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Accurately predicting the adsorbed gas content in coal reservoirs is crucial for evaluating the gas content in deep coal seams. However, due to the significant variations in temperature and pressure conditions across different coal reservoirs, accurately assessing the adsorbed gas quantity presents challenges. Based on the adsorption potential theory, this paper proposes a prediction model of adsorbed gas that is applicable under various temperature and pressure conditions. The results indicate that the adsorbed gas content in deep coal reservoirs is influenced by a combination of temperature, pressure, and coal rank. The increase in pressure and coal rank enhances the inhibitory effect of temperature on methane adsorption. Meanwhile, there are significant differences in the results obtained from various virtual saturated vapor pressure models. Among them, the Amankwah model theoretically satisfies the uniqueness of the adsorption characteristic curve, with the optimal k values for different coal rank samples ranging between 2 and 9. In terms of predicting the adsorption gas, the performance of the models is ranked as follows: Amankwah model > Antonie model > Astakhov model > Dubinin model > Reid model. The Amankwah model exhibits the smallest average relative error and root mean square error. In addition, as burial depth increases, the influence of the pressure on methane adsorption decreases, while the significance of temperature increases, with the critical depth located around 1600 m. At depths shallower than the critical depth, adsorbed gas tends to preferentially accumulate and form reservoirs, which generally have lower commercial value. At depths deeper than the critical depth, free gas has the potential to form reservoirs. At this stage, gas reservoirs dominated by adsorbed gas start transitioning to those containing free gas. These findings are expected to deepen the understanding of deep coalbed methane and provide a scientific basis for exploration and development in the study area. [ABSTRACT FROM AUTHOR]

The objective of this study is to develop a remediation technology for composited heavy metal-contaminated soil. Biochars (BC300, BC400, and BC500) derived from corn were combined with potassium dihydrogen phosphate (KH2PO4) to immobilize and remove heavy metal ions, including mercury (Hg2+), cadmium (Cd2+), and lead (Pb2+). The adsorption kinetics of metal ions in aqueous solutions with different concentrations was tested, and the fitting effects of the two models were compared. The findings demonstrate that the joint application of biochar and KH2PO4 could markedly enhance the immobilization efficacy of Pb2+, whereas the utilization of KH2PO4 on its own exhibited a more pronounced immobilization impact on Cd2+. Furthermore, the present study underscores the shortcomings of various remediation techniques that must be taken into account when addressing heavy metal-contaminated soils. It also emphasizes the value of comprehensive remediation techniques that integrate multiple remediation agents. This study offers a novel approach and methodology for addressing the intricate and evolving challenges posed by heavy metal contamination in soil. Its practical value and potential for application are significant. [ABSTRACT FROM AUTHOR]

The gas adsorption characteristics in deep coal reservoirs are the focus of deep coalbed methane geology research. In order to reveal the adsorption characteristics in deep coal reservoirs and quantitatively characterize the amount of adsorbed methane in the deep coal seams, four coals were collected from the Permian Longtan Formation in southern Sichuan Province. Methane isothermal adsorption tests were carried out on the collected coal samples at 30 °C. The adsorption characteristic curve was established based on the data of the isothermal adsorption. The adsorption potential theory was used to predict the isothermal adsorption curves under different temperatures and the evolutionary relationship between the methane adsorption capacity and the coal seam burial depth in the C17 and C25 coal seams of the Permian in southern Sichuan Province, China. The results showed that the methane isothermal adsorption curve at 30 °C belonged to the Type I isotherm adsorption curve. The methane isothermal adsorption curves for various samples at 45 °C, 60 °C, and 75 °C were predicted based on the uniqueness of the methane adsorption characteristic curve. The amount of adsorbed gas in deep coal reservoirs was comprehensively controlled by pressure and temperature. The pressure showed a positive effect on the amount of methane adsorbed, while the temperature showed a negative effect on the adsorption of methane. The negative effect of temperature became more significant with the increase in pressure. The results of the study are beneficial for further promoting the exploration and development of deep coalbed methane in the southern Sichuan Province of China. [ABSTRACT FROM AUTHOR]

Coal reservoirs have a complex pore structure, which is accompanied by energy changes during the adsorption of methane gas. To study the heterogeneity of energy changes during the pore and methane adsorption processes in coal reservoirs, fractal dimension analysis was employed to analyze the heterogeneity of coal pores. The heterogeneity of energy changes during the isothermal adsorption process was analyzed using adsorption potential and surface free energy theory. The results show that sample PY-1, PB-1, and PB-2 mainly develop micropores, while sample PY-2 mainly develops macropores, and the pore distribution of different samples is significantly different. Micropores are the main sites for methane adsorption, but not the determining factor affecting methane adsorption. Coal􀆳s pore structure and inherent properties exert a significant influence on the heterogeneity of methane adsorption. As the vitrinite content increases, the complexity of pore structure and the fractal dimension of pores also increase, leading to enhanced heterogeneity. Consequently, methane adsorption exhibits higher uptake, accompanied by more pronounced variations in adsorption potential and surface free energy. [ABSTRACT FROM AUTHOR]

The objective of this study is to develop a remediation technology for composited heavy metal-contaminated soil. Biochars (BC300, BC400, and BC500) derived from corn were combined with potassium dihydrogen phosphate (KH2PO4) to immobilize and remove heavy metal ions, including mercury (Hg2+), cadmium (Cd2+), and lead (Pb2+). The adsorption kinetics of metal ions in aqueous solutions with different concentrations was tested, and the fitting effects of the two models were compared. The findings demonstrate that the joint application of biochar and KH2PO4 could markedly enhance the immobilization efficacy of Pb2+, whereas the utilization of KH2PO4 on its own exhibited a more pronounced immobilization impact on Cd2+. Furthermore, the present study underscores the shortcomings of various remediation techniques that must be taken into account when addressing heavy metal-contaminated soils. It also emphasizes the value of comprehensive remediation techniques that integrate multiple remediation agents. This study offers a novel approach and methodology for addressing the intricate and evolving challenges posed by heavy metal contamination in soil. Its practical value and potential for application are significant.

The gas adsorption characteristics in deep coal reservoirs are the focus of deep coalbed methane geology research. In order to reveal the adsorption characteristics in deep coal reservoirs and quantitatively characterize the amount of adsorbed methane in the deep coal seams, four coals were collected from the Permian Longtan Formation in southern Sichuan Province. Methane isothermal adsorption tests were carried out on the collected coal samples at 30 °C. The adsorption characteristic curve was established based on the data of the isothermal adsorption. The adsorption potential theory was used to predict the isothermal adsorption curves under different temperatures and the evolutionary relationship between the methane adsorption capacity and the coal seam burial depth in the C17 and C25 coal seams of the Permian in southern Sichuan Province, China. The results showed that the methane isothermal adsorption curve at 30 °C belonged to the Type I isotherm adsorption curve. The methane isothermal adsorption curves for various samples at 45 °C, 60 °C, and 75 °C were predicted based on the uniqueness of the methane adsorption characteristic curve. The amount of adsorbed gas in deep coal reservoirs was comprehensively controlled by pressure and temperature. The pressure showed a positive effect on the amount of methane adsorbed, while the temperature showed a negative effect on the adsorption of methane. The negative effect of temperature became more significant with the increase in pressure. The results of the study are beneficial for further promoting the exploration and development of deep coalbed methane in the southern Sichuan Province of China.

Adsorptive heat transformation is an emerging technology that can store heat, convert it to heat with another temperature potential, and generate cold. Progress in this field is determined by the development of new advanced adsorbents, implementing efficient cycles, and harmonizing the adsorbent with the cycle. The article examines how the fundamental potential theory of adsorption is used to reach these applied goals and highlights the progress resulted from its application to adsorptive heat transformation. [ABSTRACT FROM AUTHOR]

In order to further clarify the adsorption thermodynamic characteristics of CH4 and CO2 in coal, the giant canonical ensemble Monte Carlo method was used to simulate the adsorption behavior of CH4 and CO2 in coal at different temperatures and different moisture content. The results show that the adsorption capacity of CH4 and CO2 in coal molecules decreases with the increasing temperature and moisture content. By comparing the adsorption amounts of the two components, it is found that both high temperature and the presence of water molecules are not conducive to displace CH4 by CO2; the average adsorption heat of CH4 is negatively correlated with temperature and water content, and average adsorption heat of CO2 has a negative correlation with temperature and a positive correlation with water content. Water molecules are more inclined to react with CO2; the overall adsorption potential of CH4 and CO2 is negatively correlated with temperature and moisture content. When the pressure is low, the adsorption potential of CO2 increases slightly with the increasing of temperature; the adsorption entropy of CH4 and CO2 increases with the increasing of temperature and decreases with the increasing of moisture content. The influence of water on CO2 is stronger than CH4. When two components are injected, the existence of water molecules makes the whole system more stable, which is not conducive to CH4 output.

Dubinin–Radushkevich (D – R) isotherm remains one of the widely used adsorption models in solid/liquid interface. However, adsorption potential (ε), as a function of equilibrium concentration (Ce) and solubility (Cs) of adsorbate, is frequently expressed through a dimensionally inconsistent form i.e. ε = R T ln 1 + 1 C e , instead of the correct form i.e. ε = R T ln C s C e . Although Hu and Zhang (2019) have pointed out the misinterpretation, incorrect use of isotherm however continues. All of the 10 all-time highly cited articles on D-R isotherm and 80 out of 117 articles citing the work of Hu and Zhang (2019) adopted the incorrect or ambiguous form. Only six research articles have referred source of required Cs data, i.e. literature reported value, approximated to initial adsorbate concentration, or as an additional model parameter. Modeling of D-R isotherm using datasets extracted from three selected references suggests that using the incorrect expression would have a variable impact on maximum adsorption capacity estimates. However, sorption energy would invariably be overestimated (at least 200 times) in all data sets. In the absence of any unified approach and the practical difficulty associated with ascertaining the correct Cs value, researchers are inclined to use the inconsistent model. [ABSTRACT FROM AUTHOR]

Abstract To investigate the adsorption properties of methane in coal under low temperatures, the isothermal adsorption tests of the three coal samples with different metamorphic degrees were conducted at the ambient temperatures of 253.15−293.15 K, and the low‐temperature nitrogen adsorption (LNA) tests of coal were also performed. Then a relational expression of equilibrium pressure, temperature, and methane adsorption capacity (T−P model) was deduced to predict the adsorption isotherm at any other temperature based on the Polanyi adsorption theory. The results show that the gas adsorption capacity of coal can be significantly increased at low temperatures (below 273.15 K), and the adsorbed methane in anthracite is obviously more than that in lean coal and coking coal by the virtue of possessing a larger micropore/transition pore volume and specific surface area. The relations between adsorption potential (ε) and adsorption volume (ω) at different temperatures can be drawn on one single logarithmic curve, and a suitable pseudo‐saturation pressure can be obtained by the improved Amankwah's method. The predicted adsorbed capacities via the T−P model are in line with the measured results at other equilibrium conditions, indicating that the model can contribute to the deep coalbed methane resources estimation and the gas disaster prevention and control in coal mines.

Blending carbon particles (CPs) and nanoscale bioactive cerium dioxide is a promising approach for designing composites for biomedical applications, combining the sorption and antioxidant potentials of each individual component. To address this issue, it is crucial to assess the correlation between the components' ratio, physicochemical parameters, and biofunctionality of the composites. Thus, the current research was aimed at fabricating C@CeO 2 composites with different molar ratios and the examination of how the parameters of the composites affect their bioactivity. XRD, X-ray photoelectron spectroscopy, and electron microscopy data verified the formation of C@CeO 2 composites. CeO 2 nanoparticles (NPs) of 4-6 nm are highly dispersed on the surfaces of amorphous CPs. The presence of CeO 2 NPs on the carbon surface decreased its adsorption potential in a dose-dependent manner. Besides, the coexistence of carbon and CeO 2 in a single composite promotes some redox interactions between O-functionalities and Ce 3+ /Ce 4+ species, resulting in changes in the chemical state of the surface of the composites. These observations suggest the strong connection between these parameters and the biofunctionality of the composites. The presence of CeO 2 NPs on the surface of carbon led to a significant increase in the stability of the prepared composites in their aqueous suspensions. The enhancement of bioactivity of the newly prepared C@CeO 2 compared to bare carbon and CeO 2 was validated by testing their pseudomimetic (catalase/peroxidase-like and superoxide dismutase-like), antiamyloid, and radioprotective activities.

Chestnut shell-based activated carbon was prepared with chestnut shell as the raw material and ZnCl2 as the activating agent. Based on thermodynamic parameters, the adsorption behavior of methylene blue (MB) on chestnut shell-based activated carbon was studied, and the effect of temperature on the thermodynamic parameters and adsorption behavior was investigated. The Langmuir equilibrium constant (KL) and the standard equilibrium constant (K0) were used to calculate the thermodynamic parameters, respectively. Comparative analysis showed that spontaneous adsorption (ΔG0 < 0) was more compatible with the standard equilibrium constant (K0). Furthermore, the thermodynamic parameters at 30, 40 and 50 °C were measured, and the adsorption potential was investigated and calculated. Eventually, the mechanism of the adsorption process was determined. It was concluded that the adsorption process mainly involved chemical adsorption, which indicated that MB adsorption was caused by the force of the chemical bond. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a novel, adapted approach for computing gas adsorption properties in porous materials. Our methodology is based on the Dubinin-Polanyi's adsorption model, and we investigate various frameworks to estimate its required essential components and prediction capabilities. The required components are linked to the physicochemical properties of the adsorbates, such as the vapor saturation pressure and density in the adsorbed phase. To conduct this analysis, we obtain adsorption isotherms for several metal–organic frameworks encompassing a range of pore sizes, shapes, and chemical compositions. We then apply and evaluate multiple combinations of models for saturation pressure and density. After the evaluation of the methods, we propose a working thermodynamic model for computing adsorption isotherms, which entails using the critical isochore as an approximation of the saturation pressure above the critical point and applying Hauer's method with a universal thermal expansion coefficient for density in the adsorbed state. This framework is applicable not only to simulated isotherms but also to experimental data from the literature for various molecules and structures of different natures, demonstrating robust predictive capabilities and high transferability. Our method showcases superior performance in terms of accuracy, generalizability, and simplicity compared to existing methods currently in use. In light of our results, this method, starting from a single adsorption curve and based on physically interpretable parameters, can predict adsorption properties across a wide range of operating conditions. [Display omitted] • The adsorption potential theory can be used for predicting adsorption isotherms. • A combination of adsorbed density and vapor pressure is key to the predictive theory. • The predictive capabilities of the proposed framework are successfully tested. • Equations of state are alternative options to obtain vapor saturation pressure. [ABSTRACT FROM AUTHOR]

Prediction of adsorption isotherms under different temperatures is significant to reserve estimation of shale gas reservoirs. Based on the Polanyi adsorption potential theory and Langmuir adsorption theory, a method was presented to predict adsorption isotherms at different temperatures. In this method, the relationship between Langmuir pressure and temperature was quantified. By utilizing this method, we predicted adsorption isotherms of Longmaxi shale from 45 °C to 120 °C according to experimental data at 30 °C. Meanwhile, by considering the pressure and temperature gradients, we also predicted the adsorption capacity of Longmaxi shale with geologic depth. Results show that the adsorption data predicted by our method are in accord with experimental data and the error coefficient is less than 5%. In addition, the isosteric heat of adsorption for Longmaxi shale can be calculated by predicted adsorption data based on the Clausius–Clapeyron equation of capillary systems. Therefore, our study illustrates theoretical foundations for the efficient evaluation of adsorbed gas content in shale gas reservoirs at geologic conditions. [ABSTRACT FROM AUTHOR]

To investigate the adsorption properties of methane in coal under low temperatures, the isothermal adsorption tests of the three coal samples with different metamorphic degrees were conducted at the ambient temperatures of 253.15−293.15 K, and the low‐temperature nitrogen adsorption (LNA) tests of coal were also performed. Then a relational expression of equilibrium pressure, temperature, and methane adsorption capacity (T−P model) was deduced to predict the adsorption isotherm at any other temperature based on the Polanyi adsorption theory. The results show that the gas adsorption capacity of coal can be significantly increased at low temperatures (below 273.15 K), and the adsorbed methane in anthracite is obviously more than that in lean coal and coking coal by the virtue of possessing a larger micropore/transition pore volume and specific surface area. The relations between adsorption potential (ε) and adsorption volume (ω) at different temperatures can be drawn on one single logarithmic curve, and a suitable pseudo‐saturation pressure can be obtained by the improved Amankwah's method. The predicted adsorbed capacities via the T−P model are in line with the measured results at other equilibrium conditions, indicating that the model can contribute to the deep coalbed methane resources estimation and the gas disaster prevention and control in coal mines. [ABSTRACT FROM AUTHOR]

A study on the adsorption capacity and mechanisms on cow manure (CM400-5) and corn stover (CS700-2) biochar to remove typical heavy ions from water has been performed. The Cd2+ , Cu2+ , Pb2+ , and Zn2+ , commonly found in the first flush of the urban/industrial stormwater runoff, were tested under controlled conditions. The obtained experimental data were modeled with the Freundlich, Langmuir, and Harkins–Jura isotherms to describe the adsorption pathways. The novel solubility-normalized Dubinin–Radushkevich (D-R) approach is introduced for the determination of the adsorption mechanisms. The solubility-normalized mode emphasizes the importance of the solubility concentration in calculating the mean free energies of adsorption used to identify removal mechanisms. The proposed model was experimentally validated for the carbon-based (biochar) adsorbers and inorganic (heavy metals) ions. Comparison of obtained results with the commonly used nonnormalized D-R model shows a likely underestimation of the mean free energy values, which could misrepresent the dominant mechanism of adsorption. [ABSTRACT FROM AUTHOR]

This work focused on thermodynamic analysis of carbon dioxide (CO2) adsorption on a promising biochar as a CO2 adsorbent. The biochar was prepared by catalytic pyrolysis of cellulose material in ionic liquid at moderate temperature. The adsorption characteristics, such as adsorption capacity, interfacial potential, Gibbs free energy change, enthalpy change, entropy change, and internal energy change, influenced by adsorption temperature and gas pressure, were systematically investigated. The results indicated that CO2 adsorption on cellulose‐derived biochar was a spontaneous, physical, exothermic, and entropic decrement process, accompanied by adsorption capacity of 5.2 mmol/g and interfacial potential of −18.2 J/g at 273 K and 100 kPa. The process could be well described by adsorption potential theory. Then a quasi‐Gaussian distribution of site energy was verified for CO2 adsorption. The interfacial potential was found to be a monotropic function of the amount of CO2 adsorbed, and the latter was actually a differential of the former via adsorption potential. The positive temperature effect and negative pressure effect on negative Gibbs free energy change indicated that reducing adsorption temperature and increasing gas pressure were beneficial to CO2 uptake, accompanied by the increase of adsorption capacity and the reduction of interfacial energy, entropy, enthalpy, and internal energy. The strongest temperature effects on entropy change, enthalpy change, and internal energy change existed at given pressure or temperature. The pressure effect was stronger and more sensitive to pressure at lower adsorption pressure. More interestingly, the peak pressure or peak temperature with the strongest pressure effect possibly existed during CO2 adsorption. [ABSTRACT FROM AUTHOR]

Prediction of adsorption isotherms under different temperatures is significant to reserve estimation of shale gas reservoirs. Based on the Polanyi adsorption potential theory and Langmuir adsorption theory, a method was presented to predict adsorption isotherms at different temperatures. In this method, the relationship between Langmuir pressure and temperature was quantified. By utilizing this method, we predicted adsorption isotherms of Longmaxi shale from 45 °C to 120 °C according to experimental data at 30 °C. Meanwhile, by considering the pressure and temperature gradients, we also predicted the adsorption capacity of Longmaxi shale with geologic depth. Results show that the adsorption data predicted by our method are in accord with experimental data and the error coefficient is less than 5%. In addition, the isosteric heat of adsorption for Longmaxi shale can be calculated by predicted adsorption data based on the Clausius–Clapeyron equation of capillary systems. Therefore, our study illustrates theoretical foundations for the efficient evaluation of adsorbed gas content in shale gas reservoirs at geologic conditions.

Nitrogen-doped bamboo-like carbon nanotubes (N-BCNTs) were synthetized by catalytic chemical vapor deposition (CCVD) and characterized by electron microscopy. The produced nanotubes were oxidized in different degree by using of various oxidizing agents (H2O2, HClO4 and HNO3) in order to change their adsorption potential by creating dissociable functional groups (e.g. -OH) on their surface. The appearance of oxygen containing groups was confirmed by spectroscopic analysis and the zeta potential (ζ of the samples was measured. The HNO3 treatment has led to the emergence of the most polar groups on the nanotube surface (ζ = −27.1 mV), while the other two oxidizing agents were less effective (H2O2 and HClO4, ζ = −18.3 and −19.8 mV, respectively). The adsorption potential of the oxidized N-BCNT samples were tested with copper(II)-ion. Despite the difference in their surface properties, the oxidized nanotubes adsorbed copper to the same extent. The contribution of the oxidized surface for the adsorption capacity is smaller than the effects of nitrogen doping. Thus, more things involved in the adsorption mechanism not only electrostatic attraction, but sorption-precipitation, and complex formation between copper and heteroatoms of the nanotubes. Thus, it is not enough to discuss the effect of dissociable functional groups, but the contribution of e.g. heteroatoms must also be taken into account to fully understand metal ion adsorption on oxidized carbon materials. [ABSTRACT FROM AUTHOR]

Gossweilerdendron balsamiferum (Tola wood) dust, as a precursor was used for the production of acid-activated carbon (TDAC) employed in the adsorptive removal of Cu2+ and Pb2+ ions. The relational adsorptive behaviour of TDAC, equilibrium studies and statistical evaluation of the data prediction performance of the respective models were conducted. The adsorbent was characterized using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. Removal efficiencies of 75.66 % (for Cu-loaded TDAC) and 72.22 % (for Pb-loaded TDAC) were recorded at optimum pH (pH 6.0). The values of adsorption density, adsorption potential, hopping number and surface coverage were 7.256E-13 mol/L; -4920.78 J/mol; 8.44; 0.86 and 9.623E-13 mol/L; -5648.6 J/mol; 8.53; 0.86, for Cu- and Pb-loaded TDAC, respectively. Modified Langmuir model emerged as the best fit model for both adsorption system, as it depicted the lowest average error values of 1.8E-11 (for Cu-loaded TDAC) and 1.43E-12 (for Pb-loaded TdAc). Furthermore, model prediction performance showed that 5-parameter equation with t- and p-values of -0.862; 0.439 (for Cu-loaded TDAC) and -0.804; 0.466 (for Pb-loaded TDAC), was the least predictive among the isotherm models. The study demonstrated the effective application of TDAC in Cu2+ and Pb2+ adsorption, with the Cu-loaded TDAC being more efficient. [ABSTRACT FROM AUTHOR]

A promising biochar as solid adsorbent for CO2 uptake was prepared by the catalytic pyrolysis of coconut shell in moderate‐temperature ionic liquid (IL). Then, it was characterized by means of SEM, EDS, BPEA, BET, NLDFT, FTIR, and TG‐DSC, and a mechanism interpretation of the porous biochar formation was conducted. In addition, the adsorption characteristics of CO2 on the as‐prepared biochar, such as adsorption capacity, adsorption potential, isosteric heat, and static selectivity at different adsorption temperatures and pressures, were systematically evaluated. The results indicated that the as‐prepared biochar exhibited an adequate CO2 adsorption with a capacity of 4.5 mmol/g at 273 K and 100 kPa. Then, a significant number of slit‐like pores were revealed to exist on the as‐prepared biochar with a peak pore size between a range of 0.6 nm‐2 nm. The porous structure formation was ascribed to the release of carbon‐, hydrogen‐, oxygen‐, sulphur‐, and nitrogen‐containing compounds during biochar preparation. Meanwhile, both the adsorption potential and isosteric heat of the CO2 uptake under the tested conditions decreased with an increase in the adsorption capacity, which ranged from 33 kJ/mol‐21 kJ/mol and 23 kJ/mol‐7 kJ/mol, respectively. Therefore, the isosteric heat could be considered as a piecewise function of adsorption capacity. In addition, the molar ratios of CO2 over N2 adsorbed under the tested conditions were above 11 and were accompanied by molar ratio peaks of 26 at 273 K and 19 at 298 K, respectively. Moreover, an interesting phenomenon occurred: the static adsorptive selectivity of CO2 over N2 first increased and then decreased and there was an increase in the adsorption pressure at the tested adsorption temperatures. [ABSTRACT FROM AUTHOR]

[Display omitted] • Different pore classification characteristics and spatial structures of lignite with different cycles of water immersion. • The transformation and accumulation of functional groups could be affected by water immersion. • An application and validation method for adsorption kinetics was proposed. • The evolution mechanism of microscopic functional groups of water-immersed lignite was revealed. As the mining of the overlying coal seam advances, the risk of spontaneous combustion (SC) of water-immersed and air-dried coal in the overlying goaf increases. The structure of functional groups in coal is the fundamental factor for the occurrence of oxidation and heat production, and the surface pores are the main sites of oxidation reactions. In order to explore the mechanism of action of water immersion on the macrostructure and micro-group of lignite, the water-immersed coals (WIC) of 30 days (I 30), 60 days (I 60), 90 days (I 90), 120 days (I 120) and 150 days (I 150) were prepared. The surface pore characteristics of coal and the evolution of active functional group structure were studied by nitrogen adsorption and infrared spectroscopy. The adsorption capacity of pores and surface structure of coal were quantitatively characterized by pore adsorption kinetic equations and fractal methods. The results showed that the fine-necked bottle-shaped pore structure of water-immersed lignite decreased, and the wedge-shaped pores and parallel plate slits increased. After water-soaking, the specific surface area of lignite increased first and then decreased, the pore volume and pore diameter increased gradually, D 1 decreased gradually, D 2 increased gradually, and the pore adsorption potential increased gradually, which characterized the gradual pore structure complexity and enhanced adsorption capacity. Water-soaking triggered the conversion of active carbon-hydrogen bonds at the α-position of lignite molecules into active carbon–oxygen single bonds with alcohol-oxygen bonds. I 90 and I 120 have the highest content of active functional groups, indicating that the oxidation activity of lignite immersed in water for 90–120 days is the highest. This study provides a new method for the quantitative characterization of coal adsorption and has reference value for the study of SC mechanism of water-immersed, air-dried coal in the overlying goaf of close distance coal seam. [ABSTRACT FROM AUTHOR]

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To fill the knowledge of adsorption characteristics of CH4 and CO2 associated with equilibrium and thermodynamics, adsorption equilibrium tests of pure gas on a coal were conducted under the different temperatures (35 °C, 50 °C, and 65 °C by the static volumetric method. The equilibrium data were well matched by the SLD-PR model. The influence of some significant factors including temperature, pressure, adsorption potential and surface free energy on gas adsorption capacity were discussed. The results showed that the higher temperature (gas pressure) corresponds to the smaller (larger) adsorption capacity and the larger adsorption potential is, the smaller adsorption capacity is. Taking CH4 as adsorbent, the modified Langmuir equation can well match the SLD-PR model. However, when the adsorption medium is CO2, modified Freundlich equation is better. Using the two modified equations, we study further the relationship among the variation of surface free energy, its reduction rate and gas adsorption capacity. It can be concluded the larger the gas adsorption capacity is, the greater the reduction of surface free energy is, and the smaller the reduction rate of surface free energy is. [ABSTRACT FROM AUTHOR]

Adsorption heat transformation (AHT) is energy and environment saving technology that allows the effective utilization of renewable and waste heat with low-temperature potential. For the enhancement of AHT efficiency, properties of the working pair "adsorbent–adsorbate" have to be intelligently adapted to the operating conditions of the specific AHT cycle. In this work, the applicability of ATH technology in the Russian Federation (RF) was analyzed. For various geographic zones of the RF, the proper AHT application (cooling, heating, heat amplification, or storage) was selected depending on the zone climatic conditions. Data on the adsorption equilibrium for more than 40 "adsorbent–adsorbate" pairs collected from the literature were analyzed to select the most suitable pairs for the particular application/zone. Recommendations on AHT applications and the proper working pairs for the considered RF climatic zones are made. [ABSTRACT FROM AUTHOR]

Recently, owing to the discovery of graphene, porous carbons experienced a revitalization in their explorations. However, nowadays, the focus is more on search for suitable energy advancing catalysts sensing, energy storage or thermal/light absorbing features than on separations. In many of these processes, adsorption, although not emphasized sufficiently, can be a significant step. It can just provide a surface accumulation of molecules used in other application-driving chemical or physical phenomena or can be even an additional mechanism adding to the efficiency of the overall performance. However, that aspect of confined molecules in pores and their involvement in the overall performance is often underrated. In many applications, nanopores might silently advance the target processes or might very directly affect or change the outcomes. Therefore, the objective of this communication is to bring awareness to the role of nanopores in carbon materials, and also in other solids, to scientists working on cutting-edge application of nonporous carbons, not necessary involving the adsorption process directly. It is not our intention to provide a clear explanation of the small pore effects, but we rather tend to indicate that such effects exist and that their full explanation is complex, as complex is the surface of nanoporous carbons.

Systematic understanding of the occurrence mechanism of multiple fluids in coal reservoirs is the basis for efficient development of coalbed methane (CBM). In this study, the adsorption capacity, adsorption potential and adsorption heat data of coal samples of different metamorphic degrees under single/multi components isothermal adsorption were obtained through isothermal adsorption equipment and the atomic force microscopy (AFM). The adsorption potential energy and electric potential energy were innovatively combined to expound the characteristics of the thermodynamic energy change in coal reservoirs, and the occurrence mechanism of multiple fluids in coal reservoirs were discussed. It is found that: (a) the adsorption amount of these two gases decreases first and then increases with the increase of coal rank in both single-phase adsorption and competitive adsorption. (b) CO 2 shows superior adsorption in comparison to CH 4. The larger the proportion of a certain component in the mixed gases system, the better this component's adsorption performance. (c) The adsorption potential of the two gases is not affected by temperature, and with the increase of coal metamorphism, the adsorption potential shows first a decrease, followed by an increase. (d) The CH 4 adsorption heat of coal samples increase with higher adsorption amount, but the CO 2 adsorption heat of some coal samples has a negative linear correlation with adsorption amount. • The competitive adsorption behavior of supercritical CO 2 and CH 4 at high temperature and high pressure conditions were characterized. • The correlation between the thermodynamic energy changes of the system and the maceral properties of coal were innovatively explored. • For the first time, adsorption potential theory and electric potential theory are combined to explore the gas occurrence mechanism in coal reservoir. [ABSTRACT FROM AUTHOR]

In order to explore the thermodynamic mechanism of multicomponent gas adsorption on coal, the Grand Canonical Monte Carlo simulation method was used to study the adsorption behavior of CH4, CO2 and N2 in the coal molecular model at different temperatures from the perspective of thermodynamics. The simu-lation results show that CH4 shows a dotted distribution, CO2 shows a cluster distribution, and N2 shows a strip distribution in the unit cell. The relationship between the adsorption capacity, adsorption heat and adsorption entropy of the three gases is CO2> CH4> N2. And the relationship between the adsorption potential of the three gases is CO2

In order to reveal the deep coal reservoir adsorption characteristics of coal and the quantitative characterization on the amount of adsorbed gas of coalbed methane, this paper studied the coal samples of carboniferous-permian in eastern Ordos Basin and analyzed the methane isothermal adsorption experiments of high temperatures and pressures of coal samples. An interpretation of the adsorption characteristics was made under high temperatures and pressures from the geological factors including coal rank, temperature and pressure. The curves of coal adsorption characteristic and the prediction model of amount of adsorbed gas with different coal ranks were established based on the adsorption potential theory. Meanwhile, a case study on the amount of adsorbed gas of the No. 8+9 coal seam in Linxing area was analyzed based on this model. The results show that the adsorption characteristics of deep coal reservoir are comprehensively influenced by temperature,pressure and coal rank. When the coal rank is between 0.77% and 2.18%, which is from gas coal to poor coal, the coal rank and pressure show a positive effect on adsorption ability, but temperature has a negative effect. In addition, the negative effect is more significant with the pressure increases. Different coal ranks have different curves of coal adsorption characteristic. The higher of coal rank, the slower of rate at which the adsorption potential decreases as the adsorption space increases. The calculation of the amount of absolute adsorbed is between 19.6 cm3/g and 31.1 cm3/g, and the gas saturation is between 37.8% and 78.8% in the study area [ABSTRACT FROM AUTHOR]

• Evaluation of CO 2 -ECBM effects by thermodynamic characterization of coal adsorption of CH 4 and CO 2. • As the moisture content increases, the overall effect of CO 2 replacement of CH 4 becomes worse, but in some cases the opposite occurs. • The presence of H 2 O can enhance the adsorption of CO 2 in some cases. • Smaller pore size of coal will produce stronger wall superimposed effect. • Multiple H 2 O molecules form H 2 O clusters, which will attract CO 2 with high potential. In order to further clarify the thermodynamic properties of CH 4 and CO 2 adsorption in coal, a Monte Carlo method with a giant regular system was used to simulate the adsorption behavior of CH 4 and CO 2 in coal at different moisture contents and pore sizes. The results show that the adsorption of CH 4 and CO 2 in coal molecules is negatively correlated with the moisture content. As the pore size increases, the wall superimposed effect decreases, the stability of adsorption becomes less stable, and the selectivity of CO 2 adsorption decreases, but the space to accommodate gas molecules becomes larger, which makes the adsorption amount rise. The average heat of adsorption of CH 4 and CO 2 showed a decreasing and then increasing relationship with the moisture content, and a negative correlation with the pore size, and the effect of H 2 O on CO 2 is stronger than that of CH 4. With the increase of moisture content, the absolute value of adsorption energy increases overall, and the high potential of water clusters tends to attract CO 2 molecules more. With the increase of pore size, the wall superimposed effect weakens and the adsorption stability becomes worse, which makes the absolute value of adsorption energy smaller. The overall adsorption entropy of CH 4 and CO 2 has a negative correlation with moisture content and a positive correlation with pore size. The comparison of the slope of the fitted curves of adsorption entropy at different moisture contents adds that CO 2 mainly displaces CH 4 molecules in the middle of the pores at 3% moisture content. [ABSTRACT FROM AUTHOR]

Adsorption heat transformation (AHT) is energy and environment saving technology that allows the effective utilization of renewable and waste heat with low-temperature potential. For the enhancement of AHT efficiency, properties of the working pair “adsorbent–adsorbate” have to be intelligently adapted to the operating conditions of the specific AHT cycle. In this work, the applicability of ATH technology in the Russian Federation (RF) was analyzed. For various geographic zones of the RF, the proper AHT application (cooling, heating, heat amplification, or storage) was selected depending on the zone climatic conditions. Data on the adsorption equilibrium for more than 40 “adsorbent–adsorbate” pairs collected from the literature were analyzed to select the most suitable pairs for the particular application/zone. Recommendations on AHT applications and the proper working pairs for the considered RF climatic zones are made.

The adsorption capacity and thermodynamic properties of high-rank tectonically deformed coal (TDC) samples from the Yangquan coalfield in North China were analyzed by combining isothermal adsorption and Polanyi potential theory. The adsorption capacities of mylonitic- (10.7015-17.2065 cm/g) and scaly (9.8237-11.5386 cm/g) coals are higher than those of cataclastic- (8.3496-9.5238 cm/g) and schistose (7.7990-8.0467 cm/g) coals. The primary- and wrinkle coals have the lowest adsorption capacities. The adsorption potential (the change of surface free energy per mole during physical adsorption) decreases with the increasing adsorption space in a parabola characteristic. For different TDCs, the interval length of the adsorption potential distribution is in the same order with the adsorption capacity. The interval lengths of primary-, schistose-, and mylonitic coals are 0-0.014, 0-0.020, and 0-0.025 cm/g, respectively. The reduction amounts of surface free energy for mylonitic- (6.040-10.082 kJ/cm) and scaly (2.075-6.047 kJ/cm) coals are higher than those of the cataclastic- (3.069-4.249 kJ/cm) and wrinkle (2.222-3.434 kJ/cm) coals. The initial and saturated adsorption surface free energies of mylonitic- and scaly coals are higher than those of the primary- and schistose coals. Based on the difference in the surface free energy reduction values, the TDCs, especially the mylonitic- and scaly coals, have a greater adsorption potential than primary- and other TDCs. [ABSTRACT FROM AUTHOR]

Silica nanoparticles with a surface area of 673.60 m2/g and particle size of 8-12 nm were prepared using aerogel process (AP) followed by super critical drying. Zero valent Fe, Co, Pt, and bimetallic Fe/Pt and Fe/Co were loaded using an incipient wetness impregnation technique and subsequent reduction. Scanning electron microscopy-energy dispersive X-ray (SEM-EDX) and transmission electron microscopy-energy dispersive X-ray (TEM-EDX) characterizations indicated fine dispersion of iron on AP-SiO2 +Fe system. Prepared nanoparticles were evaluated for the adsorptive removal of 2,4,6-trinitrotoluene (TNT) from water. Surface area normalized rate constant values indicated the adsorptive removal potential of prepared nanoparticles to be: AP-SiO2 + Fe/Co>AP-SiO2 + Fe>CM (commercial) SiO2 + Fe>AP-SiO2 + Co> AP-SiO2 + Fe/Pt> AP-SiO2 + Pt. Lower pH helped in accelerating the reactive removal of TNT on zero valent iron loaded silica. AP-SiO2 + Fe/Co system showed the maximum adsorption potential (74 mg/g) after five cycles. [ABSTRACT FROM AUTHOR]

Abstract The Dubinin–Radushkevich (D–R) isotherm model was frequently applied in adsorption equilibrium studies. However, its mathematical characteristics with respect to the parameter β and the correct calculation of the adsorption potential ε have still not been discussed. In this work, attempts have been made to address these problems. This work indicated that the D–R isotherm model represented three types of the isotherm curves: S-, L- and H-shaped isotherm. The logarithmic term must be dimensionless in the formula of the adsorption potential. A misconception pertaining to the calculation of the adsorption potential in past publications was identified to avoid the repetition of this mistake in future publications. The author hopes that this work will help readers to better understand the D–R isotherm model. Highlights • Shape and curvature of the isotherm curves depend on β for the D–R isotherm model. • D–R isotherm model can represent different types of the isotherm curves. • Correct calculation of the adsorption potential is discussed in detail. [ABSTRACT FROM AUTHOR]

The formation of solid solutions (alloys) is a well-established route for tuning the functional properties in materials science, e.g. steels, semiconductors, ceramics. As will be discussed below in this contribution, it appears as a convenient way to control the pore windows accessibility and surface properties. This study illustrates the tuning of the adsorption potential for aromatic hydrocarbons through the formation of solid solutions of Co(II) and Zn(II) imidazolates. The best separation capability and the highest adsorption heats were observed for the mixed compositions (alloys). The random substitution of Zn by Co atoms in the network of zinc methyl-imidazolate, and vice versa, create anisotropies in the metal coordination environment, which are responsible for the appearance of local electron field gradients. This is equivalent to an increase for the adsorption potential able to interact with molecules (adsorbates) with dipole and/or quadrupole moments. Such hypothesis was corroborated for the separation of benzene, toluene and p -xylene, three molecules with quadrupole moments. The highest adsorption heat values for these adsorbates correspond to the solid solution containing Zn and Co. The materials under study were characterized from chemical analysis, X-ray diffraction data, thermal analysis, and specific surface measurements. [ABSTRACT FROM AUTHOR]

Methane adsorption capacity of coal is one of the major factors influencing total gas-in-place and it is linked to coal structure, while our knowledge of it is still limited. In this study, coal structures were classified into five categories, including integrated, blocky, cataclastic, granulated and mylonitized. The integrated and blocky coals are intact and the other three are deformed. To investigate the methane adsorption capacity, adsorption potential and surface free energy of different structure coals, four high rank coal samples were collected from No.3 coal seam of the Zhaozhuang coal mine in Southeastern Qinshui Basin China, and a series of methane isothermal adsorption experiments and pore distribution measurements were carried out in the laboratory, and then the adsorption potential and the surface free energy were analyzed. It turns out that, there are no obvious differences in the methane adsorption capacity for the various structure coals when the equilibrium pressure is below 2 MPa; while there are significant differences when the pressure is above 2 MPa. The higher the gas pressure is, the greater the difference is. Methane adsorption capacity of different structure coals can be arranged in a descending order: mylonitized>granulated>cataclastic>intact. That is, the methane adsorption capacity is higher for the deformed coal samples than for the intact ones. Both the specific surface area and the pore volume increase with the increase of deformation degree. Mesopores contribute most to the total pore ​​volume; while the adsorption pores have the greatest contribution to the total specific surface area. The adsorption potential and surface free energy for different-structure coals under the same adsorption space volume increase with the increase of deformation degree. Adsorption potential decreases with the increase of adsorption space, and the adsorption potential of micropore is considerably higher than that of mesopore and macropore. As the temperature rises, the cumulative reduction of surface free energy decreases and the surface free energy decreases significantly at each equilibrium pressure. Methane adsorption in coal is dominated by adsorption potential and surface free energy. [ABSTRACT FROM AUTHOR]

Since the parameter k has a great arbitrariness in hypothetical saturation-vapor pressure P0 calculation，the adsorption potential theoretical model，which contains the two indexes P0 and adsorbed-phase density ρa，has a low-precision description in the field of coal-methane adsorption. In this paper，a series of adsorption equilibrium experiments of methane on different coals (low-to medium-grade metamorphic tectonic and its intergrowth untectonic coal samples) were separately conducted at a wide temperature range. Adsorption isotherms from the experiment data were applied to respectively calibrate the P0 and ρa of each coal-methane adsorbed system，and then an adsorption characteristic curve of different adsorbed systems has been derived. It is found that P0 via the k value is closely related with the adsorption characteristics curve，and each coal sample has its own ‘the optimal k value’，such as kP1N=3.2，kP1D=3.4，kP8N=3.1 and kP8D=3.0.Lastly，the coal-methane adsorption isotherms at the temperatures of 243，283，303 and 323 K were forecasted base on the adsorption data at 313 K，and it demonstrates that the forecasted results via the P0，which comes from a combination of Amankwah' calculation，and the optimal k value could tally well with actual results. [ABSTRACT FROM AUTHOR]

The variations of kinetic energy and heat always occur in the process of coal adsorption to methane，and it is the internal dynamic of adsorption. Calculation of parameters related to the energy changes on the isothermal adsorption process were deduced. Data acquired from isothermal adsorption experiment were used to calculate the energy change on the adsorption process of coals with different coal-body structure at different temperatures，and the mechanism of energy change in the adsorption processes was discussed. Studies showed that mylonitized coals possessthe strongest adsorption capacity，then followed by granulated coals，cataclastic coals，and intact coals. Adsorption potential decreases with the increase of adsorption space，and the adsorption potential in microporesis much greater than that in mesopores and macropores，which explain the adsorption process first occurs in micropores. The adsorption potential and cumulative reduction value of surface free energy follow the rule:mylonitized coals>granulated coals>cataclastic coals>intact coals，Energy variation mechanisms in the process of coal methane adsorption was revealed. [ABSTRACT FROM AUTHOR]