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Volatile organic compounds (VOCs) released in air represent a major potential for environmental pollution. Capture methods based on activated biochar have attracted attention because of their low cost and for the high removal capacity of the material due to its physical and chemical properties. In this paper, activated biochars were developed and their adsorption performance for VOC capture was evaluated. In the first step, biochars derived from rapeseed cake (RSC) and walnut shells (WSC) were obtained through a carbonization process and then were activated using basic/acid agents (KOH/H2SO4) to increase their performance as adsorbents. Acetone and toluene were used as the VOC templates. The adsorption capacities of toluene and acetone for non-activated biochars were reduced (26.65 mg/g), while that of activated biochars increased quite significantly, up to 166.72 mg/g, and the biochars activated with H2SO4 presented a higher adsorption capacity of VOCs than the biochars activated with KOH. The higher adsorption capacity of biochars activated with H2SO4 can be attributed to their large surface area, and also to their larger pore volume. This activated biochar adsorbent could be used with good results to equip air purification filters to capture and remove VOCs. [ABSTRACT FROM AUTHOR]

β Zeolites with a high SiO2/Al2O3 ratio (SAR) are of great importance in the adsorption of VOCs. However, the higher the SAR of β zeolites, the more difficult they are to synthesize because of kinetic limitations. Herein, adopting a seed-assisted synthesis ensures that β zeolites have a high yield and a wide range of SAR (up to 600, named Nano-B600). Furthermore, a comprehensive insight into the evolution of particle structure in the synthesis system and the influence of seed crystals was gained by a synchrotron radiation small-angle X-ray scattering (SAXS) technology, FT-IR, SEM, and TEM. The results showed that the species dissolved from seed crystals present appropriate fractal structure, promoting the formation of a large number of structural units and leading to the rapid growth of β zeolites. Typically, Nano-B600 possesses a larger surface area and mesopore volume as well as strong hydrophobicity, which shows super toluene adsorption capacity, with an increase of 43% compared to that of the bulk β zeolites with a similar SAR, and can also maintain adsorption performance under moisture. For other organic compounds, Nano-B600 shows a much higher adsorption capacity compared to that of the usual ZSM-5 and Y zeolites. The high-silica nanosized β zeolites demonstrate strong applicability as super adsorption materials for VOCs. [ABSTRACT FROM AUTHOR]

High-quality biochars/activated carbons were prepared, optimizing individual parameters of energetically-save microwave pyrolysis (raw material loading - 20 vs. 60 g, nitrogen atmosphere - flow vs. batch, ZnCl 2 activation) from two agricultural wastes - corn cobs, red mombin seeds. Most promising carbons were examined for gaseous xylene adsorption and showed higher sorption capacity (∼250–475 mg xylene · g−1) than commercial carbon (∼214 mg xylene · g−1). ZnCl 2 activation of both raw materials reduces the fixed carbon content and increases volatiles in activated carbon, suggesting microwave pyrolysis of activated feedstock should take 25 min. While biochars are microporous materials with inhomogeneous low-surface mesopore/macropore network, activated carbons are highly microporous-mesoporous. ZnCl 2 activation of both raw materials contributes to formation of extensive high-surface mesopore network (with pore-size < 20 nm) and enlargement of micropore-size, but does not affect the micropore volume. ZnCl 2 activation increases H 2 and decreases CH 4 production. Microwave pyrolysis of larger raw material loading with ZnCl 2 leads to CO 2 increase. Best xylene adsorption capacity (475 mg xylene · g−1) was determined for activated carbon produced from 60 g loading of corn cobs in batch nitrogen atmosphere, showing the largest micropore volume, lowest surface polarity and medium rate of graphitization. Large micropore volume, low surface polarity and high rate of graphitization of carbon are xylene sorption capacity-determining factors. [Display omitted] • Microwave pyrolysis optimization of corn cobs and red mombin seeds was done. • Pyrolysis time shortened from hours to 15 min in flow and 20 min in batch of nitrogen. • Novel highly-microporous activated carbons investigated in xylene adsorption. • Promoted H 2 + CO 2 production by larger biomass loading and ZnCl 2. • Large micropore volume, low surface polarity, high rate of graphitization are key for xylene sorption. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) pose an ever-growing threat on human health and environment. Predicting VOC affinity coefficient and consequently estimating activated carbon adsorption requires fundamental understanding of adsorbate-adsorbent interaction, shape and hydrophilicity effects. Hence, a model which expressed these three factors with molecular descriptors was investigated with Ridge and V-matrix regression methods in two cases, k-fold cross-validation and random sampling technique. The results showed, the sole interaction term and the complete model decreased the root mean square error (RMSE) of polarizability ratio by approximately 19% and 26% respectively. The V-matrix regression, reduced the average Ridge RMSE by 9 and 19% for the first and second case. Lower than 10% errors were displayed by 104 out of 155 data and only 4 data which were small molecules with very high polarity had more than 30% error. For both cases the proposed model with V-matrix regression had better or similar results compared to previous research. However, the effect of reference compounds on highly polar VOCs requires further investigation. From the VOC adsorption estimation, it was evident that affinity and adsorption errors were in the same magnitude. Hence, with accurate prediction of affinity coefficient, adsorption isotherms of any VOC can be calculated. [ABSTRACT FROM AUTHOR]

Metal-organic framework (MOF) activation is crucial for the use of MOFs in several applications and solvent-exchange process is a necessary step in many activation methods. In this contribution, we have explored in situ MOF monolayer film formation at the air-water interface. Nanoparticles (NPs) of the Al trimesate MIL-96(Al) retain chloroform into their micropores, which considerably diminishes the CO 2 adsorption capacity of MOF films. However, a solvent-exchange process between chloroform and water increases CO 2 film adsorption capacity by 30%. Total Reflection X-Ray Fluorescence (TRXF) allows studying the kinetics of this process at the air-water interface, that strongly depends on the NP size. The conclusions derived from in situ studies allow optimizing the ex situ activation procedure of MIL-96(Al) films deposited onto quartz crystal microbalance (QCM) substrates in order to maximize CO 2 and methanol adsorption. [ABSTRACT FROM AUTHOR]

Mixed matrix composite membranes (MMCMs) have shown advantages in reducing VOCs and CO 2 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 CO 2 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-NH 2 and PDMS is confirmed by molecular simulations. The Si─O functional group and UiO-66-NH 2 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 CO 2 transport. The MMCMs show strong four VOCs adsorption and high CO 2 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-NH 2 , improving the affinity towards CO 2 and thus promoting the permea-selectivity for CO 2 , 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 CO 2 permea-selectivity., (© 2024 Wiley‐VCH GmbH.)

The adsorption of benzene vapor, as a volatile organic component, from inert gas (N2) by activated carbon was studied experimentally in the isothermal fixed bed reactor at various operating conditions. The activated carbon used in this study had pistachio shell base with high surface area. To improve the adsorption capacity of VOC vapor, the activated carbon was chemically treated with H2SO4, HNO3, NaOH, and NH3 solutions. The saturated adsorption capacities of benzene on initial activated carbon and treated samples were measured and compared. The results showed that the activated carbon treated with nitric acid had higher adsorption capacity than others samples, 640 mg/g. In addition, a mathematical model for adsorption in a fixed bed reactor was proposed in this study. The model results had good agreement with experimental data. In order to demonstrate the effects of operating conditions on adsorption and breakthrough curve, the experimental tests and simulation runs were carried out at various gas flow rate, temperature, and benzene concentration. The results showed that with increase VOC concentration from 700 to 1000 ppm, the total time of adsorption was decreased from 25 to 21 h and breakthrough point appeared earlier. [ABSTRACT FROM AUTHOR]

It is challenging to prepare biomass-based super activated carbon (SAC) simultaneously possessing a surface area larger than 2500 m2/g and a pore volume up to 2.2 cm3/g. In this research, SACs were prepared by impregnating coconut shell with H 3 PO 4 at high impregnation ratio before suddenly heating them in CO 2 flow. The SAC prepared at impregnation ratio of 3 displayed a specific surface area of 2763 m2/g, a total pore volume of 2.376 cm3/g, and a mesopore volume of 1.365 cm3/g. All these pore parameters ranked among the highest corresponding values reported for porous carbons. Because of the well-developed pore structure of this sample, its adsorption capacities for benzene, methanol, n -hexane and cyclohexane reached 1846, 1777, 1510, 1766 mg/g, respectively, all of which were high compared with the corresponding values previously reported for porous adsorbents. This sample also showed superior adsorption rate and excellent recyclability for the tested VOCs. Raising the impregnation ratio from 3 to 4 did not enhance the pore properties and VOC adsorption performance. This research provided a feasible route to manufacture biomass-based SAC which possessed simultaneously large surface area, superior pore volume, and high broad-spectrum VOC adsorption performance. Image 1 • SACs simultaneously having large surface area and pore volume were prepared. • The best SAC showed surface area of 2763 m2/g and pore volume of 2.376 cm3/g. • The surface area and pore volume were among the highest values for active carbons. • The SAC showed high adsorption capacity and excellent recyclability for four VOCs. • The uptakes for the four VOCs were all among the high values for porous adsorbents. [ABSTRACT FROM AUTHOR]

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 ( S BET up to 929 m 2 ·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 ).

Silicalite-1 is a pure-silica MFI-type zeolite, which is widely used in the field of adsorption and separation of organic compounds. Herein, the high-micropore-volume silicalite-1 with less silanol defects was obtained under a near-neutral condition free of fluoride ions adjusted by anionic polyelectrolytes, which exhibited excellent adsorption of a wide variety of toxic volatile organic compounds. The performance for capturing VOCs could be improved along with the decrease of silanol defects in pure silica zeolites. Image 1 • Firstly synthesize pure-silica zeolites from a fluoride-free polyelectrolyte-containing near-neutral system • Zeolite from the neutral system had larger amounts of micropores than that from the traditional basic synthesis. • Displaying the better adsorption properties for volatile organic compounds at the high temperatures. • This novel polyelectrolyte-containing neutral system showed great potential for synthesizing other types of zeolites. [ABSTRACT FROM AUTHOR]

• A pilot-scale bubbling fluidized bed adsorption device was designed and operated. • Bubbling fluidized bed is suitable to recovery the industrial VOCs. • Diffusion is the rate-determining factor of adsorption. • The adsorption rate of the bubbling fluidized bed is significantly high. • The optimized conditions of bed height is 40 mm for the bubbling fluidized bed. Adsorption is one of the most efficient inexpensive strategies for the removal of volatile organic compounds (VOCs). However, adsorption of VOCs by fixed beds has certain limitations, such as considerable energy consumption and high operating costs. To treat VOCs with high volume and low concentration, a pilot-scale multistage bubbling fluidized bed adsorber was developed herein and was used to conduct the adsorption experiments. Experimental investigation of ethanol adsorption on the adsorbent under static and dynamic conditions revealed that ethanol adsorption on the adsorbent followed the Langmuir adsorption model. The adsorption kinetics followed a linear driving force (LDF) model, which showed that diffusion was the rate-determining factor. Moreover, the effects of operating conditions, such as bed height, superficial gas velocity, inlet concentration, and desorption temperature, on adsorption were investigated. The results showed that adsorption efficiency in the bubbling fluidized bed varied from 85.7% to 94.5%. The findings of this study could provide the basic data for the design and development of a bubbling fluidized bed for application in the recovery of low-to-medium concentrations of industrial VOCs. [ABSTRACT FROM AUTHOR]

Novel tetrakis [(4-(hydroxymethyl)-2,6-dimethoxyphenoxyl)] substituted zinc(II), cobalt(II) and iron(II) phthalocyanines were synthesized by the reaction of (4-(hydroxymethyl)-2,6-dimethoxyphenoxy)phthalonitrile with suitable metal salts in 2- N , N -dimethylaminoethanol. The phthalonitrile ligand was prepared from 4-hydroxy-3,5-dimethoxy benzyl alcohol and 4-nitrophthalonitrile using potassium carbonate as catalyst in N , N -dimethylformamide at 50 °C. The structural characterization of the compounds was carried out by elemental analysis, FTIR, UV–vis and MALDI-TOF Mass spectroscopic methods. Electron transfer properties and electrocatalytic oxygen reducing performances of the compounds were also investigated by electrochemical, in situ spectroelectrochemical and in situ electrocolorimetric measurements. Electrochemical, in situ spectroelectrochemical, and in situ electrocolorimetric measurements showed that rich redox behavior of the complexes leads to their high electrocatalytic activity for oxygen reduction and net electrocolorimetric changes suitable for electrochromic applications. Phthalocyanine central metal ion effect on the sensing properties and the adsorption kinetics of four main groups of volatile organic compounds (alkanes, alcohols, chlorinated hydrocarbons and amines) onto these novel compounds were also examined by three different models. While the sensitivity of the sensors was strongly dependent on the nature of the metal ion, no considerable effect was observed on the adsorption kinetics. The evaluation of the kinetics of adsorption processes with respect to three different models showed that pseudo second order rate equation best describes the adsorption of alcohols and chlorinated hydrocarbons while the adsorption of alkanes and amines on these compounds can be represented by Elovich equation. [ABSTRACT FROM AUTHOR]

A novel one-step hyper-cross-linking method, using 1,2-dichloroethane (DCE) and 1,6-dichlorohexane (DCH) cross-linkers, expands the micropore volume of commercial styrenic polymers. Performance of virgin and modified polymers was evaluated by measuring hexane, toluene, and methyl-ethyl-ketone (MEK) adsorption capacity, adsorption/desorption kinetics, and desorption efficiency. Hyper-cross-linked polymers have up to 128% higher adsorption capacity than virgin polymers at P/P 0  = 0.05 due to micropore volume increases up to 330%. Improvements are most pronounced with the DCE cross-linker. Hyper-cross-linking has minimal impact on hexane adsorption kinetics, but adsorption rates for toluene and MEK decrease by 6–41%. Desorption rates decreased (3–36%) for all materials after hyper-cross-linking, with larger decreases for DCE hyper-cross-linked polymers due to smaller average pore widths. For room temperature desorption, 20–220% more adsorbate remains in hyper-cross-linked polymers after regeneration compared to virgin materials. DCE hyper-cross-linked polymers have 13–92% more residual adsorbate than DCH counterparts. Higher temperatures were required for DCE hyper-cross-linked polymers to completely desorb VOCs compared to the DCH hyper-cross-linked and virgin counterparts. Results show that the one-step hyper-cross-linking method for modifying styrenic polymers improves adsorption capacity because of added micropores, but decreases adsorption/desorption kinetics and desorption efficiency for large VOCs due to a decrease in average pore width. [ABSTRACT FROM AUTHOR]

Agricultural waste produced by the industry is a huge threat for the global environment. Utilization of agricultural waste is necessary and there is an urgent need to develop new techniques to solve this important problem. The main objective of this research was to evaluate the applicability of the activated carbon (AC) derived from industrial sisal fiber waste as passive samplers in monitoring toluene by comparing them to industry standard wafer and granular activated carbon (GAC). Carbonization time and ball milling effect on sisal fiber derived AC sample adsorption properties were investigated. Toluene adsorption isotherms were used to predict toluene adsorption capacities. Surface characteristics including surface area and pore volume were used to determine the relationships between them and adsorption capacity. Even though prepared AC samples have mesoporous structure, commercial samples have microporous structure. Surface area from 1245 m2/g to 1297 m2/g and toluene adsorption capacity from 21.4 % to 26.6 % was improved by increasing carbonization time from 1 h to 3 h at 650 °C carbonization temperature and 94.4 ml/min flow rate. Conversely, ball milling technique had negative effect by decreasing the surface area (674 m2/g) and the adsorption capacity of toluene (12.27 %). It is concluded that industrial sisal fiber waste have great potential as a precursor of AC for application in passive monitoring against toluene, particularly the produced mesoporous AC with 3 h carbonization time performs higher adsorption capacity (26.6 %) than commercially available microporous passive sampler (24.1 %) and GAC (22.8 %). [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) are hazardous chemicals present in outdoor and indoor air. They can be odorous and cause human health problems even at very low concentrations. Therefore, regulations on VOC gas emission are becoming stricter every year. Acetaldehyde is a VOC gas that not only has a very stinging smell but can also harm the human body by inhalation. Representative commercial adsorbents are activated carbon and silica gel. These materials feature a large surface area, which is directly related to the number of adsorption sites. In this study, a silica xerogel was synthesized by sol-gel method. The new material was tested for the adsorption of acetaldehyde in a continuous bed system, and its performance was compared to those of commercial silica gel and activated carbon. The physical properties of the samples were studied by BET analysis. Silica xerogel was characterized by XRD, FT-IR, and Si MAS NMR. The inlet and outlet concentrations of the VOC gas were measured from adsorption test tubes using a VOC detecting monitor. The synthesized silica xerogel presented a larger surface area and number of functional groups than the commercial silica gel, leading to improved adsorption performance and selectivity. [ABSTRACT FROM AUTHOR]

FAU-*BEA-types zeolites pellets were elaborated with a hydraulic press in the presence of a small amount (5 wt%) of binder [methylcellulose (MC) or anhydrous sodium metasilicate (NaSiO)] for molecular decontamination, in particular for the space field. Nitrogen sorption-desorption revealed a small loss of micropore volume (10%) with a compression load of 6 tons (0.24 cm/g instead of 0.27 cm/g for the mixture of FAU and *BEA-types zeolites powders), which can be attributed to a partial amorphization. Adsorption kinetics of n-hexane, and cyclohexane showed that the optimum pellets can adsorb volatile organic compounds. For example, FAU-*BEA-type zeolite powder mixture (50 wt% of each zeolite) adsorb 130 mg of n-hexane per g of anhydrous zeolite whereas the pellets made with 5 wt% of MC or NaSiO adsorb about 117-118 mg of n-hexane per g of anhydrous zeolite. These results are coherent with the ones obtained with the cyclohexane and nitrogen adsorption where a small loss of the adsorption capacities was observed. [ABSTRACT FROM AUTHOR]

This study explored a new facile method of preparing ordered porous electrospun honeycomb fibers to obtain the most promising composites for maximal adsorption of volatile organic compounds (VOCs). The self-assembly ordered porous material (OPM) and polyacrylonitrile (PAN) were formulated into a blend solution to prepare honeycomb fibers. SEM and TEM images showed that OPM was effectively bonded in PAN fibers because of the composite’s structure. Acetone was used as a model to assess the VOC adsorption performances of electrospun honeycomb fibers with different OPM contents. Experimental results revealed that the adsorption capacity of honeycomb fibers increased with the increase of loaded OPM within the PAN fibers. The highest adsorption capacity was 58.2 μg g−1 by the fibers containing with 60% OPM in weight. After several recycling times, the adsorption capacities of the reused honeycomb fibers were almost the same with the fresh fibers. This finding indicated that the electrospun honeycomb fibers have potential application in removing VOCs in the workplace, and promote the performance of masks for odor removal.

The unburned carbon in bagasse ash was separated and used as a starting material for activated carbon and carbon monolith preparation. The separated carbon was steam activated in a rotary kiln under different conditions and compared with carbon activated in limited supply of air. The activated carbon from the rotary kiln showed surface areas ranging from 324 to 601 m 2 /g. Different phenolic resins and cellulosic binders were used to prepare the monoliths using slurry casting method. The effects of different preparation conditions on the properties of the monolith were studied. Upon monolith formation, the surface area was reduced slightly and surface areas in the range 92–479 m 2 /g were achieved. The activated carbons and monoliths were tested for static adsorption of volatile organic compounds (VOCs) using benzene, xylene, hexane and toluene as model compounds. With the activated carbons, adsorption capacities as high as 22.5, 31.1, 27.5 and 25.0 g/100 g sample were obtained for toluene, benzene, xylene and hexane, respectively. The adsorption capacities were reduced for the corresponding monoliths. The waste derived activated carbons and monoliths show promising results as adsorbents for the removal of volatile organic compounds. [ABSTRACT FROM AUTHOR]

A laboratory test apparatus was used to obtain adsorption onto granular activated carbon at temperatures between 50 °C and 130 °C. Despite the kinetic advantage of activated carbon cloth, which was solely investigated in the apparatus before, it is shown that by a new sample holder it is also possible to obtain adsorption isotherms onto granulated activated carbon fast, economically and within a large measuring range. Measurement results, namely adsorption isotherms, were evaluated by the ALIc model as well as by the models of Dubinin-Asthakov, Toth and Do&Do. The model equations were evaluated regarding their fitting quality and further criteria. [ABSTRACT FROM AUTHOR]

This study has been undertaken to the optimization of chlorobenzene adsorption of onto carbonate material outcropping in Tataouine region located in Southern Tunisia. Response surface methodology was adopted as a tool for the experimental design; A Hoke D6 experimental design model was applied. In order to improve the adsorption capacity of raw material, different adsorbents were prepared by addition of three salts (NaSO, NaCl and NaSO) and then heated to 300, 450 and 600 °C. The obtained results indicated that the studied samples were mainly composed of calcite. Temperature and salt concentration were the most controlling factors in activation process. Optimum adsorption conditions were obtained for 5 % of NaCl as activation salt and 450 °C of activation temperature of carbonate samples. The activated carbonate showed an increase in its porosity (8 to 58.35 %) and surface area (2-14.6 m g). Moreover, chlorobenzene adsorbed amount showed an enhanced value, varying from 30 to 120 mg g at 25 °C. [ABSTRACT FROM AUTHOR]

The depollution of some gaseous streams containing n-hexane is studied by adsorption in a fixed bed column, under dynamic conditions, using granular activated carbon and two types of non-functionalized hypercross-linked polymeric resins. In order to model the process, a new neuro-evolutionary approach is proposed. It is a combination of a modified differential evolution (DE) with neural networks (NNs) and two local search algorithms, the global and local optimizers, working together to determine the optimal NN model. The main elements that characterize the applied variant of DE consist in using an opposition-based learning initialization, a simple self-adaptive procedure for the control parameters, and a modified mutation principle based on the fitness function as a criterion for reorganization. The results obtained prove that the proposed algorithm is able to determine a good model of the considered process, its performance being better than those of an available phenomenological model. [ABSTRACT FROM AUTHOR]

Abstract: Four pure silica zeolites, chabazite (CHA-structure type) and SSZ-23 (STT-structure type) with cage-like structure and silicalite-1 (MFI-structure type) and beta (∗BEA-structure type) with channel structure, were synthesized and fully characterized. Their sorption properties were examined using gravimetric method combined with Grand Canonical Monte Carlo simulations (GCMC). Of particular interest is the large difference in the adsorption rates of n-hexane, p-xylene and acetone observed for these zeosils at 25, 75 and 150°C. As expected, in most cases, a decrease in the adsorption capacity is observed with increasing the molar volume of the used probe molecule and the temperature. An exception is observed for the pure silica CHA-type zeolite due to its small pore size which prevents molecules from entering its porosity. However, at higher temperature, the window size widens slightly and allows n-hexane and acetone, which have kinetic diameter close to the pore opening, to enter easily in chabazite. As a result, for this zeosil, an increase in the adsorption capacity compared to that obtained at 25°C is observed. All these zeosils are promising for technological uses in car exhaust gas decontamination. [Copyright &y& Elsevier]

This paper presents the results of a factorial experiment design analysis to investigate volatile organic compounds (VOC) adsorption on a ceiling tile. The impacts of three factors, VOC gas phase concentration, relative humidity, and VOC type, as single parameters and as a combination, on adsorption have been investigated. Cyclohexane, toluene, ethyl acetate, isopropyl alcohol and methanol were the five VOCs used in this study. A factor significant level was determined through evaluating its F value and comparing it with the critical value of F distribution at 95% confidence level. It was found that: (i) neither the relative humidity and gas phase concentration nor any interaction effect between them had significant impacts on toluene adsorption on the ceiling tile; (ii) the adsorption isotherm appeared to be linear for the non-polar compounds and non-linear for the semi-polar and polar compounds; (iii) no significant impact of relative humidity on adsorption was observed for most VOC compounds except for methanol; and (iv) the ceiling tile had the highest adsorption capacity toward the polar compounds, followed by the aromatic compounds and aliphatic compounds. In addition, the statistical analysis regarding the experimental results of toluene as a single compound or as a part of a mixture showed that toluene adsorption capacity on the ceiling tile as a single compound was higher than as a part of a mixture. Practical Implications Building materials and furnishings may act as source and sink of VOCs in the indoor environment. In this study, a factorial experiment design analysis technique was used to show the impact of three factors, VOC gas phase concentration, relative humidity, and VOC type, as single parameters and as a combination, on the adsorption process (sink effect). The aim was to better understand the interaction between these parameters and to verify the common assumptions made in the model development and measurement of indoor air quality. [ABSTRACT FROM AUTHOR]

To remove toluene and methyl ethyl ketone (MEK) through adsorption, a honeycomb that is 60 cm in diameter and 40 cm in length was manufactured using ceramic paper as supporting material for adsorbents. Then, a mixture of Y type and ZSM-5 type zeolites with a ratio of 7:3 was impregnated on the surface of the honeycomb. By drying the impregnated material, the honeycomb adsorption rotor (HAR) was successfully manufactured. The amount of zeolites impregnated in the HAR was calculated to be 28 wt% and the peaks of the X-ray diffraction pattern of HAR were identical to those of the two kinds of zeolite powders. The small reduction in the BET surface area resulted from the reduction of mesopores while there was little reduction of micropores smaller than 100 nm, which plays a main role in the adsorptive separation of VOCs. Equilibrium adsorption for toluene and MEK of the HAR was measured 3.6 wt% and 3.3 wt%, respectively, at partial pressure of 0.2 mmHg. The experimental curves of equilibrium adsorption amount fitted well to the calculated curve by the Langmuir model; the interpretation of the breakthrough curve using material balances agreed with the test results. With 3 rph HAR rotation speed, 1.2 m/s face velocity, and 360 ppmv toluene and MEK inlet concentration, the rotary adsorption system showed average outlet concentrations of 18 ppmv and 14 ppmv, respectively, indicating removal efficiency was higher than 95%. [ABSTRACT FROM AUTHOR]

[Display omitted] • A facile and green strategy to synthesize N/P co-doped porous carbon from fungi residue. • Hydrothermal treatment with (NH 4) 3 PO 4 activation contributed to high carbon yield. • Abundant N/P heteroatoms and hierarchical pores brought excellent VOC adsorption. • The adsorption capacity based on carbon yield was proposed to evaluate the economy. This paper reports a facile and green strategy using hydrothermal treatment coupled with (NH 4) 3 PO 4 activation of fungi residue to synthesize N/P co-doped porous carbon. (NH 4) 3 PO 4 has no corrosion effect on reactor and attains high carbon yield, ca. 64.5 wt%. Hydrothermal treatment, cross-linked action by (NH 4) 3 PO 4 , and low-temperature pyrolysis contribute to high carbon yield. To evaluate the economy, another index Q fr (mg/g-fr) is proposed to express the adsorption capacity based on the dosage of original fungi residue. Comparing with H 3 PO 4 and CO(NH 2) 2 , (NH 4) 3 PO 4 activation exhibits the highest adsorption capacity of PhH (benzene). Accordingly, its Q fr has surpassed KOH activated carbon, ca. 84.2 > 31.4 mg/g-fr. The abundant surface functional groups of N/P (7.20 and 5.54 at.%) and mesopores-dominant hierarchical pore structure contribute to its excellent adsorption performance. DFT (density functional theory) calculations demonstrate that N/P co-doped porous carbon possesses the highest adsorption binding energy, ca. −1.07 eV. Next, four types of VOC compounds with different physicochemical properties are evaluated for adsorption, i.e., PhH (84.2 mg/g-fr), DCE (dichloroethane, 128.7 mg/g-fr), MeOH (methanol, 23.7 mg/g-fr) and MTHM (methyl mercaptan, 26.0 mg/g-fr). Multi components co-adsorption, adsorption thermodynamics, and recyclability analysis are also evaluated for industrial application. Competitive adsorption still exists but the total adsorption capacity is close to or slightly lower than sole adsorption capacity. After four cycles by low-temperature regeneration, the capacity of tri-component adsorption only decreases 28.0%. Economic analysis demonstrates that the cost of (NH 4) 3 PO 4 activation is obviously lower than KOH activation and even superior to commercial activated carbon. Above all, this paper successfully exploits new approach for renewable adsorbents synthesis with facile and green strategy. [ABSTRACT FROM AUTHOR]

Fungi residue, vinasse, and biogas residue differ from general biomass waste due to natural microbial action. Microbial fermentation helps create natural channels for the permeation of activators and produces proteins for natural nitrogen doping. Inspired by these advantages on porous carbon synthesis, this study adopted dual activators of KOH and KHCO 3 to synthesize porous carbon with different pore ratios for efficient adsorption of volatile organic compounds (VOCs). The fungi residue possessed the least lignin due to the most severe microbial action, contributing to the best pore structures after activation. The etching effect from potassium compounds and gas foaming from the carbonate decomposition contributed to creating hierarchical porous carbon with ultra-high surface area, ca. 1536.8–2326.5 m2/g. However, KHCO 3 addition also caused nitrogen erosion, such that lower adsorption capacity was attained even with a higher surface area when the mass ratio of KOH/KHCO 3 decreased from 2.5:0.5 to 2:1. The maximum adsorption capacities of chlorobenzene (CB) and benzene (PhH) reached 594.0 and 394.3 mg/g, respectively. Pore structure variations after adsorption were evaluated by freeze treatment to discover the adsorption mechanism. The surface area after CB and PhH adsorption decreased 40.3% and 34.5%, respectively. Most of the mesopores might transform into micropores due to the mono/multilayer stacking of adsorbates. The VOC adsorption kinetics were simulated by the Pseudo-first- and -second-order models and Y–N model. This paper provides a new approach for high-value biomass waste utilization after microbial action to synthesize efficient adsorbents for VOCs. • Biomass wastes after microbial action have loose structure and natural N sources. • Dual activators of KOH/KHCO3 produced the high porosity with hierarchical pores. • Mesopores act as transport channels and supplement for micropores after stacking. • The adsorption capacities of CB and PhH reached 594.0 and 394.3 mg/g, respectively. [ABSTRACT FROM AUTHOR]

• Activated carbon fiber filter with pleated structure. • Equipotential conductors in the pleat-tips for thermo-electrical regeneration. • Adsorption, pressure drop and electrical properties were determined. • Optimization of the filter configuration with CFD. A novel type of activated carbon fiber filter was developed for indoor air purification. The filter is equipped with electrodes for thermo-electrical regeneration at the point of saturation. The electrodes are arranged in such a way that the filter forms a pleated structure with an electrode in the tip of each pleat. This allows for a uniform temperature distribution on the filter surface during the regeneration process and the pleated structure reduces the overall pressure drop across the filter. The latter was validated by Computational Fluid Dynamics, using Darcy-Forchheimer parameters derived in previous work. The CFD model was further used to perform a virtual sensitivity study in search for the optimal ACF filter design by varying the pleat length, pleat height and filter thickness. Finally, adsorption and desorption properties were investigated with acetaldehyde and toluene as model compounds. Freundlich and Langmuir adsorption parameters, derived in previous work were successfully validated with a Multiphysics model. [ABSTRACT FROM AUTHOR]

Reductively activate carbon fibers fabricated from cellulosic biomass can enable high capacity adsorption of nonpolar VOCs, and can be regenerated electrically for reuse. Reductive carbonization of cellulosic fibers via nano-sized nickel catalyst in the presence of hydrogen was examined for production of activated carbon fibers (ACFs). The results showed that 99.5 % of oxygen originally presented in the biomass was removed as measured by using X-ray Photoelectron Spectroscopy (XPS), with over 63 % carbon in form of reductive species. Such reductive ACFs demonstrated high adsorption capacities for non-polar volatile organic compounds (VOCs). Particularly, the reductive ACFs absorbed benzene at a capacity that was 8 times higher than traditionally prepared carbon fibers. That can be attributed to both the reductive surface chemistry and morphology generated by the activity of the nanocatalysts. The unique network structure of the ACFs also provided a fine conductivity, that made it possible for efficient material regeneration via electrothermal desorption. The absorbed VOCs could be completely released within 1 min upon application of a moderate electrical current, and the regenerated materials could regain 100 % of its adsorption capacity even after repeated adsorption and desorption cycles. This work demonstrated for the first time the use of nanocatalyst-assisted reductive carbonization in manipulating surface properties of bio-based carbon materials, promising the production of a new class of carbon materials for industrial applications including air quality control, gas separation, and fuel storage. [ABSTRACT FROM AUTHOR]

• Models were developed to simulate adsorption in a multistage fluidized bed. • The two phase model predicted the effect of different variables well. • Internal diffusion within the BAC was rate-limiting for adsorption. • Particle size strongly influenced the overall removal efficiency. The adsorption of 1,2,4-trimethylbenzene (TMB) on beaded activated carbon (BAC) in a six-stage countercurrent fluidized bed adsorber was simulated employing a two-phase model, assuming the gas in particulate phase to be either in plug flow (EGPF model) or in perfectly mixed flow (EGPM model). A rather simple model considering equilibrium state on each stage (Equilibrium model) was also used for comparison. Simulation results were compared with experimental data obtained at different values of adsorbent feed rate, superficial gas velocity, TMB initial concentration and weir height (which influences the effective bed height). The results demonstrate that the Equilibrium model overpredicts the overall removal efficiencies when the adsorbate-adsorbent system is far from equilibrium condition. On the other hand, both EGPF and EGPM show good agreement with the experimental results over industrially relevant operating conditions. Stage-wise removal efficiencies show that the EGPF model tends to predict removal efficiency better than EGPM when the weir height is high. The sensitivity analysis of the EGPM model indicates that internal diffusion within the BAC is rate-limiting for adsorption, while BAC diameter strongly influences the overall removal efficiency and can be optimized for different conditions. The effect of changes in BAC adsorption capacity on overall removal efficiency depends on the number of available adsorption sites, as well as proximity to equilibrium condition. The model developed in this study is also able to predict the effect of the number of stages on overall removal efficiency of the adsorber. The results of this study could pave the way for optimizing the design and operation of fluidized bed adsorbers, leading to cost savings and performance improvements. [ABSTRACT FROM AUTHOR]

• Novel reclaimable adsorbents of bacterial/fungal-support biomaterials were developed. • Aminomethylation was the best chemical modification method for lyophilized biomass. • The modified fungal adsorbent performed better than the bacterial one for adsorption. • The adsorption of VOCs by the modified biosorbents was mainly a physical adsorption. • The modified fungal biosorbent was a promising alternative material for VOC removal. Adsorption is an efficient and low-cost technology used to purify volatile organic compounds (VOCs). In the current study, novel microbial adsorbents were synthesized using cells of lyophilized fungi (Ophiostoma stenoceras LLC) or bacteria (Pseudomonas veronii ZW) that were modified by aminomethylation. Based on the adsorption performance and structural characterization results, the modified fungal biosorbent was the best. Its maximum adsorption capacities for ethyl acetate, α-pinene, and n-hexane were 620, 454, and 374 mg·g−1, respectively, which were much higher than those of other synthesized biosorbents. The specific surface area of the fungal biosorbent was 20 m2·g−1, and most of the components were hydrocarbon compounds and polysaccharides. The VOC adsorption process on these synthesized biosorbents was in accordance with the Langmuir isothermal model and the pseudo-first-order kinetic model, thereby suggesting that physical adsorption was the dominant mechanism. The fungal biosorbent could be used for five consecutive VOC sorption-desorption cycles without any obvious decrease in adsorption capacity. [ABSTRACT FROM AUTHOR]

In order to reduce the possible harm caused by air pollution, excellent personal protective materials are attracting more and more attention. Therefore, the research of multifunctional materials that can filter particulate matter (PM) and volatile organic compounds (VOCs) simultaneously is of great significance. In addition, in cold weather, water vapor in the exhaled gas condenses into small droplets inside the respirator causing uncomfortable feeling of dampness. Herein, we prepared several types of cyclodextrin-containing Janus nanofibrous porous membranes by electrospinning, which can efficiently filter PM of different sizes in the air, effectively adsorb VOCs, and orientate moisture from exhaled gas to the outside of the membranes to provide a dry and comfortable environment. These advantageous features, combined with the cheap price and easy availability of component materials and low respiratory resistance, highlight the great potential of these Janus nanofibrous porous membranes in the development of personal wearable air purifiers.

To help address efficient separation of C 2 H n light hydrocarbons and C 2 H 2 /CO 2 in the chemical industry, the self-assembly via an azolate-carboxylate ligand and Co(II) ion gave rise to a new porous MOF material, [Co(btzip)(H 2 btzip)]·2DMF·2H 2 O ( 1 ) (H 2 btzip = 4,6-bis(triazol-1-yl)isophthalic acid). In the MOF, the pores are modified by rich uncoordinated triazolyl Lewis basic N atoms and acidic -COOH groups, which strengthen interactions with C 2 H n hydrocarbons and CO 2 molecules, leading to high adsorption amounts for C 2 H 2, C 2 H 4 , C 2 H 6 , and CO 2 and remarkable separation efficiency for C 2 H n -CH 4 , CO 2 -CH 4 , and C 2 H 2 -CO 2 mixtures, as confirmed by breakthrough experiments on the realistic gas mixtures. The MOF also reveals outstanding selective adsorption ability for benzene/toluene, methanol/1-propanol, methanol/2-propanol, and 2-propanol/1-propanol isomers. Molecular simulations disclose the different adsorption sites in the MOF for various adsorbates.

This study explored a new facile method of preparing ordered porous electrospun honeycomb fibers to obtain the most promising composites for maximal adsorption of volatile organic compounds (VOCs). The self-assembly ordered porous material (OPM) and polyacrylonitrile (PAN) were formulated into a blend solution to prepare honeycomb fibers. SEM and TEM images showed that OPM was effectively bonded in PAN fibers because of the composite’s structure. Acetone was used as a model to assess the VOC adsorption performances of electrospun honeycomb fibers with different OPM contents. Experimental results revealed that the adsorption capacity of honeycomb fibers increased with the increase of loaded OPM within the PAN fibers. The highest adsorption capacity was 58.2 μg g−1 by the fibers containing with 60% OPM in weight. After several recycling times, the adsorption capacities of the reused honeycomb fibers were almost the same with the fresh fibers. This finding indicated that the electrospun honeycomb fibers have potential application in removing VOCs in the workplace, and promote the performance of masks for odor removal. [ABSTRACT FROM AUTHOR]

The specific adsorption of oxygenated and aliphatic gasoline components onto activated carbons (ACs) was studied under static and dynamic conditions. Ethanol and n-octane were selected as target molecules. A highly porous activated carbon (CA) was prepared by means of two processes: carbonization and chemical activation of olive stone residues. Different types of oxygenated groups, identified and quantified by TPD and XPS, were generated on the CA surface using an oxidation treatment with ammonium peroxydisulfate and then selectively removed by thermal treatments, as confirmed by TPD results. Chemical and porous transformations were carefully analyzed throughout these processes and related to their VOC removal performance. The analysis of the adsorption process under static conditions and the thermal desorption of VOCs enabled us to determine the total adsorption capacity and regeneration possibilities. Breakthrough curves obtained for the adsorption process carried out under dynamic conditions provided information about the mass transfer zone in each adsorption bed. While n-octane adsorption is mainly determined by the porosity of activated carbons, ethanol adsorption is related to their surface chemistry, and in particular is enhanced by the presence of carboxylic acid groups., (Copyright © 2013 Elsevier B.V. All rights reserved.)