Formation Of Intermediate Compounds Research Articles

Investigating the efficiency of electrocoagulation using similar/dissimilar electrodes for the detoxification of Coralene Rubine dye: a cost effective approach.

Efficient treatment of textile dyeing wastewater can be achieved through electrocoagulation (EC) with minimal sludge production; however, the selection of the appropriate electrode is essential in lowering overall costs. Also, the reuse of the treated aqueous azo dye solution from this process has not been explored in detail. With these objectives, this study aims to treat synthetic azo dye solutions and achieve high colour removal efficiency (CRE%) using similar (Ti-Ti) and dissimilar (Ti-Cu) metal electrodes through EC with an attempt to reduce the cost. The aqueous Coralene Rubine GFL azo dye was used to examine the efficiency and cost of the EC process. X-Ray Photoelectron Spectroscopy was used to study the EC mechanism, while High Performance Liquid Chromatography was used to analyse the degradation of the dye and the formation of intermediate compounds. The concentration of metal ions in the treated dye solution was quantified using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), with Ti-Ti treated solution having 14.20mg/L concentration of Ti and Ti-Cu treated solution having 0.078mg/L of Ti and 0.001mg/L of Cu, respectively. Colour removal efficiency of 99.49% was obtained for both electrode sets, with a lower operating time and voltage for dissimilar metal combination. Ecotoxicity studies showed negligible toxicity of Ti-Cu treated dye samples compared to untreated solutions. Survival rate, protein estimation, and catalase activity was used to validate the treatment method's efficacy. The study found that the dissimilar electrode material exhibited reduced toxicity due to the presence of heavy metals below the permissible limit.

Advances in Computational Methods for Modeling Photocatalytic Reactions: A Review of Recent Developments.

Photocatalysis is a fascinating process in which a photocatalyst plays a pivotal role in driving a chemical reaction when exposed to light. Its capacity to harness light energy triggers a cascade of reactions that lead to the formation of intermediate compounds, culminating in the desired final product(s). The essence of this process is the interaction between the photocatalyst's excited state and its specific interactions with reactants, resulting in the creation of intermediates. The process's appeal is further enhanced by its cyclic nature-the photocatalyst is rejuvenated after each cycle, ensuring ongoing and sustainable catalytic action. Nevertheless, comprehending the photocatalytic process through the modeling of photoactive materials and molecular devices demands advanced computational techniques founded on effective quantum chemistry methods, multiscale modeling, and machine learning. This review analyzes contemporary theoretical methods, spanning a range of lengths and accuracy scales, and assesses the strengths and limitations of these methods. It also explores the future challenges in modeling complex nano-photocatalysts, underscoring the necessity of integrating various methods hierarchically to optimize resource distribution across different scales. Additionally, the discussion includes the role of excited state chemistry, a crucial element in understanding photocatalysis.

Unraveling the deactivation mechanism of Co-LiH composite catalyst for ammonia synthesis at milder conditions

An efficient ammonia synthesis catalyst that operates under mild conditions has been a long-cherished goal in heterogeneous catalysis. The challenges associated with low-temperature ammonia synthesis arise from both the activation of inert N2 molecules and the presence of scaling relations between reactant dissociation and intermediate adsorption energies. Transition metals-metal hydride (TM-MH) composite catalysts have shown promise to overcome these challenges as both TM and MH actively participate in the reaction, enabling improved ammonia synthesis rates at lower temperatures (150 ºC). Considering this prospect, two types of Co-LiH catalyst were synthesized by ball-milling of precursors (CoCl2 and LiH- denoted as Co-LiH(rxn)) and pure components (Co and LiH- denoted as Co-LiH(pur)), and their catalytic activity was evaluated at several reaction conditions to investigate the stability for long-term operation. Co-LiH(rxn) was found to deactivate in less than 150 h whereas Co-LiH(pur) displayed a continuous production although the synthesis rate was 3 times lower than the former. Structural characterization techniques, such as XRD, SEM, and TEM were used, and it was found that Co metal in the FCC phase was primarily sintered due to its small particle size in the fresh catalyst. Temperature-programmed desorption (TPD) test on the spent Co-LiH(rxn) catalyst also displayed an ammonia release profile similar to that of LiNH2 decomposition, which confirms the presence of ammonia in the spent catalyst structure. Hence, another major finding is speculated that irreversible ammonia absorption by LiH at the target ammonia reaction conditions contributes to the deactivation of the catalyst and the formation of intermediate compounds that are required for continuous ammonia generation in this composite catalyst.

Experimental investigation and thermodynamic assessment of the BaCl2–CeCl3 system

The thermodynamic and thermo-physical properties of the molten salt system ▪ have been investigated using an experimental and modelling approach. This molten salt system includes a single intermediate compound ▪, whose structure has been investigated using X-ray and neutron diffraction. Furthermore, this system exhibits solubility of ▪ in ▪ at high temperatures up to a concentration of around 25% ▪ at 1060 K. Additionally, our measurements show solubility of ▪ in ▪ up to about 5% ▪ at 973 K. The investigation of these solid solutions has been performed using quenching experiments and subsequent post-characterisation by X-ray diffraction (XRD). Phase diagram equilibria have also been investigated using differential scanning calorimetry (DSC). Using the aforementioned information on phase transitions, intermediate compound formation, and mutual solid solubility, a thermodynamic assessment of the system has been performed using the CALPHAD method. The model for the Gibbs energy of the liquid solution is the quasi-chemical formalism in the quadruplet approximation, while the model for the Gibbs energy of the solid solutions is a two-sublattice polynomial model.

Hydrogen storage properties and reaction mechanism of the Mg-Li-Na-Al ternary hydride system

This research uses the ball milling technique to study the preparation of the MgH2-LiAlH4-NaAlH4 with a molar ratio of 4:1:1 ternary-hydride system. The hydrogen storage behavior and reaction mechanisms have been carefully explored. The result demonstrates a reduction in the onset decomposition temperature of the 4MgH2-LiAlH4-NaAlH4 ternary composite compared to the as-milled MgH2, LiAlH4, and NaAlH4 components. Four substantial dehydrogenation processes, corresponding to the decomposition of LiAlH4, NaAlH4, and MgH2 were detected in a system with a total hydrogen capacity of 8.4 wt%. The onset decomposition temperature of LiAlH4 in this system is around 110 °C, while NaAlH4-relevant decomposition began releasing hydrogen at 153 °C, approximately 52 °C lower than the as-milled NaAlH4. Meanwhile, the destabilized system modifies the reaction route of MgH2, where MgH2-relevant decomposition begins around 270 °C, 82 °C lower than the as-milled MgH2. The apparent activation energy, Ea, for the decomposition of MgH2 in the composite was lowered to 124 kJ/mol based on the Kissinger analysis. It is believed that the enhancement of the dehydrogenation properties was attributed to the formation of intermediate compounds, including Li-Mg, Mg-Al and Li-Al alloys, upon dehydrogenation, which improved the thermodynamics properties by altering the de/rehydrogenation pathway.

Experimental investigation and thermodynamic modelling of the ThF4-PuF3 phase diagram

Phase equilibria in the ThF4-PuF3 system were measured by differential scanning calorimetry. Samples were encapsulated to prevent leakage during the measurements and to prevent fluoride contamination of the instrument. Formation of intermediate compounds and solid solutions was investigated by X-ray diffraction. A thermodynamic model based on the CALPHAD approach was developed for the measured system. Good fit between measurements and phase equilibria calculated using the model was achieved.

Synergy of grain boundary and interface diffusion during intermediate compound formation

ABSTRACT The kinetics of reactive growth of a compound with a columnar structure with frozen bulk diffusion is revisited. The finite rate of redistribution and reaction along moving interfaces between reagents and growing compound is taken into account. Cases of planar and curved inter-phase interfaces are discussed. A new kinetic equation for the phase growth with evolving grain boundaries is suggested. Three cases are considered: (1) frozen grain structure, (2) normal lateral grain growth which does not depend on phase growth and on diffusion fluxes, (3) flux-driven grain growth which is induced by grain-boundary diffusion fluxes across the growing compound layer. The latter model provides the best fit to the experimental data.

Facile One-Pot Synthesis of Nickel Nanoparticles by Hydrothermal Method.

The one-pot synthesis process has emerged as an economical synthesis method without the involvement of purification or formation of intermediate compounds. Therefore, nickel nanoparticles were selectively synthesized by a simple hydrothermal method using nickel(II) chloride hexahydrate and borane-ammonia complex as a precursor and reducing agent, respectively. The morphology and crystal growth were observed by controlling the precursor concentration ratio of Ni:AB from 1:0.1 to 1:4 under various temperatures ranging from 80 to 140 degrees. In addition, we observed that the crystal growth rate under the influence of NaCl and KCl resulted in spherical Ni particles with size distributions controlled in the range of 297.65 nm to 1082.15 nm and 358.6 nm to 605 nm, respectively.

Estimation of the Thermodynamic Properties of Mixing Binary Systems Based on Silver Nitrate and Alkali Nitrates using Ionic Model

This work was devoted to the formulation of thermodynamic properties of binary systems of molten salts by using an ionic model which requires three physical parameters for each salt : the crystal lattice energy, the latent heat of melting and the sum of the ionic radii. This formulation, whose adjustable parameters have been obtained by smoothing from the experimental mixing properties available in the literature, allowed us to calculate the molar enthalpies of mixing for twelve (12) binary systems of alkali nitrate and silver nitrate. The different results obtained show satisfactory general agreement between calculation and experiment with regression coefficients within the range 0.992 and 0.999 and relative uncertainties between experimental and calculated values of less than 6% throughout the compositional range for all systems studied. The present formulation more accurately determines the enthalpies of mixing of binary systems with a volume effect (without intermediate compounds) predominating over the chemical effect (formation of intermediate compounds) ; Furthermore, we were able to show that in binary systems of alkali nitrates based on lithium nitrate and sodium nitrate, the solutions are strictly regular and that the deviation from regularity increases as one goes down in the alkali metal family namely from lihium to caesium.

Formation of Intermediate Compounds and Poly- and Disulfide Ions during the Pressure Oxidation of Pyrrhotite

Formation of Intermediate Compounds and Poly- and Disulfide Ions during the Pressure Oxidation of Pyrrhotite

MECHANISM OF CATALYTIC ISOMERIZATION–DISPROPORTIONATION PROCESSING OF STRAIGHT-RUN GASOLINE

The isomerization-disproportionation conversion of straight-run gasoline over the Co/HZSM/SO42--ZrO2 (SZ) composite catalytic system at atmospheric hydrogen pressure has been studied. Optimal process conditions (1800С; Н2/СН=3; WHSV = 2.5 h-1) was established, under which the conversion of С8+ hydrocarbons is 77.3%, and the sum of high-octane gasoline components С5–С6 alkanes increases from 11% to 61%. Тhe effect of C4-, C5–C6 products and H2O on this isomerization-disproportionation process have been studied. It is shown that, unlike the main C5–C6 products, side C4-products affect the stability of the process, and the catalyst is deactivated under the water's influence. Comparative studies of the conversion of a mixture of straight-run gasoline and C2H5OH showed that H2O vapor formed sites deactivate the centers located on the SZ. It has been established that the mechanism of isomerization-disproportionation conversion of straight-run gasoline with the participation of a composite catalytic system is realized through the conjugated interaction of red-ox centers contained on SZ with acid-base centers of Co/HZSM-5, responsible, respectively, for the formation of intermediate compounds [С4+C7] and their and their further hydro cleavage

Effect of Temperature and MgCl2 Concentration on the Catalytic Pyrolysis of Malt Waste Using Response Surface Methodology

AbstractIn the search of new energy sources, this work aimed to investigate the pyrolysis of malt waste, the major by‐product generated from the brewing industry, to produce biochar and bio‐oil. The study also explored the effects of pyrolysis temperature and concentration of MgCl2 catalyst on the yields of bio‐oil, biochar and pyrolytic gas. The pyrolysis products were analyzed using Fourier transform infrared spectroscopy. The effects of the studied variables on the yields and quality of the pyrolysis products were quantified using regression technique. It was found that the use of MgCl2 favored dehydration reactions and generated biochar and bio‐oil with less oxygen and greater calorific value, thus improving their use as a fuel. In addition, the MgCl2 accelerated the formation of intermediate compounds at low temperatures, changed the reaction pathways and decreased the reaction complexity, consequently reducing the activation energy value and the order of reactions.

Non-isothermal solid-state synthesis kinetics of the tetragonal barium titanate

The solid-state synthesis kinetics of the barium titanate is investigated through thermogravimetry analysis (TGA), and derivative thermogravimetry (DTG). The XRD results confirmed the formation of pure tetragonal BaTiO3 after thermal analysis. The thermodynamic parameters (ΔH,ΔS,ΔG) are calculated for all possible reactions involved during the formation of BaTiO3. The thermodynamic analysis predicted the formation of intermediate compounds (BaO, Ba2TiO4). The thermal kinetic analysis is also performed by using the deconvolution kinetic method. The thermal profile is convoluted in three peaks and the kinetic triplets are calculated. The activation energy is calculated by using the iso-conversional KAS kinetic model based on the Straink approximation. The order of the average activation energy is Peak III (225.81 ​kJ/mol) ​> ​Peak II (223.88 ​kJ/mol) ​> ​Peak I (197.67 ​kJ/mol). The reaction mechanism and pre-exponential are identified by the integral master plot method. The F1, R2 and A4 reaction mechanisms dominated the reaction occurring in peak I, peak II and peak III, respectively.

Removal of Organic Dyes from Water and Wastewater Using Magnetic Ferrite-Based Titanium Oxide and Zinc Oxide Nanocomposites: A Review

Heterogeneous photocatalysis using titanium dioxide (TiO2) and zinc oxide (ZnO) has been widely studied in various applications, including organic pollutant remediation in aqueous systems. The popularity of these materials is based on their high photocatalytic activity, strong photosensitivity, and relatively low cost. However, their commercial application has been limited by their wide bandgaps, inability to absorb visible light, fast electron/hole recombination, and limited recyclability since the nanomaterial is difficult to recover. Researchers have developed several strategies to overcome these limitations. Chief amongst these is the coupling of different semi-conductor materials to produce heterojunction nanocomposite materials, which are both visible-light-active and easily recoverable. This review focuses on the advances made in the development of magnetic ferrite-based titanium oxide and zinc oxide nanocomposites. The physical and magnetic properties of the most widely used ferrite compounds are discussed. The spinel structured material had superior catalytic and magnetic performance when coupled to TiO2 and ZnO. An assessment of the range of synthesis methods is also presented. A comprehensive review of the photocatalytic degradation of various priority organic pollutants using the ferrite-based nanocomposites revealed that degradation efficiency and magnetic recovery potential are dependent on factors such as the chemical composition of the heterojunction material, synthesis method, irradiation source, and structure of pollutant. It should be noted that very few studies have gone beyond the degradation efficiency studies. Very little information is available on the extent of mineralization and the subsequent formation of intermediate compounds when these composite catalysts are used. Additionally, potential degradation mechanisms have not been adequately reported.

Historical Contingency in Microbial Resilience to Hydrologic Perturbations

Development of reliable biogeochemical models requires a mechanistic consideration of microbial interactions with hydrology. Microbial response to and its recovery after hydrologic perturbations (i.e., resilience) is a critical component to understand in this regard, but generally difficult to predict because the impacts of future events can be dependent on the history of perturbations (i.e., historical contingency). Fundamental issues underlying this phenomenon include how microbial resilience to hydrologic perturbations is influenced by historical contingency and how their relationships vary depending on the characteristics of microbial functions. To answer these questions, we considered a simple microbial community composed of two species that redundantly consume a common substrate but specialize in producing distinct products and developed a continuous flow reactor model where the two species grow with trade-offs along the flow rate. Simulations of this model revealed that (1) the history of hydrologic perturbations can lead to the shifts in microbial populations, which consequently affect the community's functional dynamics, and (2) while historical contingency in resilience was consistently predicted for all microbial functions, it was more pronounced for specialized functions, compared to the redundant function. As a signature of historical contingency, our model also predicted the emergence of hysteresis in the transitions across conditions, a critical aspect that can affect transient formation of intermediate compounds in biogeochemistry. This work presents microbial growth traits and their functional redundancy or specialization as fundamental factors that control historical contingencies in resilience.

Optimization of processing parameters to control Maillard browning in ready-to-eat processed potatoes.

Relationship among pH, aw and Maillard browning was investigated in processed potatoes ready-to-eat during cooking and sterilization in autoclave to prevent their colors changes. Central composite rotational design was used for optimization of color (L*, a* and b*), browning index and intermediate compounds index. Reduction in the L* value and increase in the a*, b* value and browning index, indicators for Maillard browning of the processed potatoes were mitigated at pH 4.0-5.0 and aw 0.96-1.00 and accelerated at pH less than 3.0 or more than 7.0 and aw less than 0.84. Formation of intermediate compounds was intensified at pH 5.0 and aw 0.99 and mitigated at pH 7.0 and aw 0.84. Adjustment of the pH to 5.0 and keeping aw at to 0.99 were the most effective parameters of to control Maillard browning in processed potatoes ready-to-eat.

Inhibition of chemical interaction of molybdenum and silicon in a Mo/Si multilayer structure by the formation of intermediate compounds.

In the present study, the formation of intermediate compounds in the Mo/Si multilayer was realized by the introduction of barrier layers at the interfaces. Their impact on the interdiffusion of Mo and Si was analyzed via X-ray photoelectron spectroscopy. It was established that the insertion of a thin Be barrier layer led to the formation of beryllide MoBe12 at the interface Si-on-Mo, which prevented the formation of molybdenum disilicide and improved the interface. The insertion of the B4C barrier layer led to its complete decomposition with the formation of borides and carbides of molybdenum and silicon (MoBx, SiBx, MoxC and SiCx) at the Si-on-Mo interface. The formation of only MoBx and SiCx was detected at the Mo-on-Si interface. It was important that the insertion of a thin B4C barrier layer did not fully prevent the formation of MoSi2 at both (Si-on-Mo and Mo-on-Si) the interfaces. These facts allowed us to assume that the diffusion barrier function of the B4C interlayer could be caused by the stability of the formed compounds, rather than the stability of the B4C layer itself.

Browning and pigmentation in food through the Maillard reaction.

The Maillard reaction was discovered in 1912 by Louis C. Maillard when he observed the browning phenomena with aroma formation in a heated solution containing a sugar and an amino acid. The Maillard reaction starts from the reactions between carbonyl groups of various sugars and amino groups of amino acids/ proteins, following the formation of intermediate compounds or poly-carbonyl compounds, which further react with each other and amino acids/proteins. Through various chemical reactions such as condensation, polymerization, degradation, cyclization etc., color and aroma are formed. The imparting of brown color is mainly attributed to melanoidins. However, the chemical structure of melanoidins remains unclear because melanoidins are complex and heterogeneous polymers. On the other hand, various kinds of low-molecular-weight pigments formed through the Maillard reaction have been isolated and their structures have been identified. Even though the contribution of each pigment is small, the recognition of color is cumulative. In some case, these pigments form brown polymers or significantly contribute to the total color of a model solution. These chemically clear information gives us a novel aspect for an overview of browning or pigmentation through the Maillard reaction. Graphical abstract.

Transient light emission from the silicothermic reduction of magnesium oxide with potential for monitoring intermediate compound formation and decay

Small silicon samples were brought into contact with magnesium oxide substrate plates and heated under vacuum. At heating temperatures above 1400 K, a transient light emission effect in the Si/MgO interface was observed. The changes in sample brightness are likely caused by a thermal effect. Typically the sample temperature decreases gradually by 40–80 K and is followed by a very fast rise in temperature. The light emission effect may be correlated to the transient formation and decomposition of an inhibiting layer of magnesium silicate and the endothermic formation of gaseous silicon oxide. Tempering a silicon sample on a magnesium oxide plate for several hours produced an etch pit in the substrate material from which the silicon sample split off during the cooling phase. The etch pit was investigated via electron microscopy. EDXS analysis of the finely structured surface of the reaction zone reports a composition of 2/1/5 (Mg/Si/O). A cross-section of the same area reveals a thin layer of reaction products on top of the substrate material.

Enhanced photocatalytic degradation of acephate pesticide over MCM-41/Co3O4 nanocomposite synthesized from rice husk silica gel and Peach leaves

Novel green nanocomposite from mesoporous MCM-41 and Co3O4 was synthesized from rice husk based silica gel and using the green extract of Peach leaves as reducing reagent. The composite was labeled as RH-MCM-41/Co3O4 and characterized by different techniques as green photocatalyst in the degradation of Acephate pesticide under visible light illumination. The composite showed well developed spherical MCM-41 particles decorated by nano Co3O4 nanoparticles with stunning surface area and low bandgap energy (1.51 eV). The composite displayed superior photocatalytic activities in the oxidation of Acephate which reflected in a complete degradation of different concentrations of it after 40 min (50 mg/L), 60 min (100 mg/L), 100 min (150 mg/L) and 140 min (200 mg/L) using 0.25 g of the composite. The complete removal of the present TOC for treatment of 100 mg/L acephate was achieved using 0.25 g after 70 min reflecting the formation of intermediate compounds during the oxidation steps. The reported intermediate compounds are CH3C(O)NH2, CH3O(CH3S)P(O)NH2, (CH3O)2P(O)SCH3, CH3OP(O)(OH)2, CH3SS(O)2CH3, and (COOH)2. All the formed intermediate compounds were degraded under the visible light photocatalytic activity of RH-MCM-41/Co3O4 into NO3−, SO42-, PO43-, and CO2 as final products.