of 13X zeolite for enhanced VOC elimination by cycled storage and discharge process

A non-thermal plasma (NTP) discharge is used in this study for the activation and regeneration of MS-13X pellets packed in a MS-13X & glass beads packed bed dielectric barrier discharge (DBD) reactor. NTP activation (in-situ) of MS-13X efficiently removes the adsorbed carbonaceous compounds and moisture resulting in an improved VOC adsorption. In addition, NTP exposure is used for the regeneration of the used MS-13X for cycled storage and discharge (CSD) removal of VOC from air. The amount of adsorbed toluene, products formed and the surface and bulk properties of the regenerated used MS-13X shows complete regeneration of used MS-13X. Finally, the stability of MS-13X during 10 cycles of CSD shows no degradation in performance. Thus, NTP exposure is proven to be successful for both the activation and regeneration of MS-13X pellets used for cyclic CSD process.

Porous carbon fibers from low-temperature sodium amide activation for acetone adsorption

The low energy consumption and facile activation methods are of great significance to synthesize porous carbon fibers. In this work, polyacrylonitrile-based porous carbon fiber (ACFN-X) was synthesized by sodium amide activation at the temperature ranges of 400–600 °C. The characterization of ACFN-X proves the formation of porous structure and N–O doped surface. Acetone was used as an adsorbate to explore the adsorption performance of the ACFN-X samples. The maximum acetone adsorption capacity is 4.80 mmol g−1 (at 25 °C, 18 kPa). The experimental results are well fitted by the Freundlich model, Sips model and Langmuir model to express the equilibrium adsorption, which indicates that the ACFN-X has a positive adsorption cooperativity on the acetone. Besides, the pseudo-first-order and pseudo-second-order kinetic model could well describe the kinetic processes. The rate constant k2 is mainly affected by the positive effect of the nitrogen functional groups. Moreover, the coupling roles of pore structure and functional groups on acetone adsorption performance were also explored. The results show that micropores play a crucial role in acetone adsorption. Nitrogen functional groups play a promoting role in micropores, and the addition of the pyrrolic exhibits the highest affinity with acetone molecules in the presence of oxygen functional groups. This study provides ideas an option for the preparation of porous carbon fibers as VOCs adsorption.

Atomic layer deposited Pt/TiO2-SiO2 and Pt/ZrO2-SiO2 for sequential adsorption and oxidation of VOCs

In this work, Pt nanoparticles were loaded on SiO2, TiO2-thin-film-modified SiO2 (TiO2-SiO2), or ZrO2-thin-film-modified SiO2 (ZrO2-SiO2) particles and the composites were investigated for sequential adsorption and desorption/catalytic oxidation of benzene. The SiO2 was prepared via sol–gel method, while TiO2-SiO2 and ZrO2-SiO2 were synthesized via atomic layer deposition (ALD) thin film coating of TiO2 or ZrO2 on SiO2 particles substrate. In the sequential capture-reaction tests, the materials were first exposed to ca. 500 ppmv benzene gas at 25 °C and 1 atm until 5% breakthrough was attained, followed by tandem desorption and catalytic oxidation while raising bed temperature to 200 °C. The benzene vapor adsorption isotherms followed type-IV isotherm classification, revealing a combination of monolayer, multilayer and capillary condensation adsorption mechanisms in sequence. The xPt/ZrO2-SiO2 materials exhibited superior capture-conversion capabilities relative to their xPt/TiO2-SiO2. In particular, 3Pt/ZrO2-SiO2, prepared with 3 cycles of Pt ALD, exhibited the maximum in-situ conversion at ∼ 100% and turnover frequency of 17.1 mmolC6H6/molPt/s with a dynamic adsorption capacity of 0.45 mmol/g, indicating synergistic effects of Pt nanoparticles and ZrO2 in the ALD-based dual-function materials.

Removal of volatile components from plastic waste in liquid media: effect of temperature and particle size

Plastic recycling faces a range of challenges, including the removal of VOCs and odorous compounds. Despite the industrial relevance, understanding and optimizing washing procedures for plastics is often based on trial and error. To gain more understanding of the removal kinetics of VOCs, which contribute to the odor profile, the influence of temperature and particle size on their removal from plastic films and bottles were investigated at lab scale. For this purpose, the VOC removal from plastic films and bottles in water, caustic soda and a caustic soda + detergent solution was monitored at different temperatures and particle sizes by means of GC-MS analysis. It was found that an increase in temperature from 28°C to 85°C results in an improved removal for all washing media (from 69 to 79% in water, 43 to 65% in caustic soda, and 65 to 72% using a caustic soda + detergent solution). Reducing particle size of plastic films from 1.1 cm to 0.045 cm increases the VOC removal from approximately 35% to 70%. For PE bottles, the effect of particle size was more pronounced than for films, due to the bigger change in specific surface area. The desorption-adsorption kinetics were most accurately described by a reversible first order kinetic model by implementing the Arrhenius equation for modelling the temperature dependence and a Power Law to account for the particle size. Thermodynamics indicate that adsorption of VOCs is favored over desorption, explaining why washing medium management is crucial for efficient removal of VOCs from plastic waste.

Enhanced VOC adsorption capacity on MOF thin layer with reduced particle size by cryogrinding and microwave method

Metal-organic framework (MOF) thin films are widely used for catalysis, separation, sensors, and electronic devices because of their unique properties such as large surface area, highly ordered crystalline structure, and tunable electrical conductivity. In this research, the sorption behavior of three aromatic hydrocarbons (benzene, toluene, and chlorobenzene) on the MOFs of UTSA-16, HKUST-1, MIL-101, UiO-66, and ZIF-8 was studied. A thin layer of MOF was formed on a gold sensor by solution drop-casting a MOF solution with different compositions. The adsorption capacities were analyzed using a quartz crystal microbalance, and the relative capacities were confirmed using a volumetric method. To investigate the effect of the MOF particle size on the adsorption capacity, a novel cryogrinding method was adopted and the cryoground HKUST-1 showed a 21% (benzene), 23% (toluene), and 20% (chlorobenzene), increase in adsorption capacity over the parent HKUST-1. Similarly, cryoground MIL-101 showed 14% (benzene), 13% (toluene), and 13% (chlorobenzene) increase, while UiO-66 showed 16% (benzene), 19% (toluene), and 16% (chlorobenzene) improvement compared to samples without cryogrinding due to an improved VOC accessibility in small particles. Adsorption capacities for microwave synthesized UTSA-16 were further increased by 12–30% by the cryogrinding process. Morphological properties of the MOFs were investigated using X-ray diffraction, Brunauer–Emmett–Teller analysis, scanning electron microscopy, and thermo-gravimetric analysis.

Synthesis and VOCs adsorption performance of surfactant-templated USY zeolites with controllable mesopores

Adsorption is one of the most effective methods to control the concentration of VOCs pollution. In this work, the hierarchical USY zeolites with size-controlled mesopores are obtained via NH4HF2-etching and surfactant-templating process. It is found that the non-framework aluminum inside USY is effectively removed by NH4HF2-etching, and the irregular mesopores inside NH4HF2-etched USY are transformed into small-sized mesopores with a size of ∼4 nm after subsequent surfactant-templating treatment. The formation mechanism of the small mesopores with controllable pore size is elucidated, and the adsorption properties of NH4HF2-etched USY-s for different VOCs molecules are demonstrated.

Preparing hierarchical porous carbon with well-developed microporosity using alkali metal-catalyzed hydrothermal carbonization for VOCs adsorption

Biomass-derived porous carbonaceous materials are efficient adsorbents for VOCs, but their traditional preparation method, pyrolysis combined with activation, suffers from high energy consumption, equipment corrosion, and low pore-making efficiency, which hinders their large-scale practical application. A novel method of alkali metal-catalyzed hydrothermal carbonization coupling with chemical activation for the preparation of microporous carbon is presented. Porous carbon with well-developed microporosity deriving from corn husk were prepared through the hydrothermal carbonization using potassium persulfate (K2S2O8) as a catalyst and programmed heating activation process. And the products were applied to removal of typical oxygen-containing VOCs, ethyl acetate. The addition of K2S2O8 in hydrothermal carbonization accelerated the biomass hydrolysis, decomposed the biopolymer, and formed functional hydrochars. Potassium salts introduced into the hydrochars, which acted as an activator in this programmed heating activation process, formed a great deal of micropores. The specific surface area of micropores increased by 81%, and the specific surface area of micropores less than 1 nm increased by 180%. The introduction of K2S2O8 in preparation improved the adsorption performance of CH-based porous carbons 16.46% and 60.00% respectively at different preparation temperatures (600 °C and 800 °C). Basing on these results, the improvement of micropores less than 1 nm is directly related to the adsorption performance. This indicates that pores (<1 nm) respond well to the adsorption of ethyl acetate.

Confinement and synergy effect of bimetallic Pt-Mn nanoparticles encapsulated in ZSM-5 zeolite with superior performance for acetone catalytic oxidation

Catalytic oxidation is one of the most promising methods to remove VOCs. Herein, a zeolite-confined PtMn bimetal catalyst (PtMn0.2 @ZSM5) was synthesized using a ligand-assisted hydrothermal method, which showed extraordinary catalytic activity with a T95 of 165 ℃ for the acetone oxidation in the presence of 5 vol% water. Thanks to the zeolite confinement and bimetallic synergy effect, the PtMn0.2 @ZSM5 exhibited small nanoparticle sizes, abundant acid sites, higher active Pt0 content, and sufficient active oxygen species. These excellent properties promoted the adsorption of VOC, the deep oxidation of VOC, and the desorption of CO2. In-situ DRIFTS proposed an L-H mechanism for acetone oxidation over PtMn0.2 @ZSM5. Significantly, the PtMn0.2 @ZSM5 presented good durability and water resistance under high GHSV conditions. Also, it was confirmed effective for various VOCs oxidation, such as toluene, ethyl acetate, propane, and dichloromethane, showing a promising industrial prospect for eliminating VOCs.

Research on the Progress of VOCs Adsorption by Biomass Nanocomposites

The avoidance and control of the air is forthcoming, and its deterioration sources have a wide range of origin. Among them, the emission of VOCs is worthy of our attention. Its source is very wide, which seriously define the improvement of green chemical industry in our country. There are many types of VOCs, and when the concentration is too high, it will cause serious harm to the human body. Therefore, the avoidance and control of VOCs gas has become one of the current research tosspots. In this paper, several methods for alter VOCs gas are related, and it is found that adsorption is more economical and safer, and the core is the preparation of adsorbents. At the same time, the preparation of high-performance VOCs adsorbents based on TiO2 as the matrix and manganese-based as the raw material of biomass waste is also prospected.

Adsorption and desorption mechanism of aromatic VOCs onto porous carbon adsorbents for emission control and resource recovery: recent progress and challenges

This review highlights the characteristics of adsorption and desorption of aromatic VOCs on various PCAs as well as the integrated technologies for emission control and resource recovery of industrial VOC exhaust.

Size Controllable Synthesis of Zif-8 and Derived Nitrogen-Rich Porous Carbon for Co2 and Vocs Adsorption

Size Controllable Synthesis of Zif-8 and Derived Nitrogen-Rich Porous Carbon for Co2 and Vocs Adsorption

Mesoporous Organic-inorganic Hybrid Siliceous Hollow Spheres: Synthesis and VOCs Adsorption

Mesoporous Organic-inorganic Hybrid Siliceous Hollow Spheres: Synthesis and VOCs Adsorption

Adsorption of Multicomponent Vocs on Various Biomass-Derived Hierarchical Porous Carbon: A Study on Adsorption Mechanism and Competitive Effect

Adsorption of Multicomponent Vocs on Various Biomass-Derived Hierarchical Porous Carbon: A Study on Adsorption Mechanism and Competitive Effect

Adsorption of Multicomponent Vocs on Various Biomass-Derived Hierarchically Porous Carbon: A Study on Adsorption Mechanism and Competitive Effect

Adsorption of Multicomponent Vocs on Various Biomass-Derived Hierarchically Porous Carbon: A Study on Adsorption Mechanism and Competitive Effect

Adsorption and Adsorption-Photocatalytic Degradation of VOCs Based on Carbon Materials: A Review

Adsorption and Adsorption-Photocatalytic Degradation of VOCs Based on Carbon Materials: A Review

Adsorption of Volatile Organic Compounds Onto Biomass-Derived Activated Carbons: Experimental Measurement and Comparison

Abstract Volatile organic compounds (VOCs) are a class of hazardous gaseous materials emitted from certain solids or liquids. They are thought to possess serious short- or long-term adverse effects on human health. Nowadays, an energy-efficient and cost-effective volatile organic compound removal system is of absolute necessity due to its adverse effects. In this regard, solar or waste heat-driven adsorption-based technologies can provide an energy-efficient system; however, most of the time, their utilization is limited by the high cost of the adsorbent materials. Right now, only one commercial high-grade activated carbon named Maxsorb III is known to have high capturing capacities. The purchasing cost of this adsorbent is very high, and it is derived from a non-renewable source. Therefore, this study is intended for the quest for low-priced biomass-derived activated carbons for an energy-efficient and cost-effective VOCs removal system. Two biomass-derived activated carbons synthesized from mangrove wood and waste palm trunk precursors are chosen, and four types of VOCs (ethanol, dichloromethane, acetone, and ethyl acetate) adsorption onto them are measured experimentally using the inverse gas chromatography technique. The zero uptake adsorption enthalpy and specific entropy of the adsorption are theoretically computed for all the adsorbent/adsorbate pairs. After that, these data are compared with the obtained data for Maxsorb III to assess the performance of the biomass-derived activated carbons. Results show that, for all the VOCs, the cost-effective mangrove-based activated carbon can be an excellent alternative to the high-priced Maxsorb III when employed as an adsorbent material for VOCs removal.