Surface Chemical Reactions Research Articles

What Controls the Leaching of Magnesite with Concentrated Solutions of Hydrochloric or Nitric Acid?

ABSTRACT The kinetics of the leaching of natural magnesite with hydrochloric or nitric acid has been studied. Relatively high values of the apparent activation energy (from 46.5 to 70.0 kJ mol−1), but especially the low values of the apparent reaction order for H+ cations, n , have shown that the whole process is controlled by the surface chemical reaction. The value of n decreases continuously with increasing activity of H+ cations in the range of pH 5 to −1.4. At pH < 2.6 there is a transition from the kinetic regime characterized by n ≅ 0.5 to another one with n close to zero.

Simulation-based design of 1-D copper nanograting device for sensing application by studying electromagnetic properties on Cu/Air interface

Sensing devices has been an interesting area of study because of their immense application in practical life. In the present work, the extraordinary optical transmission (EOT) along with surface plasmon polaritons (SPPs) excitation at the metal/ dielectric interface is investigated RF-module of COMSOL Multiphysics 5.3a has been used to investigate copper (Cu) nanograting structure on the glass substrate in periodic arrangement of 1-dimensional (1D). The visible-infrared electromagnetic wavelength of 400–900 nm has been used to excite the SPPs at the interface and a light port is provided from the substrate side. The optimum EOT has been investigated at transmission spectra of 0th order. During this process thickness of the slit is fixed at 50 nm, the periodicity of the unit cell is fixed at 700 nm, and the width of the slit changed to check its effect on the EOT. Additionally, phenomena of near field investigation have also used to explore the transmission-based performance of field at thespecificboundary of copper (Cu) and airwhich confirm spectraoutcomesof transmission thorough the fabricated device. The optimum value of EOT foundwhenthe width of slit isat250 nm for the Cu/air interface.The deviceused for this purpose is modeled in COMSOL. Along the EOT the SPPs phenomena is also investigated by using present modeled device.These phenomena are observed by studying the electric and magnetic parts of the device that models the Cu/Air interface. We tested it with different slit widths ranging from 50-450 nm. The coupling efficiency and sensitivity of Cu/Air 1D device design at optimum slit width of 250 nm calculated. Such devices are increasingly applicable in bio photonics sensing of DNA structure, in vivo study of the internal structure of the body, imaging, surface chemical reaction, environmental remediation, and in various solar cell industries (plasmonic solar cell).

Account of doping photocatalyst for water splitting

In the field of photocatalytic water splitting, the strategy of doping photocatalysts has emerged as a significant and extensively studied approach. Doping can effectively facilitate the modification of both the microstructure and energy band structure of the photocatalyst, addressing key performance limitations such as light absorption, position of the conduction and valence band minima (CBM and VBM), photogenerated carrier separation, and surface chemical reactions. In recent years, we have reported several works about the doping of rare earth elements into bismuth-based composite oxides. These endeavors are aimed at enhancing the conduction band minimum and achieving overall water splitting under visible light. Based on these bismuth-based composite oxides, we studied the effects of doping on the microstructures of photocatalysts, including exposed surfaces, surface properties, and defects. Recently, we introduce an innovative asymmetric doping technique—Selected Local Gradient Doping, intricately placing doped ions within nanocapsules. This approach allows for the gradual, controlled, and localized release of doped ions to the primary photocatalyst. Therefore, this account is to review our related research in the field of doping for photocatalytic water splitting. The primary focus on doping bismuth-based composite oxides and Asymmetry doping would significantly make contribution to the exploration of novel materials for photocatalytic water splitting under visible light and the enhancement of energy conversion efficiency.

Investigation of the Leaching Kinetics of Zinc from Smithsonite in Ammonium Citrate Solution

In this study, the response surface method is used to develop a model for analyzing and optimizing zinc leaching experiments. An investigation into the leaching kinetics of smithsonite in ammonium citrate solution is also conducted. A model of kinetics is studied in order to represent these effects. The experimental data show that an increase in the solution temperature, concentration, and stirring speed has a positive impact on the leaching rate, while an increase in the particle size has a negative impact on it. The optimal experimental conditions consist of a leaching temperature of 70 °C, ammonium citrate concentration of 5 mol/L, particle size of 38 µm, and rotational speed of 1000 rpm. Under these optimal conditions, the leaching rate of zinc from smithsonite is 83.51%. It is speculated that the kinetic model will change when the temperature is higher than 60 °C. When the temperature is lower than 60 °C, the leaching process is under the control of the shrinking core model of the surface chemical reactions. The calculated activation energy of the leaching reaction is equal to 42 kJ/mol. The model of the leaching process can be described by the following equation: 1−1−x1/3=k0⋅(C)0.6181⋅r0−0.5868⋅SS0.6901exp⁡−42/RT]t. This demonstrates that an ammonium citrate solution can be used in the leaching process of zinc in smithsonite as an effective and clean leaching agent.

Basic principles of modeling reactive sputtering

This work describes a number of principles, which are proved to be effective in modeling various physical and chemical processes. In the article, a process model is defined as its representation using another similar (or identical) process built on a number of simplifying assumptions. This model is called physicochemical. The main phenomena on the surfaces and in the gas environment of the sputtering system, used for modeling, are identified. A scheme for deriving a system of equations describing the process is given. An example of modeling based on a non-isothermal surface chemical reaction is described. It shows the possibility of studying experimentally immeasurable dependencies characterizing the process of reactive sputtering. The article is addressed mainly to aspiring researchers who have dared to try to understand the features of reactive sputtering models proposed by different authors.

Study on uranium leaching from uranium purification residue with ammonium hydrogen fluoride

Residues generated from the uranium purification process, characterized by a high uranium content, pose a significant challenge for recovery through leaching and present a considerable environmental threat. After using XRD and SEM-mapping characterization analysis combined with the BCR continuous graded extraction test to analyze the content of different states of uranium, it was found that the main reason why the uranium in the residue was difficult to leach because it was encapsulated by SiO2 crystals. Using NH4HF2 as a leaching agent, a leaching study of uranium in the residue was carried out, and the results showed that the H+ and F− produced by NH4HF2could react with SiO2, destroying the crystal lattice of SiO2 and causing the encapsulated uranium to come into contact with the leaching agent, facilitating the leaching of uranium in the residue. The optimum conditions for uranium leaching were 10% mass fraction of NH4HF2, a liquid-solid ratio of 30:1, a reaction temperature of 30 °C and a reaction time of 120 min, and the leaching efficiency of uranium from the residue was as high as 98.95%. The leaching kinetics of uranium by NH4HF2 were consistent with the mixed controlled model in the shrinking core models, indicating that the surface chemical reaction and mass diffusion dominated both uranium leaching processes. This may provide a viable method for resource recovery and the treatment of uranium purification residues.

Photoelectrochemical Lithium Extraction from Waste Batteries.

The amount of global hybrid-electric and all electric vehicle has increased dramatically in just five years and reached an all-time high of over 10 million units in 2022. A good deal of waste lithium (Li)-containing batteries from dead vehicles are invaluable unconventional resources with high usage of Li. However, the recycle of Li by green approaches is extremely inefficient and rare from waste batteries, giving rise to severe environmental pollutions and huge squandering of resources. Thus, in this mini review, we briefly summarized a green and promising route-photoelectrochemical (PEC) technology for extracting the Li from the waste lithium-containing batteries. This review first focuses on the critical factors of PEC performance, including light harvesting, charge-carrier dynamics, and surface chemical reactions. Subsequently, the conventional and PEC technologies applying in the area of Li recovery processes are analyzed and discussed in depth, and the potential challenges and future perspective for rational and healthy development of PEC Li extraction are provided positively.

Engineering MgHPO4·3H2O/Mg(OH)2 composite for boosting NH3 adsorption properties

The emission of ammonia gas (NH3) in agricultural composting not only leads to a decrease in fertilizer efficiency, but also causes environmental pollution. Here, an alkaline, insoluble composites was prepared and its adsorption performance for NH3 was explored. The results indicate that the material synthesized using a one-pot method with magnesium hydroxide (Mg(OH)2) and phosphoric acid (H3PO4) consists of a mixture of MgHPO4·3 H2O and Mg(OH)2 (M1). TEM images reveal the adhesion of the two materials together, with Raman spectroscopy indicating that MgHPO4·3 H2O is located on the outer surface of Mg(OH)2. The microenvironment formed by the adhesive construction of MgHPO4·3 H2O and Mg(OH)2 mixture not only provides sufficient magnesium salts and phosphate for the growth of struvite but also creates alkaline conditions conducive to struvite formation. The kinetic results show that the NH3 adsorption of M1 follows pseudo second-order adsorption kinetics and belongs to surface chemical reaction control. Compared with a simple mixture of MgHPO4·3 H2O and Mg(OH)2, M1 has a 4.5 fold increase in NH3 adsorption rate and a 3.15 fold increase in equilibrium adsorption capacity. Preliminary on-site tests demonstrated the potential application of the M1 adsorbent for NH3 adsorption in composting.

Recovery of Cobalt, Nickel, and Lithium from Spent Lithium-Ion Batteries with Gluconic Acid Leaching Process: Kinetics Study

The demand for lithium-ion batteries (LIBs) is driven by environmental concerns and market growth, particularly in the transportation sector. The EU’s push for net-zero emissions and the European Green Deal accentuates the role of battery technologies in sustainable energy supply. Organic acids, like gluconic acid, are explored for the eco-friendly leaching of valuable metals from spent batteries. This study investigates leaching kinetics using gluconic acid (hydrolyzed glucono-1.5-lacton), analyzing factors such as temperature, acid concentration, particle size, and reaction time. Results reveal the temperature’s influence on leaching efficiency for cobalt, nickel, and lithium. The mechanism for Co follows a surface chemical reaction model with an activation energy of 28.2 kJ·mol−1. Nickel, on the contrary, shows a diffusion-controlled regime and an activation energy of 70.1 kJ·mol−1. The reaction of leaching Ni and Co using gluconic acid was determined to be first-order. The process within this environmentally friendly alternative leaching agent shows great potential for sustainable metal recovery.

Soret effect on stability of Darcy problem in a bidispersive porous medium with an exothermic chemical surface reaction

AbstractWe examine a saturated bidispersive porous medium undergoing an exothermic chemical reaction at its lower boundary. The fluid flow within this medium is modelled using the Darcy approach. While the Dufour effect is disregarded, the influence of the Soret effect is thoroughly explored. This problem represents a complex multiphysical phenomenon that integrates fluid dynamics, heat and mass transfer, chemical kinetics and thermoelectric effects. This problem finds relevance in various scientific and engineering applications, including enhanced oil recovery, chemical engineering, environmental engineering and energy systems. We introduce a complementary energy theory alongside a linear theoretical framework for the model. The Chebyshev collocation method is employed to derive both linear and nonlinear results. Our findings reveal that the effect of enhancing the Soret coefficient on the system's stability is contingent upon the boundary conditions and the Lewis number. Specifically, an increase in the Soret coefficient generally stabilises the system during stationary convection. Conversely, in scenarios where oscillatory convection prevails, a higher Soret coefficient tends to destabilise the system.

Nox impact on mercury removal based on TAC: A comprehensive DFT and XAFS analysis

The simplification of surface chemical reactions is crucial for comprehending the role of nitrogen oxides (NOx) in the adsorption behavior of elemental mercury (Hg0) onto carbon-based sorbents, thereby contributing to technological advancements in reducing mercury emissions. In this study, we developed two fundamental models for activated carbon and investigated the interactions among the carbon surface, NO/NO2, and Hg0 using density functional theory (DFT) calculations. Additionally, thermally-treated activated carbon (TAC) was utilized for Hg0 adsorption, and X-ray absorption fine structure (XAFS) analysis was conducted to examine the morphology and bonding environment of captured Hg. The results suggest that the carbon surface exhibits weak physisorption towards Hg0, but effectively adsorbs NO/NO2. Adsorption of NO/NO2 on the carbon surface with a zigzag edge leads to a decrease in the ADCH charge and surrounding electrostatic potential (ESP) of neighboring carbon vertices, thereby enhancing Hg0 adsorption in those regions through the Eley-Rideal reaction mechanism. The interaction between Hg0 and the surface with ZNO1, ZNO2, or ZNOO2 configurations involves electron transfer and subsequent formation of Hg-C ionic bonds, resulting in adsorption energies ranging from −91.33 to −87.56 kJ/mol. Notably, the adsorption of Hg0 onto the surface with ZNOO1 configuration results in a more extensive electron transfer, facilitating the formation of a robust Hg-O ionic bond and leading to a further reduction in Hg0 adsorption energy to −430.02 kJ/mol. XAFS analysis confirms that predominant formation of Hg-O species occurs following Hg0 adsorption on TAC under syngas containing NO2.

The Stabilizing Effect of Chitosan‐Modified Biochar (β‐CD/C‐BC) on Agricultural Soil Contaminated by the Cd‐Pyr Complex

AbstractThe composite pollution of heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) in agricultural soil is increasingly severe. HMs can undergo surface adsorption, complexation, or chemical reactions to transform from bioavailable species to residual species, achieving chemical morphological stability. However, these processes have no effect on PAHs. Biochar (BC), due to its inherent characteristics, can significantly enhance the stability of PAHs and is recommended as a potential co‐stabilizing material for both heavy metals and PAHs. In this study, rice husk biochar modified with β‐cyclodextrin and chitosan (β‐CD/C‐BC) was utilized to stabilize agricultural soil contaminated by Cd and Pyrene (Pyr). One‐way tests were conducted on the dosage and curing time of biochar after a complete cycle of treatment. The results demonstrated that the optimal effect was achieved when the dosage of β‐CD/C‐BC was 7.5 % or the curing time was 21 days. The removal efficiencies for Cd and Pyr were found to be 84.62 %, 64.22 % or 85.90 %, 65.78 %, respectively. Additionally, BCR testing revealed that β‐CD/C‐BC could convert HMs in soil into a residual state (from 32 % to 82 %) with the highest stabilization rate, thereby reducing their migration ability and ecological risk.

Peculiarities of Calcite Interaction with Carboxylic Acids

This research examined the interaction of calcite with carboxylic acids (formic, citric, malic, and oxalic acids) at temperatures ranging from 22 to 80 °C. Experiments were carried out using an open batch reactor to prevent the impact of aggressive CO2 byproducts. The dissolution rate was determined to be a combination of the chemical interaction of calcite with acid and the promotion of dissolution by calcium carboxylate salt. When acid concentrations are low, the surface chemical reaction acts as a limiting step with an activation energy of 42 kJ∙mol-1. Conversely, at higher acid concentrations, the formation of calcium carboxylate with reduced solubility hinders its dissolution, thereby restricting the overall calcite dissolution process. Both stages are significantly influenced by temperature. The specific functional groups present in the acids aid in the formation of surface species with Ca2+ cations. The properties of these functional groups impact the stability of the species and the dissolution of calcite.

Waste cigarette butts-templated synthesis of in-situ graphitic carbon-doped ZnO fibers boosting dual-selectivity NO2/butanone at different temperatures

How to build a dual-selective ZnO-based gas sensor remains challenging due to the fact that the great majority of reported gas sensors were designed to monitor only a single given harmful gas. Herein, discarded cigarette butts were chose as template, and dipped in zinc nitrate solution. Then, the obtained precursors were calcined to synthesize two types of ZnO-based fibers with V-shaped grooves. Among, the fiber component (GC/ZnO, GC being graphitic carbon) calcined at 400 °C composes of 7.02 wt% GC and small nanoparticles, which possesses multistage mesopores, large specific surface area and abundant oxygen vacancies. These factors not only optimize the percentage and state of oxygen species adsorbed in sensing layer, but also expose more active sites and facilitate surface chemical reactions, thereby providing a dual-selective platform for different gases. The GC/ZnO sensor shows high response of 624 for 10 ppm NO2 at 92 °C, and good response of 22.5 for 100 ppm butanone at 170 °C. Also, it has reversible response-recovery, low detection limit, as well as satisfactory stability and humidity resistance. This is the first report on a conductometric sensor that achieves the rapid and accurate detection of above harmful gases. In addition, its temperature-controlled dual-functional sensing mechanism was also analyzed.

Deep-Learning Driven, High-Precision Plasmonic Scattering Interferometry for Single-Particle Identification.

Label-free probing of the material composition of (bio)nano-objects directly in solution at the single-particle level is crucial in various fields, including colloid analysis and medical diagnostics. However, it remains challenging to decipher the constituents of heterogeneous mixtures of nano-objects with high sensitivity and resolution. Here, we present deep-learning plasmonic scattering interferometric microscopy, which is capable of identifying the composition of nanoparticles automatically with high throughput at the single-particle level. By employing deep learning to decode the quantitative relationship between the interferometric scattering patterns of nanoparticles and their intrinsic material properties, this technique is capable of high-throughput, label-free identification of diverse nanoparticle types. We demonstrate its versatility in analyzing dynamic surface chemical reactions on single nanoparticles, revealing its potential as a universal platform for nanoparticle imaging and reaction analysis. This technique not only streamlines the process of nanoparticle characterization, but also proposes a methodology for a deeper understanding of nanoscale dynamics, holding great potential for addressing extensive fundamental questions in nanoscience and nanotechnology.

Biomimetic design of micro- and nano-wrinkle wood surface via coating reinforced with hyperbranched polymer grafted cellulose nanofibers for skin-tactile performance

Inspired from human skin, micro- and nano-wrinkled wood surface with skin-tactile performance was designed and developed using a waterborne UV-curable polyurethane acrylate coating and cellulose nofibers (CNF). To further improve the properties, the CNF was diacetylated to D-CNF and further grafted with a hyperbranched polymer containing rich end amino groups (HB-CNF). The surface structure and chemical reactions were characterized, and the skin-tactile performance of the coating was comprehensively investigated. The HB-CNF exhibited excellent dispersion in the coating, and extensive reactions occurred between the two through the –NH2 and terminal –NCO groups, resulting in much improved mechanical properties and durability. Micro-wrinkles with a width of approximately 12–15 μm and a height of 8–14 μm were created, and nano-protrusions of wrinkles ranging from to 50–100 nm were obtained. The coated surface was hydrophobic and exhibited high resilience after compression, with a gloss of 3.3 GU at an incident angle of 60° and a static friction coefficient of 0.26, both of which were similar to those of human skin. The results presented an effective strategy for high-performance wood products with a good feeling, which is helpful to improve the market competitiveness and meet the people's pursuit of a better life.

Oxidation Mechanism and Surface Characterization of Pyrolytic Graphite in Simulated Air for Pyrochemical Reprocessing Application

Accidental air ingress into the containment chamber of pyrochemical reprocessing of spent nuclear fuels can cause severe oxidation of graphite components. Pyrolytic graphite (PyG) coating on conventional high-density graphite (HDG) is proposed for protection against oxidation, molten salt, and molten metal corrosion. The aim of the present study is to evaluate the thermal stability and kinetic parameters and propose a suitable oxidation mechanism of PyG under simulated air using thermogravimetry analysis (TGA). In dynamic oxidation, a linear increase in the oxidation onset, peak, and burnout temperature is observed for PyG synthesized at increasing pyrolysis temperature from 1200 to 2400°C except for 1400°C. The isothermal oxidation study showed a similar trend i.e., a decrease in the linear oxidation rate constant value for any given isotherm with increasing pyrolysis. The Arrhenius plot showed two-stage oxidation regimes operating between 600 to 1000°C. In regime-I, between 600 to ∼800°C controlled by surface chemical reaction kinetics, the activation energy is measured between 100-200 kJ.mol−1. The graphite-oxygen reaction initiates and propagates preferentially along the prismatic planes at the sample edges, where the dangling bonds of stacked graphite layer structures are exposed. In regime-II operating above ∼800°C, the surface reaction rate is infinitely faster, and the diffusional mass transport becomes a rate-limiting factor. In this regime, the graphite-oxygen initiates by pore formation on defective reactive sites on the bulk surface and propagates by pore-widening and pore-coalescence mechanism. The observed differences in the oxidation rates for different pyrolysis PyG attributed to its intrinsic material properties are investigated. This work provides new insights into the oxidation mechanism of the PyG during accidental air ingress in a pyrochemical reprocessing plant.

Thermal atomic layer deposition of aluminum oxide, nitride, and oxynitride: A mechanistic investigation

Atomic layer deposition (ALD) has been proven to be a versatile method for the deposition of thin films of various materials. It yields films with exceptional conformality and allows tunable film compositions with control of film thickness at the atomic level. Thin films of Al oxide, nitride, and oxynitride are deposited via ALD using Al(CH3)3 (TMA)/AlCl3 with H2O/NH3. Herein, surface chemical reactions are examined using density functional theory calculations to elucidate the adsorption, oxidation, and nitridation of precursors [TMA and AlCl3] as well as the mechanism controlling the composition of Al oxynitride thin films obtained through ALD. The hydrogen-terminated substrate surface is transformed into a CH3/Cl-terminated surface after the reaction with the TMA/AlCl3 precursors. The molecular adsorption of TMA occurs through a spontaneous reaction, whereas that of AlCl3 requires a slight energy input. Although the adsorption energy of AlCl3 is higher than that of TMA, the activation energy and energy change of AlCl3 adsorption are higher and lower than those of TMA, respectively; furthermore, the use of AlCl3 results in the generation of a corrosive by-product (HCl). A similar tendency is observed in the second ALD half reaction, which is oxidation. Nitride formation is endothermic for molecularly adsorbed AlCl3 but exothermic for TMA. Furthermore, the investigation of the exchange reactions between surface moieties and excess gaseous reactants reveals a preference for the substitution of N by O, which is attributed to differences in bond energies between the surface moieties and the surface metal atom, as well as between H2O and NH3.

Fluorinated TiO2 Hollow Spheres for Detecting Formaldehyde under UV Irradiation.

The fluorinated titanium dioxide (F-TiO2) hollow spheres with varying F to Ti molar ratios were prepared by a simple one-step hydrothermal method followed by thermal processing. The diameter of the F-TiO2-0.3 hollow spheres with a nominal ratio of F:Ti = 0.3:1 was about 200-400 nm. Compared with the sensor based on pristine TiO2 sensing materials, the F-TiO2-0.3 sensor displayed an enhanced sensing performance toward gaseous formaldehyde (HCHO) vapor at room temperature under ultraviolet (UV) light irradiation. The F-TiO2-0.3 sensor demonstrated an approximately 18-fold enhanced response (1.56) compared to the pristine TiO2 sensor (0.085). The response and recovery times of the F-TiO2-0.3 sensor to 10 ppm HCHO were about 56 s and 64 s, respectively, and a limit-of-detection value of 0.5 ppm HCHO was estimated. The F-TiO2-0.3 sensor also demonstrated good repeatability and selectivity to HCHO gas under UV light irradiation. The outstanding HCHO gas-sensing properties of the F-TiO2-0.3 sensor were related to the following factors: the excitation effect caused by the UV light facilitated surface chemical reactions with analyte gas species; the hollow sphere structure provided sufficient active sites; and the surface fluoride (≡Ti-F) created additional chemisorption sites on the surface of the TiO2 material.

Blow-Spun Si3N4-Incorporated Nanofibrous Dressing with Antibacterial, Anti-Inflammatory, and Angiogenic Activities for Chronic Wound Treatment

The effective and safe healing of chronic wounds, such as diabetic ulcers, presents a significant clinical challenge due to the adverse microenvironment in the wound that hinders essential processes of wound healing, including angiogenesis, inflammation resolution, and bacterial control. Therefore, there is an urgent demand for the development of safe and cost-effective multifunctional therapeutic dressings. Silicon nitride, with its distinctive antibacterial properties and bioactivities, shows great potential as a promising candidate for the treatment of chronic wounds. In this study, a silicon nitride-incorporated collagen/chitosan nanofibrous dressing (CCS) were successfully fabricated using the solution blow spinning technique (SBS). SBS offers compelling advantages in fabricating uniform nanofibers, resulting in a three-dimensional fluffy nanofibrous scaffold that creates an optimal wound healing environment. This blow-spun nanofibrous dressing exhibits excellent hygroscopicity and breathability, enabling effective absorption of wound exudate. Importantly, the incorporated silicon nitride within the fibers triggers surface chemical reactions in the aqueous environment, leading to the release of bioactive ions that modulate the wound microenvironment. Here, the CCS demonstrated exceptional capabilities in absorbing wound exudate, facilitating water vapor transmission, and displaying remarkable antibacterial properties in vitro and in a rat infected wound model (up to 99.7%, 4.5 × 107 CFU/cm2 for Staphylococcus aureus). Furthermore, the CCS exhibited an enhanced wound closure rate, angiogenesis, and anti-inflammatory effects in a rat diabetic wound model, compared to the control group without silicon nitride incorporation.Graphical abstract