Adsorption Of VOCs Research Articles

Rapid One-Pot Synthesis of Hyper-Cross-Linked Polymers at Room Temperature for the Efficient Adsorption of VOCs

Rapid One-Pot Synthesis of Hyper-Cross-Linked Polymers at Room Temperature for the Efficient Adsorption of VOCs

Tight coupling of oxygen vacancies and acidity on α-MnO2 through cerium doping engineering for efficient removal of multi-component VOCs

An α-MnO2-based MnCe catalyst was synthesised by incorporating Ce, which demonstrated outstanding catalytic performance in the oxidation of multicomponent VOCs. Notably, the MnCe-7% catalyst achieved over 90% conversion and CO2 selectivity at temperatures below 300 °C in the presence of both toluene and chlorobenzene (CB). Furthermore, the catalytic activity remained above 80% at 256 °C in the presence of 5.0 vol.% H2O vapor. Structural analyses and DFT calculations indicated that the highly dispersed Ce could replace K in the interlayer and Mn in the intralayer of α-MnO2, resulting in a substantial increase in the number of oxygen vacancies and acidic sites. The close interaction between oxygen vacancies and acidic sites facilitated the oxidation and adsorption of VOCs, which was crucial for the high activity demonstrated by the MnCe-7% catalyst. Furthermore, the VOC-TPD and in situ DRIFTS results suggested that the mixed catalysis of toluene and CB on MnCe-7% concurrently engaged the MvK and E-R mechanisms. Toluene was found to supply additional H atoms, promoting the cleavage of C–Cl bonds in CB and enhancing the reaction kinetics.

The role of adsorbent microstructure and its packing arrangement in optimising the performance of an adsorption column

Physical adsorption takes place inside narrow pores where the attractive interaction between the surface of the adsorbent and the contaminant molecules is strong enough to retain the molecules. Adsorption columns involve a range of mass-transport mechanisms: advection through the free spaces between the adsorbent pellets, diffusion through the macro/mesopores of the adsorbent, and adsorption at the surface, where the micropores exist. The adsorbent specifications along with its assembly within the sorption column are key factors when optimizing the filtration of pollutants. In this work we present a mathematical model based on advection–diffusion equations coupled with Langmuir kinetics that accounts for a geometrical approach to the porosity structure inside the adsorbent, formed by a radial lattice of cylinders, and the channels through which the fluid flows surrounding the cylindrical pellets. The model is tested using typical lab-scale values based on VOC adsorption, and we use it to identify optimal macro/mesopore size and column porosity for energetic considerations.

Highly efficient regeneration of VOCs-saturated activated carbon by vacuum-thermal treatment

The substantial energy consumption and carbon loss associated with conventional thermal regeneration of activated carbon (AC) pose significant constraints on the advancement of deactivated AC recycling. Here, a vacuum-thermal process was applied to regenerate AC saturated with VOCs. Results showed that desorption efficiency under vacuum conditions (99 % at 200 °C) was significantly higher than that in air and nitrogen (85.2 % and 86.4 %, respectively). The adsorption capacities of different AC samples were maintained at 74.2 %, 97.8 %, 90.9 %, and 96.4 % after seven regeneration cycles, respectively. Pore structure analysis showed that vacuum-thermal regeneration caused less damage to the AC pore structure compared to the air and nitrogen. In addition, micropores were shown to be most conducive to the adsorption of VOCs, while mesopores larger than 4 nm are conducive to desorption. The larger the saturated vapor pressure of the VOCs, the larger the driving force it is subjected to, and the easier it is to desorption. Density field theory (DFT) calculations showed that the higher the binding energy between VOCs and AC surface, the more stable the adsorption system, making it more difficult to regenerate the adsorbent. This work provides insight into the development of an economical and environmentally friendly regeneration route for AC adsorption.

Development of nitrogen-rich hierarchical porous carbon for high selective adsorption of methanol in multi-VOCs waste gas recovery processes

Methanol is a typical polar volatile organic compound that has been commonly used as a solvent in industrial processes and is considered as an important resource. It often appears with aromatic compounds in practical application scenarios. Conducting methanol and aromatic compounds recycle technology can provide us with a sustainable carbon source for fuels and materials well beyond the fleeting fossil fuel era. Post-synthesis modification (PSM) has been utilized to incorporate 3-amino-1,2,4-triazole (Atz) into ZIF-8, thereby enabling the derivation of mesopore structure and enhancement of nitrogen content in ZIF-8 derived carbon. With this method the obtained carbon exhibited a highly polarizable micro-mesoporous structure, resulting in high adsorption capacity for methanol adsorption at low concentrations. The experimental results showed that the VOCs adsorption on porous carbon is primarily dictated by its microporous structure at high pressure, and predominantly governed by the presence of nitrogen functional groups and the micro-mesoporous properties at low pressure. DFT theoretical analysis also showed that nitrogen functional group can improve the absorption capacity of methanol by adsorbents through changing the electron distribution and surface polarity of carbon-based materials. Finally, based on the emission properties that is low concentration and high volume of VOCs waste gas in industrial application, ZIF8-24-700 and BACs-36 materials (Wang et al., 2023) were used to further prove the feasibility of this technology under low VOCs concentration, which achieve recovery rates of 99 % for toluene and 95 % for methanol, respectively.

Simulation of inhibition and targeted adsorption of rubberized asphalt VOCs by UiO-66 based on molecular dynamics

The adsorption kinetics and molecular dynamics were modeled based on the structure-assembled technique of MOFs, conjugate bonding and targeted adsorption of characteristic pollutants. The mechanism of interaction between UiO-66 and rubber-modified asphalt (RMA) was simulated. The adsorption characteristics between UiO-66 and five class I carcinogens, high concentration VOCs components were simulated by Sorption module. The conjugate bonding and targeting adsorption mechanism between UiO-66 on VOCs was elucidated by combining the GC-MS analysis data. The results were showed that the interaction between UiO-66 and rubberized asphalt was influenced by the number of molecules, contact area, spatial site resistance, and active groups. The content of UiO-66 should be controlled below 3.31 %. The small size of vinyl chloride molecules made it easier to enter the pore structure of UiO-66 with a maximum inhibition rate of 91.75 %. The 1,2-dichloropropane has a large molecular size, spatial site resistance, non-conjugation effect, and the smallest adsorption amount of 72.2 %. The total concentration of VOCs was decreased from 726.38 mg/cm3 to 166.12 mg/cm3, a reduction of 77.13 %. The adsorption of UiO-66 on VOCs molecules was affected by molecular size, carbon chain length, conjugation effect, polarity and other factors. VOCs and UiO-66 form a p-d, d-d π conjugation effect based on the conjugated structure, targeting adsorption within the benzene ring of the organic framework.

Assembling an S-type heterojunction comprising vacancy-rich CeO2-x and CuBi2O4 for improved photocatalytic oxidation of gaseous toluene

The exploration of highly efficient methods for degrading VOCs, with concurrent low energy consumption and lasting reusability, holds significant appeal. In this regard, an S-type CuBi2O4/CeO2-x heterojunction with the robust interfacial interactions is presented as an active photocatalyst for the efficient decomposition of gaseous toluene under full-spectrum irradiation. The optimal sample CC15 effectively degrades gaseous toluene at a high concentration of 1800 ppm within 2 h, achieving a notable CO2 yield of 87.05 %, and a TOC (total organic carbon) removal rate of 89.33 %. Furthermore, CuBi2O4/CeO2-x exhibits exceptional stability, maintaining its 100 % degradation capability over 32 cycles for nearly 64 h. Comparative characterization reveals that the superior performance derives from an abundance of oxygen vacancies and effective pre-adsorption capabilities, which facilitate rapid adsorption of VOCs on the catalyst surface, thereby increasing the likelihood of degradation reactions. Additionally, the formation of an S-type heterojunction, valence pairing between Bi3+ and Ce3+/4+ ions, and strong interfacial interactions serve as the primary pathways for the efficient separation of photogenerated carriers, contributing to the high CO2 production rate and prolonged cycle stability. The present investigation underscores the significant potential of vacancy-rich S-type heterojunctions and interfacial interactions between composite components, offering excellent activity and long-term availability for VOCs removal.

Amidation-Reaction Strategy Constructs Versatile Mixed Matrix Composite Membranes towards Efficient Volatile Organic Compounds Adsorption and CO2 Separation.

Mixed matrix composite membranes (MMCMs) have shown advantages in reducing VOCs and CO2 emissions. Suitable composite layer, substrate, and good compatibility between the filler and the matrix in the composite layer are critical issues in designing MMCMs. This work develops a high-performance UiO-66-NA@PDMS/MCE for VOCs adsorption and CO2 permea-selectivity, based on a simple and facile fabrication of composite layer using amidation-reaction approach on the substrate. The composite layer shows a continuous morphological appearance without interface voids. This outstanding compatibility interaction between UiO-66-NH2 and PDMS is confirmed by molecular simulations. The Si─O functional group and UiO-66-NH2 in the layer leads to improved VOCs adsorption via active sites, skeleton interaction, electrostatic interaction, and van der Waals force. The layer and ─CONH─ also facilitate CO2 transport. The MMCMs show strong four VOCs adsorption and high CO2 permeance of 276.5 GPU with a selectivity of 36.2. The existence of VOCs in UiO-66-NA@PDMS/MCE increases the polarity and fine-tunes the pore size of UiO-66-NH2, improving the affinity towards CO2 and thus promoting the permea-selectivity for CO2, which is further verified by GCMC and EMD methods. This work is expected to offer a facile composite layer manufacturing method for MMCMs with high VOC adsorption and CO2 permea-selectivity.

Green synthesis of porous bamboo-based activated carbon with high VOCs adsorption performance via steam activation method

Green synthesis of porous bamboo-based activated carbon with high VOCs adsorption performance via steam activation method

Graphene as a Sensor for Lung Cancer: Insights into Adsorption of VOCs Using vdW DFT.

The adsorption mechanism of individual volatile organic compounds (VOCs) on the surface of graphene is investigated using nonempirical van der Waals (vdW) density functional theory. The VOCs chosen as adsorbates are ethanol, benzene, and toluene, which are found in the exhaled breath of lung cancer patients. The most energetically favorable configurations of the adsorbed systems, adsorption energy profiles, charge transfer, and work function are calculated. The fundamental insight into the interactions between the considered VOC molecules and graphene through molecular doping, i.e., charge transfer, is estimated. It is found that the adsorption energy is highly sensitive to the vdW functionals. Adsorption energies calculated by revPBE-vdW are in good agreement with the available experimental data, and the revPBE-vdW functional can cover well the physical phenomena behind the adsorption of these VOCs on graphene. Bader charge analysis shows that 0.064, 0.042, and 0.061e of charge were transferred from the graphene surface to ethanol, benzene, and toluene, respectively. All of the considered VOCs act as electron acceptors from graphene. By analyzing the electronic structure of the adsorption systems, we found that the energy level of the highest occupied molecular orbitals of these considered VOCs is shifted backward toward the Fermi level. The interaction of the VOCs with the π and π* states of the C atoms in graphene breaks the symmetry of graphene, leading to the opening of a band gap at the Fermi level. The adsorption of these considered VOCs onto the pristine graphene produces a band gap of 5-12 meV.

Room-temperature rapid synthesis of hierarchically porous ZIF-93 for effective adsorption of volatile organic compounds

A rapid synthesis strategy was developed to produce HP-ZIFs at room temperature and ambient pressure within just 1 min, resulting in a high STY. The synthesized HP-ZIFs exhibit abundant porosity and enhanced VOCs adsorption properties.

Improvement study of duct heater in VOCs adsorption concentration-catalytic oxidation process

Aiming at the catalytic oxidation process of VOCs in conjunction with fixed adsorption bed, the electric heating unit has the problem of large energy consumption, this paper understands the role of the electric heating unit in the process--providing energy for the process, and analyzes the energy consumption of the process, and the results show that the heat transfer efficiency of the electrically heated gas is a key factor affecting the energy consumption of the process. In order to improve the heat transfer efficiency, this paper explores the effect of flow rate on the heat transfer efficiency, and simulation verification is carried out by Fluent software, and the results show that increasing the flow rate can effectively improve the heat transfer efficiency and reduce the process energy consumption. Based on the above analysis, a pipeline heating scheme is proposed, which has the advantages of fast gas flow rate and high heat transfer efficiency in the pipeline, and effectively reduces the operational energy consumption of the process.

Nitrogen/oxygen doped hierarchical porous carbon with adjustable pore structure for efficient adsorption, separation, and enhancement mechanism of methanol and acetone azeotropes: Experimental and theoretical study

The adsorption and separation of methanol and acetone are crucial for environmental protection and recycling. However, the separation of methanol and acetone azeotropes using carbon-based materials remains challenging, and the underlying mechanism is still unclear. Here, we propose the synthesis of porous carbon (NaOCs) using benzimidazole as a precursor and NaOH as an activator. With the increase of the proportion of NaOH and benzimidazole, the activation reaction was intensified, leading to the formation of numerous mesopores. NaOCs exhibit a maximum specific surface area (SBET) of 3084 m2/g, and has extremely high adsorption capacity of methanol (56.9 mmol/g at 13 kPa) and acetone (34.6 mmol/g at 18 kPa) at 25 °C. The results of experiments and molecular simulations indicate that the saturation adsorption capacity of methanol and acetone is determined by micropores and narrow mesopores at 25 °C, whereas the adsorption capacity at relatively low pressure is primary determined by ultramicropores and oxygen group. Furthermore, for methanol-acetone azeotropes separation, the acetone/methanol selectivity at low pressure depends on carbon surface polarity and ultramicropore, while methanol/acetone selectivity at high pressure depends on micropores of 1–2 nm. Our findings provide insights into the design and further development of adsorbents for VOCs adsorption and azeotrope separation applications.

Design and Synthesis of a Water-Resistant Mesoporous Silica Gel for the VOC Adsorption–Desorption Treatment

Design and Synthesis of a Water-Resistant Mesoporous Silica Gel for the VOC Adsorption–Desorption Treatment

Enhanced adsorption of aromatic VOCs on hydrophobic porous biochar produced via microwave rapid pyrolysis

To customize biochar suitable for efficient adsorption of benzene derivatives, this study presents programmed microwave pyrolysis to produce hydrophobic porous biochar with low-dose ferric chloride. Designated control of the ramping rates in the carbonization stage and the temperatures in the activation stage were conducive to enlarging the specific surface area. Iron species, including amorphous iron minerals, could create small-scale hotspots during microwave pyrolysis to promote microporous structure development. Compared with conventional pyrolysis, programmed microwave pyrolysis could increase the specific surface area from 288.6 m2 g−1 to 455.9 m2 g−1 with a short heating time (15 min vs. 2 h) under 650 °C. Engineered biochar exhibited higher adsorption capacity for benzene and toluene (136.6 and 94.6 mg g−1), and lower adsorption capacity for water vapour (6.2 mg g−1). These findings provide an innovative design of engineered biochar for the adsorption of volatile organic compounds in the environment.

Bagasse heavy ash-derived Zn-loaded porous silica with tunable mesopores: Effect of monomodal and bimodal pores on VOCs adsorption

Bagasse heavy ash-derived Zn-loaded porous silica with tunable mesopores: Effect of monomodal and bimodal pores on VOCs adsorption

A facile, green strategy to synthesize N/P self-doped, biomass-derived, hierarchical porous carbon from water hyacinth for efficient VOCs adsorption

Carbon materials prepared using conventional strategies tend to have serious defects such as low porosity and a single pore structure, which compromise their VOC removal performance. Herein we report on a group of experimental porous carbons that were fabricated using water hyacinth (WH) as the starting material which is abundant in of N and P. The experimental results showed that the HWK-H prepared using a co-hydrothermal method exhibited the best performance in adsorbing methylbenzene with a saturated adsorption capacity of 624.7 mg/g. The results of several characterization tests revealed that HWK-H exhibited a high specific surface area (2199.9 m2/g), large pore volume (1.415 cm3/g), a specific micro/mesoporous structure, surface functional groups (mainly C = O, C-O and COOH), and a very disordered structure. All these properties were the reason for its superb methylbenzene adsorption performance. DFT calculations showed that the presence of N and P groups in the samples improved the energy of adsorption of the porous carbon materials for methylbenzene, thereby promoting its adsorption. GCMC simulation results also revealed that the carbon's micro/mesoporous pores in the range of 0.45–5.0 nm also facilitated the adsorption of methylbenzene. In addition, the multi-component co-adsorption performance and reusability of HWK-H were evaluated and the results showed that HWK-H offered good prospects for industrial application.

Preparation of a Novel Straw-Sludge Activated Biochar and Its Adsorption Mechanisms for Removal of VOCs.

To simultaneously achieve the objectives of waste resource utilization and clean production, a novel approach involving the utilization of corn straw-sludge hybrid biochar was proposed for the adsorption of VOCs emitted from biomass power plants. This study analyzed the effect of straw-sludge biochar on the adsorption characteristics of VOCs (toluene, isopentane, and ethylene) under different preparation conditions (raw material ratio, activation temperature, and activation time). The findings revealed that the adsorption efficiency of the mixed biochar was significantly superior to that of individual corn straw biochar and sludge biochar. The adsorption of methylbenzene, isopentane, and ethylene was 78.32, 40.81, and 41.18% higher, respectively, compared to the control groups consisting of pure sludge biochar and pure corn straw biochar. Moreover, the adsorption performance of the activated biochar followed the sequence of ethylene < isopentane < methylbenzene in terms of both saturation time and adsorption capacity. The adsorption capacity of VOCs on straw biochar-sludge biochar demonstrated a consistent correlation with the boiling point and molecular weight of the adsorbate, with higher adsorption capacities observed for adsorbates with larger boiling points and molecular weights, specifically methylbenzene > isopentane > ethylene.

Enhanced VOCs adsorption and oxidation by hydrophobic-layer-modified YMn2O5 mullite catalyst with ultralow single-atom Pt loading

Hydrophobic-layer-modified mullite YMn2O5 catalysts with ultralow single-atom Pt loadings and three-dimensionally ordered macroporous (3DOM) structures (denoted as × wt% Pt/YMO/Ph-3DOM) were synthesized via a facile strategy and assessed for toluene oxidation. The 3DOM structure provides a large surface area, while the ultralow Pt doping (0.1 wt%) reduces catalyst costs, improves low-temperature reducibility, and provides more oxygen vacancies, which are beneficial for O2 adsorption and activation. Surface modification with phenyltriethoxysilane significantly improves activity under wet conditions and promotes the adsorption of toluene. 0.1 wt% Pt/YMO/Ph-3DOM achieves 100% toluene oxidation at 160 °C at a WHSV of 36,000 mL g−1h−1 under wet conditions. In-situ DRIFTS experiments were carried out to investigate the reaction mechanism. Furthermore, DFT calculations were used to investigate the adsorption and activation of O2, toluene, and the intermediates on the catalyst surface, providing new insight into VOC oxidation for future investigations.

Synthesis of high hydrophobicity USY zeolite with excellent VOCs adsorption performance under humid condition: Combined strategy of high temperature steam and acid treatment

Y Zeolite and its ultra-stabilized hierarchical derivative (USY) as absorbents have low adsorption capacity for VOCs under humid conditions thus limits their industrial applications. It is well known that high SiO2/Al2O3 ratio (SAR) can improve the hydrophobicity of zeolite, and the increase of pore volume can enhance the adsorption performance. In the present work, SAR and the pore size of CY were enlarged by oxalic acid-high temperature steam-citric acid treatment, as the framework aluminum in the zeolite was removed and maintaining its structural integrity. The surface morphology and structure of samples were characterized by XRD, BET, TEM, SEM and TG. 27Al MAS NMR, XPS and Pyridine infrared analysis the mechanism of aluminum removal from the CY framework. The dynamic adsorption properties of the samples were systematically investigated with toluene selected as representative volatile organic compounds. The hydrophobicity of the samples was investigated by static water adsorption, and the adsorption kinetics model of the samples were plotted to study their adsorption characteristics. N2 adsorption-desorption results showed that the modified CY material has larger surface area, wider pore size and larger microporous volume than the raw material. On the other hand, with the improved SiO2/Al2O3 ratio and hydrophobicity, the modified USY also exhibited excellent adsorption performance under humid conditions, with 4.2 times more capacity to adsorb toluene. Therefore, this method can provide effective adsorption of VOCs in humid environments.