Toluene Adsorption Capacity Research Articles

Fabrication and adsorption properties of hierarchical NaY zeolite with mesopores in the range of 2∼5 nm

Adsorption is one of the most effective methods for controlling the concentration of VOCs pollution. In this work, the hierarchical NaY zeolites with size-controlled mesopores in the range of 2–5 nm are obtained via NH4HF2-etching and surfactant-templating process. By using the different cationic surfactant (CnTAB), we fabricate the surfactant-templated zeolite with controllable mesopores, and improve its adsorption capacity for toluene. In addition, the modified zeolite’s hydrophobicity is enhanced, and it maintains a high adsorption capacity in a complex humid environment.

Ceria-zirconia solid solution supported platinum catalysts for toluene oxidation: Studying the improved catalytic activity by tungsten addition

The catalytic oxidation of toluene at low temperatures is still an urgent issue to be solved. The key to addressing this issue is the preparation of a high-efficiency catalyst. Herein, ceria-zirconia (CZ) solid solution supported platinum (Pt) catalysts were prepared by citric acid (C)-assisted impregnation method. Surprisingly, the catalytic oxidation activity of the catalyst for toluene combustion significantly improved after introducing W into Pt-C/CZ. In addition, introducing W improved the redox property of the Pt-based catalyst, optimized the distribution of the oxygen vacancies, increased the average particle size of the catalyst particle, modulated the valence state and electronic structure of Pt, elevated the surface lattice oxygen activity, increased the number of surface moderate acidic sites and enhanced toluene adsorption capacity. In this study, the electronic structure of the Pt active site is modulated by introducing a W promoter, providing valuable guidance for the rational design of efficient noble metal catalysts.

Adsorption performance and mechanism of single-component and multi-component VOCs by Beta zeolites with different Si/Al ratios

The physical and chemical properties of VOCs and zeolite materials generally affect adsorption efficacy for VOCs removal. Here, toluene and methanol were chosen as typical VOCs with different polarities and molecular diameters to investigate the performance and mechanism of their adsorption on Beta zeolites with various Si/Al ratios. It was found that high-silica Beta exhibited superior toluene adsorption capacity, while low-silica Beta showed higher methanol adsorption capacity. Compared with single-component adsorption, in the case of co-adsorption of toluene and methanol, the saturation adsorption capacities for toluene and methanol only changed slightly even with the existence of competitive adsorption and weakened adsorption strength. Importantly, there was almost no decrease in absorption capacity after 10 repeated adsorption-regeneration cycles, showing the excellent reusability of Beta zeolites for toluene and methanol removal. Whether on low-silica or high-silica Beta, physical adsorption of toluene and methanol was dominant, along with a small proportion of chemical adsorption on low-silica Beta based on acid sites. Similar size between the diameters of toluene and the pore channels of Beta zeolites was responsible for strong adsorption force, increase of adsorption capacity, and minor effect on absorption performance in the process of competitive adsorption. Strong interaction between acid sites and polar methanol through H-bond or non-polar toluene by electrostatic attraction promoted chemical adsorption. Furthermore, toluene and methanol both tended to absorb in the twelve-membered-ring of Beta zeolites on Si-OH-Al, Al-OH, and Si-OH sites. This study provides insight into the factors influencing the adsorption performance and mechanism of toluene and methanol on zeolites, which gives potential guidance for the selection of adsorbents for high-efficiency VOCs removal.

Construction of hydrophobic HKUST-1 in wood with selective adsorption performance for toluene and moisture blends

The effect of moisture on the volatile organic compound (VOC) adsorption on biomass-derived metal–organic framework composites is significant in practical applications. In this study, wood-based metal organic frameworks (MOF199-W) and hydrophobic MOF199-W (HMOF199-W) were developed using HKUST-1 (MOF199) and long alkyl chains to investigate the adsorption performance of toluene and enhance the selectivity of adsorption under high humidity conditions. The results demonstrated that HKUST-1 could be anchored onto the surface of wood vessels and fibers through coordination with Cu2+, resulting in an improved surface area in comparison to natural wood. The toluene adsorption capacity of MOF199-W with a 20 % loading was comparable to that of an equivalent amount of MOF199, with adsorption capacities of 323.5 mg/g and 369.9 mg/g, respectively. Further, the Yoon-Nelson model was found to adequately describe the dynamic adsorption process. Following the introduction of long alkyl chains, MOF199 and MOF199-W were endowed with strong hydrophobic character (water contact angle of 107.0◦, 104.0◦, and water uptake of 30.5 mL/g, 55.3 mL/g). With the increase in humidity, the adsorption performance of MOF199 and MOF199-W for toluene sharply decreased, but HMOF199 and HMOF199-W still maintained the adsorption capacities at 304.7 mg/g and 226.7 mg/g, even under 80 % RH conditions. Therefore, HMOF199-W has shown great potential in wooden building materials with the ability for toluene capture under humid conditions.

Unveiling the role of oxygen vacancy of manganese oxide coating on Ni foam to magnetocaloric catalytic oxidation of toluene

Using a pulsed-voltage technique, the manganese oxide (MnOx) coating on Ni foam (NF) was regulated to encourage magnetocaloric oxidation, which lowers volatile organic compounds (VOCs). The MnOx/NF was obtained by electrodeposition of MnOx onto NF. Subsequently, MnOx/NF-PV was obtained by pulsed-voltage modification. According to the structural characterization, the pulsed-voltage modification changed the interaction between the coating and the support, resulting in increased toluene adsorption capacity, oxygen desorption capability, oxygen vacancy (OV) quantity of MnOx/NF-PV. The MnOx/NF-PV exhibits excellent catalytic performance, with a 90 % conversion of toluene at 170 °C, where OV play an important role as electronic intermediates in magnetocaloric oxidation reactions. Furthermore, compared to traditional thermal catalysis, electromagnetic induction heating (EMIH) can promote the reactivity of OV in magnetocaloric catalysts by increasing the activation and dissociation of oxygen species and thus catalytic activity, which was demonstrated in the 18O isotope exchange experiment.

Regulation of the co-transport of toluene and dichloromethane by adsorbed phase humic acid under different hydro-chemical conditions

The transport behavior of combined organic pollutants in soil and groundwater has attracted significant attention in recent years. Research on the influence of humic acid (HA) on organic pollutant transport behavior mainly focuses on the study of the mobile phase HA, with less research on the adsorbed phase HA, especially regarding its interaction with combined pollutants. To enhance understanding of the regulation of co-transport and retention of combined pollutants by adsorbed phase HA, in this study, tests were conducted to investigate how toluene (TOL) and dichloromethane (DCM) are transported in the presence of adsorbed phase HA at different pH levels and ionic strengths. As the proportions of HA-coated sand increased, so did its adsorption capacity for TOL and DCM, which can be attributed to adsorbed phase HA providing more adsorption sites compared to plain sand, thereby reducing the transport potential of the pollutants. The presence of both TOL and DCM facilitated their mutual transportation due to competitive adsorption controlled by the adsorbed phase HA content in the porous medium. Furthermore, it was observed that pH levels influenced the transport behavior of TOL and DCM when adsorbed phase HA was present since adsorbed phase HA transformation into mobile phase was regulated by pH levels. The transport patterns can be effectively simulated using the chemical nonequilibrium two-site sorption model in HYDRUS-1D, accurately reflecting the retardation coefficients and transport distances based on model parameters. This work sheds new light on the regulatory role of adsorbed phase HA in TOL and DCM transport under diverse hydrochemical conditions, with implications for accurately depicting the behavior of combined pollutants, optimizing the remediation strategies and improving remediation efficiency in contaminated sites.

Constructing binuclear sites to modulate the charge distribution of MIL-101 for enhanced toluene adsorption performance: experimental and theoretical studies

Toluene is a class of volatile organic compounds (VOCs) in the air that harm environmental quality and human health. To enhance the adsorption performance of adsorbents for toluene, based on the principle that unsaturated metal sites in MOFs can be replaced, nanoscale M@MIL-101(M represents Mg, Ca, Sr) with binuclear sites was prepared by a one-step solvothermal method. The second metal was successfully introduced into the topology of MIL-101 by partially substituting Cr sites. The results of the dynamic adsorption experiments showed that 20%Sr@MIL-101 exhibited the highest toluene adsorption capacity, which was about 60% higher than that of the undoped MIL-101. Analysis using a monolayer and multilayer model based on statistical physics theory indicated that the Sr/Cr binuclear sites could enhance the interaction strength of the adsorption system, promoting the adsorption of more layers of toluene molecules on the surface of MIL-101. Characterization and simulation together confirmed that constructing Sr/Cr binuclear sites in MIL-101 can cause significant redistribution of charge within the pores, enhancing the van der Waals interactions, π-π stacking interactions, hydrogen bonding, and Lewis acid-base interactions between the pore interior and the adsorbate molecules. Additionally, density functional theory (DFT) revealed that the adsorption sites of toluene in MIL-101 were distributed in a trigonal prism arrangement and were symmetrically aligned with a 180° rotation of the MIL-101 triangular cage.

Unveiling the Role of Hydrophobicity on Multilayer Carbon Nanosheets Enriched in sp2-Carbon for Toluene Adsorption under Humid Conditions.

Carbon materials are regarded as a promising adsorbent for the adsorption of volatile organic compounds (VOCs). However, their adsorption behaviors are usually compromised at ambient conditions, attributed to the competitive VOCs adsorption with water vapor. In this study, we demonstrated that the selectivity for toluene than water of carbon can be effectively enhanced by introducing more sp2-carbon with two-dimensional nanosheets stacked. The multilayer carbon nanosheets enriched with sp2-carbon (CNS-MCA) exhibit a 151° H2O-contact angle, indicating hydrophobicity. Dynamic adsorption behaviors revealed that CNS-MCA retain 71% of their toluene adsorption capacity (91 mg/g) even at 60% relative humidity. Density functional theory (DFT) calculations, static adsorption studies, in situ Raman spectroscopy, and time-resolved in situ nuclear magnetic resonance (NMR) spectroscopy collectively indicate that toluene exhibits enhanced adsorption and selectivity due to π-π* interactions between its aromatic rings and the sp2-carbon. Conversely, water adsorption is attenuated, attributed to the reduced availability of surface-exposed hydrogen bonds associated with sp2-carbon and the inherent hydrophobic nature of multilayer graphene. This study extends a novel solution for the enhancement of VOCs adsorption under humid conditions.

Insight into the Better Collaboration of NiO and MnOx in NiMn2O4 Spinel for Enhanced the Catalytic Oxidation Performance of Toluene

AbstractNiMn oxides with different ratios (NixMnyOz) as well as spinel‐type NiMn2O4 oxides were synthesized and utilized in the catalytic oxidation of toluene. The results indicate that NiMn2Ox synthesized by the oxygen‐only roasting method exhibits superior catalytic activity due to the appropriate metal valence distribution. The catalytic activity is strongly related with the crystalline phase structures, NiMn2O4 spinel oxides catalyst shows the best low‐temperature performance with 90 % conversion (T90) at 230 °C. Characterization results reveal that the superb catalytic performance of NiMn2O4 spinel oxide is mainly profit by the larger surface area, more abundant surface fugacious oxygen, stronger toluene adsorption capacity than that of the other NixMnyOz catalysts, which in favor of the speedy conversion of benzoic acid, improving the toluene catalytic performance. This finding provides a novel design strategy of NiMn composite oxides for synthesis of high‐efficiency performance toluene catalysts.

Enhanced Adsorption of Gaseous Naphthalene by Activated Carbon Fibers at Elevated Temperatures.

This study utilized activated carbon fibers (ACFs) as adsorbents to investigate the removal efficiency of naphthalene and toluene at elevated temperatures and their competitive adsorption behavior. Three types of ACFs, inlet concentrations of naphthalene (343, 457, and 572 mg·Nm-3), and toluene (2055, 2877, and 4110 mg·Nm-3) were investigated to determine the adsorption capacities of naphthalene and toluene. To study the reaction mechanisms of naphthalene and toluene on the ACFs, the BET, SEM, FTIR, and TGA methods were used to examine the physical and chemical characteristics of ACFs. Results showed ACF-A's superior adsorption capacity for naphthalene that was attributed to its mesoporous structure and hydrophobicity. Adsorption equilibrium studies indicated multilayer adsorption behavior. Competitive adsorption experiments demonstrated the displacement of toluene by naphthalene on ACF-A, highlighting its higher selectivity for naphthalene. Functional group analysis revealed changes in ACF surfaces after naphthalene adsorption, suggesting π-π dispersion and electron donor-acceptor interactions. Overall, this study underscores the importance of pore structure and surface properties in designing ACFs for the efficient adsorption of high-boiling-point organic pollutants.

Excellent adsorption and catalytic oxidation of toluene facilitated by metal-free nitrogen-doped mesoporous biochar

In this study, we synthesized a series of nitrogen-doped mesoporous biochar by a salt-templating method to assess the potential of our modified biochar for advanced remediation of toluene through either adsorption or catalytic oxidation. The principal findings indicated that the incorporation of nitrogen and the mesopore-forming agent significantly influenced the toluene removal performance by altering the physicochemical properties of the biochar. Notably, the sample synthesized at 900 °C (BUPZ-900) exhibited the exceptional toluene adsorption capacity, reaching 283.85 mg/g, due to its high surface area and mesopore volume. Advanced characterizations revealed that different nitrogen functionalities played distinct roles in the adsorption performance. The presence of graphitic nitrogen in BUPZ-900 enhanced toluene adsorption through π-π dispersion interactions. Conversely, BUPZ-600, boasting a high nitrogen content (8.66 at%) and a predominance of pyridinic-N (3.92 at%), exhibited the highest catalytic activity, despite its low adsorption capacity attributed to a smaller surface area. This heightened activity was attributed to the basicity of pyridinic-N, which acted as active sites, despite the material’s lower surface area. Our study highlights the promise of nitrogen-doped mesoporous biochar as an effective adsorbent or catalyst for advanced remediation of volatile organic compounds (VOCs), even in the absence of metal catalysts. This work emphasizes the critical role of synthesis temperature and nitrogen functionalization in optimizing biochar properties for environmental applications.

Molecular simulation of different VOCs adsorption on nitrogen-doped biochar

Nitrogen-doped biochar has potential application in the removal of volatile organic compounds (VOCs) from coal-fired flue gas. To explore the adsorption characteristics of different VOCs on nitrogen-doped biochar by molecular simulation, in this study, six typical aromatic VOCs (benzene, toluene, phenol, naphthalene, p-xylene, and chlorobenzene), and an amorphous carbon model with nitrogen/oxygen groups were selected and constructed. Grand Canonical Monte Carlo (GCMC) simulations were performed to evaluate the adsorption capacities of VOCs on nitrogen-doped biochar. The results showed that the optimized carbon model was in good agreement with the pore structure parameters of nitrogen-doped biochar, and the agreement of toluene adsorption capacities was more than 80 % at room temperature. The adsorption capacity of nitrogen-doped biochar for different VOCs was 184 − 317 mg/g with the order of phenol > naphthalene > p-xylene > toluene ≈ benzene ≈ chlorobenzene (single-component adsorption). Among them, the phenol molecule is more easily adsorbed due to its strong polarity, resulting in stronger electrostatic interaction with the adsorbent. The decrease rate of benzene adsorption capacity is the lowest with increasing adsorption temperature because of its low molecular weight. As gas concentration increases, van der Waals interactions between molecules and between molecules and porous carbon also increase, leading to an increase in VOCs adsorption capacity. Nitrogen-doped biochar not only has the highest VOCs/N2 selective adsorption coefficient for phenol (up to 36) but also has the highest adsorption capacity of 63 mg/g when 6 kinds of VOCs are multi-component adsorption at 25 °C. This study can provide references for the practical application of adsorption method in the removal of VOCs from coal-fired flue gas.

Insights into the removal of volatile organic compounds by three-dimensional ordered microporous zeolite-templated carbon: A combined experimental study and density functional theory calculation

Volatile organic compounds (VOCs) threaten human health and the ecological environment, requiring to be removed timely. Zeolite-templated carbon with and without sulfur (ZTC and S-doped ZTC) was prepared by the chemical vapor deposition (CVD) method in a rotating bed reactor and used to remove VOCs. ZTC samples showed narrow and ordered microporous structure (0–2 nm), high specific surface area (2049.05–1732.06 m2/g), abundant pore volume (1.28 – 1.16 cm3/g), and uniform sulfur distribution (S-doped ZTC). Afterwards, the VOCs adsorption capacity was tested at 30, 60, and 90 °C. The results showed that S-doped ZTC exhibited higher benzene (138.2 mg/g) and toluene (171.8 mg/g) adsorption capacities at 30 °C than those performed at 60 and 90 °C owing to the exothermic process. Moreover, S-doped ZTC showed better VOCs adsorption capacity than ZTC-RC due to the combination of physical and weak chemical adsorption. Subsequently, S-doped ZTC captured more toluene (171.8 mg/g) than benzene (138.2 mg/g) because of the dipole–dipole interaction. Furthermore, Fourier transform infrared spectrum (FTIR) and density functional theory (DFT) calculation revealed that inorganic components (NH3, NO, and SO2) imposed a negative effect on VOCs adsorption due to the comparative adsorption. This study offered insights into how ZTC structure and sulfur modification affected the adsorption of VOCs, providing a reliable guideline for the preparation and utilization of adsorbents used to remove VOCs.

Simultaneously enhancing toluene adsorption and regeneration process by hierarchical pore in activated coke: a combined experimental and adsorption kinetic modeling study.

Activated coke is a type of commonly used adsorbent for benzene series VOCs such as toluene, but traditional microporous activated coke usually faces the challenge of poor regeneration performance. Herein, based on self-made activated cokes with typical pore configuration, we found that adsorption and regeneration of toluene can be simultaneously enhanced by constructing hierarchical pore in activated coke. Correlations of pore configuration with toluene adsorption capacity and regeneration efficiency reveal that micropore contributes for strong toluene adsorption; meso-macropore provides mass transfer channel for toluene desorption and regeneration process. Hierarchical porous activated coke prepared from Zhundong subbituminous coal not only achieves the highest toluene adsorption capacity of 340.92mg·g-1, but also can retain more than 90% of initial adsorption capacity after five adsorption-regeneration cycles. By contrast, micropore-dominant activated cokes can only retain 70% of initial adsorption capacity. Adsorption kinetic modelling on adsorption breakthrough curves shows that hierarchical porous activated coke prepared from Zhundong subbituminous coal exhibits high adsorption and diffusion rate constants of 14.39 and 33.45min-1, respectively, much higher than those of micropore-dominant activated cokes. Due to the accelerated surface adsorption and diffusion processes induced by meso-macropore, toluene adsorption and regeneration behavior can be simultaneously improved. Results from this work validated the role of pore hierarchy in toluene adsorption-regeneration process, providing guidance for designing high-performance activated coke with synergistically improved toluene adsorption capacity and regeneration performance.

Hydrophobic hypercrosslinked polymers prepared by secondary pore-forming method as excellent toluene adsorbents

In this work, inspired by molecular imprinting technology, we developed a secondary pore-forming method to chemically etch three hypercrosslinked polymers which are constructed from three novel hexapolar monomers containing imine groups, resulting in three novel hydrophobic porous hyper-crosslinked polymers (HCPs) pGly-TPA, pP-TPA and pBP-TPA. The structures were determined by FT-IR and solid-state 13C NMR spectroscopic techniques. The specific surface areas of pGly-TPA, pP-TPA and pBP-TPA are 694.1, 197.9 and 497.7 m2/g, respectively. All three porous polymers exhibit high hydrophobic properties with wetting angles of much greater than 90°. The breakthrough adsorption experiments revealed that the three prepared polymers exhibited significant adsorption capacity for toluene (322.05 mg/g for pGly-TPA, 114.43 mg/g for pP-TPA and 279.14 mg/g for pBP-TPA), but showed almost no adsorption for ethyl acetate, cyclohexane, and n-hexane, exhibiting certain molecular size and polarity selectivity. The adsorption behaviors of toluene on pGly-TPA, pP-TPA and pBP-TPA can be fit by the Boltzmann model and the Yoon-Nelson model, suggesting that the fixed bed has low mass transfer resistance. The adsorption rate is controlled by both external diffusion and intraparticle diffusion, as shown by the intraparticle diffusion model analysis. In addition, the adsorption capacity of toluene on pGly-TPA is almost unchanged under high humidity (70 %) or five adsorption–desorption processes, which demonstrates exceptional water-resistance and stability. This work is a reference for preparing novel hydrophobic HCPs using the secondary pore-forming method for removing VOCs from humid air.

Biomimetic dendritic‐networks‐inspired oil-water separation fiber membrane based on TBAC and CNC/PVDF porous nanostructures

Inspired by the multi-level structure of trees in nature, using cellulose nanocrystals/polyvinylidene fluoride (CNC/PVDF) fibers as the support layer and CNC/PVDF/organic branched salt (TBAC) fibers as the filtering layer, to construct oil–water separation membrane with tree-like structure. The membrane's surface (nano spherical) and internal (interconnected pores) structures were regulated by phase separation of CNC induced. The high conductivity of TBAC was utilized to construct branched fibers (d = 53.3 nm) on the backbone fibers (d = 1.2 μm). The impact of TBAC on the microstructure, wetting behavior, and oil–water separation performance of membranes was investigated. Note, TBAC concentration was 0.02 mol/L, the membrane exhibits a highly porous dendritic network structure (with porosity of 85 % and pore size of 6.1 nm), and outstanding wetting properties (water contact angle underoil ˃ 150°). This distinctive structure endows membranes with a high oil adsorption capacity (64.1 g/g of engine oil), oil flux (22873 L/m−2h−1 of toluene). Following ten testing cycles, the toluene adsorption capacity remains at 83.1 % of the initial adsorption, while the separation flux of emulsion (5645 L/m−2h−1) remains nearly constant. Overall, successfully fabricating CNC/PVDF/T-0.02 fibers with a tree-like structure provides a novel approach to designing and developing efficient membrane separation materials.

Performance on adsorption of toluene by ionic liquid-modified AC in high-humidity exhaust gas.

Volatile organic compounds (VOCs) frequently pose a threat to the biosphere, impacting ecosystems, flora, fauna, and the surrounding environment. Industrial emissions of VOCs often include the presence of water vapor, which, in turn, diminishes the adsorption capacity and efficacy of adsorbents. This occurs due to the competitive adsorption of water vapor, which competes with target pollutants for adsorption sites on the adsorbent material. In this study, hydrophobic activated carbons (BMIMPF6-AC (L), BMIMPF6-AC (g), and BMIMPF6-AC-H) were successfully prepared using 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) to adsorb toluene under humidity environment. The adsorption performance and mechanism of the resulting ionic liquid-modified activated carbon for toluene in a high-humidity environment were evaluated to explore the potential application of ionic liquids as hydrophobic modifiers. The results indicated that BMIMPF6-AC-H exhibited superior hydrophobicity. The toluene adsorption capacity of BMIMPF6-AC-H was 1.53 times higher than that of original activated carbon, while the adsorption capacity for water vapor was only 37.30% of it at 27 °C and 77% RH. The Y-N model well-fitted the dynamic adsorption experiments. To elucidate the microscopic mechanism of hydrophobic modification, the Independent Gradient Model (IGM) method was employed to characterize the intermolecular interactions between BMIMPF6 and toluene. Overall, this study introduces a new modifier for hydrophobic modification of activated carbon, which could enhance the efficiency of activated carbon in treating industrial VOCs.

Study on the adsorption mechanism of polar and non-polar VOCs by the activated carbon with surface oxygen

In this study, CO2 was converted to activated carbon by the molten salt CO2 capture and electrochemical conversion (MSCC-EC) method, and the surface oxygen content of the activated carbon was further modified for the adsorption of polar molecules (chlorobenzene) and nonpolar molecules (toluene), the role of the pore structure and surface O-containing functional groups of the adsorbents in contributing to the adsorption process was systematically investigated. The results showed that MS-AC500-10, MS-AC500-15, and MS-AC550-15 have rich pore structures with specific surface areas of 811.56 m2/g, 835.35 m2/g, 1249.104 m2/g, and surface oxygen contents of about 10 %, 15 %, 15 %, respectively. The toluene adsorption capacity of MS-AC500-10, MS-AC500-15, and MS-AC550-15 was 203.82 mg/g, 229.72 mg/g, and 358.97 mg/g, respectively, and was dominated by pore adsorption, which was positively proportional to the specific surface areas and pore volumes, the adsorption process belonged to the pseudo-first-order kinetic model. The adsorption amounts of chlorobenzene by MS-AC500-10, MS-AC500-15, and MS-AC550-15 were 287.98 mg/g, 363.11 mg/g, and 495.41 mg/g, respectively. In addition to the pore adsorption, the oxygen content on the surface of the adsorbents had a non-negligible promotion effect on the adsorption of chlorobenzene, mainly because chlorobenzene is a polar molecule, and the asymmetric electrons on its surface have strong interactions with the O-containing functional groups on the surface of the adsorbents. Moreover, the prepared adsorbents were thermally stable, and the decay rate of adsorption performance was less than 5 % after five adsorption–desorption cycles.

Modelling and prediction of toluene adsorption saturation basing on characteristic values of activated carbons

Herein, the association between the dynamic adsorption capacity of toluene and several important characteristic values on activated carbon (AC) samples was investigated by multidimensional linear regression. Among the characteristic values, the carbon tetrachloride (CTC) adsorption value has demonstrated relatively stronger correlation with the toluene adsorption capacity on AC samples with diverse sources and forms, particularly in exposure to high-concentration toluene. Notably, the relevance of the toluene adsorption capacity to the CTC value could also be extended to a series of other porous adsorbents, which proved the wide applicability of CTC value in characterizing the adsorption behaviors. Based on these results, a mathematical and visual model was then established to predict the toluene adsorption saturation under different conditions (inlet concentration, adsorption time, initial CTC value, etc.) on diverse AC samples, of which the accuracy has later been verified by experimental data. As such, a fast and accurate estimation of the adsorption behaviors over AC samples, and possibly other porous adsorbents, was realized.

Tackling the challenge of efficient VOCs removal across varied molecular sizes over zeolite adsorbent under humid conditions

Efficient removal of volatile organic compounds (VOCs) with different molecular sizes over a single zeolite remains a great challenge, especially under humid conditions. Here, we introduced an innovative base leaching strategy to construct hierarchical pores within high-silica MFI zeolite on premise of maintaining a similar high micropore volume. The key points were the introduction of Al3+ and B3+ as pore directing agents into the base solution and meticulous regulation of the acid washing process. Because of the introduction of mesopores, the adsorption capacities for m-xylene increased by 16.1 times compared to that on conventional MFI adsorbent. Meanwhile, it exhibited comparable adsorption capacities for smaller VOCs, including dichloromethane and toluene. The adsorption capacities for ethanol showed a notable increase, accompanied by a decrease in the desorption temperature. This was attributed to the generation of additional silanol adsorption sites, as confirmed by 1H MAS NMR and in situ FT-IR spectra. Moreover, the optimal adsorbent presented good regeneration performance throughout the four dynamic adsorption–desorption cycling tests for all VOCs.