Adsorption最新文献

Quantitative knowledge of competitive adsorption isotherms is essential for the design and optimization of adsorption based separation processes. Since the experimental determination of these thermodynamic functions is complicated and time consuming, there is a need for fast and easy to apply methods. In particular attractive are methods that evaluate measured breakthrough curves (BTC). Key features of these curves can be predicted with the equilibrium theory, which ignores kinetic effects that cause band broadening. If the adsorption equilibria can be described by the classical competitive Langmuir isotherm model, outlet concentration profiles can be calculated analytically. The paper summarizes and illustrates well-known classical results for N-component systems. The theory is applied to analyze experimentally determined BTC for a ternary mixture fed into an initially fully regenerated column under constant flowrate and under isothermal conditions. It is demonstrated that the retention times and intermediate plateau concentrations, which are observable for example in a single ternary BTC experiment, allow estimating a defined number of characteristic equilibrium loadings. These loadings can be directly used for easy estimation of the parameters of an assumed isotherm model. Various possibilities to use a reduced number of loadings and to include complementary results of standard pulse experiments are described. The isotherms generated from the ternary BTC are successfully validated by results of single component and ternary BTC experiments carried out subsequently. Options to generalize the method to determine isotherm model parameters from measured BTC to initially preloaded columns and to more complex mixtures are finally outlined.

A large surface area, wide band gap, and unique bonding property between Zn and O atoms make the hexagonal ZnO monolayer attractive as a gas sensor. In the present work, the adsorption and evolution of nitrogen (N₂) molecules over a ZnO monolayer have been studied using two different theoretical methods: van der Waals density functional theory (vdW-DFT) and kinetic Monte-Carlo (kMC) simulation. The adsorption and diffusion (hopping over the surface) energy of a N₂ gas molecule has been calculated considering the different sites over the ZnO substrate using the revPBE-vdW functional. Bader charge, electron localization function analysis, density of states and band structure plotting have been used to understand the adsorption mechanism. Lateral repulsive interaction between two N₂ molecules limits the maximum packing number of gas molecules within one hexagonal ring. The output of the vdW-DFT calculation has been fed to the kMC code to predict the rate of adsorption, desorption, and diffusion, along with the overall surface coverage at different temperatures and pressures. Finally, the change in the N₂ adsorption energy has been predicted with the increase of the ZnO layer number.

Numerous dynamic mass balances in the literature that describe the adsorption of gases in a column are written in terms of actual or absolute adsorption, while unwittingly and incorrectly utilizing excess adsorption isotherms. Perhaps this is because the actual and absolute adsorption isotherms cannot be experimentally measured nor predicted without making uncertain assumptions. The objective here was to derive unambiguous relationships between actual, absolute, excess, net and column amounts adsorbed that provide a straightforward understanding of the subtle differences between these quantities and that provide a simple means for incorporating them into dynamic mass balances. For this purpose, the actual, absolute, excess, net and column amounts adsorbed (loadings) were clearly defined, along with various volumes, porosities and densities that exist inside and outside an adsorbent contained in a column with a gaseous adsorbate. These adsorption definitions and quantities were used to derive four interconversion relationships for each type of adsorption in terms of the actual loading. The resulting expressions, based on intensive properties, can be used to relate any adsorption definition to any other adsorption definition. These relationships were also used to derive five dynamic mass balances, one for each type of adsorption. The similarities and differences in the terms between each of these five dynamic mass balances were discussed, along with their applicability to real world problems. In some cases at low pressure where the isotherms do not differ appreciably, it may be approximately correct to use excess or net adsorption isotherms in a dynamic mass balance written in terms of actual or absolute adsorption. However, the extent of the incorrectness is unknown due to mass transfer effects. So, it is recommended to use the dynamic mass balance with its specific type of adsorption, most likely excess adsorption. Then, when certain assumptions are made about the adsorbing and non-adsorbing void fractions, these expressions can be readily used in adsorption process simulation.

In this work adsorption of toxic CH₃X (X = Cl, Br) molecules was studied on pristine arsenene (p-As), single metal atom M (M = Au, Pt) doped arsenene (M-As), and AuPt-dimer decorated arsenene (AuPt-As) using first-principles calculations. The stability of M-As systems was determined with formation energy and molecular dynamics simulations. The electronic structure analysis revealed both M-As systems metallic. The adsorption process was analyzed using adsorption energy, adsorption height, charge transfer, change in electronic and magnetic properties, electron localized function (ELF) and work function. The results showed that CH₃X molecules are physically adsorbed on p-As and M-As. However, decorating arsenene with AuPt-dimer significantly improved the adsorption. Both molecules are chemically adsorbed on AuPt-As with adsorption energy of -0.64 and − 0.78 eV, respectively for CH₃Cl and CH₃Br. These findings predict the potential use of noble metal-based dimers decorated arsenene for the detection of toxic CH₃Cl and CH₃Br molecules.

This study investigated the potential of utilizing pomegranate peel (PP) waste for producing activated carbon (PPBAC) aimed at removing phenolic contaminants, specifically protocatechuic acid (PCA), from wastewater, and recovery from potato peel extract. The PPBAC was prepared through chemical activation with phosphoric acid (H₃PO₄) followed by thermal treatment at 350℃. Comprehensive characterization of the PPBAC was performed using FTIR, Raman spectroscopy, XRD, BET surface area analysis, FESEM analysis. Key operational factors, including dosage, concentration, contact time, and pH, were systematically optimized to improve adsorption efficiency, achieving a value of 18.89 mg/g within 30 min. The adsorption process was well described by the Freundlich isotherm model and followed pseudo-second-order kinetics. Additionally, DFT computations highlighted the reactivity of PCA in its neutral and protonated forms, which correlated with the observed effective adsorption performance. This research underscores the feasibility of converting agricultural waste into a valuable adsorbent for waste water treatment.

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This paper presents a comprehensive review of the physical and chemical properties of hydrogen peroxide as well as some regularities of its decomposition in the liquid phase. Hydrogen peroxide has been known for many decades and currently is one of the most important products of the chemical industry. Until recently, its use in the liquid state in rocket engines in space and defense has been limited due to storage and safety concerns. The latest research results made it possible to obtain hydrogen peroxide with higher purity and concentration as well as improved properties, safe and convenient in storage. As a result, hydrogen peroxide is widely considered for use in a wide range of rocket propulsion systems both as a bipropellant oxidizer and a monopropellant. As the size of the satellites being designed decreases, it is more and more difficult to select appropriate propulsion systems (PSs) ensuring required controllability and maneuverability. Currently, the smallest satellites (5–50 kg) usually use compressed gas. It is proposed to use hydrogen peroxide to improve efficiency, while reducing the cost compared to hydrazine PSs. As a monopropellant, hydrogen peroxide is characterized by high density (> 1,300 kg/m³) and specific impulse in vacuum of approx. 150 s (approx. 1,500 m/s). Its use in combination with hydrocarbons, pentaborane, and beryllium hydride is quite promising. The hydrogen peroxide/kerosene combination has particular advantages that make it convenient to use in rockets, especially when thrust control in a wide range is required. Its exceptional advantages are as follows: among various liquid fuel combinations, the hydrogen peroxide/kerosene combination is characterized by one of the highest fuel densities (approx. 1,270 kg/m³); besides, hydrogen peroxide tanks can be made of aluminum alloys, which significantly reduces their weight. Hydrogen peroxide is quite easy to handle since, unlike other oxidizers, it does not emit toxic vapors when stored and does not release toxic substances after combustion. The maximum permissible concentration of hydrogen peroxide vapors in the air of the working area is 0.3 mg/m³. Hazard class—2 according to GOST 12.1.007. From an environmental perspective, this fuel combination is comparable to the liquid oxygen/liquid hydrogen fuel. The need to install control engines for small satellites (e.g. Cubesat) is currently becoming a pressing issue. The use of neutral gases as a working fluid for control systems in such cases cannot compete with the use of, for example, hydrogen peroxide. At the same time, the creation of electric engines for small satellites is limited by the low available electrical power.

Marine pollution, particularly oil spills, can occur as a result of tanker operations (air ballast), ship daily operational in the terminals, ship scrapping, and most frequently caused by accidents and collisions. The aftereffects range from fish migration and death to altered behaviour and reproduction in marine species, plankton pollution, fish migration, ecosystem harm, and economic loss. These give long term hazardous effect for ecosystem balance. Bio-based adsorbents such as biochar can be an alternative that environmentally friendly to replace chemical sorbents that till date effective to adsorb oil spills. However, its small particle size complicates at the time of separation. Adding magnetic properties to biochar is important to make it easy to separate and reuse so that its sustainability can be achieved. This study investigated the synthesization and performance of magnetic biochar to remove oil spills. Using the hydrothermal process at 200°C, it also involves the synthesis of magnetic biochar from agricultural waste, specifically rice husks. Because it can be done at low temperatures—between 180° and 250°C—hydrothermal carbonization is thought to be a cost-effective technique of producing biochar. The presence of FeO on the samples, as shown by FTIR, further supports the SEM-EDX study results showing the presence of Fe elements in magnetic biochar. Magnetic rice husk biochar has an area functional group of 20.79 and a surface area of 27.65 m²/g. It supports in adsorbing petroleum spill with an adsorption capacity of 0.593 g.g-1 and the effectiveness achieved at 63.1%. The reaction kinetics follows pseudo-second-order non-linear with R² of 0.99. Magnetic rice husk biochar has a saturated magnetization of 0.46 emu/gr.

Increasing apprehension about water pollution has stimulated the pursuit of sustainable remedies, resulting in an upsurge in scholastic investigations that focus on biobased material for wastewater treatment. Since ages adsorption through activated carbon (AC) has been considered a reliable method. This study has examined different surface chemistry techniques utilized in biobased ACs for pollutant absorption from wastewater. Successful creation of eco-friendly adsorbents, from natural biomaterials like plant-derived fibers, biopolymers, and biofunctionalized surfaces, has efficiently eliminated metallic contaminants from wastewater. ACs derived from plant wastes are a favorable choice due to cost-effectiveness, biodegradability, minimal sludge generation, high regression percentage, and efficient metal adsorption capabilities. In addition, this study highlights their ability to be scaled up, their affordability, and their positive impact on the environment. The field of surface chemistry of biobased materials is constantly evolving through interdisciplinary collaborations between chemists, materials scientists, and environmental engineers. This progress offers promising avenues for addressing the urgent challenges of water pollution and contributing to the development of a cleaner and healthier environment. This review compiles the latest literature on AC production from various biowaste sources, utilizing different methods such as physical, chemical, or thermochemical activation, ultrasonication, and oxidation. The focus is on its application in waste water treatment, specifically in metal adsorption.

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This study reported the synthesis, characterization, and electrochemical performance of sea-urchins γ-MnO₂ structure and its composites with carbon aerogel (CA) derived from Waste-corn-stalk for capacitive deionization (CDI) application. Scanning electron microscopy revealed distinct sea-urchin morphologies where γ-MnO₂ exhibited a fibrous, porous structure, and its integration with CA resulted in composites with varied porosity and particle size distributions; X-ray diffraction analysis confirmed the crystalline nature of γ-MnO₂. It indicated a successful composite formation with CA, which was observed to enhance the electrochemical performance via the synergistic charge storage effect. Cyclic voltammetry and charge-discharge tests showed that the composites, particularly CA/γ-MnO₂-30, had superior electrochemical performance compared to γ-MnO₂ pristine, with improved capacitance and rate capabilities. CDI performance assessments demonstrated that the composite CA/γ-MnO₂-30 significantly outperformed in salt adsorption capacity of 32.7 mg/g, highlighting the potential of these materials for efficient water desalination. The electrosorption kinetic process of CA/γ-MnO₂ composites is suitable for the pseudo-second-order (PSO) model by combining the double-layer adsorption and the pseudo-capacitance process.