Desorption Step Research Articles

Continuous Electrochemical Carbon Capture via Redox-Mediated pH Swing─Experimental Performance and Process Modeling.

We investigate a continuous electrochemical pH-swing method to capture CO2 from a gas phase. The electrochemical cell consists of a single cation-exchange membrane (CEM) and a recirculation of a mixture of salt and phenazine-based redox-active molecules. In the absorption compartment, this solution is saturated by CO2 from a mixed gas phase at high pH. In the electrochemical cell, pH is reduced, and CO2 is selectively released in a desorption step. We investigate the influence of redox molecule concentration on the charge storage capacity of the solution, as well as the impact of current density and solution recirculation rate on process performance. A theoretical framework, based on a minimal set of assumptions, is established. This framework describes the data very accurately and can be used for system design and optimization. We evaluate the trade-off between energy consumption and CO2 capture rate and compare with published reports. We report a low energy consumption of 32 kJ/mol of CO2 at a capture rate of 39 mmol/m2/min.

Exploring the Activation of Atomically Precise [Pt17(CO)12(PPh3)8]2+ Clusters: Mechanism and Energetics in Gas Phase and on an Inert Surface.

Atomically precise clusters such as [Pt17(CO)12(PPh3)8]x+ (x = 1,2) (PPh3 is triphenylphosphine) are known as precursors for making oxidation catalysts. However, the changes occurring to the cluster upon thermal activation during the formation of the active catalyst are poorly understood. We have used a combination of hybrid mass spectrometry and surface science to map the thermal decomposition of [Pt17(CO)12(PPh3)8](NO3)2. High-resolution mass and ion mobility spectrometry together with DFT-based modeling were used to probe the sequence of fragmentation reactions and fragment structures generated upon collisional excitation of [Pt17(CO)12(PPh3)8]2+. This was compared with thermal desorption spectroscopy of [Pt17(CO)12(PPh3)8](NO3)2 dropcast onto an inert graphite surface. In both cases, a characteristic sequence of CO and benzene desorption steps is observed followed at higher excitation energy by H2 loss. This behavior is indicative of Pt-catalyzed C-H activation of phenyl groups during partial stripping of the ligand shell while the Pt17P8 cluster core is retained.

Electrocatalytic performance of transition metal mono-carbides (TM: CrC, FeC, MnC, TiC, VC) decorated on palladium-encapsulated fullerenes (TM-Pd@C60) for hydrogen evolution reaction (HER): A DFT perspective

The search for efficient and cost-effective electrocatalysts for the hydrogen evolution reaction (HER) is critical for advancing renewable energy technologies. This study employs density functional theory (DFT) at the MN12-SX/GenECP/Def2svp/LanL2DZ computational method to investigate the electronic, structural, and catalytic properties of modified fullerene (C60) systems encapsulated with palladium (Pd) and doped with transition metal carbides: CrC, FeC, MnC, TiC, and VC. Frontier molecular orbital (FMO) analysis reveals significant changes in the HOMO-LUMO gap upon doping, indicating enhanced electronic conductivity essential for catalytic activity. The lowest energy gaps 0.081 eV for MnC–Pd@C60 and 0.096 eV for VC-Pd@C60 were observed thus showing their readiness in terms of electron transfer. HER activity was assessed through the calculation of Gibbs free energy changes (ΔGH) for hydrogen adsorption. The results highlight TiC–Pd@C60, FeC–Pd@C60, and CrC–Pd@C60 as having optimal ΔGH values close to zero, suggesting their superior catalytic performance. Structural analysis confirms the stability of these doped systems, with minimal distortions observed in the fullerene framework upon metal encapsulation and doping. Vibrational analysis revealed that Pd@C₆₀ complexes show reduced M − C vibrations and the formation of M − H bonds, indicating efficient hydrogen adsorption, especially in MnC–Pd@C₆₀ and VC-Pd@C₆₀. Thermodynamics investigation show MnC–Pd@C₆₀ and VC-Pd@C₆₀ to exhibit highly exothermic and spontaneous hydrogen adsorption. Overall, Ti, Fe, and Cr-based catalysts show weaker interactions, which might favor the desorption step in HER. On the other hand, catalysts with V and Mn show strong hydrogen interactions via the Tafel step, which might benefit initial hydrogen adsorption but could require optimization to ensure efficient hydrogen release.

Bimetallic metal-organic framework based dispersive solid phase extraction followed by using a carbon dot solution as the elution solvent; application in the extraction of imidacloprid and acetamiprid from pepper samples.

This study focuses on the dispersive solid phase extraction technique for the efficient extraction and enrichment of imidacloprid and acetamiprid from pepper samples. A synthesized sorbent was used for this purpose. Once the target analytes were adsorbed, the sorbent was separated using a centrifuge and the analytes were desorbed using a carbon dot solution. After centrifugation, a portion of the eluent was injected into a high-performance liquid chromatography-tandem mass spectrometry system for analysis of the analytes. Several parameters affecting the performance of the method were investigated, such as the amount of sorbent, the type and volume of elution solvent, pH, and so on. By optimizing these parameters, the method showed favorable results under the following conditions: a sample solution volume of 5 mL, a sorbent amount of 10 mg, vortexing for 2 min, 150 μL of carbon dot solution as the elution solvent, a pH of 10, and 3 min of agitation during the desorption step. Notably, this optimized method exhibited high extraction recoveries ranging from 67% to 78% as well as low detection limits (0.44 μg L-1 and 0.32 μg L-1) and quantification limits (1.4 μg L-1 and 1.0 μg L-1) for imidacloprid and acetamiprid, respectively. To validate the effectiveness of the method, four pepper samples were successfully analyzed and no analyte was detected in any of them using this approach. Overall, the developed DSPE method represents a reliable and sensitive technique for the extraction and analysis of the studied pesticides in pepper samples.

Optimizing Hydrazine Activation on Dual‐Site Co‐Zn Catalysts for Direct Hydrazine‐Hydrogen Peroxide Fuel Cells

ABSTRACTDirect hydrazine‐hydrogen peroxide fuel cells (DHzHPFCs) offer unique advantages for air‐independent applications, but their commercialization is impeded by the lack of high‐performance and low‐cost catalysts. This study reports a novel dual‐site Co‐Zn catalyst designed to enhance the hydrazine oxidation reaction (HzOR) activity. Density functional theory calculations suggested that incorporating Zn into Co catalysts can weaken the binding strength of the crucial N2H3* intermediate, which limits the rate‐determining N2H3* desorption step. The synthesized p‐Co9Zn1 catalyst exhibited a remarkably low reaction potential of −0.15 V versus RHE at 10 mA cm−2, outperforming monometallic Co catalysts. Experimental and computational analyses revealed dual active sites at the Co/ZnO interface, which facilitate N2H3* desorption and subsequent N2H2* formation. A liquid N2H4‐H2O2 fuel cell with p‐Co9Zn1 catalyst achieved a high open circuit voltage of 1.916 V and a maximum power density of 195 mW cm−2, demonstrating the potential application of the dual‐site Co‐Zn catalyst. This rational design strategy of tuning the N2H3* binding energy through bimetallic interactions provides a pathway for developing efficient and economical non‐precious metal electrocatalysts for DHzHPFCs.

Brewer’s spent grain as a potential sorbent for toxicology methods: Application to antidepressant analysis in urine

The use of antidepressants is well-documented for several health conditions. The determination of these drugs in biological fluids is often important in intoxication cases. However, appropriate sample preparation needs to be employed, such as dispersive liquid phase microextraction (DSPME). Therefore, this study aimed to develop a method for the determination of antidepressants in urine using Brewer’s spent grain (BSG) as sorbent in a DSPME procedure, followed by GC-MS analysis. In this methodology, only 500 µL of urine was required, alongside 15 mg of BSG as the sorbent for the DSPME technique. Desorption step was performed with 500 µL of ethyl acetate:MTBE solution (1:1, v/v), followed by evaporation of the organic layer, reconstitution in acetonitrile and injection into the analytical system. BSG was further characterized by several analytical techniques. The DSPME procedure was optimized using multivariate strategies, and the method was fully validated according to proper guidelines. Lower limits of quantitation (LLOQ) were set between 50 and 200 ng/mL, while linearity was achieved over the specified range of LLOQ to 5000 ng/mL, with R2 ≥ 0.99. Additionally, the method was applied to the analyses of 109 urine samples. Of these, 76 were positive for at least one antidepressant, with the most prevalent being nortriptyline, amitriptyline, and fluoxetine. This study is the first to report the use of BSG as a sorbent for DSPME, demonstrating good efficiency as indicated by the analytical figures of merit. Moreover, the method proved to be applicable in real poisoning case samples. The analytical performance, combined with advantages such as high throughput and a green profile, suggests this method as a valuable alternative for toxicological laboratories.

Experimental exploring of Ti3C2Tx MXene for efficient and deep removal of magnesium in water sample

In this work, the mechanism and behaviour of magnesium adsorption with Ti3C2Tx adsorbent is investigated. Ti3C2Tx was synthesized by selective exfoliation of Al layer from Ti3AlC2 using acidic solutions of HF 40% and 12 M LiF/ 9 M HCl. The effect of the synthesis method on the structure, the interlayer distance, the type and abundance of the functional groups, the bonds formed, the surface area and the volume of the formed cavities were evaluated by X-ray diffraction, scanning electron microscopy, Energy-dispersive X-ray spectroscopy, Brunauer–Emmett–Teller and fourier transform infrared analyses. The preliminary discontinuous tests of magnesium adsorption with Ti3C2Fx and Ti3C2(OH)x in 100 ppm concentration, pH ~ 7.00, ambient temperature and time of 3 h show 182.5 and 99 mg.g-1 the adsorption intensity, respectively. The difference in adsorption intensity with Ti3C2Fx is the result of the extensive tendency of Mg2+ to conduct electrochemical reactions with F- twice as much as OH- functional groups. By designing the RSM experiment, analytical, qualitative, optimization and modelling of the magnesium adsorption process with Ti3C2Fx adsorbent was carried out with the input variables of magnesium concentration, pH, ambient temperature and time. Isothermal modelling shows the agreement of the experimental results with the Langmuir model and endothermic thermodynamic modelling shows the spontaneity of the adsorption reaction. MXene adsorption–desorption with 0.1 M HCl was done in up to 4 steps. The adsorption results show that Ti3C2Fx can show up to 15% initial adsorption intensity by maintaining stability in up to 4 adsorption–desorption steps.

Parallel-disposable pipette extraction (Pa-DPX) using cork as a green high-throughput method for the determination of four pesticides in environmental water samples with quantification by HPLC-DAD.

This study utilized cork powder as a green alternative for extractor phase using the parallel-disposable pipette extraction (Pa-DPX) method for the determination of pesticides such as atrazine, carbofuran, diuron, and simazine from aqueous environmental samples. The separation/detection was performed by HPLC-DAD. Optimization experimental conditions was achieved through univariate and multivariate designs, resulting in the following parameters: 15mg of cork as extractor phase, 7 extraction cycles with 7.5% (m/v) NaCl in the sample, and 10s were fixed per extraction cycle. For the desorption step, 300 µL of acetonitrile was used as solvent with 1 desorption cycle. The limit of detection and limit of quantification values were 7.5µg L-1 and 25µg L-1 for atrazine, carbofuran, and diuron, and 15.1µg L-1 and 50µg L-1 for simazine, respectively. Linear working range varied from 25 to 400µg L-1 with coefficients of determination (R2) ≥ 0.983. The values of intraday precision varied from 4.9 to 18.1%, and those of interday precision varied from 21.3 to 32.2%. The accuracy of the method was determined through relative recoveries and the values ranged from 63.4 to 119.9%. The water environmental samples were collected at two different locations in Florianópolis, Santa Catarina, Brazil, and showed no detectable pesticides. The method presented here stands out due to the low consumption of sample and reagents, as well as the use of a renewable and biodegradable extraction phase (cork). The method is also a high-throughput alternative, due to the use of the Pa-DPX apparatus, which allows the preparation of up to five samples simultaneously.

Balanced Adsorption Toward Highly Selective Electrochemical Reduction of CO2 to Formate.

Tin-based materials have been designed as potential catalysts for the electrochemical conversion of CO2 into a single product. However, such tin-based materials still face the challenges of unsatisfactory selectivity, because the rate-determining step is situated within the slow desorption step. In this work, a variety of tin-based materials are synthesized using the electrospinning technique in an effort to control the adsorption strength during electrochemical reduction, therefore improving the selectivity of CO2 reduction toward formate. The optimized SnS material exhibits moderate adsorption strength to *OCHO and *HCOOH, and the appropriate atomic distance of Sn-Sn maintained the balanced adsorption posture of both intermediate. Therefore, the rate-determining step can be shifted from the slow desorption of the *HCOOH step (Sn) to the first hydrogenation of the *OCHO species step (SnS). Due to this shift, the SnS/C electrode demonstrated excellent selectivity, with a Faradaic efficiency of 96% for the production of formate. A maximum current density of -12.5mA cm-2 for formate is also achieved for a period of33h.

Evolution of Nitrogen-Coordinated Metal Single Atoms Toward Single-Atom Alloys on MgH₂ as Efficient and Stable Hydrogen Spillover Catalysts.

M-N-C catalysts with nitrogen-coordinated metal single-atom active sites have demonstrated high activity for hydrogen storage materials, but their stability in this application remains uncertain. This study addresses this issue by using nickel phthalocyanine (NiPc) molecules on MgH₂ particles as a model system. It is found that the N-coordinated high-valence Ni single atoms in the NiN₄ active site are unstable in the reducing environment of hydrogen storage, spontaneously evolving into zero-valence Ni, forming a Ni₁-Mg single-atom alloy (SAA). The Ni₁-Mg SAA exhibits remarkable stability in catalyzing Mg hydrogen storage reactions. Furthermore, it demonstrates comprehensive catalytic activity for each step of hydrogen absorption and desorption from Mg, surpassing the efficiency of the NiN₄ active site, especially in the critical steps of hydrogenation and dehydrogenation. Overall, the catalytic performance of Ni₁-Mg SAA is superior to most known nickel-based catalysts. This evolutionary process is also observed in FePc, CoPc, and tetraphenylporphyrin nickel (Ni-TPP), suggesting that this reducing transformation is a universal phenomenon for MN₄-type active sites in hydrogen storage catalysis.

Vacuum-Assisted MonoTrapTM Extraction for Volatile Organic Compounds (VOCs) Profiling from Hot Mix Asphalt.

MonoTrapTM was introduced in 2009 as a novel miniaturized configuration for sorptive sampling. The method for the characterization of volatile organic compound (VOC) emission profiles from hot mix asphalt (HMA) consisted of a two-step procedure: the analytes, initially adsorbed into the coating in no vacuum- or vacuum-assistance mode, were then analyzed following an automated thermal desorption (TD) step. We took advantage of the theoretical formulation to reach some conclusions on the relationship between the physical characteristics of the monolithic material and uptake rates. A total of 35 odor-active volatile compounds, determined by gas chromatography-mass spectrometry/olfactometry analysis, contributed as key odor compounds for HMA, consisting mainly of aldehydes, alcohols, and ketones. Chemometric analysis revealed that MonoTrapTM RGC18-TD was the better coating in terms of peak area and equilibrium time. A comparison of performance showed that Vac/no-Vac ratios increased, about an order of magnitude, as the boiling point of target analytes increased. The innovative hybrid adsorbent of silica and graphite carbon monolith technology, having a large surface area bonded with octadecylsilane, showed effective adsorption capability, especially to polar compounds.

Highly asymmetrically configured single atoms anchored on flame-roasting deposited carbon black as cathode catalysts for ultrahigh power density Zn-air batteries

Iron group element-based single atom (SA) catalysts are highly regarded as promising alternatives to commercial Pt/C for catalysis of oxygen reduction reaction (ORR). For applications in rechargeable zinc-air batteries (ZABs), achieving the necessary high catalytic efficiency of the SAs toward oxygen evolution reaction (OER) however remains a significant challenge. Here, highly asymmetrically configured Fe SAs created with N,S co-coordination and anchored on flame-roasting deposited carbon black (CB), Fe-N3S1/CB, are developed, achieving outstanding bifunctional oxygen catalytic efficiency, with an ultra-small potential gap of 0.661 V at 10 mA cm-2 (ΔE10), outperforming the (Pt/C+RuO2) composite catalyst (0.697 V). With a newly proposed binder-free composite air cathode design, the Fe-N3S1/CB based ZAB achieves an ultrahigh power density of 365.7 mW cm-2 at a current density of 511.3 mA cm-2, largely outperforming the (Pt/C+RuO2) based ZAB (225.9 mW cm-2 at 344.7 mA cm-2). Furthermore, the Fe-N3S1/CB based ZAB demonstrates excellent long-term stability, with only 8.2 % decay in round-trip efficiency over 1000 (333.3 h) charge-discharge cycles at 10 mA cm-2. Density functional theory calculations elucidate that incorporation of sulfur into the coordination sphere of Fe facilitates the electrochemical dehydroxylation step for ORR and accelerates the electrochemical O2 desorption step for OER, thereby reducing the corresponding free energy differences on Fe SAs for largely enhanced catalytic efficiency.1. A large size hetero-atom element, sulfur, is introduced to create highly asymmetrically configured Fe single atoms for enhancements in catalytic efficiency toward both oxygen reduction reaction and oxygen evolution reaction, and a binder-free composite air cathode design is proposed to improve electrochemical performances of zinc-air batteries.2. An ultra-small potential gap of 0.661 V at 10 mA cm-2 (ΔE10) is achieved for the air cathode, and an ultrahigh discharge power density of 365.7 mW cm-2 at a current density of 511.3 mA cm-2 is acquired for the zinc-air battery.

Electrocatalytic Hydrogenation of Pyridines and Other Nitrogen-Containing Aromatic Compounds.

The production of cyclic amines, which are vital to the pharmaceutical industry, relies on energy-intensive thermochemical hydrogenation. Herein, we demonstrate the electrocatalytic hydrogenation of nitrogen-containing aromatic compounds, specifically pyridine, at ambient temperature and pressure via a membrane electrode assembly with an anion-exchange membrane. We synthesized piperidine using a carbon-supported rhodium catalyst, achieving a current density of 25 mA cm-2 and a current efficiency of 99% under a circular flow until 5 F mol-1. Quantitative conversion of pyridine into piperidine with 98% yield was observed after passing 9 F mol-1, corresponding to 65% of current efficiency. The reduction of Rh oxides on the catalyst surface was crucial for catalysis. The Rh(0) surface interacts moderately with piperidine, decreasing the energy required for the rate-determining desorption step. The proposed process is applicable to other nitrogen-containing aromatic compounds and could be efficiently scaled up. This method presents clear advantages over traditional high-temperature and high-pressure thermochemical catalytic processes.

Industrial-scale 12-layered-bed vacuum pressure swing adsorption for fuel cell-grade H2 production from carbon-captured steam methane reforming syngas

Vacuum pressure swing adsorption (VPSA) is primarily used to produce high-purity H2 from CO2-rich syngas in steam methane reforming (SMR) plants. Since carbon capture is essential, the performance of current H2 VPSA processes is affected by feeding carbon-captured SMR syngas (CO2-lean SMR syngas). This study conducted the performance evaluation and optimization for a fuel cell-grade H2 production by an industrial-scale 12-layered-bed VPSA process with a 24-step cycle from CO2-lean SMR syngas. The multi-scale dynamic model for the VPSA process was validated with petrochemical industry data from a current SMR-VPSA plant. A sensitivity analysis using CO2-lean SMR syngas indicated the high loss of H2 during desorption steps, suggesting the need for optimization of the VPSA process. Owing to the complex interconnectivity of 12 beds via 24 steps, the framework of a dynamic model-based deep neural network (DNN) and DNN-based optimization was developed to design and optimize the VPSA process. Even without changing equipment or adsorbent configuration, the VPSA process achieved fuel cell-grade H2 production (>99.9999 % H2 and > 88 % recovery with < 0.2 ppm CO). The results indicate that CO2 capture rates, ranging from 90 to 99 %, can be independently determined under techno-economic and environmental conditions, as this capture range of CO2-lean SMR syngas gives a minor impact on the performance of VPSA process. The proposed three-step framework, which encompasses dynamic modeling, surrogate modeling, and multi-objective optimization, provides a systematic and feasible approach for designing and optimizing the VPSA process in an SMR plant integrated with a carbon capture process, to achieve a low-carbon economy.

Analysis of forensic polymer samples using double shot pyrolysis gas chromatography – Mass spectrometry

Polymers are present in many different products, such as paints, plastics, and rubbers, which are routinely encountered in forensic casework. Comparison of such samples involves an initial visual examination followed by comparison of the chemical compositions of the exhibits. Techniques such as Fourier transform infrared spectroscopy (FTIR) and pyrolysis gas chromatography – mass spectrometry (PyGC-MS) have been reported for determining the chemical compositions of polymers in forensic samples. Double-shot pyrolysis gas chromatography – mass spectrometry (DS-PyGC-MS) is an extension of single-shot pyrolysis gas chromatography – mass spectrometry (SS-PyGC-MS) which is the current PyGC-MS method used in most forensic laboratories. DS-PyGC-MS involves a preliminary thermal desorption GC-MS step, followed by the pyrolysis GC-MS step, with this second step being analogous to SS-PyGC-MS. The pyrolyser furnace operates at a lower temperature during the thermal desorption step, allowing low volatility compounds, such as additives, to be thermally desorbed and detected, minimising interference from the polymeric component of the sample. This pilot study analysed four different polymeric substrates, commonly encountered in forensic casework, by DS-PyGC-MS. The substrates chosen were tyre rubber, road cones, cling film, and shotgun wads. The aim was to investigate whether more chemical information was generated by DS-PyGC-MS compared to SS-PyGC-MS, potentially providing increased discrimination of such samples. Qualitative results showed that tyre rubber and road cones were ideal substrates for DS-PyGC-MS. A wide range of additives were detected in these samples in the thermal desorption step, which were not detected using SS-PyGC-MS. All of the rubber tyres (n=5) and road cones (n=6) were able to be uniquely distinguished using DS-PyGC-MS. Some additional compounds were detected in the thermal desorption analysis of shotgun wads (n=4), providing increased discrimination compared to SS-PyGC-MS. For the cling film samples analysed (n=7) the polyethylene-based cling films (n=6) could not be distinguished from each other, with no compounds detected in the thermal desorption step. The other cling film sample contained a mixture of polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT) and could easily be distinguished from the polyethylene-based cling films using either SS- or DS-PyGC-MS, or other common analytical methods such as Fourier transform infrared spectroscopy (FTIR). This pilot study has demonstrated that DS-PyGC-MS has the potential to provide more comprehensive chemical composition information for some polymeric substrates and is a promising method for the forensic comparison of polymer evidence.

Atomically Dispersed Palladium Catalyst for Chemoselective Hydrogenation of Quinolines.

Chemoselective hydrogenation of quinoline and its derivatives is a significant strategy to achieve the corresponding 1,2,3,4-tetrahydroquinolines (py-THQ) for various potential applications. Here, we precisely constructed a titanium carbide supported atomically dispersed Pd catalyst (PdSA+NC/TiC) for quinoline hydrogenation, delivering above 99% py-THQ selectivity at complete conversion with an outstanding turnover frequency (TOF) of 463 h-1. AC-HAADF-STEM and XAFS demonstrate that the atomic dispersion of Pd includes Pd-Ti2C2 single atoms and Pd clusters with atomic-layer thickness. Theoretical calculation and experimental results revealed that H2 dissociation and subsequent hydrogenation rates were greatly promoted over Pd clusters. Although the adsorption of quinolines and intermediates are easier on Pd clusters than on Pd single atoms, the desorption of py-THQ is more favored over Pd single atoms than over Pd clusters. The desorption step may be the main reason for 5,6,7,8-tetrahydroquinoline (bz-THQ) and decahydroquinoline (DHQ) formation. Thus, a low reaction activity and py-THQ selectivity were received over PdSA/TiC and PdNP/TiC, respectively.

Cyclic Atomic Layer Etching of PdSe2

AbstractThe unique characteristic of 2D transition‐metal dichalcogenide (TMD) semiconductor materials such as PdSe2 is the ability of the bandgap to vary on the basis of the number of layers present. This variation results in a broad bandgap range spanning from semi‐metallic to semiconducting materials, underscoring the significance of precisely controlling the material thickness. In this study, the thicknesses of chemical vapor deposited PdSe2 films are precisely controlled layer‐by‐layer via cyclic atomic layer etching (ALE), which comprised a radical adsorption step generated by oxygen and chlorine plasmas, followed by a desorption step with an organic solvent vapor such as formic acid. Cyclic etching with one monolayer of PdSe2/cycle is achieved using both types of adsorption gases while maintaining the ratio of Se/Pd underlying PdSe2 at ≈2. This cyclic ALE method is also applicable for smoothing TMD material surfaces by isotropically removing individual rough surface layers. Because this etching method only utilizes chemical reactions with radicals generated by plasmas and organic vapors, it is not only unaffected by the physical damage caused by the irradiation of energetic particles such as ions in plasmas, but also is applicable to 3D structure processing.

Exploring enhanced CO2 separation from blast furnace gas: A multicolumn vacuum swing adsorption approach with process design and experimental assessment

Excessive emissions of carbon dioxide (CO2) are a major driver of global warming. Blast furnace gas (BFG) represents a major source of CO2 emissions in the steel industry, accounting for approximately 30 % CO2 emissions among the industry sectors. Hence, effective CO2 capture from BFG is imperative. This study presents an approach utilizing the vacuum swing adsorption (VSA) technology to capture CO2 from BFG. A 6-column VSA rig was designed and constructed to separate CO2 from a simulated BFG (CO2/N2 = 20 %/80 %) using zeolite 13X as adsorbents. The VSA process involved steps of adsorption, desorption, heavy product purge, light product re-pressurization, and pressure equalization. Five different process modes, i.e., 1-column and 3-step, 2-column and 6-step, 2-column and 8-step, 3-column and 9-step, and 4-column and 16-step configurations, were implemented to evaluate the influence of various process design factors on the separation performance. Additionally, a 6-column and 36-step process was devised to conduct a parametric study of VSA cycles by varying the adsorption duration and desorption pressure. Results revealed the pivotal role of heavy product purge and pressure equalization on the separation performance. The six-column process achieved a CO2 purity and recovery of 94 % and 82 %, respectively, with a energy consumption of 0.76 GJ/tonCO2 when employing a desorption step duration of 240 s and pressure of 8 kPa. In addition, a method of process optimization based on the bed capacity ratio, C, was introduced in this study, which provides a dimensionless quantity of the utilization of the adsorption column. Moreover, capturing CO2 from BFG through the VSA cycle not only enhances its heating value but also yields substantial advantages in terms of mitigating CO2 emissions.

Methanogenesis kinetics of organic matter of the leachate in an up-flow anaerobic sludge blanket reactor

Understanding the treatment of leachate mediated by the development of anaerobic sludge makes it possible to create an effective design process of biodegradation technology. This study used an up-flow anaerobic sludge blanket (UASB) reactor equipped with a gas–liquid-solid separator to capture CH4 for treating landfill leachate to improve understanding of methanogenesis kinetics of organic matter. The performance of UASB was able to remove 154.75 g/L of chemical oxygen demand (COD) content of the leachate originally anticipated to emit 2.99 L of CH4 production into the atmosphere. The trend in the variation of internal mass transfer (IMT) factor was close to the global mass transfer factor; however, it was far higher than that of external mass transfer (EMT) factor. After 30 days of the experiment, methanogenesis kinetics of organic matter of the leachate were supported mainly by the breakdown of complex molecules. The rate-limiting step of CH4 desorption was controlled by IMT at the beginning and then by EMT after 30 days of the experiment. The strongly decreased EMT factor was counterbalanced by an increased value of the IMT factor at before 5 days of the experiment. It would be of interest to predict the methanogenesis kinetics of CH4 desorption using the Generalized Fulazzaky equations, which cannot be evaluated using other models. Analysis of the methanogenesis kinetics of organic matter of the leachate provides a new insight into the performance of UASB reactor, which may contribute to advanced treatment of landfill leachate in the future.

Enhancing Electrocatalytic Semihydrogenation of Alkynes via Weakening Alkene Adsorption over Electron-Depleted Cu Nanowires.

Electrochemical semihydrogenation (ESH) of alkynes to alkenes is an appealing technique for producing pharmaceutical precursors and polymer monomers, while also preventing catalyst poisoning by alkyne impurities. Cu is recognized as a cost-effective and highly selective catalyst for ESH, whereas its activity is somewhat limited. Here, from a mechanistic standpoint, we hypothesize that electron-deficient Cu can enhance ESH activity by promoting the rate-determining step of alkene desorption. We test this hypothesis by utilizing Cu-Ag hybrids as electrocatalysts, developed through a welding process of Ag nanoparticles with Cu nanowires. Our findings reveal that these rationally engineered Cu-Ag hybrids exhibit a notable enhancement (2-4 times greater) in alkyne conversion rates compared to isolated Ag NPs or Cu NWs, while maintaining over 99% selectivity for alkene products. Through a combination of operando and computational studies, we verify that the electron-depleted Cu sites, resulting from electron transfer between Ag nanoparticles and Cu nanowires, effectively weaken the adsorption of alkenes, thereby substantially boosting ESH activity. This work not only provides mechanistic insights into ESH but also stimulates compelling strategies involving hybridizing distinct metals to optimize ESH activity.