Reaction Order Research Articles

Kinetics of kaolinite dissolution and hydrosodalite precipitation during alkali leaching of diasporic bauxite

Alkali leaching is an effective desilication method for improving the alumina-silica mass ratio (A/S) of bauxite. The paper aims to study the kinetics of kaolinite dissolution and hydrosodalite precipitation during alkali leaching of kaolinite-rich diasporic bauxite. Alkali leaching of bauxite in NaOH solutions was studied at Na2O concentrations of 200–260 g/L, temperatures of 90–105 °C, and times of 30–150 min. The leached bauxites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) techniques. The rate equations describing kaolinite dissolution and hydrosodalite precipitation were derived by fitting the Avrami model. The results show that kaolinite with finer particle sizes was preferentially dissolved during alkali leaching, providing a material basis for the precipitation of hydrosodalite. Hydrosodalite was heterogeneously nucleated on the dissolved edges of some kaolinite and grew in both one- and two-dimensions, presenting acicular and lamellar morphology. The dissolution rate of kaolinite and the crystallization mechanism of hydrosodalite were primarily influenced by Na2O concentration and temperature. Both kaolinite dissolution and hydrosodalite precipitation were controlled by chemical reactions with activation energies of 70.152 (± 1.429) kJ/mol and 289.089 (± 2.063) kJ/mol, respectively, and the orders of reaction with respect to Na2O of 0.733 (± 0.070) and 7.165 (± 0.047), respectively. The kinetic equations describing kaolinite dissolution, hydrosodalite precipitation and even the leaching of SiO2 were eventually modeled with Na2O concentration, temperature and time as variables.

Kinetic study on the thermal decomposition of iron (II) sulfate using a global optimization approach

The thermal decomposition of sulfates is a major intermediate reaction in oxidizing roasting processes associated with metal sulfides. The optimization of iron (II) sulfate could contribute to lowering processes’ temperatures in complex systems. The present work presents the experimental and modeling results of the thermal decomposition of iron (II) sulfate heptahydrate. The investigation was first based on thermodynamic simulations followed by non-isothermal thermogravimetric analysis. The modeling technique consisted of differential equations formulated to describe each decomposition step individually, with the kinetic parameters estimated using particle swarm optimization (PSO). Using this modeling methodology over a graphical method is advantageous as it can simulate reactions that may occur simultaneously. The modeling succeeded in dehydration and desulfation steps, with an overall R2 value of 0.99. The activation energies and apparent reaction order associated with the dehydration steps were 53.3kJ.mol−1/n=1.65, 88.8kJ.mol−1/n=1.12, and 124kJ.mol−1/n=2.0 for FeSO4.7H2O, FeSO4.4H2O, and FeSO4.H2O, respectively. The desulfation steps were associated with higher activation energy values. In that case, 184kJ.mol−1 and 264kJ.mol−1 for FeSO4 and Fe2(SO4)3, respectively. Regarding the apparent reaction order, both desulfation steps showed to be first-order reactions.

Negative Reaction Order for CO during CO2 Electroreduction on Au.

The potential-dependent negative fractional reaction orders with respect to the CO partial pressures were measured for CO2 electroreduction (CO2R) on Au under mass-transfer-controlled conditions using a rotating ring-disk electrode setup. At high overpotentials, the CO reaction order approaches -1 due to enhanced CO adsorption on Au, which is supported by kinetic analysis and density functional theory (DFT) simulations. This work illustrates that the CO site-blocking effect cannot be ignored, even on a weak CO-binding metal such as Au in the electrochemical environment. The CO site-blocking effect can greatly hamper the activity and the selectivity of the CO2R to CO. This observation enriches the current mechanistic understanding of the CO2R and could have significant implications not only in the theoretical modeling of the CO2R but also in the evaluation of intrinsic CO2R activity at practical current density and high conversion conditions.

Effects of atmosphere and stepwise pyrolysis on the pyrolysis behavior, product characteristics, and N/S migration mechanism of vancomycin fermentation residue

Vancomycin fermentation residue (VFR) urgently needs proper treatment due to its complex and hazardous nature. Pyrolysis is a promising treatment method, while the product characteristics of VFR pyrolysis remain unclear. Therefore, the influence of different atmospheres and stepwise pyrolysis (including one-stage reaction in N2 or CO2 and two-stage reaction in N2) on pyrolysis behavior, product characteristics, and N/S migration mechanism during VFR pyrolysis were investigated for the first time in this work. The results showed that VFR mainly decomposed at 180–600 °C, forming non-condensable gas, bio-oil, and biochar. The main released gases included CO2, H2O, NH3, HCN, SO2, and H2S, whereas the N-containing pollutant gas, notably NH3, should be focused due to its high emission (>10 %). Bio-oil was rich in N-containing compounds with a content exceeding 46 %, mainly consisting of Indolizne (9.2–11.5 %), 5H-1-Pyrindine (5.0–9.9 %), and Indole (8.4–9.0 %), and 9-Octadecenamide, (Z)- (1.8–10.1 %). Moreover, the effects of different conditions on the product characteristics were as follows: For the one-stage reaction, compared to N2, the CO2 atmosphere promoted the formation of alcohols (intended product, increasing 2.2–14.6 %), whereas the two-stage reaction in N2 inhibited alcohol production (decreasing 1.1–2.5 %). At CO2 condition, the harmless temperature of VFR reduced from 600 °C (pyrolysis in N2) to 400 °C. Both CO2 (increasing 0.6–1.5 %) and the two-stage reaction in N2 (increasing 0.4–1.0 %) retained more N in the solid. Kinetics showed that the pyrolysis process of VFR conformed to diffusion models and reaction order models (F2/D1/F3/D1 for N2 and F2/D2/F3/D1 for CO2). The VFR transformed to the chemicals and fuels mainly through the deamination, desulfurization, dehydration, decarboxylation, and dehydrogenation reactions. This work provides guidance for harmless disposal and resource utilization during VFR pyrolysis.

Kinetic Modeling of Mass Loss during Carbonization of Sodium Carboxymethyl Cellulose (CMC) Aerogels

The carbonization of sodium carboxymethyl cellulose (CMC) aerogels involves complex thermal decomposition processes leading to the formation of carbonaceous residues. Understanding the kinetics of mass loss during carbonization is vital for optimizing the production of CMC carbon aerogels with desired properties. In this study, a mathematical model is presented that describes the kinetics of mass loss during the carbonization process of CMC aerogels. This model considers the temperature and concentration dependence of CMC decomposition reactions and is validated against experimental data obtained at various conditions. The proposed kinetic model elucidates the underlying mechanisms governing mass loss during carbonization, offering valuable insights for the design and optimization of CMC carbon aerogels across diverse applications. Furthermore, the analysis of the experimental data reveals variations in both the reaction order and the rate constant for different concentrations of CMC aerogels, indicating distinct kinetic behavior. These findings contribute to a deeper understanding of the carbonization process and pave the way for tailored synthesis approaches to meet specific application requirements.

A Study of Micellar Catalyses on Oxidation of Glycine by QDC in the Presence of Sodium Dodecyl Sulphate (SDS) in Aqueous Perchloric Acid Medium

Aims: To study the micellar effect of SDS on the oxidation of glycine by Quinolinium Dichromate (QDC) in perchloric acid medium. Background: Among the amino acids, glycine plays a major role in multiple metabolic reactions, such as glutathione synthesis and one-carbon metabolism. The oxidation of glycine has received importance because it is the major neurotransmitter inhibitor in the spinal cord and brainstem. In the oxidation process of amino acids, highly toxic chromium (VI) compounds are converted into non-toxic chromium (III) by quinolinium dichromate (QDC) oxidant in an appropriate pH value medium. Objective: 1. To study the catalytic role of anionic surfactant (SDS) on the oxidation of glycine by QDC through micellization, evaluation of critical micelles concentration (CMC) in the presence and absence of glycine and other surface properties along with thermodynamic quantities. 2. Determination of rate constant and order of reaction with respect to QDC, glycine, acid and surfactant which will help to study the kinetics of the reaction 3. Analysis of oxidation product by FT-IR and calculation of activation parameters. 4. Synthesis of oxidant (QDC) and its characterization by UV-Visible spectrophotometer and NMR spectroscopy. Results: First-order kinetics was observed with respect to oxidant, glycine and hydrogen ions. The rate of reaction increased remarkably with an increase in the concentration of surfactant (SDS). The kinetic results show that the ionic strength variation does not have any significant effect on the rate whereas the increase in the dielectric constant of the medium shows a remarkable effect on the rate constant. From stoichiometry study, it was found that 2 moles of oxidant (QDC) consumed 3 moles of glycine to produce aldehyde (Formaldehyde). Conclusion: The observed negative value of (ΔS) entropy of activation and positive (ΔH) enthalpy of activation suggests a more ordered activated complex formation and highly solvated transition state. The kinetics of the reaction in a perchloric acid medium is found to be accelerated in the presence of surfactant (SDS). The kinetics of the reaction follow pseudo first-order decay of Cr(VI) species (QDC), a unity dependence of rate on glycine and perchloric acid. The oxidation product formaldehyde was identified by FTIR. NMR spectrum analysis of synthesized QDC shows a resemblance with pure QDC.

Photo Fenton-like oxidation of real textile wastewater: Operating conditions, kinetic modelling and cost analysis

The reusability of the pretreated textile wastewater was improved by using bismuth ferrite/activated carbon hybrid photocatalysts in photo-Fenton-like oxidation process. BiFeO3/WAC (WAC: walnut shell based activated carbon) and BiFeO3/CAC (CAC: Commercial activated carbon) catalysts were synthesized and used for the photocatalytic oxidation of in-situ pretreated textile wastewater. The influences of the mixing speed, oxidant dosage, light source, catalyst loading, and temperature were studied. The highest TOC removal efficiencies were evaluated as 56.3% and 76.2% in the presence of BiFeO3/WAC and BiFeO3/CAC, respectively. A kinetic study was performed to derive the kinetic models expressing the TOC removal as a basis for the semi-pilot and industrial scale studies. The kinetic data fit to a two-step second order reaction rate model in the presence of both of the catalysts. The activation energies of the first and the second steps were calculated as 36.0 and 16.0 kJ/mol, respectively, on BiFeO3/WAC catalyst while 43.4 and 13.3 kJ/mol of activation energies were calculated on BiFeO3/CAC.

Study of curing kinetics of 4‐ (dimethylsilyl) butyl ferrocene grafted HTPB and effect of catalysts by differential scanning calorimetry

AbstractThe cure kinetics of 4‐ (dimethylsilyl) butyl ferrocene grafted hydroxyl terminated polybutadiene (HTPB) with Isophorone diisocyante (IPDI) was investigated using differential scanning calorimeter (DSC). Furthermore, the catalytic effect of Iron (III) acetylacetonate (Fe(AA)3) and Dibutyltin dilaurate (DBTDL) on the curing reaction was studied. The experimental data was fitted to Kissinger and Ozawa models, and the kinetic parameters were expressed as Arrhenius activation energy (E), pre‐exponential factor (A) and rate constants. The Crane model was explored to determine the reaction order of the curing reaction. The study categorically showed that the activation energy of the curing reaction with 4‐ (dimethylsilyl) butyl ferrocene grafted HTPB is higher as compared to the pure hydroxyl terminated polybutadiene (HTPB) based system. However, the rate of curing reaction is higher with 4‐ (dimethylsilyl) butyl ferrocene grafted HTPB as compared to HTPB, and the viscosity build‐up data is too aligned with the DSC kinetic study. In addition, both catalysts increased the rate of the curing reaction but Fe(AA)3 displayed a superior catalytic effect.

Design, Reactivity, and Active Site of Atomically Dispersed Pt Catalysts for Electrochemical Chlorine Evolution Reaction

The electrochemical chlorine evolution reaction (CER) is a key anodic reaction in the chlor−alkali process for Cl2 production, on-site generation of ClO–, and Cl2-mediated electrosynthesis.1−3 For more than a half-century precious metal-based mixed metal oxides (MMOs) have been mainstays as CER catalysts, however, they intrinsically suffer from the selectivity problem arising from a parasitic oxygen evolution reaction (OER). We have recently developed a new CER catalyst based on atomically dispersed Pt sites on a carbon nanotube (Pt1/CNT), which catalyzes the CER with excellent activity and selectivity.4 The Pt1/CNT catalyst shows superior CER activity to a commercial Ru/Ir-based MMO and a Pt nanoparticle-based catalyst. Importantly, Pt1/CNT exhibits very high CER selectivity near 100% even in low Cl− concentrations (0.1 M) and neutral media, under which the OER is favored over the CER. In situ X-ray absorption spectroscopy and density functional theory calculations reveal that the CER over Pt1/CNT augments with the direct adsorption of Cl− ion on Pt, which can break the scaling relationship between CER and OER. The Pt1/CNT catalyst also shows unusual potential-dependent switching behavior of CER kinetics and rate-determining step.5 Pt1/CNT shows a reaction order of ~1.8 in the low overpotential regime, where the Volmer step is the rate-determining step (RDS). Interestingly, in the high overpotential region, the CER over Pt1/CNT proceeds with a lower reaction order and the RDS switches to the Heyrovský step. We also show that the Pt1/CNT catalyst is comprised of multiple Pt sites with different coordination environments and identify a genuine active site in Pt1/CNT catalysts for the CER.6 K. B. Karlsson and A. Cornell, Selectivity between Oxygen and Chlorine Evolution in the Chlor-Alkali and Chlorate Processes. Chem. Rev. 116, 2982–3028 (2016).S. Exner, T. Lim, and S. H. Joo, Circumventing the OCl vs. OOH Scaling Relation in the Chlorine Evolution Reaction: Beyond Dimensionally Stable Anodes. Curr. Opin. Electrochem. 34, 100979 (2022).Trasatti, Electrocatalysis: Understanding the Success of DSA. Electrochim. Acta 45, 2377–2385 (2000).Lim, G. Y. Jung, J. H. Kim, S. O. Park, J. Park, Y.-T. Kim, S. J. Kang, H. Y. Jeong, S. K. Kwak, and S. H. Joo, Atomically Dispersed Pt−N4 Sites as Efficient and Selective Electrocatalysts for the Chlorine Evolution Reaction, Nat. Commun. 11, 412 (2020).Lim, J. H. Kim, J. Kim, D. S. Baek, T. J. Shin, H. Y. Jeong, K.-S. Lee, K. S. Exner, and S. H. Joo, General Efficacy of Atomically Dispersed Pt Catalysts for the Chlorine Evolution Reaction: Potential-Dependent Switching of the Kinetics and Mechanism, ACS Catal. 11, 12232−12246 (2021).Cho, T. Lim, H. Kim, L. Meng, J. Kim, J. H. Lee, G. Y. Jung, F. Viñes, F. Illas, K. S. Exner, S. H. Joo, and C. H. Choi, Importance of Broken Geometric Symmetry of Single-Atom Pt Sites for Efficient Electrocatalysis, Nat. Commun. 14, 3233 (2023).

Pore-Scale Study of Diffusion and Adsorption Mechanisms during Capture of Atmospheric Carbon Dioxide

The surge in the global average temperatures has necessitated a decrease in the level of the released carbon dioxide (CO2) from different anthropogenic sources. In addition to curtailing the various emissions, there is a growing demand to remove the CO2 already existing in the atmosphere. As such, there is an impetus for synergistic experimental and modeling studies as it can propel the endeavor toward the development of durable and less energy-intensive CO2 capture systems. In this work, a physics-based numerical model employing the Lattice-Boltzmann Method (LBM) is formulated to simulate the coupled mass transfer and adsorption phenomena occurring during CO2 capture. A modeling workflow integrated with experiments will be presented which aids in the determination of the pertinent reaction order and adsorption rate constant based on a mixed-order kinetic model. The influence of Damköhler number, porosity, and microporosity content of the carbon fiber domain on key metrics such as the adsorption efficiencies and time constants will be further delineated.

A Study of Hydroxyl-Terminated Block Copolyether-Based Binder Curing Kinetics.

In order to determine the curing reaction model and corresponding parameters of hydroxyl-terminated block copolyether (HTPE) and provide a theoretical reference for its practical application, the non-isothermal differential scanning calorimetry (DSC) method was used to analyze the curing processes of three curing systems with HTPE and N-100 (an aliphatic polyisocyanate curing agent), isophorone diisocyanate (IPDI), and a mixture of N-100 and IPDI as curing agents. The results show that the curing activation energy of N-100 and HTPE was about 69.37 kJ/mol, slightly lower than the curing activation energy of IPDI and HTPE (75.60 kJ/mol), and the curing activation energy of the mixed curing agent and HTPE was 69.79 kJ/mol. The curing process of HTPE conformed to the autocatalytic reaction model. The non-catalytic reaction order (n) of N-100 and HTPE was about 1.2, and the autocatalytic order (m) was about 0.3, both lower than those of IPDI and HTPE. The reaction kinetics parameters of the N-100 and IPDI mixed curing agent with HTPE were close to those of N-100 and HTPE. The verification results indicate a high degree of overlap between the experimental data and the calculated data.

Production of Industrial-Grade Monoclinic Lead Chromate (PbCrO4) from Indigenous Chromite ore for Paint Pigment Utilization

Decades of use have proven that lead chromate (PbCrO4) powder is an excellent paint pigment material. Unfortunately, practically this entire superb chromate compound used for decorative systems, protective systems, and mass dyeing of paper and polymer materials is conventionally made using inorganic synthetic chromium salts. In this study, we reported a promising simple, low-cost lead chromate production route derived from chromite ore from Nigeria. The Nigerian chromite ore was roasted in a 1:1 NaOH salt and then leached with water at 60°C. Lead nitrate was added to the leached liquor to further co-precipitate it. The resulting precipitate was then cleaned in ethanol and oven dried for ten hours at 80°C. The experimental results showed that lead ion concentration, temperature and flow rate have large influence on lead chromate precipitation, and the precipitation data fit a diffusion model. The activation energy of lead precipitation obtained was 4.76 kJ/mol, and the reaction order was 0.873 nearly one in relation to the concentration of lead ion. Additionally, XRD, FT-IR, and SEM/EDS comparative investigation of the properties established which favourable paint pigment performance similar to that of commercial industrial lead chromate powder in a range of all established physicochemical properties clarified the developing direction of research on lead chromate synthesis from Chromite leached liquor.

Enhanced production of Pirfenidone through a microfluidic system: A novel and thorough chemical kinetics investigation

Batch and continuous systems were fabricated to synthesize Pirfenidone (PFD). Effects of parameters on reaction yield including; microreactors, micromixer, solvents, temperature, reaction time, and catalysts were understudied. Moreover, FTIR, NMR and HPLC analyses used to evaluate the prepared PFD. Its yield in microfluidic (30.5 %) was higher than that of batch (17.1 %) reactor. Besides, reaction yield in the presence of DMSO was higher than DMF in both reactors. It was shown that, adding a micromixer enhanced reaction time. leading to a higher PFD yield. Nonetheless, the yield was reduced by enhancing the temperature when DMF was utilized. Additionally, the traditional synthesis method of PFD in a batch system, which reached a yield of 53.7 % after 19 h, now reached 30.5 % in a microreactor under similar conditions within 40 min. Utilizing the Design Expert Software, the results revealed a maximum overall reaction yield of 31 % achieved at reactant ratio of K2CO3 to 2‑hydroxy-5-methylpyridine of 7, Temperature of 160 °C and reaction time of 60 min completely matching the experimental results. Ultimately, kinetics of PFD was understudied incorporating a Molecular Dynamic Software where a new 3-steps mechanism was proposed. Moreover, a power law model revealed an empirical reaction order of 1.45.

Ammonia-regulated dynamic evolution of Ti precursor incorporating into dealuminized beta for efficient 1-Hexene epoxidation

Demetalation-metalation method has gained prominence for its higher metal loading, efficiency and shortened synthetic period, particularly in the incorporation of metal atoms with large radii into zeolite framework in recent years. An ammonia-regulated approach has been developed for selectively evolved deep-substituted Ti precursors in dealuminized beta zeolites, which enables a controlled promotion of metalation of Ti atoms. Additionally, this ammonia-regulated approach could also enhance 1-hexene kinetic adsorption by constructing mesopores, which is demonstrated by the lower reaction order of 1-hexene. The synthesized ammonia-regulated N-Ti-beta exhibits rich framework Ti species and a high specific surface area, leading to significantly improved 1-hexene epoxidation performance (conversion of 61%, selectivity of 98%, and a high H2O2 utilization efficiency of 93%). This study not only provides a new strategy to dynamically regulate evolution of Ti precursors by ammonia but also holds promise for advancing related industrial processes in demetalation-metalation methods.

Effect of different boundary conditions on the combustion properties and fire characteristics of typical woods

To provide guidance on the bioenergy potential of wood and its fire spread numerical simulation, insights into the combustion properties and fire characteristics of one hardwood (sassafras) and two softwoods (pine and fir) were investigated. The effect of different boundary conditions are focused. The condensed phase decomposition in thermogravimetric analysis indicated that the main degradation processes for all wood combustion could be divided into two stages, and the corresponding demarcation point of conversion rate is 0.4 and 0.35 for hardwood and softwood, respectively. Three specific regions could further be established based on the activation energies variations in Stage Ⅰ. The governing reaction mechanism of sassafras wood is determined to be the diffusion model connect with order-based model, while the reaction mechanism of softwoods (pine and fir) can be considered as the reaction order (1st to three-halves) type followed by diffusion model. The gas phase flaming in FPA combustion experiments suggest that fir and pine wood have a faster charring rate and produce less CO and CO2 during pyrolysis and combustion. Sassafras requires more time to be ignited owing to its high density, which causes higher thermal inertia therefore decelerating the temperature increase on the sample surface. In addition, the dense structure of sassafras leads to an early appearance of the second HRR and MLR peaks. As hardwood has a higher density than softwood, the thermal insulation in hardwood delays char cracking on sassafras wood surface and enhances the duration between ignition and flameout. Such findings should provide guidance for wood combustion modeling and flame spread simulation in future works.

Removal of Diethylene Glycol from Wastewater by Photo Aeration

Photo air oxidation combines the use of ultraviolet (UV) light and air as an oxidant to degrade diethylene glycol (DEG) in wastewater. DEG is well known for its high chemical oxygen demand and has raised some serious environmental issues, since the conventional biological treatment package in plants may not be able to treat the waste in an effective manner. UV light generates highly reactive species, such as hydroxyl radicals (•OH), which can react with DEG and break it down into smaller, less harmful compounds. Air, specifically oxygen (O2), can act as an additional oxidant in the process, assisting in the degradation of DEG. The UV light source, such as low-pressure mercury lamps that emit at around 254 nm, is still needed to initiate the generation of hydroxyl radicals. The presence of oxygen in wastewater allows the hydroxyl radicals to react with DEG more effectively, improving the oxidation process. In the present research work, the effect of airflow rate, UV light intensities, oxygen partial pressure, and initial DEG concentration on photo-oxidation of DEG in wastewater was examined. We have also performed a kinetic study, from which the reaction order and the rate constant were determined.

An ionic liquid in Core-shell structure: Halogen-free, metal-free bifunctional catalyst for olefin epoxidation and CO2 cycloaddition

We synthesized a core-shell resin structure with abundant architecture and excellent thermal stability through polymerization. Imidazole ionic liquid with varying carbon chain lengths was immobilized on the surface, resulting in the preparation of metal-free, halogen-free core-shell catalysts with different carbon chain lengths via HCO3- exchange. Characterization using FT-IR, XPS, and various techniques revealed the exceptional performance of our synthetic catalyst in terms of its internal structure. After extensive experimentation, we discovered that the synthesized catalyst exhibits dual functionality for epoxidation and CO2 cycloaddition reactions without requiring solvents or co-catalysts. The epoxidation system demonstrated remarkable conversion rates and selectivity while also exhibiting strong recyclability in heterogeneous reactions, according to kinetic parameters, the reaction order of styrene, TBHP and catalyst during epoxidation is approximately 1, the reference factor for this reaction was calculated to be 6.7×109 (L2·mol−2·min−1), with an activation energy of 48.9 kJ/mol obtained from analyzing reaction rates at different temperatures. In the CO2 cycloaddition reaction, our catalyst exhibited an advantage in catalyzing ring-opening reactions, achieving a conversion rate of 95 % for styrene oxide within six hours along with over 99 % selectivity towards cyclic carbonate formation. It is suggested that the epoxide reaction is carried out in steps, and it is inferred that the catalyst PS-ImC4HCO3 and TBHP are produced into peroxy intermediate active species TBA and HCO4, and the reaction between HCO4- and styrene is the determination step of the total reaction. The reaction rate constant k=0.009 of the absolute step is calculated based on the global optimization algorithm

Kinetics analysis of copper extraction from copper smelting slag by sulfuric acid oxidation leaching

Copper smelting slag (CSS) is generally produced from the pyrometallurgy of copper sulfide concentrate, the current storage disposal methods of CSS not only occupy precious land and pollute the environment, but also waste resources. To recover copper from the CSS and explore the atmospheric pressure oxidative leaching kinetics of copper extraction from CSS with sulfuric acid was investigated intensively. In this study, the effect of particle size, sulfuric acid concentration, temperature, liquid-to-solid ratio, and hydrogen peroxide added amount were investigated comprehensively. The results indicated that the decrease of particle size and increase of other parameters can significantly promote the leaching of copper. Under the optimum conditions, 90.7 % of the copper in the CSS was effectively leached, other copper in the leaching slag mainly existed in the form of fine-grained embedded copper sulfide. The dominant phase of the leaching slag is magnetite, which could be further recovered by conventional magnetic separation. Moreover, the kinetics of copper atmospheric pressure oxidative leaching in CSS were further expounded. The results indicated that the copper leaching kinetic conforms to the shrinking core model, and the overall leaching reaction was controlled by the internal diffusion control with an activation energy of 11.22 KJ/mol. The apparent reaction order of sulfuric acid and particle size are determined to be 0.965 and 0.478 respectively. Finally, the kinetics model equation is established for copper at normal pressure as:1-23η-1-η2/3=0.032·CH2SO40.965·r0-0.956·t. This research could provide an alternative solution for the efficient utilization of CSS.

Exploring the sorption and degradation dynamics of validamycin-A in agricultural soils for environmental management.

Validamycin A (VA) is one of the antibiotics that have been utilized in agriculture in Asia; nevertheless, there haven't been many investigations on what happens to VA in soil. The rate at which pesticides are adsorbed into the soil must be determined, since their usage in agriculture is growing. In order to accomplish this, the current study investigated the sorption and degradation of VA in ten distinct soil samples via batch equilibrium studies while maintaining strict laboratory controls. In thermodynamic analysis with a C-type curve, the negative values of Gibbs free energy (ΔG) are thoroughly evaluated using both linear and Freundlich models. These values vary from - 16.8 to - 22.2kJ/mol. Impact of temperature (18, 23, and 30°C) and pH (5, 7, and 9) on the degradation of this antibiotic in soil was also scrutinized. Our findings demonstrated that, as a result of enhanced microbial activity at higher temperatures, VA deteriorated more quickly at 23°C and 30°C than at 18°C. In comparison to lower pH values, the VA removal efficiencies with sample-4 was significantly greater at pH 7.4 (92.9%) and pH 9 (97.4%). Moreover, first order reaction kinetics were followed in the degradation of VA. The results demonstrated that VA bound to the selected soils, resulting in medium to low persistence as demonstrated by degradation values. In summary, this study provides important information regarding the behavior and fate of VA in different types of soil, information that might be useful in developing workable management strategies and environmental risk assessments.

Desorption of humic monomers from Y zeolite: A high-temperature X-ray diffraction and thermogravimetric study

In this work, the thermal behaviour and kinetic modelling of p-hydroxybenzaldehyde (HBA) desorption was studied using both isothermal and non-isothermal methods from Y zeolite, to obtain a detailed structural and kinetic interpretation of the process. Rietveld refinement of in situ powder XRD patterns and TG analysis highlighted that the HBA thermal degradation occurred in the temperature range ∼530–750 K. This process significantly affects the geometry of the zeolite framework, thus causing a cooperative tilting of the tetrahedra and resulting in the deformation of both 6MRs and 12MRs rings. The HBA desorption experiment was also carried out in isothermal conditions at four different temperatures (473, 523, 623 and 673 K) which are selected on the basis of the relevant features from DTG/DTA curves. The value for the reaction order is nearly the same for all isothermal rates, providing strong confirmation of the validity of the reported apparent activation energy of the p-HBA decomposition process. The corresponding activation energy value (60.92 kJ/mol) agrees with literature data reported for dealuminated HZY (58 kJ/mol) and NaY.