Micropore Surface Area Research Articles

Quantitative Analysis of Pore Structure and Its Impact on Methane Adsorption Capacity of Coal

Better understanding of the storage and transportation characteristics of methane in coal seams is important to further develop and utilize the methane resources in the coalbed. This study is devoted to investigating the relationship between methane adsorption performance and pore structure by analyzing twelve coal samples derived from the typical methane-rich coalbeds in China. To eliminate the influence of inorganic components such as ash in different coal samples, a specific fixed-bed reactor with internals was employed for the coal treatment. Based on N2/CO2 adsorption analysis at low-pressure condition, the pores in coal were classified into three types in this study: ultra-micropore (pore width ultra-micropore surface area (0.8976) > fractal dimension D1 (0.8862) > N2-BET surface area (0.7915) > micropore volume (0.5035) > micropore surface area (0.5006). This study shows the influence of parameters of pore structure on methane adsorption of coal and clarifies the order importance of these parameters by the GRA method.

Production and evaluation of properties of waste-based carbon adsorbent

This paper focuses on the study of the production method, evaluation of quality indicators and application of adsorbents based on wood and common polymer wastes. The co-pyrolysis technique of polyethylene, polypropylene, polyethylene terephthalate and other polymers with sawdust at the weight ratio of 1:1 and 1:2 and temperature 370−500 °C is used for the production of adsorbents. Influence of polymer and wood type on the product quality is discussed. For the composition of birch wood and polypropylene, linear models for the yield estimation and indicators of the porous structure of adsorbents, based on the experiment planning method, are proposed, which allow us to forecast their quality under the joint influence of their production factors. The adsorbent at 500 °C was also characterized by optical and electron microscopy, X-ray fluorimetry, infrared spectrometry and low-temperature nitrogen adsorption method: its surface area (Brunauer–Emmett–Teller) is 435 m2/g, surface area of micropores (t-plot) is 316 m2/g; the average pore diameter is 1.93 nm; the total pore volume is 0.20 cm3/g. The sample at 370 °C has maximal volume of pores sorbing 0.662 cm3/g of benzene and 0.703 cm3/g of tetrachlormethane and expressed hydrophobic properties; these values are superior to those of birch activated carbon twice. Its use for the vapor recovery of benzene from the airflow was evaluated, which showed its high activity (322 mg/g) and superiority over commercial activated carbon. An approximate ecological and economic evaluation of this adsorbent production has been carried out, demonstrating its profitability and environmental effectiveness.

P-nitrophenol degradation by pine-wood derived biochar: The role of redox-active moieties and pore structures

Biochar can both adsorb and degrade p-nitrophenol (PNP); however, the PNP degradation mechanism has not been well investigated. We prepared two biochars at pyrolysis temperatures of 500 °C (B500) and 700 °C (B700). Although B500 showed much stronger free radical signals (which are associated with organic degradation, according to previous studies), the apparent PNP degradation was approximately 3 times higher in the B700 system. The degradation increased significantly after the biochars were washed with water. According to a quantitative analysis of the sorption and degradation and two-compartment first-order kinetics modeling of the apparent removal kinetics, sorption occurred mainly in the initial period, whereas degradation continued throughout the removal process. The PNP degradation rate constant depended mainly on the external surface area at a relatively low concentration (200 mg/L) and was controlled by the microporous surface area at a relatively high concentration (800 mg/L). In addition, the apparent degradation did not depend on the biochar particle size. Therefore, PNP degradation may be related to the three-dimensional structure of the biochar in addition to the exposed external surface. The well-developed pore structure, more accessible surface, and larger electron exchange capacity of B700 may promote electron transfer between the biochar and PNP, and thus accelerate PNP degradation. This study demonstrates that various properties of the biochar may contribute to PNP degradation.

Testing the carbonization condition for high surface area preparation of activated carbon following type IV green alga Ulva lactuca

Activated carbon with high specific surface area has been produced from green alga Ulva lactuca by using zinc chloride (ZnCl2) solution as an activating agent under carbonization temperature ranged from 500 to 900 °C. The effects of carbonization temperatures, holding time, and amount of ZnCl2 followed by soaking in hydrochloric acid on the specific surface area, pore morphology, and mass yield of the prepared activated carbon were investigated. In this work, the activated carbon with high specific surface area was achieved using 1:2 (ZiCl2: Ulva lactuca) impregnation agent, 700 °C as activation temperature, 30 min as holding time, and soaking with 3.0 M hydrochloric acid as the optimum conditions. This condition produced an activated carbon with specific surface area (SBET) and micropore surface area (Smi) of 1486.3 and 1582.04 m2/g, respectively, with mean pore diameter (DP) of 2.39 nm. The results showed that the chemical activation by ZnCl2 is a useful technique for obtaining activated carbon from Ulva lactuca with desired pore size distributions and morphology at moderate activation temperatures.

Natural Aluminosilicate-based Y Zeolite for Catalytic Cracking of n-Hexadecane

Natural zeolite and kaolin are abundant in Indonesia especially in Java and Belitung islands. These materials generally contain high aluminosilicate minerals that can be used as silica and alumina sources for the formation of NaY zeolite. This research aimed to identify the modification of NaY zeolite structure using Bayat natural zeolite as alumina source and Belitung kaolin as silica source and its catalytic activity for n-hexadecane cracking. Pretreatment of materials were performed in several steps: activation, purification, fragmentation for Bayat–Klaten natural zeolite, and silica extraction for Belitung kaolin. The synthesis of NaY was performed hydrothermally using seed-assisted method with crystallization times of 24 and 48 h. The surface area analysis showed a typical surface area of microporous zeolite (i.e., a pore diameter of 1.897 nm) and surface area of 309.4 cm2/g. Meanwhile, powder X-ray diffraction characterization showed that the as-synthesized materials have the structure of NaY zeolite. The optimum crystallization time was 24 h with Si/Al ratio of 4.10. Furthermore, both synthetic and natural sourced NaY zeolites were converted into HY zeolites and employed as cracking catalyst of n-hexadecane in a fixed-bed reactor at 500 °C for 75 s. The natural sourced HY resulted in 59.80% conversion and 59.80% yield of gasoline product (C9–C12). These values were lower than the results given by synthetic HY (80%).

Development of hierarchical and phosphorous-modified HZSM-5 zeolites by sequential alkaline/acid treatments and their catalytic performances for methanol-to-olefins

An efficient and simple method was proposed to synthesize hierarchical and phosphorous-modified HZSM-5 zeolites by sequential alkaline and acid treatment. In the first NaOH alkaline treatment, intracrystalline mesoporosity was introduced into the zeolites by the crystal defect formation and growth of crystal defects due to desilication. The excessive defect growth caused amorphization of the zeolites, dramatically decreasing their surface area and micropore volume. The aluminum-related debris resulting from the desilication deposited on the extra-framework positions and had a dramatic influence on the crystallinity and microporosity of the zeolites. In the subsequent H3PO4 treatment for the alkaline-treated HZSM-5, the deposited extra-framework aluminum species were selectively removed, thus increasing the micropore volume and surface area of the zeolites. Along with the dealumination, the phosphorous species were introduced into the framework to occupy the silicon sites, leading to a crystalline structure repair. The post-treatments could modify the structural and acidic properties of the HZSM-5 zeolite. Catalytic tests showed that the hierarchical and phosphorous-modified HZSM-5 zeolite exhibited higher methanol conversion and propylene selectivity in methanol-to-olefins reactions over a longer period compared with the parent HZSM-5.

Development of mesoporous ZSM-5 zeolite with microporosity preservation through induced desilication

Alkali treatment is a widely used strategy to create mesopores for microporous zeolites to decrease the diffusion limitation in micropores. However, many of the micropore losses existed due to the uncontrollable destruction of framework. In this paper, a series of mesoporous ZSM-5 with well-maintained micropores was synthesized through induced desilication strategy. To induce the diffusion of alkali solution for the homogenizing desilication and mesopore formation, abundant and uniform small mesopores were firstly built for ZSM-5 by protective desilication in tetrapropylammonium hydroxide solution. The pore structure and acidity of the obtained ZSM-5 were characterized by XRD, TEM, N2 physisorption, NH3-TPD and Py-IR. Through induced desilication, the external surface area of obtained ZSM-5 increased from 42 m2 g−1 of parent ZSM-5 to 148 m2 g−1 and only 17% of micropore surface area was sacrificed, which was far lower than 37% of the loss in traditional NaOH treatment. Meanwhile, the strong acid sites were well preserved and the external acid sites were reduced. Compared with the sample treated by NaOH solution, the obtained catalyst exhibited higher catalytic stability and aromatics, especially PX selectivity. Good regenerated performance with long catalytic lifetime and high liquid hydrocarbon yield could also be found for the obtained catalyst. The strategy proposed in this paper is simple and ingenious in tailoring the porosity since it only relies on the desilication method, which is different from the usual coupling of dealumination and desilication.

Facile synthesis of hierarchical structure of NaY zeolite using silica from cogon grass for acid blue 185 removal from water

Abstract Facile preparation of hierarchical structure NaY zeolite from cogon grass silica is synthesized by microwave-assisted hydrothermal method and subsequently desilicated in ultrasonic-assisted alkaline treatment. This work aims to improve the removal efficiency of acid blue-185 (AB-185) by using hierarchical NaY zeolite. When treated the parent NaY in NaOH solution with various concentrations (0.1, 0.5 and 1.0 M), the Si/Al ratios and micropore surface area decrease but increase a maximum pore size distribution of mesopore with the NaOH concentration due to the desilication effect. Moreover, the mesopore surface area and volume significantly increase and reach to the maximum value with a concentration of 0.5 M (132 m2 g−1 and 0.12 cm3 g−1). Consequently, the NaY (0.5 M) gives the highest percentage of AB-185 removal (80 ± 1.2 %) at a pH of 5 owing to the abundant adsorption sites and the eased accessibility of dye molecules. The adsorption data fit well with the Langmuir isotherm rather than Freundlich isotherm models with a correlation coefficient of 0.99. Maximum adsorption capacity of AB-185 on NaY (0.5 M) is larger than that on the parent NaY (84.5 mg/g vs 19.4 mg/g). In addition, the adsorption process of AB-185 on NaY (0.5 M) is more favorable by the pseudo-second-order kinetic model indicating the main rate-control is chemisorption. The existence of interactions between AB-185 and the NaY (0.5 M) is confirmed by FTIR and XPS. The reusability of the NaY (0.5 M) preserves original adsorption capacity, up to five cycles indicating a promising adsorbent for water treatment.

Pore structure and diffusion characteristics of intact and tectonic coals: Implications for selection of CO2 geological sequestration site

With the increasing amount of CO2 in the atmosphere, geologic sequestration becomes a promising measure to reduce the rising concentration of CO2. During the process of CO2 injection into coal seam to store CO2, it is critical to select the appropriate coal seam. In order to study whether the intact or tectonic coal is more suitable for CO2 geological sequestration, the pore structure characteristics and fractal dimensions of these coal samples were analyzed by mercury intrusion porosimetry, N2 (77 K)/CO2 (273 K) adsorption methods, and methane adsorption and diffusion properties of these coal samples were obtained. The results show that tectonic coals have greater pore volume and specific surface area of micropore, mesopore and macropore, while the fractal dimensions of the tectonic coals are smaller (that is, simpler pore structure, smaller pore surface roughness) than that of the intact coals, indicating that tectonic coal has more favorable pore structure to provide more adsorption sites for CO2 storage. Furthermore, better connectivity as well as the adsorption and diffusion capacity of tectonic coals have been significantly improved compared to intact coals, which indicates that CO2 is easier to migrate into the internal pore system of tectonic coal in a short time, reducing the time consumed by CO2 injection into the coal seam, thus saving the cost of CO2 storage. Interestingly, a fractal conceptual model is proposed to account for the evolution of original long and complex pores were converted into short and simple pores, and closed pores transformed into connectivity pores during the formation of tectonic coals. Therefore, the results of this study contribute to understand the advantages of tectonic coal reservoirs as target sites for CO2 geological sequestration.

Catalytic degradation of chlorpheniramine over GO-Fe3O4 in the presence of H2O2 in water: The synergistic effect of adsorption

Chlorpheniramine is a pharmaceutical widely used and found in water environments. Besides hormone disruption and adverse environmental effects, chlorpheniramine forms carcinogenic nitrosamines during disinfection. We have demonstrated previously the efficient adsorption of chlorpheniramine from aqueous solution onto graphene oxide-magnetite composite (GO-Fe3O4). The present study focused on the elimination of chlorpheniramine and the formation of nitrosamine byproducts during reaction with H2O2 over GO-Fe3O4 catalyst. The effects of the morphology of GO-Fe3O4 in terms of iron fraction, pH, concentrations of H2O2 and organic matters on chlorpheniramine removal in the GO-Fe3O4-H2O2 system were investigated. Chlorpheniramine was efficiently removed at pH 9 when GO-Fe3O4 had a higher micropore volume and surface area. Kinetics study showed that both oxidation (k = 5.1(±0.2) × 10−3 (mg g−1)−1 min−1) and adsorption reactions (k = 2.7(±0.1) × 10−3 (mg g−1)−1 min−1) fitted well with the second-order kinetics model. The adsorption sites on the GO-Fe3O4 surface could be different from those involved during catalytic oxidation. Chlorpheniramine removal decreased by 44.9% in the 5th cycle without regeneration due to the structural fracture of GO-Fe3O4. A tentative pathway of chlorpheniramine degradation and nitrosamine formation by GO-Fe3O4-H2O2 was proposed. GO-Fe3O4 was an adsorbent and effective catalyst in chlorpheniramine degradation by H2O2 that exhibited limited nitrosamine formation at moderate reaction time.

Zeolitic imidazolate framework-8 (ZIF-8) doped TiZSM-5 and Mesoporous carbon for antibacterial characterization.

Drug resistant bacteria affects millions worldwide and remains a serious threat to health care system. The study reports the first application of hybrid nanocomposites based on zeolitic imidazolate framework-8 (ZIF-8) with MFI structured zeolite Ti-ZSM-5 (TiZ5) and mesoporous carbon (MC). The composite was designated as TiZ5/ZIF-8 and MC/ZIF-8 was studied for antibacterial activity. Bioactive components Zn2+ and 2-methyl imidazole present in ZIF-8 was found to exert significant antibacterial effect on Escherchia. coli and Staphyloccocus. No other antibiotic drugs are required. For comparative purpose, Fe-BTC MOF (BTC = 1,3,5‐benzenetricarboxylate) was used as second set of nanoformulations (TiZ5/Fe-BTC and MC/Fe-BTC) but showed a lower antibacterial activity. The phase (X-ray diffraction), texture (BET surface area), coordination (DRS-UV–Vis), and morphology (TEM) was investigated. XRD showed the presence of nanosized ZIF-8 over TiZ5 and MC. Surface area calculation using N2 adsorption isotherm showed a reduction in the micropore surface area of ZIF-8 from 1148 m2/g to 224 m2/g (80%) and an increased meso surface area from 31 m2/g to 59 m2/g (90%). The mesopore pore volume increased significantly from 0.05 cm3/g to 0.12 m2/g. MC/ZIF-8 showed similar textural modifications. FT-IR spectra and DRS-UV–Vis spectra showed distinct composite formation with TiZ5, while a weak absorption of ZIF-8 observed over MC. TEM revealed the presence of nanocomposite MC/ZIF-8 and TiZ5/ZIF-8 distributed in nanosize ranging between 25 and 50 nm. TiZ5/ZIF-8 showed the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of 0.5 and 1 mg/ml, respectively against E. coli. The MIC and MBC of TiZ5/ZIF-8 against S. aureus were 1 and 2 mg/ml, respectively. MC/ZIF-8 composite had second best antibacterial activity. This study shows that ZIF-8 based composite holds a great potential against E. coli and S. aureus.

Artificial Intelligence Based Methods for Asphaltenes Adsorption by Nanocomposites: Application of Group Method of Data Handling, Least Squares Support Vector Machine, and Artificial Neural Networks.

Asphaltenes deposition is considered a serious production problem. The literature does not include enough comprehensive studies on adsorption phenomenon involved in asphaltenes deposition utilizing inhibitors. In addition, effective protocols on handling asphaltenes deposition are still lacking. In this study, three efficient artificial intelligent models including group method of data handling (GMDH), least squares support vector machine (LSSVM), and artificial neural network (ANN) are proposed for estimating asphaltenes adsorption onto NiO/SAPO-5, NiO/ZSM-5, and NiO/AlPO-5 nanocomposites based on a databank of 252 points. Variables influencing asphaltenes adsorption include pH, temperature, amount of nanocomposites over asphaltenes initial concentration (D/C0), and nanocomposites characteristics such as BET surface area and volume of micropores. The models are also optimized using nine optimization techniques, namely coupled simulated annealing (CSA), genetic algorithm (GA), Bayesian regularization (BR), scaled conjugate gradient (SCG), ant colony optimization (ACO), Levenberg–Marquardt (LM), imperialistic competitive algorithm (ICA), conjugate gradient with Fletcher-Reeves updates (CGF), and particle swarm optimization (PSO). According to the statistical analysis, the proposed RBF-ACO and LSSVM-CSA are the most accurate approaches that can predict asphaltenes adsorption with average absolute percent relative errors of 0.892% and 0.94%, respectively. The sensitivity analysis shows that temperature has the most impact on asphaltenes adsorption from model oil solutions.

The interaction of metallic ions onto activated carbon surface using computational chemistry software

Activated carbon was prepared from the seeds of aguaje palm ( Mauritia flexuosa L.f.) by a chemical activation with phosphoric acid. This activated carbon was used for adsorbing metal ions: Pb(II), Cd(II), and Cr(III). To understand the mechanism of adsorption of these heavy metals (Cr, Cd, and Pb), the activated carbon surface was oxidized with nitric acid (1 M) increasing the oxygenated surface groups showing an increasing in their adsorption capacities of these metals. The oxidized activated carbon slightly increased the maximum adsorption capacity to 5–7%. The order of adsorption for unoxidized and oxidized activated carbons was Pb> Cd> Cr. This experimental information was corroborated by molecular modeling program Hyperchem 8 based adsorption mainly on two factors: the electron density and orbitals—highest occupied molecular orbital and lowest unoccupied molecular orbital.Activated carbons were characterized by adsorption/desorption of N2, obtaining an increase of microporous surface area for oxidized activated carbon. An increase of surface acidity and a reduction of isoelectric points were observed in oxidized activated carbon. According to these results, the adsorption of metal ions is favored in contact with an oxidized activated carbon, which has more amount of phenolic and carboxylic functional groups. Similarly, decreasing the isoelectric point indicates that the surface has a higher negative charge. The surface information was corroborated by Hyperchem, which indicates that the surface of the oxidized activated carbon has a higher electron density, indicating a larger amount of electrons on its surface, which means the surface of oxidized activated carbon charges negatively and thereby attracts metal ions.

Evolution of the pore and framework structure of NaY zeolite during alkali treatment and its effect on methanol oxidative carbonylation over a CuY catalyst

Alkali treatment is widely used on aluminosilicate zeolites with high Si/Al ratios in order to fabricate mesopores in the framework. However, for zeolites with low Si/Al ratios, the effect of alkali treatment on the pore and framework structure needed further study. In this work, Y zeolite is treated with NaOH solutions of different concentrations and is used as the support for Cu-based catalysts for oxidative carbonylation of methanol to dimethyl carbonate. The physicochemical properties of the supports and corresponding catalysts are characterized by N2 adsorption–desorption, X-ray diffraction, X-ray fluorescence, transmission electron microscopy, inductively coupled plasma mass spectrometry, X-ray photoelectron spectroscopy, and H2-temperature-programmed reduction analyses. The results show that no obvious mesopores are formed under alkali treatment, even at high NaOH concentration. However, amorphous species present in the micropores of Y zeolite are removed, which increases the micropore surface area as well as the crystallinity. Simultaneously, the cage structure is partially destroyed, which also leads to a slight increase of the pore volume and surface area. The altered micropore structure eventually increases the content and accessibility of the exchanged Cu species, which is beneficial to the catalytic activity. When the concentration of NaOH is 0.6 M, the space time yield of dimethyl carbonate for the corresponding catalyst was 151.4 mg g−1 h−1 which is 3.3-fold higher than that of the untreated-Y-zeolite-supported Cu catalyst. However, further increasing the alkali treatment strength can seriously destroy the basic aluminosilicate structure of the Y zeolite and decrease its intrinsic ion-exchange capacity. This results in the formation of agglomerated CuO on the catalyst surface, which was not conducive to catalytic activity.

Comparison of structural and catalytic properties of monometallic Mo and V oxides and M1 phase mixed oxides for oxidative dehydrogenation

Mo and V containing oxides are among the most important oxidative dehydrogenation catalysts. The effects of differences in structure and compostion among SiO2 supported VOx, unsupported V2O5 and MoO3 and M1 phase MoV mixed oxide catalysts on catalytic properties are probed using their reactivity and dehydrogenation selectivity in oxidative conversion of ethane (C2H6) and cyclohexane (C6H12). The C2H6 and C6H12 activation rates are nearly insensitive to VOx loading on SiO2 at low loadings that predominantly form monovanadate species, but decrease at high loadings due to the formation of V2O5 nanoparticles with low V dispersion. The C–H activation enthalpies are lower at high loadings and in unsupported V2O5, suggesting that intrinsic reactivity of V2O5 nanoparticles is higher than monovanadates. The C2H6/C6H12 rate ratios are below 0.01 on all VOx/SiO2 catalysts, consistent with weaker C–H bonds in C6H12, but are higher on V2O5 nanoparticles than on low loading VOx/SiO2 samples. MoO3 samples exhibit lower rates and higher activation energies than VOx/SiO2 and V2O5 samples, and similar C2H6/C6H12 rate ratios as V2O5. M1 phase MoVTeNb and MoV mixed oxides contain one-dimensional micropores of size similar to C2H6 but much smaller than C6H12; preparation methods significantly affect their elemental composition, accessible micropore volumes and surface areas. Post-synthesis treatment of MoVTeNbO with H2O2 improves M1 phase purity, and increases in C2H6 and C6H12 activation rates are consistent with increase in their intrapore and external surface areas. The C2H6 and C6H12 activation rates in MoVO without Te and Nb are higher than values predicted from MoVTeNbO and their surface micropores and external surface areas, because higher V content in MoVO increases their reactivity by slightly decreasing activation energies. The C2H6/C6H12 rate ratios in these samples are much higher than VOx/SiO2, V2O5, and MoO3 and roughly correlate with internal/external surface ratios, which is consistent with C2H6 and C6H12 activation occurring inside and outside the pores, respectively. The M1 phase samples exhibit much higher selectivity than VOx/SiO2, V2O5, and MoO3, but among the M1 phase samples the selectivity is slightly lower in MoVO than in MoVTeNbO. Local structure and composition affect reactivity in M1 phase oxides and oxides without heptagonal micropores, but C2H6/C6H12 rate ratios and C2H4 selectivities are much higher in the M1 phase, which confirms for a broad range of oxides previously proposed roles of micropores in activating C2H6 selectively.

Comparison of micro- and macropore evolution of coal char during pyrolysis

To characterize the changing morphology of a solid fuel with ongoing pyrolysis and gasification, we investigated the evolution of the micropore structure of a high volatile bituminous Colombian coal. In a previous study, Colombian coal was pyrolyzed in a laminar drop tube reactor, whereby the residence time, the pyrolysis temperature, and the gas atmosphere were varied. Here, we present new experimental data on the micropore structure of those chars and compare them with their meso-/macropore analysis. The micropores were investigated using volumetric adsorption measurements with CO2 at a temperature of T = 273.15 K. Micropore volumes, surface areas and homogeneities were determined on the basis of the adsorption isotherm model of Dubinin-Astakhov and, thus, a comprehensive analysis of the pore structure is presented in this work. Differences in the evolution of micropores and meso-/macropores were observed. The dry coal and the chars pyrolyzed for residence times of around 45 ms are dominated by micropores, but as pyrolysis progresses this dominance decreases, since micropores are expanding to mesopores. Nevertheless, the formation of new narrow micropores during the pyrolysis could be observed as well.

On the pressure and temperature dependence of adsorption densities and other thermodynamic properties in gas shales

Black shale source rocks have become a key natural gas resource in the US and China. Unlike in conventional hydrocarbon reservoirs, a significant fraction of the gas in shales is adsorbed onto the inordinate specific surface areas (SSA) of micropores inside organic matter with densities exceeding those of bulk gas by an order of magnitude. Yet, the distribution of adsorbed versus bulk gas remains poorly understood. Experiments measure excess adsorption isotherms, which are corrected to absolute adsorption amounts by a factor that involves the density, ρabs, of the adsorption layer(s). Constant values of ρabs are widely used in the literature but, we argue, are inconsistent with the pressure- and temperature-dependence of adsorption behavior. In this work, we propose a more reliable approach that assumes a constant volume of each adsorption layer that can be determined from the SSA of the substrate.We measure nine high-pressure methane excess adsorption isotherms up to 15 MPa for three shale samples from China and Germany at temperatures of 65, 75, and 95 °C, and low-pressure carbon dioxide and nitrogen isotherms to estimate the SSA. We also investigate another 24 isotherms at 35, 50, and 65 °C for 8 Chinese shale samples and 3 isotherms at 60, 90, and 120 °C for an Argentinian shale sample from the literature. A new variation of the multi-layer Ono-Kondo lattice model is introduced to derive the temperature and pressure dependent adsorption layer densities, which are subsequently used to obtain the absolute adsorption isotherms of interest. This practical methodology has the potential to significantly improve our estimates of shale gas-in-place resources, and adsorption modeling more broadly.

High surface area benzimidazole based porous covalent organic framework for removal of methylene blue from aqueous solutions

AbstractIn this study, a highly thermally stable benzimidazole based covalent organic framework (bCOF) was synthesized by the reaction of perlin‐tetracarboxylic anhydride, 5‐aminoisophthalic acid and diaminobenzidine in polyphosphoric acid medium. The synthesized porous bCOF was identified by different techniques. From CO2 adsorption, the micropore surface area of the bCOF was found to be 856 m2 g−1; this synthesized bCOF has a widespread netting construction, and it has various porosity. The TGA results displayed the high thermal strength of the synthesized bCOF. After characterization, the bCOF was used for the removal of methylene blue from aqueous solution, and the essential parameters such as pH of the solution, contact time and initial concentration were assessed. The maximum adsorption capacity of the bCOF for removal of methylene blue was 63.29 mg g−1 after only 40 min contact time at a pH of 6. Two kinetics and adsorption models were used for interpretation, and the outcomes showed that the pseudo‐second‐order and Langmuir models respectively were better fitted to the results. According to the results, the novel bCOF can be applied to remove methylene blue from aqueous solution. © 2020 Society of Chemical Industry

Simultaneous removal of toxic ammonia and lettuce cultivation in aquaponic system using microwave pyrolysis biochar

This study examined an aquaponic approach of circulating water containing ammonia excretions from African catfish grown in an aquaculture tank for bacterial conversion into nitrates, which then acted as a nutrient substance to cultivate lettuce in hydroponic tank. We found that microwave pyrolysis biochar (450 g) having microporous (1.803 nm) and high BET surface area (419 m2/g) was suitable for use as biological carrier to grow nitrifying bacteria (63 g of biofilm mass) that treated the water quality through removing the ammonia (67%) and total suspended solids (68%), resulting in low concentration of remaining ammonia (0.42 mg/L) and total suspended solid (59.40 mg/L). It also increased the pH (6.8), converted the ammonia into nitrate (29.7 mg/L), and increased the nitrogen uptake by the lettuce (110 mg of nitrogen per plant), resulting in higher growth in lettuce (0.0562 %/day) while maintaining BOD5 level (3.94 mg/L) at acceptable level and 100% of catfish survival rate. Our results demonstrated that microwave pyrolysis biochar can be a promising solution for growing nitrifying bacteria in aquaponic system for simultaneous toxic ammonia remediation and generation of nitrate for growing vegetable in aquaculture industry.

Comparison of nanopore evolution in vitrinite and inertinite in coalbed methane reservoirs during coalification

The different responses of vitrinite and inertinite to thermal metamorphism strongly affect the evolution of nanopores in different macerals of coal reservoirs. In order to reveal these differences during coalification, vitrinite and inertinite samples were handpicked from 10 block coal samples. A series of laboratory experiments were performed to explore the macromolecular structure and nanopores of the samples. The results indicate that the nanopore structure of the vitrinite showed obvious regularities with the reflectance of vitrinite (in oil, Ro), but that of the inertinite did not. The macromolecular structure of the inertinite did not correlate with Ro, whereas the vitrinite showed obvious correlations with Ro. Therefore, the nanopore structure of the inertinite cannot be affected by changes in Ro. The nanopore structures of both the vitrinite and inertinite were affected by the changes of macromolecular structures. The detachment of the aliphatic side chains and the promotion of the aromatic degree and the aromatic ring polycondensation degree decreased the micropore surface area (micro-SA) because the longer aliphatic side chains and lower degree of aromatic ring polycondensation make the surface of the coal particle more heterogeneous. The increases in the aromatic degree and aromatic ring polycondensation degree increased the mesopore volume (Vmes), total pore volume excluding micropores (VT), mesopore surface area (meso-SA), and Brunauer–Emmett–Teller (BET) specific surface area (BET-SA) because more isolated pores were connected with each other; thus, more interspace emerged among the aromatic ring layers with an increase in Ro. However, this does not mean that these regularities of inertinite are related to the coal rank, because macromolecular structures of the inertinite had been fixed prior to the coal formation and is not sensitive to coalification. These results are expected to enhance the understanding of the differences in vitrinite and inertinite nanopore structure evolution that occurs during coalification.