Gas Adsorption Techniques Research Articles

Oxygen Gas-Filled Metal-Organic Frameworks (MOFs) Delivery System: A Hypothetical Design for Injectable Oxygen

Oxygen delivery systems are crucial in critical care medicine, particularly for managing acute respiratory distress. This study presents a novel approach, exploring the potential of Metal-Organic Frameworks (MOFs) as oxygen delivery systems. We highlight their unique properties and potential for enhancing oxygenation in medical settings. Understanding their biocompatibility, oxygen-carrying capacity, and controlled release mechanisms is pivotal for successful implementation in clinical practice. Thanks to their exceptional porosity, structural diversity, lower crystal density, and tunability, MOFs offer a fresh perspective on developing innovative oxygen carriers. We propose that MOFs will demonstrate biocompatibility, stability, and the ability to deliver oxygen in a controlled and sustained manner when administered intravenously in living organisms. Gas adsorption and molecular simulation techniques will demonstrate reversible oxygen binding within MOFs and predict controlled release kinetics. The findings of the simulations and experiments should indicate the feasibility of utilising MOFs as intravenous oxygen carriers with controlled and reversible oxygen release behaviour.

The occurrences and mobility of shale oil in the pore space of terrestrial shale

Movable oil, the critical factor for shale oil enrichment and effective production, is influenced by the pore structure and shale oil occurrence state. However, the pore spaces storing movable oil, the occurrence state of shale oil, and the lower flowing pore size for shale oil remained unclear. To address this knowledge gap, we chose the lacustrine organic-rich Chang7 shale of the Ordos Basin as the research target. By combining gas adsorption techniques (nitrogen and carbon dioxide) with Soxhlet Extraction, we investigated the pore structure alteration of Chang7 shale after Soxhlet Extraction. Based on a comprehensive analysis of mineralogical composition, TOC, and shale oil components, we discussed the pore space in which shale oil exists. Then, we established a slit-shaped clay model and clarified the occurrence state of multi-component shale oil in the pore space with the help of molecular simulation. Our investigation revealed that (1) Chang7 shale can be categorized into three distinct types. Type I, characterized by a high clay mineral content, possesses the greatest SSA and PV and has the highest abundance of movable oil, partially filling the “ink-bottle”-type pores. Shale oil in Type II and III shales mainly exists within slit-type pores. (2) The pore space of Chang7 shale is primarily comprised of mesopores rather than micropores. Moreover, mesopores’ PV and SSA are predominantly governed by clay minerals rather than organic matter. (3) A threshold pore size of 10 nm significantly impacts the occurrence state of shale oil in the Chang7 shale. Beyond this threshold, free oil accounts for over 80% of the total. Chang7 shale oil within micropores (<2 nm) is predominantly asphaltene, existing in an adsorbed state. Within pores sized 2 to 10 nm, shale oil is present in both adsorbed and free states, and the proportion of free-state shale oil increases with the pore size. Free-state shale oil prevails in pores exceeding 10 nm, with a smaller fraction adsorbed onto organic matter and mineral surfaces. Thus, we recommend adopting 10 nm as the lower flowing pore size limit for Chang7 shale.

Understanding the relationship between pore size, surface charge density, and Cu2+ adsorption in mesoporous silica

This research delved into the influence of mesoporous silica’s surface charge density on the adsorption of Cu2+. The synthesis of mesoporous silica employed the hydrothermal method, with pore size controlled by varying the length of trimethylammonium bromide (CnTAB, n = 12, 14, 16) chains. Gas adsorption techniques and transmission electron microscopy characterized the mesoporous silica structure. Surface charge densities of the mesoporous silica were determined through potentiometric titration, while surface hydroxyl densities were assessed using the thermogravimetric method. Subsequently, batch adsorption experiments were conducted to study the adsorption of Cu2+ in mesoporous silica, and the process was comprehensively analyzed using Atomic absorption spectrometry (AAS), Fourier transform infrared (FTIR), and L3 edge X-ray absorption near edge structure (XANES). The research findings suggest a positive correlation between the pore size of mesoporous silica, its surface charge density, and the adsorption capacity for Cu2+. More specifically, as the pore size increases within the 3–4.1 nm range, the surface charge density and the adsorption capacity for Cu2+ also increase. Our findings provide valuable insights into the relationship between the physicochemical properties of mesoporous silica and the adsorption behavior of Cu2+, offering potential applications in areas such as environmental remediation and catalysis.

Quantification of Poly(ethylene glycol) Crowding on Nanodiamonds toward Quantum Biosensor for Improved Prevention Effects on Protein Adsorption and Lung Accumulation.

Nanometer-sized diamonds (NDs) containing nitrogen vacancy centers have garnered significant attention as potential quantum sensors for reading various types of physicochemical information in vitro and in vivo. However, NDs intrinsically aggregate when placed in biological environments, hampering their sensing capacities. To address this issue, the grafting of hydrophilic polymers onto the surface of NDs has been demonstrated considering their excellent ability to prevent protein adsorption. To this end, crowding of the grafted chains plays a crucial role because it is directly associated with the antiadsorption effect of proteins; however, its quantitative evaluation has not been reported previously. In this study, we graft poly(ethylene glycol) (PEG) with various molecular weights onto NDs, determine their crowding using a gas adsorption technique, and disclose the cross-correlation between the pH in the grafting reaction, crowding density, molecular weight, and the prevention effect on protein adsorption. PEG-grafted NDs exhibit a pronounced effect on the prevention of lung accumulation after intravenous injection in mice. PEG crowding was compared to that calculated by using a diameter determined by dynamic light scattering (DLS) assuming a sphere.

Construction of Multi-Stimuli Responsive Highly Porous Switchable Frameworks by In Situ Solid-State Generation of Spiropyran Switches.

Stimuli-responsive molecular systems support within permanently porous materials offer the opportunity to host dynamic functions in multifunctional smart materials. However, the construction of highly porous frameworks featuring external-stimuli responsiveness, for example by light excitation, is still in its infancy. Here a general strategy is presented to construct spiropyran-functionalized highly porous switchable aromatic frameworks by modular and high-precision anchoring of molecular hooks and an innovative in situ solid-state grafting approach. Three spiropyran-grafted frameworks bearing distinct functional groups exhibiting various stimuli-responsiveness are generated by two-step post-solid-state synthesis of a parent indole-based material. The quantitative transformation and preservation of high porosity are demonstrated by spectroscopic and gas adsorption techniques. For the first time, a highly efficient strategy is provided to construct multi-stimuli-responsive, yet structurally robust, spiropyran materials with high pore capacity which is proved essential for the reversible and quantitative isomerization in the bulk as demonstrated by solid-state NMR spectroscopy. The overall strategy allows to construct dynamic materials that undergoes reversible transformation of spiropyran to zwitterionic merocyanine, by chemical and physical stimulation, showing potential for pH active control, responsive gas uptake and release, contaminant removal, and water harvesting.

High-temperature preparation of Ni2P suspended within carbon matrix and its potential as HER electrocatalyst

Hydrogen production via electrocatalytic reduction of water is a promising clean-energy technology. For further advancement of this technology, the exploration of cost-effective and streamlined approaches for producing active phosphide-based catalysts is of great importance. This study presents a new high-temperature preparation method of a microporous Ni2P/C catalyst composed of crystalline Ni2P nanoparticles homogeneously distributed within an amorphous carbon matrix in a weight ratio of 40/60. The redox transformation leading to the formation of Ni2P from not-reduced stable inorganic salts was facilitated during thermal treatment by a polymeric precursor, which, in turn, transformed into microporous carbon matrix that prevented the newly formed phosphide particles from agglomerating and sintering. The microporous structure of the prepared composite was characterised by gas adsorption technique and modelled using density functional theory and statistical thickness methods. The t-plot revealed high micropore surface area of 333.5 m2 g−1 (accounting 97 % of total surface area) and the pore size distribution in the range of 10–12 Å. According to TEM analysis, the size range of the Ni2P inclusions varied from 5 to 200 nm. The evaluation of electrocatalytic properties of the Ni2P/C composite demonstrated its high HER activity and stability under high voltages in alkaline water electrolysis conditions. Furthermore, HER activity of the composite was substantially enhanced by grinding, which opened closed microporosity channels and increased the micropore surface area to 355.2 m2 g−1, thereby increasing the number of catalytically active sites in the sample. The result indicates the exceptional role of the microporous microstructure of the composite in its catalytic performance. The findings of this study may have a significant impact on the practical implementation of efficient hydrogen production by water electrolysis.

Oxidative effects of gaseous oxygen and ozone on Australian subbituminous and bituminous coals and the implications for coal seam permeability enhancement

The use of gaseous ozone as a means for enhancing coal seam permeability has been investigated, including the effect on subbituminous and bituminous coal from the Surat and Bowen Basins, Australia, respectively. To elucidate the oxidative mechanism, the chemical properties of the Surat coal before and after oxidation was examined using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) and X-ray Photoelectron Spectroscopy (XPS). Additionally, gas adsorption techniques and optical microscopy were used to assess physical changes arising from the ozone treatment. Although both the oxygen and ozone treatments (two days duration) increased the oxygen content in the molecular structure of the coal, the ozone introduced significantly more, specifically with the generation of aliphatic ester CO groups and aromatic carbonyl/carboxyl CO groups. In terms of the physical structure of the coal, the micropore volume was slightly reduced by the oxygen treatment but almost eliminated by the ozone treatment. Furthermore, oxygen treatment showed little impact on the coal mass loss while ozone oxidation caused a 0.7% loss in coal weight. Additional tests on a Bowen Basin coal showed an increase in the aperture (4.37%) of a cleat after ozone treatment. These results demonstrate the potential of ozone for coal seam permeability enhancement by merging micropores and increasing cleat apertures whilst maintaining the structural integrity of the coal.

Evolution of nano-pores in illite-dominant clay during consolidation

AbstractIn this paper, the evolution of nanoscale pores, covering inter-particle pores and inter-layer pores, in illite-dominant clay during consolidation is monitored using small angle X-ray scattering (SAXS) and nitrogen gas adsorption (N2GA) techniques. No obvious change observed in the characteristic peaks of SAXS intensity curves during consolidation suggests that the intra-particle structure of the clay, including interlayer spacings, is not affected by mechanical loading, at least up to 4 MPa. The N2GA test results show that the volume of inter-particle pores inside the aggregates does decrease gradually as the compression proceeds, which is accompanied by a gradual reduction in specific surface area, probably due to the rearrangement of the particles composing the aggregates. The inter-particle pores are compressed as a whole during consolidation instead of the progressive collapse in an ordered manner, from the larger to the smaller. By comparing the pore-size distributions of illite-dominant clay obtained by MIP (mercury intrusion porosimetry) and N2GA techniques, it is found that the shapes of the two distributions in the common measurement range are obviously not matched, essentially due to the sequential nature of the drying and wetting processes. While filling the research gap in the evolution of intra-aggregate pores during consolidation, this study also shows that the N2GA technique and SAXS measurement used in conjunction with each other appear as a powerful approach for clay nano-pores identification.

The Correlation between the Structure Characteristics and Gasification Characteristics of Tar Residue from Pyrolysis

Pyrolysis is an efficient method for utilizing tar residue as a resource, and the structural properties of tar residue from pyrolysis (TRP) significantly impact subsequent gasification. The study examines the changes in the microscopic morphology, surface area, and carbon structure characteristics of TRPP as a function of pyrolysis temperature to elucidate the influence of pyrolysis temperature on the CO2 gasification characteristic parameters of TRP. Additionally, the investigation explores the relationship between surface structure and carbon structure characteristic parameters and gasification parameters at various stages. The findings indicated that the surface morphology of TRP synthesized at different pyrolysis temperatures (500–900 °C) was divided into two stages: the development of pores and the jamming of pores. With increasing pyrolysis temperature, the bigger aromatic nucleus was formed in the TRP without complete graphitization, and more amorphous carbon was consumed. TRP prepared at a pyrolysis temperature of 700 °C had the best gasification reactivity. By combining XRD, Raman, and gas adsorption techniques, the correlations between the surface structure and carbon structure parameters and the gasification characteristic parameters were established to evaluate the main factors influencing the gasification reaction. In the early stage of the gasification reaction, the carbon structure played a more important role than the surface structure. As the gasification reaction proceeded, the relationship between the surface structure and the gasification reaction was closer.

Retracted: Reduction of 1/f Noise in Single-Walled Carbon Nanotubes (SWCNTs) Using Gas Adsorption Technique

Retracted: Reduction of 1/f Noise in Single-Walled Carbon Nanotubes (SWCNTs) Using Gas Adsorption Technique

Porosimetry of zeolitic imidazolate frameworks using positron annihilation lifetime spectroscopy

Zeolitic Imidazolate Frameworks (ZIFs) owing to their crystalline morphology have well designed pore architecture. ZIFs show great potential for applications in gas separation, gas storage, catalysis and sensors because of their high surface area, pore volume and well defined pore network. In order to utilize ZIFs for aforementioned applications, investigation of pore architecture (pore size, pore size distribution and interconnectivity) of ZIFs in powder or film form is highly essential. Conventional gas adsorption techniques are found to be incapable for providing complete pore architecture of ZIFs due to ultra-microporosity and pressure dependent framework flexibility. In recent years, positron annihilation lifetime spectroscopy (PALS) has been used to investigate the porosity of few ZIFs. In order to establish the applicability of PALS for pore architecture investigation of ZIFs in general, a systematic study for a number of ZIFs (ZIF-67, ZIF-8, ZIF-7l, ZIF-7n ZIF-62, ZIF-90, ZIF-70.52-8, Zn0.25Co0.75-ZIF-8, and ZIF-8A) have been carried out. These frameworks have been synthesized at room temperature or using solvothermal methods. PALS measurements of these ZIFs confirm the presence of different types of interconnected pores in these frameworks. The estimated pore sizes are compared with the pore sizes determined from other conventional techniques. The present study suggests that PALS is a powerful technique for the investigation of tuning of the pore architecture of all type of ZIFs. The determined pore sizes are the factual average pore size of desolvated bulk ZIF samples free from artifacts. These pore sizes could be correlated with the pore size dependent separation performance of ZIFs.

Adsorption of Phosphate and Nitrate Ions on Oxidic Substrates Prepared with a Variable-Charge Lithological Material

This work evaluates phosphate and nitrate ion adsorption from aqueous solutions on calcined adsorbent substrates of variable charge, prepared from three granulometric fractions of an oxidic lithological material. The adsorbent material was chemically characterized, and N2 gas adsorption (BET), X-ray diffraction, and DTA techniques were applied. The experimental conditions included the protonation of the beds with HCl and H2SO4 and the study of adsorption isotherms and kinetics. The lithological material was moderately acidic (pH 5) with very little solubility (electrical conductivity 0.013 dS m−1) and a low cation exchange capacity (53.67 cmol (+) kg−1). The protonation reaction was more efficient with HCl averaging 0.745 mmol versus 0.306 mmol with H2SO4. Likewise, the HCl-treated bed showed a better adsorption of PO4−3 ions (3.296 mg/100 g bed) compared to the H2SO4-treated bed (2.579 mg/100 g bed). The isotherms showed great affinity of the PO4−3 ions with the oxide surface, and the data fit satisfactorily to the Freundlich model, suggesting a specific type of adsorption, confirmed by the pseudo-second-order kinetic model. In contrast, the nitrate ions showed no affinity for the substrate (89.7 µg/100 g for the HCl-treated bed and 29.3 µg/100 g bed for the H2SO4-treated bed). Amphoteric iron and aluminum oxides of variable charges present in the lithological material studied allow for their use as adsorbent beds as an alternative technique to eliminate phosphates and other ions dissolved in natural water.

A novel hybrid thermodynamic model for pore size distribution characterisation for shale

Scholars often see the gas adsorption technique as a straight-to-interpret technique and adopt the pore size distribution (PSD) given by the gas adsorption technique directly to interpret pore-structure-related issues. The oversimplification of interpreting shale PSD based on monogeometric thermodynamic models leads to apparent bias to the realistic pore network. This work aims at establishing a novel thermodynamic model for shale PSD interpretation. We simplified the pore space into two geometric types—cylinder-shaped and slit-shaped. Firstly, Low-temperature Nitrogen Adsorption data were analyzed utilizing two monogeometric models (cylindrical and slit) to generate PSDcyl. and PSDslit; Secondly, pore geometric segmentation was carried out using Watershed by flooding on typical SEM images to obtain the ratio of slit-shaped ∅s and cylinder-shaped pores ∅c. Combining the results of the two, we proposed a novel hybrid model. We performed pyrolysis, XRD, FE-SEM observation, quantitative comparison with the results obtained by the DFT model, and fractal analysis to discuss the validity of the obtained PSDHybrid. The results showed that: the hybrid model proposed in this work could better reflect the real geometry of pore space and provide a more realistic PSD; compared with thermodynamic monogeometric models, PSD obtained from the hybrid model are closer to that from the DFT model, with an improvement in the deviation from the DFT model from 5.06% to 68.88%. The proposed hybrid model has essential application prospects for better interpretation of shale pore space. It is also worth noting that we suggest applying the proposed hybrid model for PSD analysis in the range of 5–100 nm.

Nano-scale physicochemical attributes and their impact on pore heterogeneity in shale

Heterogeneity in shale due to distribution of mineral and organic matter controls the disposition of pores in them. While the effect of vertical anisotropy is accounted for most cases of porosity estimation, the effect of bedding parallel heterogeneity is often ignored. This study dives deep into the shale fabric using bedding parallel sections, and the pore volume distribution is estimated in shales of varying thermal maturity and organic carbon content (2.6% − 38.2 %). Three among the five shales used in this study are early mature (Tmax: 439–444 °C), whereas the remaining two are over-mature, signified by very high S4Tpeak (670–685 °C). The higher thermal maturity indicates thermal alteration induced by igneous intrusion. The pore volume, functional groups, and organic matter distribution are systematically derived in different positions of the bedding parallel section using a combination of 3D imaging, spectroscopy, small-angle scattering and low-pressure gas adsorption techniques. These spot-specific properties are further compared with bulk properties to quantify the extent of heterogeneity. It is observed that the over-mature shales with higher aromaticity contain 150–200% more bulk accessible pore volume than the lesser-mature shales. It is also evident that the smaller mesopores (∼10 nm pore width) are more inaccessible compared to their coarser (∼20 nm pore width) counterparts. Higher matured shales show increased inaccessibility of mesopores up to 228 % due to bitumen deposition in pores during thermal maturation, resulting in a sharp decline in mesopore surface fractal dimension. The uniformity of the functional group and organic matter distribution in different parts of the shale depends on the maturity, and reflects the extent of variation in pore volume across the specimen. The 3D tomography-derived spatial abundance of organic matter in over-mature shales show higher deviation (±15-20%) from the average than lesser-mature shales (5–10%). This study proposes a multiscale methodology which can evolve and develop as a protocol for systematic, reservoir-scale maturity-dependent heterogeneity quantification in gas-shales.

Hierarchical nanostructured surface design for robust and flexible multifunctional devices

This paper investigates structural and functional properties of a hierarchical hybrid flexible material with nanostructured surface architecture. These solids comprise of carpet-like arrays of covalently bonded carbon nanotubes (CNT) on the surface of strong and flexible carbon fabric. In-depth analysis of the multi-scale morphology of this structure is provided, with emphasis on structure-property relationships relevant to surface-interaction related applications such as catalysis, sensing, microfluidics and bio-scaffolding devices. A two-step process is used to anchor carbon nanotubes directly on the surface of carbon fiber cloth, and its morphology, structure and surface chemistry analyzed in detail. Surface structure model from structural and physical property measurements predict over 2000 times increase in specific surface area (SSA) of the fabric due to CNT carpet growth. This estimate is in good agreement with direct SSA measurement using Brunauer–Emmett–Teller (BET) gas-adsorption technique, indicating full utilization of the CNT surface sites, which can be used for adsorption, functionalization, thermal or electrical transport. Electrical measurement of these materials shows a systematic increase of sheet conductivity of the fabric with increasing CNT carpet height. These results indicate that this type of material design can combine the structural durability and flexibility of advanced fabrics with the enhanced surface activity of nanomaterials for a wide variety of surface interaction devices of the future.

Compositional controls on nanopore structure in different shale lithofacies: A comparison with pure clays and isolated kerogens

Nanopore structure development in shale is intimated with lithofacies that demonstrates a large variety in different formations. It is critical to differentiate and quantify the separate impact of lithological components (minerals and organic matter (OM)) on pore structure attributes associated with shale gas storage capacity. In this study, we classified shales into 12 lithofacies for compositional and petrophysical quantification. Parameters of our main target, the Goldwyer shales (argillaceous OM-poor, argillaceous OM-moderate, and argillaceous OM-rich lithofacies) were further compared with other shale lithofacies, pure clays and isolated kerogens, using XRD, Rock-Eval pyrolysis, Ar-SEM and low-pressure CO2/N2 gas adsorption techniques. Results show that argillaceous OM-rich lithofacies (TOC > 2% and illite-dominated clay contents > 50%) develop more interconnected pores with better hydrocarbon storage potential. The argillaceous lithofacies have large amounts of cleavage-sheet pores with large pore volumes; the accumulative pore volume of the pores in diameter from 2 to 17 nm constitutes the major amount of total pore volume that is associated with free gas. The OM-rich lithofacies develop more OM-pores (particularly in pore diameter <2 nm) that contain extraordinarily high specific surface area (SSA); the SSA of micropores makes up the major total surface area that is intimated with adsorbed gas. Further investigation on pure clays and isolated kerogens clarifies that illite mainly controls the pore sizes from 2 to 17 nm, resulting in large pore volumes in argillaceous shales. By contrast, isolated kerogen dominantly controls micropores in diameter <2 nm, leading to a larger surface area with higher adsorbed gas storage in organic-rich shales.

Use of Gas Adsorption and Inversion Methods for Shale Pore Structure Characterization

The analysis of porosity and pore structure of shale rocks has received special attention in the last decades as unconventional reservoir hydrocarbons have become a larger parcel of the oil and gas market. A variety of techniques are available to provide a satisfactory description of these porous media. Some techniques are based on saturating the porous rock with a fluid to probe the pore structure. In this sense, gases have played an important role in porosity and pore structure characterization, particularly for the analysis of pore size and shapes and storage or intake capacity. In this review, we discuss the use of various gases, with emphasis on N2 and CO2, for characterization of shale pore architecture. We describe the state of the art on the related inversion methods for processing the corresponding isotherms and the procedure to obtain surface area and pore-size distribution. The state of the art is based on the collation of publications in the last 10 years. Limitations of the gas adsorption technique and the associated inversion methods as well as the most suitable scenario for its application are presented in this review. Finally, we discuss the future of gas adsorption for shale characterization, which we believe will rely on hybridization with other techniques to overcome some of the limitations.

The structural versus textural control on the methane sorption capacity of clay minerals

In the natural, high-pressure environments of sediments and sedimentary rocks, clay minerals, along with organic matter, contribute to a large portion of the available surface area and microporosity in which methane (CH4) can be adsorbed. However, most of the questions concerning the location of adsorption sites, e.g. interlayer accessibility for CH4, remain unknown. Here, we have separately investigated the textural and structural control on CH4 high-pressure adsorption on pure clay minerals by combining high- and low-pressure gas adsorption techniques, transmission electron microscopy, and thermogravimetric and X-ray diffraction analyses on various cationic forms of montmorillonite, beidellite, and two illites, with different contents of adsorbed water. The results show that CH4 adsorption capacity is controlled by N2-accesible micropore volume. CH4 adsorption sites are located mainly outside of the interlayer galleries unless they are open wide enough (e.g. pillared by organic cations or incompletely dried divalent cations). However, the structure-independent factors like the crystallite planar dimensions and the way that they assemble are the main control on CH4 adsorption capacity. This might be the reason for the inconsistencies in CH4 adsorption reported for clay minerals in the literature. CO2 adsorption measurements, assumed to provide a good proxy for the estimation of CH4 adsorption capacity in natural mudrocks, may overestimate the CH4 adsorption potential in geomaterials containing a significant amount of exchangeable divalent cations due to higher penetrability of CO2 than CH4 in the interlayers of expandable clay minerals.

Mechanism of compacted biochar-amended expansive clay subjected to drying–wetting cycles: simultaneous investigation of hydraulic and mechanical properties

Biochar has been extensively studied in the aspect of amendment of compacted sandy/clayed soils, whereas its application as amendment in expansive soil is rare. Hydraulic and mechanical properties of biochar-amended expansive soil especially impacts of drying–wetting cycles have been rarely investigated. Aiming at construction of sponge city, straw biochar-amended expansive soil and the control soil (i.e., without biochar) are subjected to drying–wetting cycles in this study. During drying–wetting cycles, energy-dispersive spectrometer and Fourier transform infrared (FTIR) spectroscopy analyses were conducted to investigate microchemical composition including. Pore size distribution and microstructure were measured using nitrogen gas-adsorption technique and scanning electron microscope, respectively. Further, changes in soil water retention curve, void ratio, crack intensity factor (CIF, i.e., ratio of cracked section area to the total soil area) and shear strength were also determined. It is found that there is no difference in water retention capacity between various soils for near-saturated samples. Under high suction, however, more water could be retained within mesopores of biochar-amended soil. FTIR analysis indicates that biochar-amended expansive soil shows stronger chemical bonding, irrespective of them being subjected to drying–wetting cycles. The weak alkalinity of straw biochar results from its main chemical composition (i.e., calcium carbonate). It is noteworthy that straw biochar improves soil water retention capacity, which further restrains desiccation cracks. Cohesion of biochar–soil composite is also improved due to chemical bonding. Aiming at green roofs, straw biochar could be promising option for expansive soil amendment technically and economically.

Adsorptive Efficiency of Activated Carbon from Corncob Compared with Commercial Activated Carbon in the Adsorption of Light Alkanes Contaminant in Hydrogen Gas Product

The adsorptive efficiency of activated carbon produced from corncob was compared to commercial activated carbon in the adsorption of light alkanes contaminant in hydrogen gas product. The adsorption was measured over a constant temperature of 27°C and at pressures up to 125 kilo pascal (kPa) using a gravimetric gas adsorption technique. The light alkanes were adsorbed on activated carbon produced from corncob using chemical method with phosphoric acid as the activating agent. The mass of adsorbent used for the adsorption was from 20 – 60 g. Pore size distribution and characteristic functional groups present on the surface of activated carbon were determined using N2 adsorption, Brunauer-Emmett-Teller (BET) method and Fourier Transform Infrared spectroscopy (FTIR spectra) respectively. BET analyses were used to characterise the activated carbons. The BET results of the produced activated carbon compared to the commercial activated carbon has a specific surface area of 1237 m2/g and 2048 m2/g and a pore volume of 0.1162 cm3/g and 0.1959 cm3/g, respectively. FTIR spectra results of the produced activated carbon compared to the commercial activated carbon showed similar band gap at 2337.80 cm-1 with an alkynl C≡C stretch functional group and a vibration type of carbonyl group (carboxylic OH) at 1550.82 cm-1. Experimental data verified using Langmuir isotherm and Freundlich isotherm adsorption models showed best fit for Langmuir adsorption isotherm model indicating the formation of a monolayer adsorbate on the outer surface of the adsorbent with an adsorptive and uptake capacity of 0.016 Pa-1. The adsorptive efficiency of the produced activated carbon compared to the commercial activated carbon was 1.05wt% and 3.55wt%, respectively. Therefore, based on the results obtained, the produced activated carbon may not completely substitute the commercial activated carbon rather it can be used as a potential blend thereby reducing quantity and cost.