Specific Surface Area SBET Research Articles

Naphthalene Tetrazole-Based Nickel Metal-Organic Framework as a Filler of Polycarbonate Membranes to Improve CO2 and H2 Separation.

A tetrazole-naphthalene linker was used to prepare a nickel MOF (metal-organic framework) (NiNDTz) with interesting properties: a specific surface area SBET of 320 m2g-1 (SLangmuir 436 m2g-1), high thermal stability (Tdonset = 300 °C), and CO2 uptake of 1.85 mmolg-1, attributed to the tetrazole groups to be used as fillers in gas separation membranes. The role of these groups was crucial in the mechanical properties of mixed membranes prepared using polycarbonate as a polymer matrix, providing a very homogeneous filler distribution and also in the gas separation properties since a simultaneous increase in permeability and selectivity was achieved, especially in the hybrid membrane containing 20% filler (PC@NiNDTz-20%). This membrane exhibited an excellent balance between permeability (P) and selectivity (α) with an increase in the permeability of CO2 and H2, 177 and 185%, respectively, and improvements in the selectivity of these gases against greenhouse gases such as methane and ethylene (between 15 and 28% improvement). These results make this membrane competitive to deal with separations in which these gases are involved, and are of special interest for the H2/CH4 separation since it clearly improves the performance of pure PC and no better PC-based membranes have been reported in the literature for this separation.

Influences of Different Acid Solutions on Pore Structures and Fractal Features of Coal

The effect of different acids on the pore structure and fractal characteristics of micropores and mesopores was determined with the help of low-temperature liquid nitrogen adsorption, X-ray diffraction, and the Frenkel–Halsey–Hill (FHH) model by using Yuwu coal as a sample and placing it in acidic environments, such as HF, HCl, HNO3, and CH3COOH. The results show that the acidization effects of HF and CH3COOH are separately dominated by the micropore and mesopore formation effects, while HCl and HNO3 mainly play their roles in expanding mesopores. After acidization, the surface fractal dimensions D1 and D1′ of micropores and mesopores in coal are always negatively correlated with the total specific surface area SBET, specific surface area Smic of micropores, and specific surface area Smes of mesopores. After being acidized by HF, D2 is negatively correlated with the total volume Vtot and the corresponding micropore volume Vmic, while acidization with HCl and HNO3 leads to the opposite result. After being acidized by CH3COOH, D2 has a negative correlation with Vtot and a positive correlation with Vmic. The structural fractal dimensions D2′ of mesopores in samples acidized by HF and CH3COOH are positively correlated with both the volume Vtot and mesopore volume Vmes, while it is the opposite for samples acidized by HNO3. D2′ of coal samples acidized by HCl is negatively correlated with Vtot while positively correlated with Vmes.

Fabrication of an efficient hierarchical mesoporous 2D-MoS2/CNT/polypyrrole based composite electrodes for competitive and selective U6+ removal using capacitive deionization: Mechanistic evaluation through cyclic voltammetry

In this work, efficient and selective carbonaceous electrode materials based on hierarchical mesoporous functionalized carbon nanotubes, 2D-MoS2 nanosheets electrodeposited with variable content of polypyrrole (PPy) were prepared. The simple etching reaction between HNO3 and carbon nanotubes did not only modify the surface but also improved its hydrophilicity. The annealing of carbon nanotubes and electrodeposition of PPy increased the mesopore volume to total volume ratio (Vmeso/Vt) from 0.42 to 0.86. The composite materials were characterized wisely using different characterization techniques and employed for efficient U6+ electro-assisted sorption through capacitive deionization. Electrode material with PPy content (0.3 M) exhibited good specific capacitance Csp (100.2 F/g), improved Vmeso (0.61 cm3/g), superb Vmeso/Vt ratio (0.86) and large specific surface area SBET (149.7 m2/g). The stated electrode showed fast sorption kinetics (teq=30 min), admirable selectivity and exhibited the experimental sorption capacity of 274.50 mg/g at − 0.90 V. Electrochemical impendence spectroscopic study revealed that the resulting material exhibited relatively small charge transfer resistance (1.19 Ωcm2), minute electrolytic resistance (0.91 Ωcm2) and large double layer constant phase element (0.0368 S sn/ cm2). These significant characteristics promoted U6+ ions diffusion inside the hierarchical porous electrode surface for better performance of electrosorption process. This new class of hierarchical mesoporous composite electrodes may be used as potential supercapacitor materials not only for removal of uranium but also for other potent desalination applications.

Crystallization of Magnetic Iron Oxide Nanoparticles during Chemical Synthesis from Iron Salt Solutions with Exposure to Ultrasound

Iron oxide nanopowders are synthesized via chemical precipitation. It is shown that synthesis produces an iron oxide phase with a magnetite structure (either a magnetite–maghemite solid solution or a mixture of this solid solution and goethite). The sizes of the CSR and particles for the main phase are ~10–20 nm. The synthesized iron oxide powders have developed surfaces, specific surface area SBET ≈ 92 and 117 m2/g, and identical fairly large specific pore volumes (VP/P0→0.99/0→0.99 = 0.35 cm3/g). It is shown that additional in situ ultrasonic treatment of the magnetic iron oxide nanoparticles in the mother liquor results in abrupt oxidation of iron(II) ions and creates a nonmagnetic impurity phase of goethite.

Performance optimization and kinetic analysis of HNO3 coupled with microwave rapidly modified coconut shell activated carbon for VOCs adsorption

As a typical carbon-based material, activated carbon (AC) has satisfied adsorption performance and is of great significance in the field of volatile organic compounds (VOCs) pollutants removal. In order to further reveal the optimization mechanism of AC adsorption performance, coconut shell-based AC was selected as the research object, and different concentrations of HNO3 coupled with microwave were used for rapid modification and activation. The characteristic changes of pore structure and surface chemical of AC before and after rapid modification were analyzed, and the performance changes of VOCs absorption were discussed from the perspective of reaction kinetics. The pore structure and surface chemical properties of before and after modification were analyzed by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Brunauer-Emmeta-Teller (BET) analysis, Fourier Transform Infrared Spectroscopy (FTIR), and Boehm titration. The results showed that HNO3 coupled with microwave could significantly eliminate impurities in the pores of AC. After impregnation in HNO3 at a concentration of 1.5 mol L−1 and under microwave irradiation of 900 W, the number of micropore on the surface of samples increased slightly. When the impregnation concentration of HNO3 continued to increase, the two adjacent pore structures of the samples merged, which lead to a large decrease in the number of micropore and a corresponding increase in the proportion of mesoporous. Meanwhile, the specific surface area SBET of the modified NAC-6 sample increased to 1,140.40 m2 g−1, and the total acidic oxygen-containing functional groups on the surface increased by 0.459 mmol g−1 compared to that of the unmodified raw carbon. Furthermore, by analyzing the experimental results of formaldehyde adsorption on AC samples, it was concluded that the saturated adsorption capacity of the modified NAC-6 sample was 43% higher than that of the raw carbon. This study provides a more convenient and faster modification method for AC in the field of gas phase pollutants purification, which is helpful to realize the practical engineering application of AC with high efficiency, energy saving and sustainable.

Адсорбція хлорфенолу активованим вугіллям з сумішей довгополуменевого вугілля та вторинних продуктів коксування.

ADSORPTION OF CHLOROPHENOL BY ACTIVATED CARBON FROM MIXTURES OF LONG FLAME COAL AND SECONDARY COKING PRODUCTS © V.А. Кucherenko, Doctor of Chemical Sciences, Ju.V. Таmarkina, PhD in Chemical Sciences, V.А. Sabierova, PhD in Chemical Sciences, I.B. Frolova, PhD in Chemical Sciences (L.M. Litvinenko Institute of Physical-Organic and Coal Chemistry of the National Academy of Sciences of Ukraine, 02160, Kyiv, Kharkiv Highway St., 50, Ukraine) The purpose of this work is to evaluate the effect of secondary coking products (SCPs) on the adsorption properties of activated carbons (ACs) from mixtures of SCP and long-flame coal D. AC samples with specific surface area SBET = 885–1173 m2/g were prepared from coal D and mixtures of coal (85 %) and SCP (15 %). Fuses (F), acid tar (AT) of the sulfate department, polymers (P) of the benzene department, cube residue (CR) and coal tar (T) were used, and the corresponding samples are designated as AC(D), AC(F), AC(AT), AC(P), AC(CR), AC(T). The adsorption capacity for 4-chlorophenol (CP) (ACP) was determined at the AC content of 1 g/L (25°C) and the CP initial concentration СCP(0) ≤ 600 mg/L. The CP concentration was determined from the solution optical density at 280 nm (Perkin-Elmer Lambda 20 spectrophotometer). The specific adsorption capacity АCP(S) (mg/m2) was determined by the ratio АCP(S) = ACP/SBET, which is proportional to the concentration of adsorption centers on the AC surface. The degree of CP extraction and the degree of surface coverage were calculated. The CP adsorption kinetics were approximated by pseudo-first order, pseudo-second order and intraparticle diffusion models. The adsorption isotherms were approximated by the Langmuir and Freundlich models. The SCP type was established to have a significant effect on the AC adsorption activity which is expressed by significant differences in the values of adsorption capacity, kinetic characteristics, and isotherm parameters. The CP adsorption kinetics was found to obey the pseudo-second order model (determination coefficient R2 ≥ 0.996) with constants varying from 2,78·10-4 g/mg·min to 6,29·10-4 g/mg·min depending on the SCP type. By comparing the calculations of the kinetics by the pseudo-first order and intraparticle diffusion models, the rate-determining stage was found to be the physical sorption and chemisorption of СP. In the range of equilibrium concentrations of СCP(е) ≤ 350 mg/l, the adsorption isotherms were approximated by the Langmuir model (R2 ≥ 0,994) better than by the Freundlich model (R2 ≥ 0,887). The calculated capacitances of the monolayer for the obtained ACs differ by a factor of ~2 and are in the interval of АCP(L) =214,3 – 414,3 mg/g, Langmuir constants are from 1,89·10-2 l/mg to 5,29·10-2 l/mg. The CP adsorption capacity was found to increase almost linearly with increasing SBET (R2 = 0.931), but the AC(AT) sample sharply drops out of this dependence and shows a 2-fold lower capacity value, which is due to the AT composition. It is determined that the CP capacity and degree of extraction increase in the series of АC(AT) < АC(D) < АC(F) < АC(T) < АC(P) < АC(CR). Judging by the effect on the AC properties, the most effective SCP is the cube residue, which maximally contributes to the formation of adsorption centers being active in relation to CP. The AC(CR) sample exhibits the highest adsorption capacity (414 mg/g), specific capacity (0.353 mg/m2), surface coverage (80.6 %), and initial CP uptake rate. During the first 5 min, AC(CR) absorbs 35.8 % of the CP total amount at CCP(0) = 600 mg/l. The values of this parameter for other samples are lower and range from 11.5 % (AC(AT)) to 29.2 % (AC(P)). Namely SPS composition is concluded to determine the set of chemical reactions forming the AC spatial framework. All SPCs (except acid tar) promote the formation of AC with a higher capacity and an increased adsorption rate, which makes their use promising for improving the ACs adsorption characteristics. Key words: long flame coal, secondary coking product, activated carbon, adsorption, 4- chlorophenol Corresponding author: Таmarkina Ju.V., e-mail: Tamarkina@nas.gov.ua

Tuning ceria catalysts in aqueous media at the nanoscale: how do surface charge and surface defects determine peroxidase- and haloperoxidase-like reactivity.

Designing the shape and size of catalyst particles, and their interfacial charge, at the nanometer scale can radically change their performance. We demonstrate this with ceria nanoparticles. In aqueous media, nanoceria is a functional mimic of haloperoxidases, a group of enzymes that oxidize organic substrates, or of peroxidases that can degrade reactive oxygen species (ROS) such as H2O2 by oxidizing an organic substrate. We show that the chemical activity of CeO2-x nanoparticles in haloperoxidase- and peroxidase-like reactions scales with their active surface area, their surface charge, given by the ζ-potential, and their surface defects (via the Ce3+/Ce4+ ratio). Haloperoxidase-like reactions are controlled through the ζ-potential as they involve the adsorption of charged halide anions to the CeO2 surface, whereas peroxidase-like reactions without charged substrates are controlled through the specific surface area SBET. Mesoporous CeO2-x particles, with large surface areas, were prepared via template-free hydrothermal reactions and characterized by small-angle X-ray scattering. Surface area, ζ-potential and the Ce3+/Ce4+ ratio are controlled in a simple and predictable manner by the synthesis time of the hydrothermal reaction as demonstrated by X-ray photoelectron spectroscopy, sorption and ζ-potential measurements. The surface area increased with synthesis time, whilst the Ce3+/Ce4+ ratio scales inversely with decreasing ζ-potential. In this way the catalytic activity of mesoporous CeO2-x particles could be tailored selectively for haloperoxidase- and peroxidase-like reactions. The ease of tuning the surface properties of mesoporous CeO2x particles by varying the synthesis time makes the synthesis a powerful general tool for the preparation of nanocatalysts according to individual needs.

Removal of indigo carmine (IC) in aqueous solution onto activated pomegranate peel (APP) by adsorption process: Kinetic and thermodynamic studies

The adsorption of indigo carmine dye onto Activated Pomegranate Peels (APP) from aqueous solutions was followed in a batch system. The adsorbent was characterized by the BET method (specific surface area SBET: 51.0674 m2/g) and point of zero charge (pHpz = 5.2). However, some examined factors were found to have significant impacts on the adsorption capacity of pomegranate peels (APP) such as the initial dye concentration (10–60 mg/L), solution pH (2–12), adsorbent dose (1–10 g/L), agitation speed (100–600 rpm), and temperature (298–308 K). The best adsorption capacity was found at pH 2 with an adsorbent dose 1 g/L, an agitation speed 300 rpm and a contact time of 45 min. The adsorption mechanism of IC onto (APP) was studied by using the first-pseudo order, second-pseudo order, Elovich, and Webber-Morris diffusion models. The adsorptions kinetic were found to follow rather a pseudo-second order kinetic model with a determination coefficient ( R2) of 0.999. The equilibrium adsorption data for IC onto (APP) were analyzed by the Langmuir, Freundlich, Elovich, and Temkin models. The results indicate that the Langmuir model provides the best correlation with capacities ( qmax of 158.73 mg/g at 298 K). The adsorption isotherms at different temperatures have been used for the determination of thermodynamic parameters like the free energy; enthalpy and entropy to predict the nature of adsorption process. The negative values Δ G° and Δ H° indicate that the overall adsorption is spontaneous and exothermic with a physisorption process. The adsorbent elaborated from pomegranate peels material was found to very effective and suitable for the removal of reactive dyes from aqueous solutions, due to its availability, low cost preparation, and good adsorption capacity.

B-Doped Carbon Powder Synthesized from PU/PF/GO Composite as Electrode Material for Supercapacitors

Graphite is a vital natural mineral material that is used to synthesize graphene oxide. In the present study, polyurethane/phenolic/graphene oxide composite materials were prepared from polyisocyanate prepolymer, phenolic resin prepolymer, and graphene oxide then treated with boric acid, ferric chloride, and zinc chloride and carbonized at high temperatures to synthesize boron-doped carbon powder (UFGC-B-Fe-Zn). The UFGC-B-Fe-Zn exhibited a Brunauer–Emmett–Teller specific surface area SBET of 885.9759 m2 g−1 and a specific pore volume of 0.550491 cm3 g−1, as well as high specific capacitance of 377.4 F g−1 at 0.5 A g−1. Used as an electrode material for supercapacitors, UFGC-B-Fe-Zn exhibited excellent rate capability and durability as well as low charge and ion diffusion resistance. In 6 M KOH electrolyte, the assembled symmetrical supercapacitor achieved relatively high energy density of 7.43 Wh kg−1 at 474 W kg−1. Moreover, it displayed excellent cycling stability (90.9% retention rate after 5000 cycles).

Study of the textural characteristics of carbon sorbents prepared by alkaline activation

The paper investigates the textural characteristics of carbon sorbents prepared by alkaline activation of brown coal from the Tisul deposit. The texture characteristics (specific surface area-SBET, m2/g, total pore volume-VΣ, cm3/g, mesopore volume-Vme, cm3/g and volume of micropores-Vmi, cm3/g) of carbon sorbents were measured on an ASAP-2020 analyzer. The production of carbon sorbents was carried out by activating coal impregnated with potassium hydroxide at a KOH/coal (RKOH) ratio of 0.5 g/g; 1 g/g and 2 g/g. The activation of brown coal was carried out at three different temperatures-700 °C, 750 °C and 800 °C. It is shown that the RKOH ratio has a greater effect on the texture characteristics of carbon sorbents, as compared to the effect of the alkaline activation temperature. Alkaline activation at an RKOH ratio of 2 g/g makes it possible to obtain carbon sorbents with the highest values of textural characteristics. High-temperature alkaline activation (800 °C) has a positive effect on the formation of a common pore space of carbon sorbents based on brown coal from the Tisulsky deposit for all studied RKOH.

Effect of hydrothermal nanosilica on the performances of cement concrete

A new technological method for producing a nano-modifier for cement concretes from renewable source of hydrothermal solution using the processes of polycondensation of orthosilicic acid and ultrafiltration membrane concentration is proposed. According to the data of dynamic light scattering, tunneling electron microscopy, and low-temperature nitrogen adsorption, it is shown that in sol samples the average diameters of amorphous SiO2 nanoparticles can be varied in the range 10–100 nm, the specific surface area of ​​SBET is 50–500 m2 / g, the density of chemically active surface silanol Si-OH groups up to σ = 4.9 nm−2. Increasing the compressive strength of concrete specimens modified with SiO2 sol (0.5–3.0 wt%) and polycarboxylate superplasticizer (0.2–3.98 wt%), liquid-binder ratio L/B = 0.5–0.7, with normal hardening and with accelerated hardening with heat-moisture treatment, it reached 128% at the age of 1 day, and up to 40% at the age of 28 days. According to the kinetic curves of water absorption, a significant decrease in the volume, average pore diameter and an increase in the uniformity of the distribution of pores along the diameter of the modified concrete were established, which led to an increase in its water impermeability. The kinetics of the pozzolanic reaction with the formation of crystalline calcium hydrosilicates has been studied by the methods of X-ray diffraction analysis, energy-dispersive spectroscopy, scanning electron microscopy, and thermogravimetry. The chemo-sorption capacity of hydrothermal SiO2 nanoparticles for binding Ca(OH)2 in CaO solution and cement matrice was determined, which, due to the high SBET and σ values ​​for the first 24 h of the reaction, is many times higher than that of silica fume. In modified Portland cement matrice at the age of 1 day, the δCaO value was 750 [mg CaO / g SiO2], which corresponded to a response of 60–70% of the introduced nano-SiO2 and an increase in the rate of alite hydration by 20–30%, and rised at the age 100 days to 1200 [mg CaO / g SiO2]. Hydrothermal sols and SiO2 nanopowders have prospects for the creation of cement composites.

Synthesis of zeolite-carbon composites using high-carbon fly ash and their adsorption abilities towards petroleum substances

In this paper, high-carbon fly ash (HCFA) was used to produce the zeolite-carbon composites of faujasite and gismondite structures (named NaX-C and NaP1-C, respectively) in pilot scale using the single-step hydrothermal conversion. The possibility of using the obtained composites in the petroleum substances removal was studied. The materials were characterized by means of particle size distribution, CHN elemental analysis, X-ray photoelectron spectroscopy, X-ray fluorescence spectroscopy, scanning electron microscopy, X-ray diffraction, DTA/TG thermal analysis, Fourier transform infrared spectroscopy, as well as BET surface area and pore structural analysis. The adsorption performance was examined using a Westinghouse procedure towards engine oil, used engine oil and kerosene. HCFA and composites exhibited high content of carbon (28.1–44.5%), accompanied by mineral phase abundant with silica and alumina (18.2–30.2% and 10.0–13.6%, respectively). The composites revealed a presence of well-defined zeolite crystals formed onto carbonaceous surface and more developed textural parameters in relation to HCFA. Specific surface area SBET of HCFA, zeolite-carbon composites NaP1-C and NaX-C was 46, 249 and 67 m2/g, respectively. The sorption capacity towards oils was 1.14–1.39 g/g for HCFA, 1.1–1.54 g/g for NaX-C, 1.32–1.69 g/g for NaP1-C depending on the oil properties as well as the particle size and pore structure of the adsorbent.

Crystallization of the Granulated Molecular Sieve SAPO-11 Having High Crystallinity and a Hierarchical Pore Structure

A method for the synthesis of the granulated molecular sieve SAPO-11 having high crystallinity and a hierarchical pore structure was proposed for the first time. Crystallization is based on the synthesis of granules comprising 70 wt.% of powdered SAPO-11 and 30 wt.% of the silicoaluminophosphate binder, which transforms into SAPO-11 during crystallization and forms a joint system of intergrown silicoaluminophosphate crystals. This crystallization method makes it possible to obtain the granulated SAPO-11 having high crystallinity and phase purity; its specific surface area SBET is 212 m2/g, micro, meso- and macropore volumes are 0.08, 0.11 and 0.55 cm3/g, respectively. Meso- and macropores were shown to form between intergrown SAPO-11 crystals.

Crystal and Supramolecular Structure of Bacterial Cellulose Hydrolyzed by Cellobiohydrolase from Scytalidium Candidum 3C: A Basis for Development of Biodegradable Wound Dressings.

The crystal and supramolecular structure of the bacterial cellulose (BC) has been studied at different stages of cellobiohydrolase hydrolysis using various physical and microscopic methods. Enzymatic hydrolysis significantly affected the crystal and supramolecular structure of native BC, in which the 3D polymer network consisted of nanoribbons with a thickness T ≈ 8 nm and a width W ≈ 50 nm, and with a developed specific surface SBET ≈ 260 m2·g−1. Biodegradation for 24 h led to a ten percent decrease in the mean crystal size Dhkl of BC, to two-fold increase in the sizes of nanoribbons, and in the specific surface area SBET up to ≈ 100 m2·g−1. Atomic force and scanning electron microscopy images showed BC microstructure “loosening“after enzymatic treatment, as well as the formation and accumulation of submicron particles in the cells of the 3D polymer network. Experiments in vitro and in vivo did not reveal cytotoxic effect by the enzyme addition to BC dressings and showed a generally positive influence on the treatment of extensive III-degree burns, significantly accelerating wound healing in rats. Thus, in our opinion, the results obtained can serve as a basis for further development of effective biodegradable dressings for wound healing.

PREPARATION OF NOVEL X% Li/TiO2 (x = 1%, 2% and 4%) AND THEIR ACTIVITIES UNDER VISIBLE LIGHT

Series of metal doped titanium dioxide were synthesized with the aim to enhance the photocatalytic activity under visible irradiation. x% Li doped TiO2 catalysts (x = 1%, 2% and 4%) were prepared using hydrothermal method. The samples were characterised by specific surface area SBET, X-ray diffraction XRD, diffuse reflectance spectroscopy DRS and photocatalytic activity.We succeeded to obtain high specific surface area samples. In fact, it increases to reach an optimum at 2%dopant amount. XRD analysis showed that all samples are single Anatse phase whatever dopant amount level. The photocatalytic activity was tested in methylene blue degradation under visible irradiation. Two different power lamps were used in order to investigate effect of irradiation condition. These new photocatalysts exhibited visible light activity similar to PC500 to degradated MB. The results were discussed in terms of donor electron level creation in the band gap.

Effect of Zinc Chloride Activation on D-Glucose Derived Carbons Based Capacitors Performance in Ionic Liquid

Various carbon materials have been synthesized applying hydrothermal carbonization process and subsequent ZnCl2 activation step using different mass ratios of activating reagent. The resulting powder materials were characterized physically and electrochemically in a two-electrode cell configuration using 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid. Activated materials porosity was highly dependent on the activation conditions i.e. on the ratio of ZnCl2 used in the activation process. The best material having Brunauer–Emmett–Teller specific surface area SBET = 2320 m2 g−1, micropore surface area Smicro = 1510 m2 g−1 and total pore volume Vtot = 1.01 cm3 g−1 where the highest amount of ZnCl2 was used for the synthesis of carbon material. High specific parallel capacitance (140 F g−1), a wide region of ideal polarizability (ΔV ≤ 3.0 V), short characteristic relaxation time (2.12 s), and high energy density (48 W h kg−1) values have been established for material with the highest porosity showing great potential for these supercapacitor systems to be used in practical application as energy storage devices.

Methane Adsorption on Cu-BTC110 Metal-Organic Framework

Cu-BTC110 metal-organic framework has been synthesized by solvothermal method using N,N '‑dimethylformamide organic solvent at 110°C. Cu-BTC110 sample has the following adsorption characteristics: micropore volume W0 = 0.38 cm3/g, specific surface area SBET = 850 m2/g, micropore radius х0 = 0.36 nm, standard characteristic energy of benzene adsorption Е0 = 33.6 kJ/mol. Methane adsorption on a Cu-BTC110 sample at temperature from 210 to 293 K and pressure up to 140 kPa has been studied. Differential molar heat of methane adsorption has been calculated from adsorption isosteres.

Ethane adsorption on microporous carbon adsorbent with a wide pore size distribution

A microporous carbon adsorbent MPU-007 with a wide pore size distribution (specific micropore volume W0 calculated within the framework of the theory of micropore volume filling is 1.44 cm3 g−1; first-mode micropore diameter X01 is 1.5 nm; second-mode micropore diameter X02 is 3.5 nm; specific surface area SBET is 2520 m2 g−1) was prepared by chemical activation of a mixture of corn dextrin, ethylene glycol, and phenol formaldehyde resin. Adsorption of ethane on this adsorbent was studied at pressures up to 4 MPa at T = 303, 313, 323, and 333 K. The maximum ethane adsorption value attained in the experiments was 25 mmol g−1 or 75 wt%. The adsorption isosteres plotted in the ln P–1/T coordinates using the data obtained can be well approximated by linear functions at constant adsorption values. The dependences of the differential molar isosteric heats of adsorption of ethane on MPU-007 on the amount adsorbed in the temperature range of 303–333 K were calculated. The heat of adsorption of ethane equal to 23 kJ mol−1 remained constant throughout the initial range of micropore fillings up to ∼7 mmol g−1 and then gradually decreased to 8 kJ mol−1 at an uptake of 24 mmol g−1 at 333 K. Such a pattern of the dependence of the heat of adsorption can be due to a wide pore size distribution and to the formation of associates in the adsorbate.

Specific surface area of combustion emitted particles: Impact of primary particle diameter and organic content

Specific surface areas of particles produced at small-scale diffusion flame burners and also in pilot and large-scale fires involving complex fuels are reported and compared. Specific surface area SBET is determined by BET (Brunauer-Emmett-Teller) analysis and also according to previously developed approach STEM relying on the primary sphere based on TEM (Tansmission Electron Microscopy) images analysis. True density is also determined and the respective influences of primary particle diameter (Dpp) and organic carbon to total carbon ratio (OC/TC) are discussed. The present study is the first to propose a careful comparison between TEM and BET specific surface areas of 20 different samples of carbonaceous particles emitted under realistic fire conditions and to bring validity range for such TEM based approach. For samples containing low and moderate OC content (less than 20%), a good agreement between STEM and SBET is reported (within ± 20% for a confidence interval of 95%), confirming the significant influence of primary particle diameter and the relevance of a purely geometrical description of the surface specific area of soot particles. For larger OC/TC, such approach fails to predict the particles specific surface area within a reasonable confidence interval.

Methane Adsorption on the Metal–Organic Framework Structure Al-BTC

Adsorption of natural gas (methane) on the synthesized metal–organic framework (MOF) Al-BTC with specific surface area SBET = 1422 m2/g was studied at pressures up to 40 MPa and temperatures of 303, 313, 323, and 333 K. The maximum adsorption of methane on Al-BTC reaches 10.36 mmol/g at 303 K and 40 MPa, and the initial heat of adsorption is ~14 kJ/mol. The amount of methane accumulated in a system with Al-BTC attains a value of 120–130 m3(NTP)/m3 in a range of pressures from 3.5 to 10.0 MPa, which is the most relevant for methane accumulation. The volumes of methane stored in the systems with Al-BTC and without an adsorbent differ by a factor of about 2 at 3.5 MPa, there is almost no distinction between these options of methane storage at 7.0 and 20.0 MPa, and the amount of gas in the system without an adsorbent exceeds by 25% that in Al-BTC. The pressure range from 3.5 to 6.0 MPa is most efficient for the methane adsorption accumulation in the MOF structure Al-BTC. The absolute efficiency of methane adsorption accumulation increases with lowering of temperature.