Initial Temperature Research Articles

Numerical study of detonation propagation in a semi-confined nonuniform layer bound by an inert gas

This study investigates detonation propagation through a stoichiometric hydrogen-oxygen layer stratified above an inert gas, i.e., argon, with a diffuse interface at atmospheric pressure. A simple model capable of replicating the detonation inert gas diffuse layer interaction was developed that simulates previously conducted experiments. Detonation propagation is modeled by solving the two-dimensional reactive Euler equations for a calorically perfect gas with single-step Arrhenius chemistry. The acoustic impedance gradient associated with the argon diffusion into the hydrogen-oxygen results in a nonuniform initial density. Because of the perfect gas assumption, for a uniform initial pressure, as in the experiment, results in an initial temperature that is artificially nonuniform. The activation energy is adjusted for the imposed temperature nonuniformity in order to yield the correct ZND reaction zone length for the local argon dilution. Numerical soot foils are compared to experiments. Detonation propagation is possible due to the generation of triple points along the diffuse layer interface. These triple points, that generate new detonation cells, form from inflections in the reaction zones that develop because of the local increases in detonation strength.

Mechanisms and mechanical properties of high-temperature high-pressure sintered vanadium carbide ceramics

Vanadium carbide (VC) is extensively employed as a reinforcing agent in coating materials and a grain refiner in hard alloys, owing to its exceptional mechanical properties. A series of bulk VC ceramics were fabricated via high-temperature high-pressure sintering, followed by a comprehensive and systematic investigation of various properties of the sintered samples. The results revealed significant influences of processing temperature on the properties of sintered VC at 5.0 GPa. However, the exact nature of temperature dependence varied depending on the specific property. It was found that VC ceramics sintered at 1100 °C and 5.0 GPa exhibited the best overall performance, providing a relatively optimal temperature condition for synthesis. The Vickers hardness of the material reached an astonishing 43.2 GPa under a 9.8 N load, placing it within the category of superhard materials. However, the sintered sample exhibited a gradually lower hardness value of 30.4 GPa under a higher load of 29.4 N. Highly dense with a relative density of 99.8%, exhibiting near full density, the vanadium carbide ceramics possess an impressive Young's modulus of 544 GPa, indentation fracture resistance of 5.4 MPa m1/2, and an oxidation initiation temperature of 758 °C. This study offers practical guidance for the design of novel transition metal carbide superhard materials and provides valuable insights for the exploration of visualizing directions in the next generation of superhard materials.

Hybrid sensible-latent heat thermal energy storage using natural stones to enhance heat transfer: Energy, exergy, and economic analysis

Latent heat thermal energy storage addresses the mismatch between energy supply and demand; however, phase change materials (PCM) commonly have the issue of low thermal conductivity. Natural stones, as low-cost and environmentally friendly sensible heat storage media, are used to enhance the heat transfer of the PCM in the current study. Different stone types, sizes, and filling heights are tested, and a comprehensive energy, exergy, and economic analysis is performed. Results indicate that granite has the best heat transfer enhancement performance owing to superior thermal diffusivity, which accelerates the melting by 108 % (initial temperature: 23 °C; heating temperature: 75 °C). Basalt with high specific heat contributes to the large energy capacity. The total exergy is hardly influenced by the stone size ranging from 15 mm to 40 mm, where the minimum is only 5.1 % lower than the maximum. The exergy storage rate benefits from stones surrounding the inner tube and is increased by 246 % with a filling height of 112.0 mm. The 40 mm-sized stones are the most cost-effective in the current testing conditions, and a 560 % increase in the economy is achieved. This study demonstrates a high-performance, low-cost, environmentally friendly energy storage configuration and provides comprehensive information for potential energy recovery applications.

Effect of fluid-particle interaction on 2D Rayleigh-Bénard laminar convection of a temperature-sensitive magnetic fluid

Rayleigh-Bénard (R–B) laminar convection of a temperature-sensitive magnetic fluid (TSMF) with an immersed nonmagnetic particle in a square cavity heated from the bottom and subject to an external magnetic field is investigated experimentally and numerically, which restricts to the initial constant temperature and stationary flow fields with perfect thermal insulated wall condition. The flow and particle behaviors as well as the heat transfer characteristic are examined at different Ra (Ra < 4 × 104) and Ram (Ram = 0, 1.89 × 108, and 3.14 × 108). The magnetic field slightly precipitates the onset of convection and the transition of the flow pattern. The particle may influence the early flow development and the final flow pattern, depending on the initial location of the particle, Ra, and Ram. Over certain ranges of the parameters, the particle stabilizes the flow by shifting the higher flow mode (bicellular) to the lower one (unicellular) and improves the heat transfer performance. The numerical results confirm the experimental findings and provide more detailed behaviors of the flow and temperature fields as well as the particle.

Adsorption characteristics of nickel (II) from aqueous solutions by Zeolite Scony Mobile-5 (ZSM-5) incorporated in sodium alginate beads

Nickel, a prevalent metal in the ecosystem, is released into the environment through various anthropogenic activities, leading to adverse effects. This research explored utilizing zeolite scony mobile-5 (ZSM-5) nanoparticles encapsulated in sodium alginate (SA) for nickel (II) removal from aqueous solutions. The adsorption characteristics of SA/ZSM-5 were examined concerning contact duration, initial metal ion concentration, pH level, temperature, and sorbent dosage. The findings revealed that a rising pH reduced Ni (II) uptake by the sorbent while increasing the Ni (II) concentration from 25 to 100 mg L−1 led to a decrease in removal percentage from 91 to 80% under optimal conditions. Furthermore, as sorbent dosage increased from 4 to 16 g L−1, uptake capacity declined from 9.972 to 1.55 mg g−1. Concurrently, SA/ZSM-5 beads' Ni (II) sorption capacity decreased from 96.12 to 59.14% with a temperature increase ranging from 25 to 55 °C. The Ni (II) sorption data on SA/ZSM-5 beads are aptly represented by Langmuir and Freundlich equilibrium isotherm models. Moreover, a second-order kinetic model characterizes the adsorption kinetics of Ni (II) on the SA/ZSM-5 beads. A negative free energy change (ΔG°) demonstrates that the process is both viable and spontaneous. The negative enthalpy values indicate an exothermic nature at the solid–liquid interface while negative entropy values suggest a decrease in randomness. In conclusion, this novel adsorbent exhibits promise for removing nickel from aqueous solutions and could potentially be employed in small-scale industries under similar conditions.

Clumped isotope reordering kinetics in strontianite and witherite: Experiments and first-principles simulations

The carbonate clumped isotope (∆47) thermometer is a powerful tool for temperature reconstruction based on the thermodynamical 13C—18O bonding preference. Accurate interpretation of temperatures requires preservation of original carbonate ∆47 signatures, which are susceptible to resetting at elevated temperatures during burial. Kinetic models of carbonate 13C—18O bond reordering derived from experimental studies constrain the evaluation of ∆47 preservation and the reconstruction of thermal histories and initial temperatures for reordered carbonates. However, application of these models to different carbonates is limited because kinetic parameters vary with materials and are believed to be affected by factors such as crystal structure, cation, trace element composition, crystal defects, and internal water whose roles in reordering are still not well-understood. Here we present reordering data for strontianite and witherite from heating experiments and evaluate the effects of crystal structure, cation chemistry, cation vacancy and substitution, and internal water on reordering using constrained ab-initio molecular dynamics (cAIMD) simulations. We show that strontianite and witherite reorder significantly faster than other carbonates. Comparing experimental studies yields the following reordering rate sequence: strontianite > witherite > aragonite > calcite > dolomite. The general trend in Arrhenius activation energy for reordering is strontianite < witherite < aragonite < dolomite < calcite (with calcite values based on the average of individual materials). Our cAIMD simulations reveal a similar trend in free energy of activation for oxygen exchange in these carbonates. We suggest that orthorhombic carbonates are more susceptible to reordering than trigonal carbonates because of the shorter distance between carbonate groups and because the weaker M—O interaction in orthorhombic carbonates reduces the structural distortion and the energy cost during transition state formation. For carbonates sharing the same structure, the weak M—O bonding can be compensated by a large unit cell volume, leading to a non-systematic relationship between the free energy of activation and the cation radius. In simulations with lattice-bound water, the free energy of activation is greatly reduced compared with cation vacancy and substitution. The influence of fluid inclusions on measured reordering rates depends on the fraction of carbonates that can exchange with water as suggested by strontianite δ¹⁸O data. Our results serve as a starting point for a more sophisticated but flexible kinetic model containing material-specific factors (e.g., substituted ions, structure water, etc.) for reordering in abiotic and biotic carbonates.

Fabrication and characterization of magnetic cobalt ferrite intercalated chitosan grafted polyaniline ternary nanocomposites for removing some heavy metals simultaneously

Chitosan grafted polyaniline (Ch-g-PANI) loaded with different concentrations of cobalt ferrite magnetic (CoFM) nanoparticles (2, 5 and 10 wt%) to form (Ch-g-PANI/CoFM) nanocomposites were fabricated. X-ray diffraction (XRD), High-Resolution Transmission Electron Microscope (HRTEM), Scanning Electron Microscope (SEM), Energy-Dispersive X-ray (EDX), Fourier transform inferred (FT-IR), and Vibrating Sample Magnetometer (VSM) were carried out to investigate the structure, morphology, chemical composition, and magnetic properties of Ch-g-PANI and Ch-g-PANI/CoFM) nanocomposites. Adsorption performance of these prepared samples towards heavy metals (Pb2+, Cu2+, Fe3+, Cd2+, Li1+, Co2+, Al3+, Mn2+, Zn2+, Ni2+, Cr2+, and V2+) was investigated. The effects of CoFM NPs concentraion doped in grafted polymer, initial metal concentration, temperature, pH, and contact time on heavy metal removal efficiency were optimized. SEM revealed abundant pores for optimum sample that enhance the heavy metal removal efficiency. Competitive adsorption tests proved that Ch-g-PANI/CoFM5 NPs showed higher efficiency for tested heavy metals. The removal efficacy of optimum sample (Ch-g-PANI/CoFM5) reached maximum values 98, 95.3, 96, 99.2, 97, 99.9, 88, 94.4, 99.8, 93.4, 98.96, 93, and 93.9 % for Pb2+, Cu2+, Fe3+, Cd2+, Li1+, Co2+, Al3+, Mn2+, Zn2+, Ni2+, Cr2+, and V2+, respectively at 90 min(equilibrium time), the element ions concentration of 10 mg/L and pH range of 4–6 depending on the kind of metal ions. Freundlich model is the best isotherm model for the equilibrium data, suggesting the multilayer adsorption on the heterogeneous surface. The kinetic data specified that the pseudo-first-order model fitted the adsorption of heavy metal ions on Ch-g-PANI/CoFM5. Thermodynamic studies elucidated the feasible, spontaneous, random, and endothermic adsorption. From an economic viewpoint, the regeneration study implied that the optimal sample Ch-g-PANI/CoFM5 was efficiently recovered up to four successive cycles.

Towards understanding the crack suppression mechanism in brittle materials with high grinding speed at different temperatures

Ductile-regime grinding has been used to eliminate the formation of subsurface cracks by setting an extremely small depth of cut (DOC). The critical DOC is affected by multiple factors, including the grinding speed and material temperature. The underlying mechanism of DOC affected by the grinding speed is still unclear. To reveal the role of grinding speed and material temperature during the formation of cracks, we conducted a series of single-point grinding experiments with the different grinding speeds (26.7–192.3 m/s) and the initial material temperatures (25–200 °C). The experimental results showed that cracks were suppressed with an increase in the grinding speed and initial material temperature even when the DOC was much deeper than the critical DOC determined by the ductile-regime grinding. To understand the mechanisms underlying crack nucleation and suppression, we conducted systematic molecular dynamics simulations. Both simulation and experimental results showed that a crack can be formed by a single slip band. The crack nucleates from a microvoid within the slip band. With the aid of the local tensile stress on one side of the slip band tip, the crack nucleation forms an opening crack. The crack suppression is primarily caused by the high‐pressure field during high‐speed grinding, where the high‐pressure field superposes the local tensile stress to forming a compressive stress state that prevents crack nucleation. In addition, the brittle‐ductile transition is induced by the high temperature on the surface during high‐speed grinding. This study provides insights into building the DOC criterion for different grinding speeds and temperatures based on a ‘bottom-up’ approach.

Highly efficient removal of tetracycline and methyl violet 2B from aqueous solution using the bimetallic FeZn-ZIFs catalyst

Abstract Residual antibiotics and organic dyes in wastewater have gained the current challenge all over the world because of their toxicity to humans and the environment. In this study, the bimetallic porous FeZn-ZIFs materials were successfully prepared under mild conditions at room temperature and atmospheric pressure and characterized by various techniques. The FeZn-ZIFs were used as a heterogeneous catalyst to remove tetracycline antibiotics (TC) and methyl violet 2B dyes (MV) in an aqueous solution by activating peroxymonosulfate (PMS) and peroxydisulfate (PDS), respectively. The catalytic activity of FeZn-ZIFs towards TC and MV under different oxidant dosages, the catalyst dosage, the initial pollutant concentration, contact time, and reaction temperature were optimized. The results indicated that FeZn-ZIFs was an efficient catalyst for removing TC and MV based on advanced oxidant processes, having a removal capacity of 92% at TC concentration of 50 mg·L−1 and 95% MV concentration of 20 mg·L−1. More importantly, this bimetallic catalyst was identified the superior structural stability when the removal efficiency of TC and MV was maintained at approximately 90% after five cycles. In short, the FeZn-ZIFs and PMS/PDS system exhibited a promising application prospect for antibiotic and dye-containing wastewater treatment.

Relationship between higher estrus-associated temperatures and the bovine preovulatory follicular fluid metabolome

IntroductionA higher estrus-associated temperature (HEAT) is a hallmark feature in sexually active females; however, its functional importance is unclear. Our objective was to examine the relationship between HEAT and the preovulatory follicular fluid metabolome. It was hypothesized that HEAT is functionally important as it affects fertility-related components in the preovulatory follicle.MethodsEstrus was synchronized in non-lactating Jersey cows. A Thermochron iButton temperature data logger was affixed to blank controlled internal drug release (CIDR) devices and intravaginally inserted after CIDR device removal. The follicular fluid was aspirated 14.9 h + 3.3 h after an animal first stood to be mounted. Regression models were performed using metabolite abundance and HEAT variables. Best-fit models were determined using backward manual selection (p &amp;lt; 0.05).ResultsA total of 86 metabolites were identified in cow follicular fluid samples. The vaginal temperature at first mount and when it was expressed as a change from baseline was positively related to the abundance of four metabolites (i.e., taurine, sn-glycerol 3-phosphate, glycine, and cysteine) and negatively related to one metabolite (i.e., serine). The vaginal temperature at the first standing mount was related to the differential abundance of two metabolites (i.e., jasmonate and N-carbamoyl-L-aspartate). Three metabolites were related to the maximum vaginal temperature (i.e., N-carbamoyl-L-aspartate, uracil, and glycodeoxycholate). When expressed as a change from baseline, the maximum vaginal temperature was related to the differential abundances of uracil, uric acid, and 6-phospho-D-gluconate. The time taken to reach maximum vaginal temperature was related to N-carbamoyl-L-aspartate, glycodeoxycholate, jasmonate, and tricarballylic acid. Pertaining to the combination of HEAT and its duration, the area under the curve associated with the time between the first increase in vaginal temperature and the maximum vaginal temperature was related to 6-phospho-D-gluconate, sulfolactate, guanidoacetic acid, and aspartate. The area under the curve associated with the time between the initial vaginal temperature increase and up to 10 h after a cow first stood to be mounted or when a cow’s temperature returned to baseline was related to the differential abundances of uracil, sn-glycerol 3-phosphate, methionine sulfoxide, and taurodeoxycholate.DiscussionOur findings support the notion that HEAT is related to changes in the preovulatory follicular fluid metabolites involved in energy metabolism, thermoregulation, and oxidative stress management.

Study on thermal effects of high-power laser-coupled water jets and the influence on the stability of water jets

In water-guided laser technology, the stability of water jets is crucial to ensure the efficient transmission of laser energy. However, the thermal effects generated when high-power lasers are coupled with water jets are bound to impact the stability of the water jets, thus becoming a critical issue that restricts the development of high-power water-guided laser technology. In addressing this issue, this paper establishes a temperature model for coupling high-power lasers with water jets. Subsequently, with validation of the model's effectiveness through experimental data, simulations are conducted to analyze the temperature distribution within the water jet. During the simulation process, lasers with different parameters were coupled with water jets to analyze the temperature variation law of the water jets. Additionally, the maximum laser power coupled with water jets of different lengths was solved. Based on the calculated temperature values of the water jet, simulate the evolution of its profile over time when it has an initial temperature gradient. Simultaneously, perform a three-dimensional reconstruction of the obtained perturbed profile and conduct ray tracing to analyze the laser's transmission losses within the perturbed profile. Finally, high-speed cameras are utilized to capture the profile of the water jet, validating the laser-induced fragmentation behavior in the water jet. The research findings will provide a significant reference value for selecting laser parameters and controlling thermal effects in water-guided high-power technology.

Analysis of factors influencing the temperature field variation in mass concrete during hydration heat release

Mass concrete is prone to cracks due to the temperature difference between the inside and outside. In this study, the effects of four factors, including the ambient temperature, initial temperature of concrete after pouring, and cooling water temperature and flow rate, on the variation characteristics of the internal temperature field of mass concrete are investigated using a combination of theoretical, empirical, and numerical simulation analyses. The results show that the service life of concrete can be prolonged by lowering the ambient temperature, lowering initial temperature of concrete after pouring, increasing the cooling water temperature or increasing the cooling water flow rate, which can effectively improve the cooling rate of concrete. The temperature difference between the inside and outside of the concrete can be effectively reduced by increasing the ambient temperature, increasing the cooling water flow rate, lowering initial temperature of concrete after pouring, or lowering the cooling water temperature, thus reducing the possibility of cracks. Through Grey relation analysis, it is found that cooling water temperature is the most important influencing factor that affects the changing characteristics of the internal temperature field of concrete The influencing factor weights can be used to provide theoretical support for subsequent temperature control measures.

Poly (Vinyl Alcohol) Hydrogels Boosted with Cross-Linked Chitosan and Silver Nanoparticles for Efficient Adsorption of Congo Red and Crystal Violet Dyes.

In our previous work, three different weight ratios of chitosan/PVA (1:3, 1:1, and 3:1) were blended and then cross-linked with trimellitic anhydride isothiocyanate (TAI) at a concentration depending on their chitosan content, obtaining three hydrogels symbolized by H13, H11, and H31. Pure chitosan was cross-linked with TAI, producing a hydrogel symbolized by H10. Further, three H31-based silver nanoparticles composites (H31/AgNPs1%, H31/AgNPs3%, and H31/AgNPs5%) were also synthesized. They were investigated, for the first time in this study, as adsorbents for Congo Red (CR) and Crystal Violet (CV) dyes. The removal efficiency of CR dye increased with increasing H10 content in the hydrogels, and with increasing AgNP content in the composites, reaching 99.91% for H31/AgNPs5%. For CV dye, the removal efficiency increased with the increase in the PVA content. Furthermore, the removal efficiency of CV dye increased with an increasing AgNP content, reaching 94.7% for H31/AgNPs5%. The adsorption capacity increased with the increase in both the initial dye concentration and temperature, while with an increasing pH it increased in the case of CV dye and decreased in the case of CR dye. The adsorption of CV dye demonstrated that the Freundlich isotherm model is better suited for the experimental results. Moreover, the results were best fitted with pseudo-second-order kinetic model.

Improved physical, thermal, and biological properties of green synthesized Ag-containing nanocomposites of a novel chitosan-based blend

Different material compositions are being prepared to improve the physiochemical properties of chitosan biopolymer and thus to create new areas of use. This study presents new chitosan(CS)-based products based on synthetic polymers and biosynthesized AgNPs, prioritizing environmentally friendly synthesis methods. Methacrylate-based functional CP copolymer was prepared by the free radical polymerization method. Thanks to the amide, ester groups, and fluorine atoms in the side branch of the CP, a compatible polymer blend (CS-CP) was prepared by the environmentally friendly hydrothermal method through hydrogen bonds with CS. Again, with green synthesis applications, AgNPs were prepared from Prunus spinosa extract by hydrothermal method, and new nanocomposites were produced by adding CS-CPs at different weight ratios. The initial decomposition temperature of 245 °C, which indicates the thermal stability of CS-CP as determined by TGA, was increased to 268 °C with the addition of 7 % AgNPs. Adding CP to CS lowered the glass transition temperature, and this trend continued in nanocomposites with the addition of AgNPs. When CP was blended with CS, the oxidative stress index of CS increased from 18.26 AU to 65.45 AU. It was determined that this oxidative effect increased up to 181 AU when AgNPs were added. Thanks to this feature of the produced nanocomposites, it was found that the MIC (100–250 µg/mL for E. coli, 250–500 µg/mL for S. aureus and for 500–1000 µg/mL C. Albicans) values of CS against microorganisms decreased, and the antimicrobial activity increased. In addition, in studies with cancer (A549 and G361) cells, it was determined that even at low (25 µg/mL) doses, nanocomposites that included 5 % and 7 % AgNPs in their formula had anticarcinogenic activity. Further studies on biocompatibility may be recommended to confirm possible commercial benefits from the materials produced in future research.

Chitosan-based molecularly imprinted sponge for selective recognition and recycling of dibenzothiophene from diesel

Recycling of high value-added dibenzothiophene (DBT) from diesel using adsorption technology is a convenient and economical strategy to realize “Resources Reuse”, but the conventional adsorbents have the disadvantages of low adsorption selectivity and difficult retrieval. Herein, in this study, we elaborately designed and constructed a chitosan-based molecularly imprinted sponge (CS-MIS) with three-dimensional network structure via a bulk polymerization-lyophilization protocol. Batch adsorption experiments were conducted three replications to appraise the potential of CS-MIS for DBT adsorption. The influence of adsorbent dosage, initial DBT concentration, adsorption time and temperature on the adsorption performance were systematically investigated. The adsorption experimental results showed that CS-MIS exhibited a superior maximum adsorption equilibrium capacity of 15.17 mg/g for DBT compared to the chitosan-based non-imprinted sponge (CS-NIS; 6.34 mg/g). The DBT adsorption on CS-MIS coincided well with the pseudo-second-order kinetic and Langmuir isotherm models. The selective tests in the presence of multiple interfering molecules indicated the remarkable selective recognition of CS-MIS toward DBT with the relative selectivity coefficients for benzothiophene, indole, and fluorene of 1.99, 2.28, and 1.41, respectively. The notable selectivity of CS-MIS for DBT adsorption were mainly attributed to the imprinted sites matched well with DBT geometry on the surface of CS-MIS. Additionally, CS-MIS exhibited the excellent regeneration performance.

Research on wear rate of train brake pads driven by small sample data

Increased wear leads to the failure of brake pads. Both the International Union of Railways (UIC) and the China Railway Production Certification (CRCC) take wear rate as an extremely important parameter that characterizes the degree of wear, and its value can provide reference for the braking performance of the brake pads. Since the braking performance test of brake pads is time-consuming and costly, the sample data of wear rate is small. In this study, we explore the coupling relationship between the wear rate of train brake pads and its features such as initial braking speed (IBS), braking pressure (FB), braking temperature and average coefficient of friction (ACOF), and propose a Butterfly Optimization Algorithm-Back Propagation (BOA-BP) method suitable for small sample data for the wear rate prediction of brake pads. The grey relational analysis (GRA) and Pearson correlation analysis (PCA) are used to arrive at preferred features for the prediction of wear rate of brake pads, such as IBS, FB, braking distance and ACOF. The dynamic GM(1, N) and the least square method are used for sample expansion. Furthermore, the wear rate is designated as the output feature parameter and the preferred features are designated as the input feature parameters, a BOA-BP model is established for predicting the wear rate of brake pads. The results show that the wear rate obtained by dynamic GM(1, N) is consistent with the actual braking test, the maximum temperature and the braking pressure are important factors affecting wear rate. Compared to the comparison methods such as PSO-BP, GA-BP, and BP, the BOA-BP exhibits better advantages in prediction with small samples, and the average prediction accuracy with 33 sets of data and 99 sets of data are 95.70 % and 97.21 % respectively.

Numerical study of the gas production process from a gas hydrate deposit in the presence of thermal and depression effects

Today the issue of gas production technology from existing gas hydrate deposits discovered on the shelf of the World Ocean and in permafrost areas is still very significant since the methane reserves in the free state are significantly inferior to its reserves in the form of its gas hydrates. One of the tasks for possible gas production from a hydrate-containing porous medium is to study the process of gas hydrate decomposition under thermal and depression effects since they are most commonly used ones. It is necessary to conduct a theoretical study including the development of a mathematical mode and its algorithmization, the creation of a computational program and the conduct of numerical experiments. The paper presents one-dimensional axisymmetric problem of heating and/or pressure reduction at the bottom of a well passing through the entire thickness of a porous formation when its pores are initially filled with methane and its hydrate. The utilized mathematical model includes the continuity equations for methane, its hydrate and water; the equation of the gas phase motion in a porous medium as the Darcy filtration law; the state equation of methane and water, the energy conservation equation considering the Joule–Thomson effects and adiabatic cooling for gas, the latent heat of the “gas hydrate  methane + water” phase transition. A numerical implementation of the proposed mathematical model and a numerical study of the thermal and/or depression impact on the studied hydrate-bearing deposit are carried out. The results of calculations show that the size of a zone containing only the gas hydrate decomposition products (gas and water) slightly increases with a smaller length of a porous layer. They also show that the thermal effect (increasing the temperature at the bottomhole of production well) on the hydrate-saturated reservoir simultaneously with the depression effect is not efficient enough due to the intensive flow of cold gas (with a temperature equal to the initial temperature of the reservoir) from the hydrate-containing deposit to the well.

Study on the Adsorption/Desorption Characteristics of Protogenetic CO in Coal Seams

ABSTRACT In recent years, abnormal CO gas overruns have often occurred in coal mining workings. CO overruns were thought to be caused by the underground blasting work or spontaneous combustion of coal seams; however, minimal attention has been given to the causes of the desorption and release of adsorbed CO in the coal seams. Additionally, insufficient research has been conducted on the generation, distribution and adsorption and desorption characteristics of protogenetic CO in coal seams. Therefore, a self-built comprehensive testing system for coal seam adsorption and desorption was used to study the characteristics of the depressurization desorption and thermal desorption of coal with different degrees of metamorphism during coal seam mining. The results showed that under isothermal conditions, the amount of CO adsorption and desorption of coal samples increased with increasing pressure; under temperature rise conditions, the gas adsorption-desorption was in a dynamic equilibrium process under certain conditions. When the temperature increased, the equilibrium was beneficial to the desorption direction. The initial temperature range of CO production at different equilibrium pressures was 45–55°C. With increasing pressure, the initial temperature point of CO gas production moves forward and was significantly lower than the initial temperature of coal spontaneous combustion. Our research results further supplement the source of underground protogenetic CO gas and provide theoretical support for the accurate prediction of CO coal spontaneous combustion.

Adsorptive performance of bentonite-chitosan nanocomposite as a dual antibacterial and reusable adsorbent for Reactive Red 195 and crystal violet removal: kinetic and thermodynamic studies

AbstractHerein, bentonite-chitosan nanocomposite (BT-CS nanocomposite) has been synthesized and exploited, for the first time, as a dual adsorbent for the removal of both of an anionic (Reactive Red 195 (RR)) and a cationic (Crystal Violet (CV)) dyes from aqueous solution. The adsorption behavior of the exploited nano-adsorbent towards the dyes under investigation were scrutinized in batch experiments as a function of several factors such as contact time, pH value, adsorbent dose, initial dye concentration, stirring rate, and temperature. The prepared nano-adsorbent achieved superior removal efficiency of 99.4 and 99.8% within 20 min at optimum pH value of 3 and 5 using adsorbent dose of 0.1 g and 0.08 g at room temperature for RR and CV dyes, respectively. Also, the developed nano-adsorbent affords higher removal efficiency of CV dye against broad pH range of 2–9. Moreover, the developed nano-adsorbent achieved significant antibacterial behavior against various pathogenic bacterial and record clear inhibition zone of 21 mm against Escherichia coli (ATCC 8739). Langmuir adsorption model and pseudo-second order adsorption can fully depict the BT-CS nanocomposite adsorption properties for both of RR and CV dyes. Furthermore, thermodynamic studies showed that the process was spontaneous and endothermic with increased in randomness. The prepared dual adsorbent in this study exhibited reversible dyes adsorption with an excellent regeneration efficiency. Whereas, after 5 successive adsorption–desorption cycles, the adsorption efficiency of the synthesized adsorbent was 99% and 98% for RR and CV dyes, respectively, affirming its capability to economically decontaminate the industrial wastewater comprising RR and CV dyes. Graphical Abstract

Zn-Al layered double hydroxide/zeolitic imidazolate framework-8 nanocomposite as a high-performance sorbent for adsorption and desorption of anticancer drugs from aqueous media

Zn-Al layered double hydroxide/zeolitic imidazolate framework-8 (Zn-Al LDH/ZIF-8) nanocomposite was synthesized through growing zeolitic imidazolate framework-8 (ZIF-8) on Zn-Al layered double hydroxide and employed as an effective pollutant adsorbent. The nanocomposite was utilized for the removal of Ifosfamide (IF) and cyclophosphamide (CK) anticancer drugs from aqueous matrices. Zn-Al LDH/ZIF-8 nanocomposite was characterized via different analyses such as Brunauer-Emmett-Teller, X-ray diffraction, X-ray photoelectron spectroscopy, Energy-dispersive X-ray spectroscopy, Elemental mapping, Fourier-transform infrared spectroscopy, Field emission scanning electron microscopy, Transmission electron microscopy, Thermogravimetric analysis, and Contact angle measurement. Batch experiments were implemented to investigate the parameters affecting the adsorption process, including adsorbent loading, pH value, ionic strength, initial pollutant concentration, temperature, and impurity. The experimental results were analyzed using various models to determine the adsorption mechanism, thermodynamics, isotherm, and kinetics. The Langmuir isotherm model presented higher consistency with the experimental data (R2 >0.990). The saturation adsorption capacity of the nanocomposite for IF and CK drugs, obtained as 929.66 and 888.94 mg/g, respectively, was found to be higher than those for ZIF-8 (759.70 and 724.53 mg/g, respectively) at a temperature of 298 ± 1 K and pH of 7.5 ± 0.1. The kinetic data had a better fit with the pseudo-second-order kinetic model (R2 >0.980). Thermodynamic studies revealed that the adsorption process was exothermic and spontaneous. The mechanism of adsorption was attributed to electrostatic interactions, hydrophobic forces, H-bonding, π-π stacking, and π-π electron-donor acceptor. Additionally, after performing four adsorption-desorption cycles, the nanocomposite indicated only a 9.3% reduction in the adsorption capacity, demonstrating the promising potential of this, for industrial applications.