Gas Stream Research Articles

Rubbery organic frameworks (ROFs) toward ultrapermeable CO2-selective membranes.

The capture of CO2 is of high interest in our society representing an essential tool to mitigate man-made climate warming. Membrane technology applied for CO2 capture offers several advantages in terms of energy savings, simple operation, and easy scale-up. Glassy membranes are associated with low gas permeability that negatively affect on their industrial implementation. Oppositely, rubbery membranes offer high permeability, but their selectivity is low. Here we report rubbery organic frameworks (ROFs) combining the high permeability of soft matrices with the high sieving selectivity of molecular frameworks. The best performing membranes provide a CO2/N2 selectivity up to 104 with a CO2 permeability up to 1000 Barrer, representing relevant performances for industrial implementation. Water vapors have a positive effect on CO2 permeability, and the CO2/N2 selectivity is higher than in dry conditions, as most of CO2 gas emissions are present in fully humidified gas streams. The synergetic high permeability/selectivity performances are superior to that observed with current state-of-the-art polymeric membranes.

Ore sulfur of Golovnin Volcano, Kunashir Island

Research subject. Hydrothermal deposits of Golovnin Caldera. Aim. To study the epithermal volcanogenic ore formation. Key points. Until now, there has been a consensus on the exogenous sedimentary (colloidal) genesis of sulfur in volcanic lakes. Our observations and microstructure studies indicate the presence of sulfur melt at the bottom of Kipyaschee Lake. Drops of this melt are carried to the surface of the lake as part of a light gray foam. The significant differences of sulfur spherules in the concentration of sulfide mineralization, in its composition, as well as in the presence or absence of numerous opal inclusions are most simply explained by the capture of droplets in various parts of the sulfur melt and their subsequent movement by a gas stream passing through the melt. Elemental sulfur condensate is formed in bottom sediments as a result of forced cooling of endogenous gas flows by lake water. The main condensation of sulfur occurs here (96% or more of the total potential of fluid sulfur). Residual condensation of sulfur occurs in the aquatic environment. Finely dispersed sulfur condensate in a mixture with water is unstable and breaks down over time with the release of hydrogen sulfide and the formation of sulfurous and sulfuric acids. The activity of bottom hydrotherms and coastal unrest prevents the formation of colloidal sulfur sediment at the bottom of lakes. In the crater depressions at the bottom of the lakes of the Golovnin Caldera, sulfidization of its melt occurs simultaneously with the condensation of sulfur itself. Gravitational deposition of sulfides in the sulfur melt leads to their enrichment of the root parts of crater depressions, where pyrite ore bodies are formed in real time. Terrestrial sulfur deposits, together with the modified rocks overlying them, demonstrate the full profile of endogenous apical oxidation under gas-hydrothermal action: sulfur and sulfur-opal rocks up the section are replaced by gypsum-jarosite rocks and, further, by an “iron hat” of limonite-cemented breccias of the dome mantle. Conclusions. Observations, microstructure studies and molecular chemical modeling indicate the endogenous condensate origin of ore sulfur in the Golovnin Caldera and exclude its exogenous sedimentary genesis.

CO2-free production of hydrogen via pyrolysis of natural gas: influence of non-methane hydrocarbons on product composition, methane conversion, hydrogen yield, and carbon capture

Methane pyrolysis represents a CO2-free hydrogen production route that enables simultaneous carbon capture. While the majority of previous studies in the field focus on pure CH4 as feed gas stream, commercial processes will typically rely on natural gas as feedstock that contains also non-methane hydrocarbons such as ethane, propane, and n-butane. Therefore, the present study evaluates how CH4 conversion, H2 selectivity, product composition, and solid carbon yield evolve when using either pure CH4 or synthetic natural gas (SNG) as feed gas stream for a thermal pyrolysis process in a lab-scale high-temperature reactor. For this, industrially viable conditions are applied, namely temperatures between 1000 °C and 1600 °C, residence times between 1 s and 7 s, and molar H2 dilution ratios between 1:1 and 4:1. Although the use of SNG results in slightly lower hydrocarbon conversions because the additional components in SNG result in a higher effective H2 dilution ratio compared to a CH4-only feed, the non-methane hydrocarbons in the SNG have a positive effect on both H2 selectivity and solid carbon yield. Taking existing mechanistic understanding into account, these positive effects are attributed to radicals formed from the non-methane hydrocarbons, which facilitate dehydrogenation steps from ethane to ethylene and hereby increase the relative amount of H2 originating from CH4. The introduction of a carbonaceous fixed bed further benefits the performance of the pyrolysis process and ultimately enables to capture more than 98% of carbon in its solid form under industrially viable process conditions.

Three-phase flow measurement by dual-energy gamma ray technique and static-equivalent multi-phase flow simulator

There is a strong desire to use three-phase flowmeters in upstream operations because of their small size, portability, and cost-effectiveness. Traditional three-phase flowmeterstypically employ two main strategies: fully separating the flow into liquid and gas streams and measuring them using common two- and single-phase meters, or simplifying the direct measurement requirements by homogenization.In order to achieve accurate measurements with these meters, it is necessary to first create a suitable simulator for generating various multiphase flow regimes with minimal systematic error. Developing such a simulator on a laboratory scale, rather than using expensive test loops is a crucial and practical option.In this research, SEMPF as a Static-Equivalent Multi-Phase Flow with flexibility in creating different multi-phase flow regimes is introduced. In the following, the mechanism of action is validated for both homogenous two- and three-phase mixtures by using dual-energy gamma ray attenuation technique in the Monte Carlo simulator environment. Finally, the three-phase component fraction measurement accuracy by dual-energy gamma meter in three different modes of gasoil-, water-, and air-continuous mixtures were investigated. The experimental results show the maximum accuracy of 2.03 %, 7.23 %, and 5.09 % for gasoil phase measurement in three different conditions that the carrier phase is air, gasoil and water respectively.

Conversion of C4F8 via plasma catalysis over Al2O3/Zr/SO4-2 catalyst: Effects of H2O(g)

Reducing the emission of octafluorocyclobutane (C4F8) which has a high global warming potential (GWP) of 10,300 is essential. This study investigated the effectiveness of C4F8 removal achieved with plasma catalysis system. Effects of Ar content in the gas stream and inlet C4F8 concentration on C4F8 conversion efficiency were evaluated with two types of catalysts including Al2O3 (A) and Al2O3 /ZrO2/SO42-(AZS). Results demonstrated a linear correlation between Ar content with C4F8 conversion, and energy efficiency (EE). Lissajous figure analysis coupled with BOLSIG + simulations revealed that the AZS catalyst applied increased the mean electron energy (MEE) to 2.68 eV and modified the electron energy distribution function (EEDF), likely contributing to its superior performance. At a C4F8 concentration of 400 ppm, the AZS catalyst coupled with plasma achieved 80 % conversion with an EE of 1.85 g/kWh. Interestingly, at an optimal inlet C4F8 concentration of 5,000 ppm, the highest EE (11 g/kWh) was obtained with a C4F8 conversion efficiency of 18 %. The addition of H2O(g) as a reactant resulted in complete C4F8 conversion when AZS catalyst was applied. The optimal plasma-catalytic conditions determined through C4F8 conversion, EE and CO2 equivalent (CO2e) assessments, yielded a CO2e emission (CO2e) to CO2 reduction (CO2r) ratio of 1:9.09. Product analysis revealed the formation of CO2, CO, and HF during C4F8 conversion with AZS catalyst in the presence of H2O(g). The system was operated at 12 kV for the gas stream containing 50 % Ar and N2 as carrier gas at a flow rate of 100 mL/min. These findings highlight the potential of plasma catalysis for the effective abatement of C4F8, offering a promising strategy for mitigating its environmental impact.

Unlocking glycerol Potential: Novel pathway for hydrogen production and Value-Added chemicals

In the global fight against climate change, the bio-based supply chain represents an interesting solution as it offers the potential to produce high-value-added products and bioenergy through the utilization of waste and by-products. In this work, a new route is proposed for the conversion of bio-based glycerol to H2/CO2 and high value-added liquid and solid products. The innovative process used pure or crude glycerol or ethanol-glycerol mixture along with water and sodium metaborate as reagents at 300 °C under discontinuous conditions. The gas stream consists mainly of hydrogen, followed by biogenic CO2 (31–54 %), CO (4–13 %) and CH4 in traces. The presence of water in the tested crude glycerol improved the hydrogen selectivity to 55 %. Characterization of the liquid reaction products revealed the synthesis of products such as 1,2-propanediol, propanoic acid, acetic acid, cyclopentenones and cyclic diglycerol. In the solid phase, an aliphatic hydrocarbon resin with oxygenated carbon along the saturated chain and an aromatic cluster were also characterized by NMR, FTIR and TG analyses. Based on these findings, the global reaction route to the general reaction products was proposed.

EXTREME TRANSLATIONAL IMPACT OF TRIPLE-SHOCK CONFIGURATIONS OF BLAST WAVES IN A CONFINED VOLUME OF AN ORBITAL STATION

The translational effects of gas streams, which form after the triple-shock configurations at Mach reflection of blast waves with normal main shock (so-called stationary Mach configurations), were analyzed. Unlike in the case of an elevated explosions of fuel as rocket starts in initially stagnant air, which is considered here as a private case, it was supposed that this shock-wave structure moves in a preceding flow with arbitrary velocity (and corresponding flow Mach number). Analyzing relations of the dynamic pressures across the slipstream, which emanates from the triple point of the Mach reflection, it was shown that the flows after the triple-shock configuration usually differ much in their translational action on surrounding objects. It was found and discussed that some configurations drag the objects initially situated above and below the triple-point trajectory in opposite directions. Moreover, the “trigger” structure was found that remains previous flow drag action on the object above the triple-point trajectory, but switches it to exactly opposite one, if the object is situated below the triple point.

Process swing adsorption with selective purge gas recirculation (PSA-SPUR): Adsorption process technology optimised for separation of heavy component from a gas mixture and its design for CO2 capture through Equilibrium Theory analysis

PSA-SPUR (Pressure Swing Adsorption with Selective Purge Gas Recirculation) has been developed aimed at separating the most strongly adsorbing component from a gas mixture at high product purity and recovery. The innovative strategy for designing a Pressure Swing Adsorption system features recycling its purge gas stream exiting the column and mixing it back into the feed. This operation enriches the mixed feed with an elevated fraction of the heavy component during the adsorption step, thus enhancing the PSA’s performance greatly. Reusing the purge gas helps significantly increase the product recovery compared to conventional methods where purge gas is simply discarded or taken as a low-quality product. For theoretical analysis of a PSA-SPUR system, a bespoke Equilibrium Theory model was developed and solved successfully, providing valuable insights into the performance of the PSA-SPUR system designed for capturing CO2 from a flue gas. The study revealed that there exists an optimum extent of purging that maximises the heavy component mole fraction in the mixed feed, leading to the best possible feed throughput of the adsorption system. Furthermore, the effects of the desorption pressure and feed composition on the PSA-SPUR system’s performance were investigated. The results indicate that the CO2 capture PSA-SPUR system using commercial zeolite 13X has excellent potential to achieve very high product purity and recovery, being allowed to operate at moderate vacuum pressures without having to compress the flue gas feed, even when the gas feed contains less than 10 mol% CO2.

Influence of Elevated Temperature and Oxygen on the Capture of Radioactive Iodine by Silver Functionalized Silica Aerogel

Reprocessing is considered a competent strategy for spent nuclear fuel management, yet radioiodine (129I) is emitted in reprocessing off-gas as a hazardous byproduct. Silver functionalized silica aerogel (Ag0-aerogel), a promising iodine capture material, experiences a reduction in its capacity after prolonged exposure to off-gas components at elevated temperatures, a phenomenon termed as aging. To fully understand this process, we isolated the contribution of each aging factor, exposing Ag0-aerogel samples to N2 and dry air gas streams, respectively, at 150°C for different time periods. Aged samples were loaded with I2 to examine the capacity change and comprehensively characterized to investigate the evolution of their properties. Results show that temperature alone did not alter Ag0-aerogel’s capacity but triggered Ag0 nanoparticles sintering and generated organic sulfur species. The presence of O2 reduced the capacity by ∼20%, causing (i) formation of silver sulfide (Ag2S) crystals and (ii) oxidation of Ag-thiolate (Ag-S-r) to Ag sulfonate (Ag-SO3-r). Given that Ag2S readily adsorbs I2, the formation of Ag-SO3-r is the major inhibitor for iodine adsorption. This hypothesis was supported by density functional theory (DFT) simulations. These findings unraveled key mechanisms of Ag0-aerogel aging, which are useful in the development of materials that withstand realistic spent-nuclear-fuel-reprocessing off-gas conditions.

Recent Advancements in Fe-Based Catalysts for the Efficient Reduction of NOx by CO.

The technology of CO selective catalytic reduction of NOx (CO-SCR) showcases the potential to simultaneously eliminate CO and NOx from industrial flue gas and automobile exhaust, making it a promising denitrification method. The development of cost-effective catalysts is crucial for the widespread implementation of this technology. Transition metal catalysts are more economically viable than noble metal catalysts. Among these, Fe emerges as a prominent choice due to its abundant availability and cost-effectiveness, exhibiting excellent catalytic performance at moderate reaction temperatures. However, a significant challenge lies in achieving high catalytic activity at low temperatures, particularly in the presence of O2, SO2, and H2O, which are prevalent in specific industrial flue gas streams. This review examines the use of Fe-based catalysts in the CO-SCR reaction and elucidates their catalytic mechanism. Furthermore, it also discusses various strategies devised to enhance low-temperature conversion, taking into account factors such as crystal phase, valence states, and oxygen vacancies. Subsequently, the review outlines the challenges encountered by Fe-based catalysts and offers recommendations to improve their catalytic efficiency for use in low-temperature and oxygen-rich environments.

Photocatalytic Semi-Hydrogenation of Acetylene to Polymer-Grade Ethylene with Molecular and Metal-Organic Framework Cobaloximes.

The semi-hydrogenation of acetylene in ethylene-rich gas streams is a high-priority industrial chemical reaction for producing polymer-grade ethylene. Traditional thermocatalytic routes for acetylene reduction to ethylene, despite progress, still require high temperatures and high H2 consumption, possess relatively low selectivity, and use a noble metal catalyst. Light-powered strategies are starting to emerge, given that they have the potential to use directly the abundant and sustainable solar irradiation, but are ineffective. Here an efficient, >99.9% selective, visible-light powered, catalytic conversion of acetylene to ethylene is reported. The catalyst is a homogeneous molecular cobaloxime that operates in tandem with a photosensitizer at room temperature and bypasses the use of non-environmentally friendly and flammable H2 gas feed. The reaction proceeds through a cobalt-hydride intermediate with ≈100% conversion of acetylene under competitive (ethylene co-feed) conditions after only 50 min, and with no evolution of H2 or over-hydrogenation to ethane. The cobaloxime is further incorporated as a linker in a metal-organic framework; the result is a heterogeneous catalyst for the conversion of acetylene under competitive (ethylene co-feed) conditions that can be recycled up to six times and remains catalytically active for 48 h, before significant loss of performance is observed.

CO2 capture enhancement by metal oxides impregnated coal fly ash: a breakthrough adsorption study.

Coal fired power plants are significant contributors to CO2 emissions and produce solid waste in the form of coal fly ash, posing severe environmental challenges. This study explores the application of dry-impregnated coal fly ash for CO2 capture from gas stream. The modification of coal fly ash was achieved using alkaline earth metal oxides, specifically CaO and MgO, to alter its physical and chemical properties. Characterization techniques like X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and BET (Brunauer-Emmett-Teller) analysis were employed for physio-chemical changes in the adsorbent. Breakthrough experiments were conducted using a laboratory-scale fixed packed-bed reactor to assess the influence of temperature and gas flow rate on CO2 adsorption. Among the synthesized sorbents, calcium oxide-impregnated ash showed the highest CO2 uptake capacity, achieving 9.41mg/g at 30°C and a flow rate of 20 L/hr under atmospheric pressure. Isotherm modeling indicated a heterogeneous adsorbent surface, with the data best fitting the Sips isotherm model. Furthermore, the adsorption data conformed well to the Yoon-Nelson and Thomas kinetic models, affirming their relevance in characterizing the adsorption process under varying conditions. This research emphasizes the potential of coal fly ash-an abundant, cost-free material-as an effective CO2 adsorbent, contributing to both CO2 mitigation and landfill waste reduction.

Continuous Biological Ex Situ Methanation of CO2 and H2 in a Novel Inverse Membrane Reactor (IMR)

A promising approach for carbon dioxide (CO2) valorization and storing excess electricity is the biological methanation of hydrogen and carbon dioxide to methane. The primary challenge here is to supply sufficient quantities of dissolved hydrogen. The newly developed Inverse Membrane Reactor (IMR) allows for the spatial separation of the required reactant gases, hydrogen (H2) and carbon dioxide (CO2), and the degassing area for methane (CH4) output through commercially available ultrafiltration membranes, enabling a reactor design as a closed circuit for continuous methane production. In addition, the Inverse Membrane Reactor (IMR) facilitates the utilization of hydraulic pressure to enhance hydrogen (H2) input. One of the process’s advantages is the potential to utilize both carbon dioxide (CO2) from conventional biogas and CO2-rich industrial waste gas streams. An outstanding result from investigating the IMR revealed that, employing the membrane gassing concept, methane concentrations of over 90 vol.% could be consistently achieved through flexible gas input over a one-year test series. Following startup, only three supplemental nutrient additions were required in addition to hydrogen (H2) and carbon dioxide (CO2), which served as energy and carbon sources, respectively. The maximum achieved methane formation rate specific to membrane area was 87.7 LN of methane per m2 of membrane area per day at a product gas composition of 94 vol.% methane, 2 vol.% H2, and 4 vol.% CO2.

Electrochemical and bioelectrochemical sulphide removal: A review

AbstractThe increased demand for energy worldwide and the focus on the green shift have raised interest in renewable energy sources such as biogas. During biogas production, sulphide (H2S, HS− and S2−) is generated as a byproduct. Due to its corrosive, toxic, odorous, and inhibitory nature, sulphide is problematic in various industrial processes. Therefore, several techniques have been developed to remove sulphide from liquid and gaseous streams, including chemical absorption, chemical dosing, bioscrubbers, and biological oxidation. This review aims to elucidate electrochemical and bioelectrochemical sulphide removal methods, which are gaining increasing interest as possible supplements to existing technologies. In these systems, the sulphide oxidation rate is affected by the reactor design and operational parameters, including electrode materials, anodic potential, pH, temperature and conductivity. Anodic and bioanodic materials are highlighted here, focusing on recent material developments and surface modification techniques. Moreover, the review focuses on sulphide generation and inhibition in biogas production processes and introduces the prospect of removing sulphide and producing methane in one single bioelectrochemical reactor. This could introduce BESs for combined biogas upgrading and cleaning, thereby increasing the methane content and removing pollutants such as sulphide and ammonia in one unit.

Exploration of initiation and stabilization properties of oblique detonation in a combustor with hydrogen fuel pre-injection

This study delves into the innovative aspects of hydrogen fuel injection and mixing within the duct of an oblique detonation engine (ODE) from both theoretical and numerical perspectives. By solving the multi-species reactive Reynolds-Averaged Navier-Stokes (RANS) equations alongside a hydrogen combustion model, the fluid dynamics and combustion processes in the combustor are thoroughly examined. The analysis shows that employing ramp-cantilever injectors for fuel delivery leads to fuel accumulation in the gas stream core, leaving a deficiency near the wall area. By supplementing ramp-cantilever injectors with wall injectors, fuel distribution adjacent to the wall is significantly enhanced, enabling the successful establishment of a detonation mode. However, the confined space and geometric constraints generate complex flow patterns, particularly due to boundary layer separation. The combustor operates in a stable configuration featuring an oblique shock-oblique detonation-separation shock (OSW-ODW-SSW) structure. Conversely, an oblique shock-oblique detonation-normal detonation-separation shock (OSW-ODW-NDW-SSW) arrangement is found to be unstable. Adjusting the position of the expansion corner on the upper wall forward stabilizes the unstable configuration, maintaining the ODW. Spatial flow inhomogeneities, especially equivalence ratio variations, are identified as crucial factors that can hinder ODW initiation and stability. These findings emphasize the pivotal role of optimizing fuel distribution, refining geometrical design, and ensuring flow uniformity in guaranteeing the efficiency and stability of oblique detonation engines. The outcomes provide valuable insights for future improvements in ODE design and operation.

Research over the effect of activated carbon treated with calcium nitrate solution on the catalytic ability in the reduction of Co(III)Triethylenetetramine

AbstractActivated carbon can be used as a catalyst for the reduction of Co(III)TETA to Co(II)TETA so as to maintain the ability of removing NO from gas stream with Co(II)TETA solution. Calcium nitrate has been utilized to treat activated carbon to improve its catalytic ability in the regeneration of Co(II)TETA. The biggest Co(III)TETA conversion is gained by the carbon being soaked in 0.3 mol/L calcium nitrate solution at 65°C for 12 h with a solid/liquid ratio of 1 g/50 mL followed being carbonized at 400°C for 2 h in nitrogen. The characterization with Fourier transform infrared spectroscopy, XPS, BET (Brunauer‐Emmett‐Teller) and Boehm titration indicates that the modification with calcium nitrate increases the specific surface area and acidic groups on activated carbon. The continuous experiments reveal that the NO removal efficiency obtained by the modified carbon is over 12% up to that by the original one.

Development of a novel bio char for CO2 capture and biogas upgrade: Static and dynamic testing

The optimization of the pyrolysis of the spruce sawdust was conducted based on the yield, textural properties, and static capture capacity of the chars to generate a new micro porous char for biogas upgrade. The nature of the precursor (C: 45.68 %, H: 6.08 %, N: 0.15 %, and 0.34 % ash content) helped to tune the porosity of the char for capturing CO2 from gas streams and biogas. The optimization of the pyrolysis at 700 °C, a heating rate of 10 °C / min and holding time of 1 hour, produced a microporous char with high yield, CO2 capture capacity and CO2/CH4 selectivity. The presence of the oxygen and nitrogen-containing functional groups in the optimum char help in the selective capture of CO2. The static CO2 capture capacity of the optimum char was 1.98 mmol/g at atmospheric pressure and 25 °C (90 % CO2 stream). The CSD (700−10−60) have capture capacity of 1.50 mmol/g (at a feed gas stream of 50 % CO2 and adsorption temperature of 25 °C and 120 kPa) which is equivalent to Norit C and Calgon BPL. Hence, spruce sawdust can be used to produce efficient biochar for biogas upgrade (CO2 capture) owing to high capture capacity and CO2/CH4 selectivity (around 3) and easy regeneration of the biochar for 10 consecutive cycles.

Development of an automated system for the purification of alkanolamine solutions

The alkanolamine solutions used in natural gas purification processes are inevitably degraded over time. This occurs due to accumulation of reaction products from the reactions with carbon dioxide, hydrogen sulphide, oxygen and other impurities present in the gas streams, as well as from thermal degradation. The degradation of solutions leads to the formation of thermostable compounds that not only reduce absorption efficiency, but also increase corrosive activity. Furthermore, part of the amine turns into a bound state and becomes ballast. The necessity of purification of alkanolamine solutions is becoming more and more urgent since the cost of maintaining efficient operation of gas treatment plants grows, and environmental safety requirements increase. Purification of solutions makes it possible to prolong their service life, reduce the cost of purchasing new reagents and reduce the negative impact on the equipment. In this work the method of anion-exchange technology of purification is used. Unlike vacuum distillation and electrodialysis, the considered technology does not require significant energy costs for generation and maintenance of vacuum, and heating of solutions, it can be easily integrated into the existing production process without any significant changes in the infrastructure. The described problem is relevant for Kazakhstan oil refineries, two of which use methyldiethanolamine, and one of which uses diethanolamine, and the existing practice of maintaining the operability of the systems is based on periodic replacement of part of the solution with pure amine. The development of automated systems for purification of such solutions makes it possible to significantly improve process control, minimise manual labour, and improve the overall economic efficiency of production.

Biogenic Synthesis of Cr‐Doped NiO/Clay Composite for Improved Dye Removal and CO2 Capture Studies

AbstractThe current work was designed to eliminate reactive yellow 18 dye (RY‐18) via adsorption from water, and CO2 from the gas stream, using the tragacanth gum‐based Cr doped NiO N.P.s/Clay (GCNC) composite. The one‐pot synthesis approach was used to produce the adsorbent, and physical and chemical properties were assessed using techniques like XRD, FTIR, UV‐visible spectroscopy, SEM, DLS, Zeta Potential, and adsorption–desorption isotherm. The GCNC composite demonstrated an impressive adsorption potential and percentage removal of 398 mg/g and 91.28%, respectively. Temkin and intraparticle diffusion models with R2 values of 0.98401 and 0.99918 were the most effective at fitting the experimental adsorption model. The thermodynamics parameters, including the change in enthalpy (H), entropy (S), and Gibbs free energy (G), demonstrated the endothermic and spontaneous nature of the adsorption process. A positive H value indicates an endothermic process, while a negative G value indicates a spontaneous process. According to the isotherms fitting model, the capacity for adsorbing CO2 at 25 °C and 1 atm was 4.8 mmol/g. The significant correlation between the slope in the log‐linear plot of the isosteric heat of adsorption and CO2 adsorption performance indicates that the isosteric heat of adsorption can be used as a predictive tool for CO2 adsorption performance. These significant results underscore the potential of the GCNC composite to revolutionize the water treatment field and CO2 capture, offering hope for a more sustainable and cleaner future.

Dimensional and experimental analysis for predicting the material removal rate in AJM

ABSTRACT One of the upcoming methods for machining brittle and heat-sensitive materials is abrasive jet machining (AJM) where the process of erosion aids in material removal. This is accomplished by the impact of abrasives transported using a stream of gas having high velocity onto the workpiece. The erosion mechanism is a complicated process, which involves cutting, fracturing and micro structural transformation, thereby causing the evaluation of response parameter like rate of material removed (MRR) an arduous task. In this paper, an effort has been made to develop a semi-empirical model for predicting MRR in hole machining of soda-lime glass by utilising dimensional analysis (DA) technique. In this model, the compressive stress developed during the impact of loading and velocity of the particle are considered as a function of work material, selected abrasive material properties and process parameters. The validation of the evolved model was carried out with experiments that involve process parameters such as operating pressure, stand of distance (SOD) and abrasive particle size. From the analysis, it’s found that the predicted MRR model created by the dimensional analysis method gave an average error of 11.8%. thereby giving a reasonably compatible value with experimental results.