Removal of VOCs by activated carbon microspheres derived from polymer: a comparative study

Retention of methyl iodide on metal and TEDA impregnated activated carbon using indigenously developed setup

Removal of methyl iodide (CH3I) from the air present within nuclear facilities is a critical issue. In case of any nuclear accident, there is a great need to mitigate the radioactive organic iodide immediately as it accumulates in human bodies, causing severe consequences. Current research focuses on removing organic iodides, for which the surface of activated carbon (AC) was modified by impregnating it with different metals individually, i.e. Ag, Ni, Zn, Cu and with the novel combination of these four metals (AZNC). After the impregnation of metals, triethylenediamine (TEDA) was coated on metal impregnated activated carbon (IAC) surface. The adsorption capacity of the combination of four metals IAC was found to be 276 mg/g as the maximum for the trapping of CH3I. Whereas TEDA-metal impregnation on ACs enhanced the removal efficiency of CH3I up to 352 mg/g. After impregnation, adsorption capacity of AZNC and AZNCT is significantly higher as compared to AC. According to the finding, t5% of AZNCT IAC is 46 min, which is considerably higher than the t5% of other tested adsorbents. According to isotherm fitting data, Langmuir isotherm was found superior for describing CH3I sorption onto AC and IACs. Kinetics study shows that pseudo second order model represented the sorption of CH3I more accurately than the pseudo first order. Thermodynamic studies gave negative value of ΔG which shows that the reaction is spontaneous in nature. Based on the findings, AZNCT IAC appears to have a great potential for air purification applications in order to obtain clean environment.

Adsorptivity and kinetics for low concentration of gaseous formaldehyde on bamboo-based activated carbon loaded with ammonium acetate particles

The highly promising formaldehyde (HCHO)-removing materials are essential for eliminating interior pollution to safeguard the public's health with increasing indoor HCHO contamination situations being recorded on a global scale. In the paper, bamboo charcoal (BC) was activated with boric acid to prepare bamboo-based activated carbon (BAC), and then impregnated with ammonium acetate solution to successfully develop porous adsorbent with ammonium acetate particles (N/BAC), which was applied to remove low concentration of HCHO at room temperature. The adsorption performance for HCHO was systematically investigated while the surface chemical properties and microstructure of the as-prepared adsorbents were described and analyzed. The specific surface area, total pore volume and microporous volume of N/BAC sample were 240.09 m²/g, 0.27 cm³/g and 0.12 cm³/g, which increased by 42.40 m²/g, 0.15 cm³/g and 0.03 cm³/g compared with BAC sample, respectively. The specific surface area and the microporous volume, as well as the content of oxygen- and nitrogen-containing functional groups of N/BAC sample were augmented by contrast with other samples, and numerous ammonium acetate particles were present on the surface. Precisely because of this, the N/BAC sample exhibited a high removal rate of 98.89%, which was 18.38% greater than that of BAC sample. A superior correlation coefficient (0.9999) from the experimental values of the kinetics and the fitted values of the pseudo-second-order kinetic model demonstrated that the adsorption process of HCHO on N/BAC sample was physical-chemical combined adsorption. The adsorption of HCHO on N/BAC sample was investigated under different humidity, and the results showed that the adsorbent yet had excellent adsorption capacity (87.93%) under RH 75%. Moreover, the N/BAC sample was renewable, and the removal rate still reached 82.81% after five cycles of regeneration. Therefore, the as-prepared adsorbent is an effective, economical and sustainable material, and could be used to remove HCHO from real contaminated indoor air.

Adsorption and membrane separation for removal and recovery of volatile organic compounds

Volatile organic compounds (VOCs) are a crucial kind of pollutants in the environment due to their obvious features of severe toxicity, high volatility, and poor degradability. It is particularly urgent to control the emission of VOCs due to the persistent increase of concentration and the stringent regulations. In China, clear directions and requirements for reduction of VOCs have been given in the "national plan on environmental improvement for the 13th Five-Year Plan period". Therefore, the development of efficient technologies for removal and recovery of VOCs is of great significance. Recovery technologies are favored by researchers due to their advantages in both recycling VOCs and reducing carbon emissions. Among them, adsorption and membrane separation processes have been extensively studied due to their remarkable industrial prospects. This overview was to provide an up-to-date progress of adsorption and membrane separation for removal and recovery of VOCs. Firstly, adsorption and membrane separation were found to be the research hotspots through bibliometric analysis. Then, a comprehensive understanding of their mechanisms, factors, and current application statuses was discussed. Finally, the challenges and perspectives in this emerging field were briefly highlighted.

Production of Activated Biochar Derived from Residual Biomass for Adsorption of Volatile Organic Compounds

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.

Graphene-based porous nanohybrid architectures for adsorptive and photocatalytic abatement of volatile organic compounds

Volatile organic compounds (VOCs) represent a considerable threat to humans and ecosystems. Strategic remediation techniques for the abatement of VOCs are immensely important and immediately needed. Given a unique set of optical, mechanical, electrical, and thermal characteristics, inimitable surface functionalities, porous structure, and substantial specific surface area, graphene and derived nanohybrid composites have emerged as exciting candidates for abating environmental pollutants through photocatalytic degradation and adsorptive removal. Graphene oxide (GO) and reduced graphene oxide (rGO) containing oxygenated function entities, i.e., carbonyl, hydroxyl, and carboxylic groups, provide anchor and dispersibility of their surface photocatalytic nanoscale particles and adsorptive sites for VOCs. Therefore, it is meaningful to recapitulate current state-of-the-art research advancements in graphene-derived nanostructures as prospective platforms for VOCs degradation. Considering this necessity, this work provides a comprehensive and valuable insight into research progress on applying graphene-based nanohybrid composites for adsorptive and photocatalytic abatement of VOCs in the aqueous media. First, we present a portrayal of graphene-based nanohybrid based on their structural attributes (i.e., pore size, specific surface area, and other surface features to adsorb VOCs) and structure-assisted performance for VOCs abatement by graphene-based nanocomposites. The adsorptive and photocatalytic potentialities of graphene-based nanohybrids for VOCs are discussed with suitable examples. In addition to regeneration, reusability, and environmental toxicity aspects, the challenges and possible future directions of graphene-based nanostructures are also outlined towards the end of the review to promote large-scale applications of this fascinating technology.

Adsorptive removal of some Cl-VOC's as dangerous environmental pollutants using feather-like γ-Al2O3 derived from aluminium waste with life cycle analysis

Herein, we designed a cost-effective preparation method of nanocomposite γ-Al₂O₃ derived from Al-waste. The produced material has a feather-like morphology, and its adsorption of some chlorinated volatile organic compounds (Cl-VOC's) such as benzyl chloride, chloroform and carbon tetrachloride (C₇H₇Cl, CHCl₃ and CCl₄) was investigated due to their potential carcinogenic effect on humans. It showed a characteristic efficiency towards the adsorptive removal of these compounds over a long period, i.e., eight continuous weeks, at ambient temperature and atmospheric pressure. After 8-weeks, the adsorbed amounts of these compounds were determined as: 325.3 mg C₇H₇Cl, 247.6 mg CHCl₃ and 253.3 mg CCl₄ per g of γ-Al₂O_3, respectively. CCl₄ was also found to be dissociatively adsorbed on the surface of γ-Al₂O₃, whereas CHCl₃ and C₇H₇Cl were found to be associatively adsorbed. The prepared γ-Al₂O₃ has a relatively high surface area (i.e., 192.2 m². g^-1) and mesoporosity with different pore diameters in the range of 25-47 Å. Furthermore, environmental impacts of the nanocomposite γ-Al₂O₃ preparation were evaluated using life cycle assessment. For prepartion of adsorbent utilising 1 kg of scrap aluminium wire, it was observed that potential energy demand was 288 MJ, climate change potential was 19 kg CO₂ equivalent, acidification potential was 0.115 kg SO₂ equivalent and eutrophication potential was 0.018 kg PO₄^3- equivalent.

Sorption behaviour of xylene isomers on biochar from a range of feedstock

Inland oil spillage is one of the widespread sources of crude oil volatile organic compound emissions (CVEs) for which the long-term remedial solutions are often complex and expensive. This paper investigates the potential of a low-cost containment solution for contaminated solids by volatile organic compounds (VOCs) using biochar. The results of an extensive experimental investigation are presented on the sorption kinetics of xylene isomers (one type of the most frequently detected CVEs) on commercial biochar produced by prevalent feedstocks (wheat, corn, rice and rape straw as well as hardwood) at affordable temperatures (300-500°C). Chemical and physical properties of biochar were analysed in terms of elemental composition, scanning electron microscopy, specific surface area, ATR-FTIR spectra and Raman spectrometry. We show that for high-temperature biochar with similar surface chemistry, the sorption efficiency is mainly controlled by porous structure and pore size distribution. Biochar samples with higher specific surface area and higher volume of mesopores showed the highest sorption capacity (45.37-50.88 mg/g) since the sorbate molecules have more access to active sites under a greater intra-particle diffusion and elevated pore-filling. P-xylene showed a slightly higher sorption affinity to biochar compared to other isomers, especially in mesoporous biochar, which can be related to its lower kinetic diameter and simpler molecular shape. The sorption capacity of biochar produced at higher pyrolysis temperatures was found to be more sensitive to changes in ambient temperature due to dominant physical adsorption. Elovich kinetic model was found to be the best model to describe xylenes' sorption on biochar which indirectly indicates π-π stacking and hydrogen bonding as the main mechanism of xylene sorption on these types of biochar.

Ball milling biochar with ammonia hydroxide or hydrogen peroxide enhances its adsorption of phenyl volatile organic compounds (VOCs)

Pristine biochar (CN600), ball-milled biochar (CN600-BM), H₂O₂ modified BM-biochar (CN600-O), and NH₄OH modified BM-biochar (CN600-N) derived from corn stalk were applied to adsorb phenyl volatile organic compounds (VOCs). H₂O₂ and NH₄OH modification of BM-biochar significantly improved its physicochemical characteristics and adsorption abilities. The specific surface area of CN600-O increased 2.05 and 1.23 times compared to CN600 and CN600-BM, respectively; while CN600-N increased 2.41 and 1.45 times, respectively. In addition, the ball milled biochars, especially CN600-O, showed higher acidity and polarity than CN600. The VOC adsorption amount onto biochars was 10.96-130.21 mg/g. CN600-O and CN600-N had high uptake of the VOCs and reached 100.07-111.79 mg/g and 110.49-130.21 mg/g, respectively. CN600-N showed the best performance with P-xylene adsorption up to 130.21 mg/g. VOC adsorption onto the CN600-O and CN600-N were mainly governed by surface adsorption and associated with morphology characteristics of the biochars as well as VOC properties such as boiling point and molecular size. Five cycles of adsorption-desorption experiments showed that CN600-O and CN600-N had good reusability with the reuse efficiencies of 88.01 %-92.21 % and 92.19 %-95.39 %, respectively. The results indicate that O- and N-doped ball-milled biochars are promising in adsorption for effective and sustainable VOC removal.

Fabrication and characterization of 3,4-diaminobenzophenone-functionalized magnetic nanoadsorbent with enhanced VOC adsorption and desorption capacity

The present study, for the first time, utilized 3,4-diaminobenzophenone (DABP)-functionalized Fe₃O₄/AC@SiO₂ (Fe₃O₄/AC@SiO₂@DABP) magnetic nanoparticles (MNPs) synthesized as a nanoadsorbent for enhancing adsorption and desorption capacity of gaseous benzene and toluene as volatile organic compounds (VOCs). The Fe₃O₄/AC@SiO₂@DABP MNPs used in adsorption and desorption of benzene and toluene were synthesized by the co-precipitation and sol-gel methods. The synthesized MNPs were characterized by SEM, FTIR, TGA/DTA, and BET surface area analysis. Moreover, the optimization of the process parameters, namely contact time, initial VOC concentration, and temperature, was performed by applying response surface methodology (RSM). Adsorption results demonstrated that the Fe₃O₄/AC@SiO₂@DABP MNPs had excellent adsorption capacity. The maximum adsorption capacities for benzene and toluene were found as 530.99 and 666.00 mg/g, respectively, under optimum process parameters (contact time 55.47 min, initial benzene concentration 17.57 ppm, and temperature 29.09 °C; and contact time 57.54 min, initial toluene concentration 17.83 ppm, and temperature 27.93 °C for benzene and toluene, respectively). In addition to the distinctive adsorptive behavior, the Fe₃O₄/AC@SiO₂@DABP MNPs exhibited a high reproducibility adsorption and desorption capacity. After the fifth adsorption and desorption cycles, the Fe₃O₄/AC@SiO₂@DABP MNPs retained 94.4% and 95.4% of its initial adsorption capacity for benzene and toluene, respectively. Kinetic and isotherm findings suggested that the adsorption mechanisms of benzene and toluene on the Fe₃O₄/AC@SiO₂@DABP MNPs were physical processes. The results indicated that the successfully synthesized Fe₃O₄/AC@SiO₂@DABP MNPs can be applied as an attractive, highly effective, reusable, and cost-effective adsorbent for the adsorption of VOC pollutants.Graphical abstract.

Hydrochar and pyrochar for sorption of pollutants in wastewater and exhaust gas: A critical review

Pollutants in wastewater and exhaust gas bring out serious concerns to public health and the environment. Biochar can be developed as a sustainable adsorbent originating from abundant bio-wastes, such as agricultural waste, forestry residue, food waste and human waste. Here we highlight the state-of-the-art research progress on pyrochar and hydrochar for the sorption of pollutants (heavy metal, organics, gas, etc) in wastewater and exhaust gases. The adsorption performance of pyrochar and hydrochar are compared and discussed in-depth, including preparation procedures (carbonization and activation), sorption possible mechanisms, and physiochemical properties. Challenges and perspective for designing efficient and environmental benign biochar-based adsorbents are finally addressed.

High-performance gas-phase adsorption of benzene and toluene on activated carbon: response surface optimization, reusability, equilibrium, kinetic, and competitive adsorption studies

In recent years, volatile organic compounds (VOCs) have become a group of major pollutants that endanger human health and the ecological environment. The main purpose of this study was to investigate the gas-phase adsorption processes of benzene and toluene, which are important VOCs, on the activated carbon (AC) produced from Elaeagnus angustifolia seeds by physical activation method. In this context, the central composite design (CCD) approach-based response surface methodology (RSM) was applied to examine and optimize the effects of process parameters on the adsorption of benzene and toluene by AC adsorbent. The characterization of the produced AC was performed by the Brunauer-Emmett-Teller surface area, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. The optimum process parameters were achieved (adsorption time of 74.98 min, initial benzene concentration of 16.68 ppm, and temperature of 26.97 °C, and adsorption time of 73.26 min, initial toluene concentration of 18.46 ppm and temperature of 29.80 °C) for benzene and toluene, respectively. The maximum adsorption capacities of benzene and toluene on AC were determined to be 437.36 and 512.03 mg/g, respectively, under optimum parameters. The adsorption process kinetics and equilibrium isotherms were also evaluated. Besides, AC reusability studies were performed five times for the gas-phase adsorption and desorption of benzene and toluene. After five cycles, it was observed that the benzene and toluene adsorption capacity of the AC decreased slightly by 8.10% and 7.42%, respectively. The results revealed that the produced AC could be utilized successfully for the removal of benzene and toluene in the gas-phase adsorption systems because of its high surface area, high adsorption capacity, and high reusability performance. Furthermore, the adsorption processes of benzene and toluene were investigated, both sole components and in a binary mixture. It was concluded that the adsorption behaviors of benzene and toluene against AC were quite different when they were in the competition (in a binary mixture) and without competition (sole components). Graphical abstract.

Comprehending adsorption of methylethylketone and toluene and microwave regeneration effectiveness for beaded activated carbon derived from recycled waste bamboo tar

Beaded activated carbons (BACs) were derived from waste bamboo tar through carbonization (500°C for 2 hr) followed by physical activation using carbon dioxide (800-900°C for 2-4 hr). The adsorbent was examined for their physical and chemical properties, adsorption capacities toward methylethylketone (MEK) and toluene, and regenerabilities under microwave heating. It was found that the maximum total surface area reached for bamboo-tar-derived BAC after physical activation was 1364 m² g^-1, and more than 95% of the area was attributed to the microporous structures. Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models were applied to the adsorption isotherm fitting, and the minimum R² for each model was 0.986, 0.915, and 0.943, respectively. The isosteric heats of adsorption calculated based on D-R parameters for methylethylketone and toluene were 44.04 to 51.50 and 45.88 to 73.27 KJ mol^-1, respectively. They were slightly over the range of physisorption and increased with adsorbate loading, which might be related to the micropore filling mechanism. Microwave regeneration under 600 W of power output removed most of the adsorbate (>93.03%) within 8 min. The results of this study are intended to benefit future study on waste-derived adsorbent in environmental applications.

IMPLICATIONS

Recycling waste bamboo tar for the novel adsorbent preparation is shown feasible in this study. Beaded activated carbon (BAC) synthesized from this waste bamboo tar possessed a high specific surface area, which aided in the capturing of volatile organic compounds (VOCs). Three adsorption isotherms, Langmuir, Freundlich, Dubinin-Radushkevich (D-R) models can be applied in interpreting the experimental adsorption data, providing information on adsorption heat and possible adsorption mechanism. A potential microwave regeneration method for BAC is tested, showing high desorption efficiencies with minimum heel formation. These findings can provide a new pathway for waste bamboo tar management and VOC abatement using adsorbents.

Adsorption of acetone and cyclohexane onto CO2 activated hydrochars

Most of the volatile organic compounds (VOCs) are toxic and harmful to human health and environment. In this study, hydrochars activated with CO₂ were applied to remove VOCs. Two typical VOCs, acetone and cyclohexane, were used as the 'model' adsorbates to evaluate hydrochars' performance. Specific surface areas of pristine hydrochars were small (<8 m²/g), whereas activated hydrochars showed much higher values (up to 1308 m²/g). As a result, the adsorption of VOCs onto the pristine hydrochars (13.24-24.64 mg/g) was lower than that of the activated ones (39.42-121.74 mg/g). The adsorption of the two VOCs onto the hydrochars was exothermal. In addition, there were significant correlations (R² > 0.91) between the VOC removal and hydrochars' specific surface area. These results suggest that the governing mechanism was mainly physical adsorption. Increasing experimental temperature (80-139 °C) desorbed the VOCs from the hydrochars. Due to its higher boiling point, cyclohexane desorption required a higher temperature than acetone desorption. The reusability of the activated hydrochars to the two VOCs was confirmed by five continuous adsorption-desorption cycles. The overall results indicated that hydrochars, particularly after CO₂ activation, are sufficient for VOC abatement.

Investigation of high-performance adsorption for benzene and toluene vapors by calix[4]arene based organosilica (CBOS)

Calix[4]arene based organosilica (CBOS) was successfully prepared, characterized, and used for the adsorption of benzene and toluene vapors for the first time. The benzene and toluene vapor uptake of CBOS was determined to be 606 and 672 mg g⁻¹, respectively.

Mesoporous graphene adsorbents for the removal of toluene and xylene at various concentrations and its reusability

As novel technologies have been developed, emissions of gases of volatile organic compounds (VOCs) have increased. These affect human health and are destructive to the environment, contributing to global warming. Hence, regulations on the use of volatile organic compounds have been strengthened. Therefore, powerful adsorbents are required for volatile organic compounds gases. In this study, we used graphene powder with a mesoporous structure to adsorb aromatic compounds such as toluene and xylene at various concentrations (30, 50, 100 ppm). The configuration and chemical composition of the adsorbents were characterized using scanning electron microscopy (SEM), N₂ adsorption-desorption isotherm measurements, and X-ray photoelectron spectroscopy (XPS). The adsorption test was carried out using a polypropylene filter, which contained the adsorbents (0.25 g), with analysis performed using a gas detector. Compared to graphite oxide (GO) powder, the specific surface area of thermally expanded graphene powder (TEGP800) increased significantly, to 542 m² g⁻¹, and its chemical properties transformed from polar to non-polar. Thermally expanded graphene powder exhibits high adsorption efficiency for toluene (92.7–98.3%) and xylene (96.7–98%) and its reusability is remarkable, being at least 91%.

Synthesis of ZSM-5/Siliceous Zeolite Composites for Improvement of Hydrophobic Adsorption of Volatile Organic Compounds

In this research, we investigated the hydrophobicity and dynamic adsorption-desorption behaviors of volatile organic compounds (VOCs) by applying different optimized coating dosage (25, 50, and 75%) on designed novel ZSM-5/MCM-41 and ZSM-5/Silicalite-1 hierarchical composites. The relatively large specific surface area and pore volume of adsorbents ZSM-5/MCM-41 and ZSM-5/Silicalite-1 composites with excellent stability were affirmed by ex-situ XRD, FTIR, BET, SEM, and water contact angle analyses. Regarding, toluene adsorption-desorption investigation, ZSM-5/MCM-41 composite lead a longer stable toluene breakthrough time no matter under dry or 50% humid conditions. However, under different loading dosage condition, the breakthrough time of 75% coating ratio was the longest, which was 1.6 times as long as that of pure ZSM-5 under wet adsorption. Meanwhile, the complete elimination of toluene for ZSM-5/MCM-41-75% was done by largest desorption peak area and the lowest desorption temperature of 101.9°C, while, the largest contact angle of ZSM-5/MCM-41-75% was 17.0° higher than pure ZSM-5 zeolite. Therefore, we believe that the present hydrophobic sorbent will provide new insight with great research potential for removing low concentration of VOCs at industrial scale.

Integrated adsorption and photocatalytic degradation of volatile organic compounds (VOCs) using carbon-based nanocomposites: A critical review

Volatile organic compounds (VOCs) are harmful for human and surrounding ecosystem, and a great number of VOC abatement technologies have been developed during the past few decades. However, the single method has some problems such as high energy consumption, unfriendly environment, and low removal efficiency. Recently, the integration of adsorption and photocatalytic degradation of VOCs is considered as a promising one. Carbon material, with large surface area, high adsorption capacity, and fast electron transfer ability, is widely used in integrated adsorptive-photocatalytic removal of VOCs. It is thus crucial to digest and summarize recent research advances in carbon-based nanocomposites as the adsorbent-photocatalyst for VOC removal. To satisfy this need, this work provides a critical review of the related literature with focuses on: (1) the advantages and disadvantages of various carbon-based nanocomposites for the applications of VOC adsorption and photocatalytic degradation; (2) models and mechanisms of adsorptive-photocatalytic removal of VOCs according to the material properties; and (3) major factors controlling adsorption-photocatalysis processes of VOCs. The review is aimed to establish the "structure-property-application" relationships for the development of innovative carbon-supported nanocomposites and to promote future research on the integrated adsorptive and photocatalytic removal of VOCs.

Sewage biogas efficient purification by means of lignocellulosic waste-based activated carbons

The present paper evaluates the efficiency of sustainable activated carbons obtained from the valorization of lignocellulosic waste in removing siloxanes and volatile organic compounds for the purification of anaerobic digester biogas. Pyrolized and non-pyrolized lignocellulosic residues generated in food and wood industries were used as precursor materials to obtain experimental adsorbents by a chemical activation process using several activating agents. The highest porosity was obtained by non-pyrolized residue activated by K₂CO₃ at 900 °C. The performance of the experimental materials was compared with that of commercial activated carbons in gas adsorption tests of siloxanes (octamethylcyclotetrasiloxane and hexamethyldisiloxane) and volatile organic compounds (toluene and limonene). The waste-based activated carbons developed in this work proved to be more efficient for the removal of both siloxanes and VOCs than the commercial samples in most of the conditions tested. Adsorption capacities correlated with porosity, while the more relevant pore size depends on the adsorbate.

Fabrication of Diatomite/Silicalite-1 Composites and Their Property for VOCs Adsorption

Adsorption technology is an effective method to remove volatile organic compounds (VOCs). In this work, we prepared hierarchical porous materials using modified diatomite (Dt) as a support and nano-sized silicalite-1 (S-1) seeds as inorganic fillers, which were applied to adsorb volatile organic compounds (VOCs). The characterization of the composites indicated that S-1 was successfully coated onto the surface of modified Dt, and the best surface area of the composites was 398.8 m²/g, nearly 40 times as large as Dt. The adsorption capacities of Dt/S-1 composites for three probe VOCs (ethyl acetate, acetone, and toluene) were rather superior to Dt, and the composites had preferential adsorption selectivity for ethyl acetate. Effects of seeded zeolite contents and hydrothermal conditions for the adsorption capacity of composites were discussed in this paper. The composite seeded with 5 wt% S-1 zeolite, which was subsequently synthesized by hydrothermal reaction at 100 °C for four days, showed the maximum adsorption capacity (1.31 mmol/g for ethyl acetate). The pseudo second-order model provided a perfect fit to adsorption kinetics, while the Langmuir model agreed the best with the adsorption isotherms. In addition, the composites had selective adsorption to ethyl acetate among these three probes VOCs. The regeneration experiments were also carried out, and the adsorption efficiency of the adsorbents was still up to 67% after five adsorption⁻desorption cycles. The hierarchical porous Dt/S-1 composites have an excellent VOC adsorption performance, satisfactory selectivity, and recycling ability.

Adsorption of VOCs onto engineered carbon materials: A review

Volatile organic compounds (VOCs) severely threaten human health and the ecological environment because most of them are toxic, mutagenic, and carcinogenic. The persistent increase of VOCs together with the stringent regulations make the reduction of VOC emissions more imperative. Up to now, numerous VOC treatment technologies have emerged, such as incineration, condensation, biological degradation, absorption, adsorption, and catalysis oxidation et al. Among them, the adsorption technology has been recognized as an efficient and economical control strategy because it has the potential to recover and reuse both adsorbent and adsorbate. Due to their large specific surface area, rich porous structure, and high adsorption capacity, carbonaceous adsorbents are widely used in gas purification, especially with respect to VOC treatment and recovery. This review discusses recent research developments of VOC adsorption onto a variety of engineered carbonaceous adsorbents, including activated carbon, biochar, activated carbon fiber, carbon nanotube, graphene and its derivatives, carbon-silica composites, ordered mesoporous carbon, etc. The key factors influence the VOC adsorption are analyzed with focuses on the physiochemical characters of adsorbents, properties of adsorbates as well as the adsorption conditions. In addition, the sources, health effect, and abatement methods of VOCs are also described.

First principles computational study on the adsorption mechanism of organic methyl iodide gas on triethylenediamine impregnated activated carbon

We study the removal of gas-phase organic methyl iodide (CH₃I) from an ambient environment via adsorption onto triethylenediamine (TEDA) impregnated activated carbon (AC).