Macropore Volume Research Articles

Aqueous MXene inks for inkjet-printing microsupercapacitors with ultrahigh energy densities

Although inkjet-printing technology has achieved significant development in preparing scalable and adaptable energy storage devices for portable and micro devices, searching for additive-free and environmentally friendly aqueous inks is a significant challenge. Hence, an aqueous MXene/sodium alginate-Fe2+ hybrid ink (denoted as MXene/SA-Fe) with solution processability and suitable viscosity is prepared for direct inkjet printing microsupercapacitors (MSCs). The SA molecules are adsorbed on the surface of MXene nanosheets to construct three-dimensional (3D) structures, thus effectively alleviating the two notorious problems of oxidation and self-restacking of MXene. Concurrently, Fe2+ ions can compress the ineffective macropore volume and make the 3D structure more compact. Moreover, the hydrogen and covalent bonding formed between the MXene nanosheet, SA, and Fe2+ effectively protects the oxidation of MXene and thus increases its stability. Thus, the MXene/SA-Fe ink endows the inkjet-printed MSC electrode with abundant active sites for ion storage and a highly conductive network for electron transfer. As a demonstration, the MXene/SA-Fe ink is used to direct inkjet-printed MSCs with an electrode spacing of 310 μm, which exhibit remarkable capacitances of 123.8 mF cm−2 (@5 mV s−1), good rate capability, an extraordinary energy density of 8.44 μWh cm−2 at a power density of 33.70 μW cm−2, long-term cycling stability of 91.4 % capacitance retention after 10,000 cycles, and surprising mechanical durability with 90.0 % of its initial capacitance retained after 10,000 bending cycles. Therefore, MXene/SA-Fe inks are expected to create various opportunities for printable electronics.

Impact of tectonic deformation on shale pore structure using adsorption experiments and 3D digital core observation: A case study of the Niutitang Formation in Northern Guizhou

Tectonic deformation has an evident impact on the pore structure of organic-rich marine shale. To study the impact of tectonic deformation on the pore structure of shale, cores were taken from different tectonic regions in the Niutitang Formation. The paleotectonic stress, pore structures, mineral composition, and geochemical parameters of the shale were determined by conducting the following tests: paleotectonic stress test, core thin-section observation, focus ion beam-scanning electron microscopy (FIB-SEM) observation, vitrinite reflectivity test, low-temperature nitrogen adsorption test, total organic carbon (TOC) test, X-ray diffraction (XRD) test, and nano-CT. The results showed that the shale in the deformed region mainly developed meso-macropores, and the pores were mainly slit-type and conical. The shale in the transition and stability regions primarily developed mesopores and micropores, which were primarily elliptical, slit-type, and columnar. The pore volumes of the shale in the deformed region were 9.54 cm3/kg and 13.9 cm3/kg higher than those in the transition and stability regions, respectively. The shale in the stability and transition regions had average microporous volumes 8.67% and 7.93% higher than that in the deformed region, respectively. The shale reservoir in the stability region developed more micropores and had a higher specific surface area and microporous volume. Furthermore, the organic matter had a greater impact on the micropores than on the meso-macropores. Thermal maturity had a greater impact on the microporous volume than on the macroporous volume. The shale pore connectivity of Well TX 1 was 86.48% and that of Well FC 1 was 22.33%. The pore connectivity of the shale in the stability region was higher than that of the shale in the deformed region. The shale samples from the deformed region had larger pore volumes and primarily developed macropores. The difference in the meso-macropores is significantly greater than the difference in the microporous volume. Hence, the geological tectonism had a greater impact on the meso-macropores than on the micropores in the shale cores.

Effects of clay minerals and organic matter on pore evolution of the early mature lacustrine shale in the Ordos Basin, China

Pores related to organic matter and clay minerals provide significant storage space for hydrocarbons in organic-rich shales. However, the pore structure evolution and its related influencing factors at the early oil window stage are unclear. This study attempts to reveal the controls of organic matter and clay minerals on the pore structure of the lacustrine organic-rich Chang 7 Shale by using thin-section observational, organic petrological, elemental, scanning electron microscopy/Energy Dispersive Spectrometer (SEM/EDS) analyses, and mineralogical analyses combined with the pore structure characterization of gas adsorption and mercury injection capillary pressure (MICP). The results show that micropores (<2nm) and mesopores (2-50 nm) contribute to the main storage space in organic-rich intervals of the Chang 7 Shale. Organic matter content controls the development of micro-pores while no effects on porosity in the early mature lacustrine shale. Shrinkage OM pores related to the expulsion of hydrocarbons are better developed than the complex pores and sponge pores. Total clay content is correlated with mesopores volume in organic-rich lacustrine shale. Multiple stepwise linear regression model between mesopores volume and different clay minerals shows that the pores with diameters in the ranges of 2-5 nm are controlled by illite, chlorite, and kaolinite, and the pores with diameters in the ranges of 5-10 nm and 10-20 nm are controlled by illite, while 20-50 nm pores rely on illite/smectite mixed layer (I/S) and illite. Thermal maturity shows a positive effect on pore volume and porosity. There are three types of transformations of clay minerals in lacustrine shale, including the smectite-illite conversion, smectite-illite-chlorite conversion, and anorthite/albite-to-kaolinite/illite conversion. These clay mineral conversions all show positive effects on pore volume, especially the anorthite/albite-to-kaolinite/illite conversion, while the smectite-illite conversion shows some negative effects on the connectivity of the pore system. Additionally, the control of macropore volume, porosity, and pore throat radius by chlorite cannot be ignored. The findings from this study contribute to a clear insight into the pore structure evolution of lacustrine shale.

Ion corrosion behavior of tunnel lining concrete in complex underground salt environment

In this study, the ion corrosion behavior of tunnel lining concrete in complex underground salt corrosion environment was investigated using a self-designed corrosion simulation test device in a complex underground environment. The results indicated the following: the corrosion of flowing water leads to the dissolution of lining concrete, and the load promotes the development of cracks in the tensile area of lining concrete and inhibits the development of defects in the compression area, resulting in the transmission speed of chloride and sulfate ions in lining concrete under different corrosion conditions given as follows: concrete in tensile zone under flowing corrosive solution and load > flowing corrosion solution acting alone > static corrosion solution > concrete in compression zone under flowing corrosive solution and load. When the flowing corrosion solution alone and flowing corrosion solution and load act on the concrete in the tensile zone, the pore volume fraction of gel decreases and the macropore volume fraction increases. Under the combined action of static corrosion solution and flowing groundwater and load, the pore volume fraction of gel in the pressurized area increases and the harmless pore volume fraction decreases.

Optimization of the Li-ion conductivity of UiO-66 coated LiCoPO4 nanocomposites

LiCoPO4 coated by different concentrations of UiO-66 (LiCoPO4@xUiO-66) samples, with x = 0.0, 0.01, and 0.02, were successfully synthesized. XRD spectra confirmed that the samples have a single orthorhombic phase with the Pnmɑ space group. The microstructure of these samples was investigated via TEM. Besides, all expected elements appeared in the XRF spectra in the same stoichiometry ratios of the raw materials. The XAS spectra of UiO-66-coated LiCoPO4 samples with varying contents are similar to that of pure LiCoPO4 both in terms of the position of the absorption edge and the highest position. The values of BET-specific surface areas and meso-to macropore volume of the LiCoPO4@UiO-66 composites increased with UiO-66 additions. Interestingly, the ionic conductivity of LiCoPO4@UiO-66 composites increased by UiO-66 additions. Because of the UiO-66 coating on LiCoPO4, these composites have a 3D tunable porous structure while retaining their composition and crystal structure. This 3D-tunable porous structure easily allows Li+ ion migration. The observed results exhibit a new type of synthetic post-modification of the organic/inorganic UiO-66 subunits, yielding a unique electrode possibly suited for Li-ion batteries.

Oleogels from mesoporous whey and potato protein based aerogel microparticles: Influence of microstructural properties on oleogelation ability

Animal-based whey protein isolate (WPI) and plant-based potato protein isolate (PPI) aerogel microparticles (particle size ∼40–77 μm) were produced via top-down wet milling of alcogels followed by supercritical–CO2–drying and used as matrices for structuring of liquid sunflower oil. pH variation (pH 3.0, 7.0, 9.0) during heat-induced gelation was used to tune aerogel microstructural properties, resulting in high specific surface areas (347–480 m2/g) and mesopore volumes (2.3–5.6 m3/g) as well as different macro-to mesoporous ratios. Oleogels oil content (70–84 wt%) and firmness (0.55–1.25 N) were related to pH during gelation, yielding firmest oleogels for aerogel templates produced at pH 9. All oleogel samples showed high physical stability, as shown by oil holding capacity (OHC) up to 95%. Minimization of macropore volume, high mesopore fractions, and high specific surface areas were found to increase OHC. Results suggest that for WPI and PPI, different aerogels microstructures induced by different gelation pH rather than protein nature, to be the driving factor affecting aerogel oleogelation ability and demonstrate the versatility of the aerogel particle-template approach in terms of protein source, thus highlighting the importance of aerogel microstructure design to fine-tune oleogel properties.

Understanding the role of coarse aggregate on tensile fatigue behaviors of ultra-high performance concrete

This work investigated the tensile fatigue behaviors of ultra-high performance concrete containing coarse aggregate (UHPC-CA), with an emphasis on exploring the underlying mechanisms induced by CA incorporation. Upon constant-amplitude fatigue tests at four different stress levels, CA incorporation-induced variations in fracture morphology, deformation capacity, and fatigue life of UHPC-CA were analyzed, which were further revealed through multiscale characterization of hydration products, pore structures, and stress state alterations within UHPC matrix. The results showed that despite the considerable enhancement in elastic modulus in comparison with CA-free UHPC, weakened fatigue deformability and accelerated damage evolution are observed for UHPC-CA. As the CA content increased, the performance degradation was continually exacerbated, and it was experimentally evidenced to be highly linear with the loss of bound water and the increase in macropore volume. Compared to CA-free UHPC, the premature fatigue failure of UHPC-CA was primarily attributed to the magnified stress concentration within the matrix.

Effect of Formation Pressure on Pore Structure Evolution and Hydrocarbon Expulsion in Organic-Rich Marine Shale

Exploring the relationship between formation pressure and shale pore evolution is helpful for the enrichment and development of marine shale gas accumulation theory. The thermal evolution experiment was carried out on the Xiamaling Formation (Pr3x) lowly matured marine shale, which has a similar sedimentary environment to the Longmaxi Formation (S1l) highly matured marine shale. Comparative experiments of open and semi-closed pyrolysis and multiple pore structure characterization techniques, including CO2 and N2 physisorption, mercury intrusion porosimetry, and field emission scanning electron microscopy, were conducted. The marine shale pore evolutionary model under formation pressure is proposed by characterizing pore evolution, and hydrocarbon expulsion and retention for shales under and without formation fluid pressures. The results show that the existence of formation pressure increases the percentage of quartz and reduces the content of clay minerals. The change in formation pressure has no obvious effect on the maturity evolution of shale samples. With the increase of formation pressure, the pore morphology of shale gradually changes from narrow slit pores to ink bottle-shaped pores. The retained hydrocarbons in shale mainly occupy the mesopore space, and the existence of formation pressure promotes hydrocarbon expulsion, especially the hydrocarbon expulsion in the mesopore. In addition, formation pressure improves pore connectivity, especially in the high-over mature stage of shale. With the increase of formation pressure, the micropore volume decreases slightly, the mesopore volume increases significantly, and the macropore volume changes have two stages.

THE INFLUENCE OF TILLAGE SYSTEMS ON SOIL COMPACTION IN THE CORN CROP

During the last decades, no-tillage has started to be used on more and more areas, being a conservative tillage system practiced in many farms in the country. The aim of this study was to quantify the effects of the no-tillage system on the physical properties of the soil compared to the conventional system, in a plateau area with cambic chernozem soil under the current climatic conditions in the north-east of Romania, in order to implement it in agricultural practice of the studied area. The soil samples were taken in natural and undisturbed conditions for bulk density and moisture content, soil penetration resistance was determined using the Eijkelkamp penetrologger. The status of soil compaction, the various porosity categories, and the soil moisture content were all determined based on field and laboratory analysis. Measurements performed at a depth of 0-40 cm showed a lower bulk density in the conventional system, and in terms of variation in values from sowing to harvesting, there was a maximum increase of 18% in the 10-20 cm soil layer, an intermediate of 10% in the topsoil and 20-30 cm layers, and a minimum of 1% in the 30-40 cm layer. Total porosity, which reflects soil pore volume, is inversely correlated with bulk density, which means that under conventional tillage practices, soil macropore volume (&gt;0.05 cm) was higher (47.79-60.82% v/v) than under no-tillage practices (45.90-50.79% v/v) for 0-40 cm depth at the sowing time. The results confirm that the no-tillage system conserves more water in the soil under current climatic conditions.

Microstructures of continental organic-rich shale and its adjacent siltstone and carbonate rocks—An example from the Lucaogou Formation, Jimusar Sag, Junggar Basin, NW China

To investigate pore structure of a continental shale and its adjacent carbonate rock and siltstone, 93 shales, 30 carbonate rocks and 10 siltstone samples from the Lucaogou Formation, Junggar Basin were examined by using low-pressure gas (N2 and CO2) adsorption, mercury intrusion and FE-SEM. Total organic carbon (TOC) evaluation, Rock-Eval pyrolysis, and X-ray diffraction (XRD) were used to characterize the organic geochemical parameters and mineralogical parameters of studied samples. The results showed that the free hydrocarbon S1 decreased in the order of siltstone, shale and carbonate rock, which is in accordance with the macropore surface area results. The carbonate rock has the highest TOC content and pyrolytic hydrocarbon S2, followed by shale and siltstone. The inter-crystalline pores of clays and intergranular pores exist widely in shale and siltstone, and a large number of dissolution pores were developed within shale, carbonate rock and siltstone. The smectite, illite and illite/smectite together control the micropores and mesopores of shale, more macropores and mesopores are present in the low TOC shale, carbonate rock and siltstone, however, the promotion effect of TOC on micropores of carbonate rock is stronger than clay. The more macropores of shale and siltstone, causes higher amounts free hydrocarbon S1. In addition, the free hydrocarbon S1 is higher at low fractal dimension D1 (D1＜2.3) and high fractal dimension D2 (D2＞2.6) of mesopore in shale. The free hydrocarbon S1 of the massive siltstone and thin layered shale are significantly higher than that of other types, which may be related to that high macropore volume and low mesopore fractal dimension D1 of the thin layered shale and the high macropore surface area of massive siltstone.

Interaction of dry and water-saturated uranium ore with microwave and enhanced extraction of uranium

Uranium encapsulated in gangue minerals is difficult to leach. How to improve the permeability of uranium ore is a key issue to promote uranium leaching. Microwave treatment can effectively weaken gangue inclusions of uranium ore. However, microwave dielectric properties and the characteristics of microwave induced microcracks have not sufficiently been investigated. Resonant cavity perturbation technology and various pore structure characterization methods are used to analyze interaction of uranium ore with microwave. Uranium ore has high dielectric properties at 150–200 °C, which is conducive to induce more microcracks. The role of microwave is mainly to induce a significant increase in macropores (>6.2 μm) volume, which increases by 213.89 % for water-saturated uranium ore. Compared with dry uranium ore, pores in water-saturated uranium ore are better developed. The microwave treatment of uranium ore enhances uranium extraction with both chemical and bioleaching.

Research on Microscopic Pore Structure Characteristics and Influencing Factors of Shale Reservoirs: A Case Study of the Second Member of the Permian Lucaogou Formation in Malang Sag, Santanghu Basin

For the second member of the Permian Lucaogou Formation in Malang Sag, Santanghu Basin, we used field emission scanning electron microscopy (SEM), cryogenic nitrogen gas adsorption, and the micro/nano CT method, combined with the fractal theory, to depict the dense reservoir space types of the reservoir and the microcosmic pore structure characteristics, perform the quantitative evaluation of aperture size, pore shape, and connectivity, and to analyze the mineral composition of the micropore structure of the reservoir. The results show that the area is dominated by sandy/argillaceous dolomite, and the reservoir space types mainly develop dissolved intergranular pores and intergranular pores, a few microfractures, and parallel plate and slit nanoscale pores. There is a positive correlation between pore volume and specific surface area, with micropore volume accounting for 14.95%, mesopore volume at 82.47%, and macropore volume at 2.58%. The mesoporous volume provides the main pore storage space. The combined specific surface area of micropores and mesoporous pores accounts for more than 99% of the total specific surface area, providing almost all the pore surface area, which is the main site for shale oil and gas adsorption. The fractal dimension D value of the samples is between 2.39 and 2.49, and the pore distribution of shale is relatively uniform, mainly developing mesoporous pores. The specific surface area and average radius are positively correlated with the content of dolomite in mineral components. The results of the CT experiment also confirm that the pore throat of samples with high dolomite content is mostly a coarse tubular and banded distribution in three-dimensional space, with good connectivity.

Selection Effect of Liquid Nitrogen Freeze-Thaw Cycles on Full Pore Size Distribution of Different Rank Coals.

In China, the capacity to produce coalbed methane and extract underground gas is restricted by the prevalence of low-permeability coal seams. Liquid nitrogen fracturing is a new low temperature-high-pressure anhydrous fracturing technology that uses low temperature and high frost heave forces to increase coal permeability. To better understand the liquid nitrogen fracturing effect on coal, we conduct the liquid nitrogen freeze-thaw cycle (LNCFT) experiments on different rank coals from Qinghai, Shanxi, and Shaanxi provinces. We combined the low-pressure nitrogen and carbon dioxide adsorption experiment with the non-local density functional theory model and mercury injection porosimetry with compressibility corrections to examine the full pore size distributions of untreated and water-saturated samples before and after LNCFT. The results found that LNCFT can effectively increase the pore volume (PV) and specific surface area of the water-saturated coal sample. Compared with the raw coal, the increased ratio of the full pore size PV is 70.41-100.17%. However, the scale-selective transformation effect on pores during liquid nitrogen fracturing is noticeable. Under the same conditions, LNCFT can significantly increase the pore volume of micropores (>2 nm) and macropores (>50 nm), and the increase ratios are 24.40-44.16 and 103.55-327.93%, respectively. The PV of mesopores (2-50 nm) shows a slightly increasing trend with the increase in metamorphic degree, and the increase ratio is between 8.7 and 56%. Comparing the full pore size distribution curves before and after LNCFT, it is found that the alteration of high-volatile bituminous coal (BLT coal) and anthracite (SH coal) has more significance in the range of less than 2 and 50-20,000 nm, while middle-volatile bituminous coal (YJL coal) varies between 50 and 2000 nm. Meanwhile, the ratio of micropore and mesopore PV to the total decreased gradually before and after LNCFT, while the proportion of macropores increased, indicating that small-scale pores would intersect and connect to form larger-scale pores during the fracturing. The combined effects of temperature gradient, water-ice phase transition, and heat transmission rate are the key factors that determine the impact of LNCFT on pore size distribution. Our results provide new information for enhancing the permeability of low-permeability coal seams of different ranks.

Effect of starch type and chitosan supplementation on physicochemical properties, morphology, and oil structuring capacity of composite starch bioaerogels

Oleogelation is a novel fat structuring method for converting liquid oils to solidified oil to reduce trans-fatty acids and saturated fat content in food formulations. In the current study, the impact of starch type and chitosan addition on the oleogelation capacity of aerogels obtained from supercritical CO2 drying technology was investigated. The starch hydrogel precursors were prepared from dent starch (27% amylose content), 55% amylose, and 72% amylose starch in the presence of 0, 0.50, and 0.75 wt% chitosan. The starch type showed a significant effect on the characteristics of resulting aerogels, where aerogels with higher content of amylose showed significantly lower shrinkage and density and higher specific surface area and macroporosity. Furthermore, chitosan addition substantially decreased the shrinkage of the aerogels, particularly those prepared with the dent starch, resulting in aerogels of lower density and higher surface area and macroporous volume. These aerogels were then powdered and employed as oil-absorbing porous materials for structuring soybean oil. Results showed that the aerogels from 55% amylose and 72% amylose starch had better oil structuring capacity compared to those from the dent starch. Furthermore, the starch aerogels supplemented with chitosan showed superior oil structuring ability than the neat starch aerogel counterparts. This work suggests that the starch type and the presence of chitosan had deep impacts on the macroporosity of the starch aerogels and their oil structuring performance.

Adsorptive Treatment of Residues on Macroporous Adsorbent for Marine Fuel Production Scheme on Refinery

Adsorptive treatment using granulated macroporous Al2O3-SiO2 adsorbent is proposed as a preliminary stage for residue pretreatment in refineries. The study evaluates the adsorptive treatment of atmospheric and visbreaking residue at 485–510 °C and 1 h−1 feed rate, resulting in a total liquid product yield of about 73.0–75.0 wt%, coke on the sorbent of 12.6–18.3 wt%, demetallization exceeding 98%, and a reduction in carbon residue of 65–72%. The paper also discusses the role of feed dilution with light gasoil, process temperature, and feed rate in optimizing the adsorptive treatment process. The high coke content on the adsorbent necessitates its regeneration, which is shown to be complete at temperatures up to 750 °C. Regeneration decreases macropore size and volume but does not significantly impact demetallization. The pretreated residual product has low viscosity and is further processed through hydrotreatment in a fixed-bed unit to produce low-sulfur marine fuel. The hydrotreated atmospheric residue meets the requirements for RMA 10 fuel, with a sulfur content lower than 0.1 wt%.

Effects of biodynamic preparations 500 and 501 on vine and berry physiology, pedology and the soil microbiome

In the pursuit of increasing sustainability, climate change resiliency and independence of synthetic pesticides in agriculture, the interest of consumers and producers in organic and biodynamic farming has been steadily increasing in recent decennia. This is, in particular, the case for the vitivinicultural industry in Europe, where more and more producers are converting from organic to biodynamic farming. However, clear scientific evidence showing that biodynamic farming improves vine physiology, vine stress resilience, soil quality related parameters and berry or wine quality is still lacking, despite the growing number of research studies on this issue. To investigate whether biodynamic farming methods have an impact on vine physiology, berry quality and the environment, a five-year experiment was set up in 2016 in a commercial vineyard in Switzerland. In this trial, the two main biodynamic preparations 500 and 501 were applied and compared to an organic control. Vine and berry physiology (net photosynthesis, vigour, sugar, organic acids, berry weight, yield) were assessed from 2016 to 2020. Soil physical properties (soil bulk density, water holding capacity, soil structural stability, macropore volume) were analysed from 2017-2020, and, soil fungal communities were analysed by DNA-sequencing in the last year of the experiment (2020). None of the parameters related to vine and berry physiology showed significant differences throughout the duration of the experiments, except photosynthesis, which was higher when biodynamic preparations were applied at one time point. Similarly, the soil’s physical properties were not influenced by the application of the two biodynamic preparations in all years. Regarding the soil microbiome, the preparations 500 and 501 neither led to significant differences in fungal diversity nor seemed to impact the soil fungal communities. The present study confirms previous findings of different research teams that did not observe significant differences between organic and biodynamic farming methods in terms of observed soil and vine parameters.

Effect of supercritical CO2-water-shale interaction on mechanical properties of shale and its implication for carbon sequestration

The mechanical behaviors of shale are important parameters influencing the CO2 storage security in shale reservoirs. Thus, understanding the mechanical properties alteration of shale induced by the injected CO2 is essential for evaluating the stability of shale reservoir rock and caprock. In this study, the impact of supercritical CO2(ScCO2)-water soak pressure and temperature (P = 0, 10, 15, 20 MPa, T = 308, 323, 338, 353 K) on the mechanical properties of shale were investigated. Mineral, pore and mechanical alterations in shale triggered by ScCO2-water soak were obtained by multiple characterization methods. The results indicated that ScCO2-water soak caused the decrease in clay and carbonate mineral contents, and the increase in macropore volume and porosity. Then, the average triaxial compressive strength and elastic modulus of shale decreased from 286.65 MPa to 156.90–247.20 MPa, and 13.62 GPa to 10.52–12.99 GPa, respectively, while Poisson's ratio v in shale increased from 0.1147 to 0.1179–0.1780. ScCO2-water soak induced mechanical weakening in shale is positively correlated with the soak pressure and negatively associated with soak temperature. The dissipated energy ratio decreased first and then increased during the stress loading process in all the tested shales, ScCO2-water soaked shale has a larger proportion of energy dissipation in each stage of stress loading. The results inferred that ScCO2-water soak caused an enhanced plastic deformation behavior in shale. The mechanical degradation in shale may increase the failure risk of reservoir rock or caprock, which should be concerned in CO2 geological storage engineering.

Identifying the critical activated carbon properties affecting the adsorption of effluent organic matter from bio-treated coking wastewater

Activated carbon is widely used to remove effluent organic matter (EfOM) from bio-treated coking wastewater. However, the critical carbon properties affecting adsorption performance are still unclear. Nine commercial powdered activated carbons (PACs) with different pore structures, surface functional groups, and surface charges were used to adsorb EfOM from bio-treated coking wastewater, which was fractionated according to their molecular weight (MW) and hydrophobicity. Good correlations were observed between the adsorption of biopolymers (MW > 20,000 Da, 7 %) and macropore volume (>50 nm), as well as between the adsorption of humics (MW = 1000 ~ Da, 36 %) and mesopore volume (2–50 nm), suggesting that the adsorption sites of EfOM depended on their molecular size. Higher isoelectric points and fewer acidic groups promoted the adsorption of the most negatively charged hydrophobic acids (HPOA, 39.5 %). According to variation partitioning analysis (VPA), mesopore-macropore greatly contributed to the adsorption capacities of EfOM (71.3 %), whereas the sum of phenolic hydroxyl and carboxyl (26.3 %) and isoelectric point (12.2 %) affected the normalized adsorption capacities of EfOM. In conclusion, PAC with a higher mesopore volume, fewer acidic groups, and a higher isoelectric point was desirable for removing EfOM from bio-treated coking wastewater. This study provides guidance for the selection of PAC for the removal of EfOM from bio-treated coking wastewater.

Fine characterization of pore evolution of oil shale during thermal simulation

Oil shale is a kind of organic‐rich fine‐grained sedimentary, whose pore evolution is affected not only by the evolution of inorganic minerals, but also by the thermal evolution of organic matter (OM). Meanwhile, the interaction between inorganic minerals and OM makes the pore evolution of oil shale more complex. Therefore, it is more important to fine the evolution characteristic of pores in different maturity stages and explore the pore size range affected by each influencing factor. This study selects immature oil shale (Tmax = 430°C, TOC = 8.2%) of Nenjiang Formation in Songliao Basin as a research object, and samples with different maturity are obtained through a series of thermal simulation experiments. Combined with petromineralogy, organic geochemistry and reservoir physical property analysis, the evolution process of pores is determined. The volume and specific surface area evolution of mesopores is different from that of macropores in the immature to mature stage, the volume and specific surface area evolution of which is same in the mature to over‐mature stage. There is a strong positive correlation between volumes of macropores and porosity (R2 = 0.94), between volumes of mesopores and specific surface area (R2 = 0.96). The influencing factors mainly affect the pore size less than 400 nm. Hydrocarbon generation of OM affects the whole pore sizes. Residual oil is stored in pores with pore size of 5–25 nm. The effect of carbonate dissolution and pyrite pyrolysis on mesopores is stronger than that of macropores. The transformation of illite/smectite to illite mainly affects the pore size greater than 100 nm. In the whole process of thermal simulation, the OM thermal evolution, the inorganic minerals dissolution and pyrolysis and the clay minerals transformation are the main influencing factors of pore evolution.

A comprehensive insight into the effects of acidification on varied-sized pores in different rank coals

Elucidating the evolution law of coal pore structure under acidification is crucial for guiding the practical application of acidizing technology and improving the production of coalbed methane. To comprehensively investigate the influence of acidification on varied-sized pores in different rank coals, in this study, fat coal, meagre coal and anthracite coal were collected and acidified with a mixed solution composed of hydrochloric acid (9 wt%) and hydrofluoric acid (3 wt%). An approach integrating low-pressure CO2 adsorption (LPGA-CO2), low-temperature N2 adsorption (LTGA-N2) and Mercury intrusion porosimetry (MIP) was adopted to fully characterize the varied-sized pore structure before and after acidification to eliminate the limitations of single method. The results demonstrated that acid treatment improved the pore opening degree and connectivity in coal, but had essentially no effect on the pore shape. After acidification, all the coal samples showed significant increases in the porosity and total pore volume, which was mainly contributed by the numerous newly formed large mesopores and macropores, especially the macropores (with an average contribution rate of 74.59%). Taken as a whole, acid treatment had the largest impact on macropores, followed by mesopores, and the smallest impact on micropores. In addition, the variation trend of total specific surface area (SSA) under acidification was primarily determined by micropores. For the three different rank coals selected in this study, the total SSA of fat coal (PM) was more easily affected by acidification and had the largest percentage increase after acid treatment, followed by anthracite coal (YM), while that of meagre coal (LA) decreased slightly. This difference was driven primarily by the different variation trend of micropore SSA in different rank coals. After acidification, the SSA of ultra-micropores and super-micropores all increased in fat coal (PM) and anthracite coal (YM), whereas for meagre coal (LA), although ultra-micropores SSA increased, super-micropores SSA decreased, which ultimately led to the slight decrease of its micropore SSA. Moreover, the total pore volume increment of coal was closely related to the macropore volume increment under acidification, but not significantly related to the coal maturity,which might indicate that, compared with coal rank, the mineral content in coal might be a more important consideration when measuring the applicability of acidification technology.