Values Of Apparent Activation Energy Research Articles

Comparative study on reduction behaviors of low- and high-grade fired hematite iron ore pellets in coal

The reduction behaviors of fired Ramallakota (low-grade) and Bolani (high-grade) iron ore pellets were studied isothermally at temperatures of 1123, 1173 and 1223 K in non-coking coal. The degree of reduction progressed with the rise in reduction temperature and time. Ramallakota iron ore pellets exhibited relatively higher reduction rates than Bolani iron ore pellets reduced under identical conditions due to their higher porosity and gangue contents. Comparison of XRD patterns confirmed almost complete reduction in Ramallakota iron ore pellets at all the studied reduction temperatures in a much shorter period. Fayalite and hercynite formations were observed in both the types of reduced iron ore pellets with higher intensities in the pellets of Ramallakota iron ore. SEM images revealed relatively more growth of iron whiskers in reduced Bolani high-grade iron ore pellets. The apparent activation energy values for the reduction of studied iron ore pellets by coal were calculated to be in the range 14–20 kJmol−1, while pellets reduced in coal char under identical conditions exhibited relatively higher values owing to their slower reduction rates.

Conversion of ammonia to hydrogen in the microwave reactor system using Mo@Alumina catalysts with the promotion of rare-earth and alkaline earth elements

In this study, microwave assisted ammonia decomposition reaction to produce high purity hydrogen over γ-Al2O3 supported molybdenum based catalysts were investigated and the effects of various promoters, rare-earth (lanthanum, cerium) and alkaline-earth (calcium and barium) elements on the catalytic activity were studied. Ammonia conversions of over 94% were obtained over the unpromoted catalysts above 350oC at a flow rate of 60 ml/min of pure ammonia. The overall hydrogen production rate per gram of catalyst was found to be 72.86 mmol/min.gcat with for 30 wt.% Mo loaded unpromoted catalyst at 350oC. The apparent activation energy (Ea) values for these catalysts were found to be around 85 kJ/mol. Among the promoters, Ba and Ce gave better performance below 350oC than Ca and La and the optimum loading was found to be 4 wt.% for them. Neither molybdenum nitride nor molybdenum carbide were detected in the spent form of the catalysts.

Influences of Sulfur-Containing Components on the Key Phases of FeS Spontaneous Combustion Dynamics

ABSTRACT In petroleum storage tanks, sulfur-containing crude oil continues to corrode equipment, generating sulfur corrosion products such as FeS. These products exhibit rapid exothermic reactions upon contact with air, thereby increasing the risk of fires and explosions. Additionally, sulfur monomers precipitated from sulfur or other compounds present in crude oil can adhere to FeS, consequently altering its spontaneous combustion characteristics. To explore the impact of associated sulfur content on the spontaneous combustion characteristics of FeS during its formation, this research synthesized FeS and its sulfur mixtures with sulfur concentrations of 5%, 10%, 15%, and 20%. These mixtures were prepared using a liquid-phase method, which involved the synthesis of self-made active FeS followed by the addition of different sulfur components. Differences in the spontaneous combustion characteristics of the five groups of samples were investigated in stages by simultaneous thermal analysis. The trends of the characteristic parameters of spontaneous combustion of FeS with different percentages of sulfur-containing components were analyzed. Finally, the apparent activation energy values of FeS with FeS and its associated sulfur were calculated by using thermodynamic analysis in the room-temperature spontaneous combustion stage (RT-75℃) and high temperature combustion stage (160–250℃). The findings indicate that the presence of sulfur components enhances the reactivity of FeS, yet reduces its oxygen absorption saturation threshold, thus advancing the oxygen absorption endpoint and facilitating entry into the high-temperature combustion stage. Moreover, FeS and its associated sulfur exhibit prolonged sustained combustion times when the sulfur component percentage is below 10%, favorably influencing the combustion behavior of FeS. As the percentage of sulfur component increases (from 10% to 20%), the combustion duration temperature rises from 60°C to 95°C. Additionally, an increase in the percentage of sulfur component (from 10% to 20%) leads to a higher combustion temperature. The activation energies of the five samples were determined using the Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) kinetic methods. During the room temperature spontaneous combustion stage, the activation energy increases from 65.05 kJ/mol to 112.44 kJ/mol as the percentage of sulfur component rises from 0% to 20%. During the high temperature combustion stage, the activation energy increased from 108.32 kJ/mol to 214.49 kJ/mol with the increase in the percentage of sulfur component. FeS and its associated sulfur necessitate energy to propel the process due to heat absorption from the melting of sulfur monomers. As the reaction progresses into the high temperature stage, the required activation energy escalates accordingly.

Effect of Intrinsic Ferroelectric Phase Transition on Hydrogen Evolution Electrocatalysis

AbstractHeterogeneous electrocatalysis closely relies on the electronic structure of the catalytic materials. The ferroelectric‐to‐paraelectric phase transition of the materials also involves a change in the state of electrons that could impact the electrocatalytic activity, but such correlation remains unexplored. Here, we demonstrate experimentally and theoretically that the intrinsic electrocatalytic activity could be regulated as exampled by hydrogen evolution reaction catalysis over two‐dimensional ferroelectric CuInP2S6. The obvious discontinuity in the overpotential and apparent activation energy values for CuInP2S6 electrode are illustrated during the ferroelectric‐to‐paraelectric phase transition caused by copper displacement around Tc point (318 K), revealing the ferroelectro‐catalytic effect on thermodynamics and kinetics of electrocatalysis. When loading Pt single atom on the CuInP2S6, the paraelectric phase one showed an improved hydrogen evolution activity with smaller apparent activation energy over the ferroelectric phase counterpart. This is attributed to the copper hopping between two sulfur planes, which alternate between strong and weak H adsorption at the Pt sites to simultaneously promote H+ reactant adsorption and H2 product desorption.

Effect of Intrinsic Ferroelectric Phase Transition on Hydrogen Evolution Electrocatalysis.

Heterogeneous electrocatalysis closely relies on the electronic structure of the catalytic materials. The ferroelectric-to-paraelectric phase transition of the materials also involves a change in the state of electrons that could impact the electrocatalytic activity, but such correlation remains unexplored. Here, we demonstrate experimentally and theoretically that the intrinsic electrocatalytic activity could be regulated as exampled by hydrogen evolution reaction catalysis over two-dimensional ferroelectric CuInP2S6. The obvious discontinuity in the overpotential and apparent activation energy values for CuInP2S6 electrode are illustrated during the ferroelectric-to-paraelectric phase transition caused by copper displacement around Tc point (318 K), revealing the ferroelectro-catalytic effect on thermodynamics and kinetics of electrocatalysis. When loading Pt single atom on the CuInP2S6, the paraelectric phase one showed an improved hydrogen evolution activity with smaller apparent activation energy over the ferroelectric phase counterpart. This is attributed to the copper hopping between two sulfur planes, which alternate between strong and weak H adsorption at the Pt sites to simultaneously promote H+ reactant adsorption and H2 product desorption.

Influence of Physico-chemical Conditions on Mobility of Uranium from Wastes

Dynamic leaching tests were carried out on solid wastes generated from the uranium mining and milling industry under different physico-chemical conditions to assess the mobility of uranium from these matrices. The mobile/ soluble fraction of uranium leached out very slowly; being faster in the initial stages and then attaining a near steady state condition in most cases. Uranium leaching was observed to increase with decreasing initial pH, reducing particle size and increasing temperatures. A maximum of 2.4% uranium was leached out under highly acidic conditions in the experimental time period. Leachability index values indicated weak leaching of uranium from the wastes under all conditions. Leaching kinetics was examined with the help of a heterogeneous reaction model. Model results and apparent activation energy values indicated the leaching process to be initially reaction controlled and subsequently diffusion controlled. The apparent rate constants displayed dependence on the particle sizes of the tailings. All results obtained from this study imply that the extent of uranium leaching from these solid mining wastes is extremely low. This indicates low mobility and negligible transfer to other environmental compartments.

Crystal-Plane-Engineered TiO2-Anchored Vanadium Single Atoms and Clusters for Boosting Ultradeep Aerobic Oxidative Desulfurization of Diesel.

The crystal plane effect has gained extensive attention in heterogeneous catalysis reactions; however, it is far from being systematically probed in titanium dioxide (TiO2)-supported vanadium catalysts. Herein, a series of vanadium (V) single atoms and clusters anchored on TiO2 with different crystal planes was fabricated by an improved "top-down" protocol. The dispersion state, electronic structure, and redox properties of the V single-atom and VOx cluster-supported catalysts were systematically analyzed by a series of characterization methods, including X-ray absorption near edge structure (XANES) and density functional theory (DFT) calculations, and their catalytic performances were examined for aerobic oxidative desulfurization (AODS) of 4,6-dimethyl-dibenzothiophen (4,6-DMDBT) with O2 as the oxidant. The results unveiled that the synergistic effect between the V single atom and the VOx cluster perceptibly promoted the catalytic performances of VOx/TiO2 samples. Therein, VOx/TiO2-(001) shows the lowest apparent activation energy (Ea) value of 46.3 kJ/mol and the optimal AODS performance with complete 4,6-DMDBT conversion to 4,6-dimethyldibenzothiophene sulfone (4,6-DMDBTO2) within 60 min at 120 °C as compared with VOx/TiO2-(101) (81.9 kJ/mol and 180 min) and VOx/TiO2-(100) (68.0 kJ/mol and 240 min), which should be attributed to its higher V5+/V4+ ratio, the optimal redox behavior of the V species, the moderate adsorption energy between 4,6-DMDBT and VOx active centers, and the synthetic effect of V single atoms and VOx clusters. Moreover, VOx/TiO2-(001) exhibits robust durability in seven cycles of reuse, showcasing the potential for practical applications in the future.

Fluorinated‐polyhedral oligomeric silsesquioxane (F‐POSS) functionalized halloysite nanotubes (HNTs) as an antifouling additive for epoxy resin

AbstractAntifouling epoxy resin serves as a member of advanced nanocomposite coatings and engineered surfaces. Nevertheless, developing an antifouling epoxy composites is a state‐of‐the‐art technology. Herein, a complex nanostructure is tailored to be served as an advanced additive giving the antifouling characteristics to the epoxy resin. F‐POSS@HNT hybrid nanostructure, that is, halloysite nanotubes (HNTs) decorated with fluorinated polyhedral oligomericsil sesquioxane (F‐POSS), was synthesized and characterized. Chemical structure changes, thermal stability and morphology of hydroxylated HNTs (hHNTs) intermediate and F‐POSS@HNT ultimate nanostructures were analyzed by FTIR spectroscopy, TGA and TEM, respectively. The F‐POSS@HNTs catalyzed the epoxy‐amine crosslinking reaction, taking “Good” or “Excellent” crosslinking tags an quantified by the “Cure Index.” The apparent activation energy values were calculated for the epoxy (reference), epoxy/hHNTs, and epoxy/F‐POSS@HNTs systems (26, 51, and 47 kJ mol−1, respectively). Contact angle measurements were performed via dynamic tests demonstrating improved hydro‐ and oleophobicity of the thermoset composites. The advancing contact angle with diiodomethane increased 36% and 30% for nanocomposites containing 5 and 10 wt.% of the developed hybrid nanostructure, respectively, compared with the neat epoxy. Likewise, 54% and 67% reduction in paraffin fouling in the same order confirmed their antifouling ability. Regarding self‐cleaning characteristics, 24% and 33% surface recovery were observed, respectively.Highlights Antifouling surface was achieved in epoxy thermoset nanocomposites for potential industrial applications. Self‐cleaning behavior correlated with low wetting and antifouling properties. F‐POSS@HNT nanofillers were synthesized and successfully added to epoxy matrix. Both hHNT and F‐POSS@HNT showed a beneficial autocatalytic effect on epoxy‐amine reaction yielding satisfactory polymer crosslinking. Activation energy was reduced by incorporating F‐POSS@HNT compared with hHNT, signature of facilitated crosslinking.

Effect of log Kow on the degradation of pharmaceutically active compounds in a heterogeneous catalytic persulfate activation system

In heterogeneous catalytic advanced oxidation processes (HC-AOP), enhancing the reaction rate is the biggest challenge. To enhance the reaction rate, it is necessary to increase the mass transfer rate of reactants toward the catalyst surface and the number of active sites that will provide better contact with the reactants and higher mass transfer. The hydrophobicity of the reactant is an important parameter that affects the transport of molecules toward solid surfaces. In this study, the effect of log Kow, an indicator of hydrophobicity, on enhancing the catalytic activity in persulfate (PS) activation for pharmaceutic compounds (PCs) degradation was investigated. For this purpose, some PCs with different log Kow were selected and their adsorption and degradation behaviors were investigated depending on the PS concentration, catalyst dosage, contact time, pH, and temperature in HC-AOP. Adsorption percentages increased significantly with increasing log Kow value. PCs with higher log Kow were completely degraded at the end of the shorter contact times in the presence of lower catalyst and PS. PCs were significantly degraded by the triple catalytic effect of AC, Fe, and temperature. The pseudo-first-order kinetic model was the best fit for the degradation reaction for all PCs. The higher apparent rate constants and lower activation energy values of the PCs belonging to high log Kow confirmed that log Kow is an effective parameter in enhancing the catalytic activity.

Preparation of SiC from carbonaceous vanadium-bearing stone coal via carbothermal reduction method

In the present study, silicon carbide (SiC) was prepared via carbothermal reduction method using carbonaceous vanadium-bearing stone coal at 1400 °C. Compared to other reported raw materials, SiC was prepared at a relatively low the reaction temperature. The effects of temperature, duration and vanadium catalysis on the process of SiC preparation were investigated, and the kinetics of SiC nucleation and growth were analyzed. The results indicate that the SiC conversion of samples with 0 wt% and 2 wt% V2O3 additions reached to 68.9 wt% and 80.7 wt% at 1450 °C for 5 h. It was observed that the reduction of vanadium oxides resulted in the formation of vanadium carbide (VC), which played an important role in catalyzing the nucleation of SiC and accelerating its growth. The mechanism of SiC nucleation and growth is consistent with the Johnson-Mehl-Avrami-Erofeev-Kolmogorov (JMAEK) model, and the apparent activation energy values of the carbothermal reduction reaction are 213.17 kJ/mol and 109.66 kJ/mol for samples with 0 wt% and 2 wt% V2O3 additions. Therefore, this method not only expanded the source of raw material but also reduced energy consumption and economic costs.

Isomerization and epimerization of fructose in phosphate buffer under subcritical water conditions

Isomerization and epimerization of fructose to glucose, mannose, allulose, and allose were executed using a subcritical phosphate buffer solution to effectively produce useful monosaccharides. The conversion of the substrate and the yield of products were dependent on the reaction temperature, initial pH, initial substrate concentration, and buffer concentration. A high yield of mannose was achieved under the optimal reaction conditions we identified. We subsequently performed the kinetic analysis based on the proposed reaction network, and evaluated the effects of temperature and pH on the reactions. We then estimated the apparent activation energy values for each reaction.

Experimental and Kinetic Study of the Catalytic Behavior of Sulfate-Treated Nanostructured Bifunctional Zirconium Oxide Catalysts in n-Heptane Hydroisomerization Reactions

In this study, a mono-functional ZrO2 nanomaterial was treated with sulfur and loaded with two different percentages of platinum metals (i.e., 0.5 and 1 wt%) to generate an acidic bi-functional Pt/SZrO2 nanocatalyst for the purpose of increasing the catalytic activity and selectivity together. This work aims to determine the least amount of the costly platinum metal that can be added to the catalyst to achieve the appropriate balance between the acidic and metallic sites. Both rapid deactivation of the super-acid nanaocatalyst and fast cleavage of the zero-octane n-heptane chain can consequently be prevented throughout the reaction. This can be achieved by accelerating the hydroisomerization reactions at a pressure of 5 bar to reach the highest selectivity towards producing the desired multi-branched compound in fuel. Several characterization techniques, including XRD, SEM, EDX, BET, and FTIR, have been used to evaluate the physical properties of the catalysts. The best reaction product was obtained at 230 °C compared to the other tested temperatures. The conversion, selectivity, and yield of reaction products over the surfaces of the prepared catalysts followed this order: 0.5 wt% Pt/SZrO2 > 1 wt% Pt/SZrO2 > 0.5 wt% Pt/ZrO2 > 1 wt% Pt/ZrO2 > SZrO2 > ZrO2. The highest conversion, selectivity, and yield values were obtained on the surface of the 0.5 wt% Pt/SZrO2 catalyst, which are 69.64, 81.4 and 56.68 wt%, respectively, while the lowest values were obtained on the surface of the parent ZrO2 catalyst, which are 43.9, 61.1 and 26.82, respectively. The kinetic model and apparent activation energies were also implemented for each of the hydroisomerization, hydrogenation/dehydrogenation, and hydrocracking reactions, which track the following order: hydroisomerization < hydrogenation/dehydrogenation < hydrocracking. The lowest apparent activation energy value of 123.39 kJ/mol was found on the surface of the most active and selective 0.5% Pt/SZrO2 nanocatalyst.

Kinetics of nitric acid leaching of bornite and chalcopyrite

The paper presents a study of the process of nitric acid dissolution of the natural minerals chalcopyrite and bornite. The influence of various parameters, including temperature, nitric acid concentration and particle sizes, on this process was examined. Based on the data obtained, the values of apparent activation energy (57.41 and 42.98 kJ/mol for chalcopyrite and bornite, respectively), empirical orders with respect to nitric acid (1.62 and 1.57 for chalcopyrite and bornite, respectively) and with respect to particle size (–1.16 and –2.53 for chalcopyrite and bornite, respectively) were calculated using the shrinking core model. Generalized kinetic equations for the dissolution process of both minerals were derived. Based on the calculations performed, it was suggested that the dissolution processes of chalcopyrite and bornite under these conditions are limited by internal diffusion.

Unveiling the role of transition metal catalysts in low-temperature, liquid-phase isopropanol oxidation

Driven by the increasing need to optimize industrial chemical reactions through effective catalysts, this study reports the comprehensive oxidation process of isopropanol under liquid phase conditions at subambient temperatures, investigating the catalytic potential of transition metal oxides. The complete oxidation of isopropanol within the liquid phase at reduced temperatures was investigated, employing transition metal oxides as catalysts (Cr2O3, Fe2O3, NiO, and ZnO). These solids were prepared using the sol–gel method and the precipitation method. The results from structural (FTIR, XRD) and textural (BET) analyses were consistent with those reported in the literature. The employed solid substances exhibited favorable catalytic activity for the full oxidation of isopropanol, maintaining a consistent selectivity of 100 %, regardless of the temperature conditions under examination (40, 60, and 80 °C). These catalytic tests reveal that chromium oxide is a typical catalyst for this type of reaction. Furthermore, a kinetic analysis of the reaction was conducted, revealing that the reaction proceeds according to a sequential A-B-C mechanistic pathway. The low values of apparent activation energy for all the solids align with the high initial reaction rates in the studied temperature range. This study revealed the effective role of transition metal oxides, particularly chromium oxide, as catalysts for the total oxidation of isopropanol under liquid phase conditions at subambient temperatures, offering vital insights to enhance efficiency in chemical industrial processes.

Studies on the Reduction Behavior of Iron Oxide Pellet Fines with Hydrogen Gas: Mechanism and Kinetic Analysis

The present study contributes to the current worldwide activities aiming to replace fossil carbon in steel making processes with hydrogen causing considerable reduction of greenhouse gas emissions. Compacts prepared from iron oxide pellets fines were isothermally reduced in pure hydrogen gas and a mixture of hydrogen and argon in the temperatures range from 700 to 1100 °C. The total weight loss produced during the reduction process was continuously recorded using thermogravimetric analysis (TG) technique. The findings demonstrated that the temperature has a considerable impact on the conversion and reduction rates. At a given temperature, the reduction rate was accelerated as the amount of H2 increased in the reducing gas. The results indicated that H2 content does not have an effect on reduction behavior, when it is higher than 80%. The reduction reaction of samples was shown to takes place in a step wise manner from hematite to metallic iron. The reduction kinetic and mechanism were deduced from the application of mathematical models and the morphological structure of the reduced samples and correlated with the apparent activation energy (Ea) values. The Ea values at the early, intermediate and final stages were 16.36, 29.24 and 49.35 kJ/mole, respectively. The early stage of the reduction process was controlled by chemical reaction, whereas the gaseous diffusion was controlled the latter stage. At the intermediate stage, the reduction process was controlled by mixed mechanism of gaseous diffusion and chemical reaction.Graphical

The Catalytic Effect of Vanadium on Sorption Properties of MgH2-Based Nanocomposites Obtained Using Low Milling Time.

The effects of catalysis using vanadium as an additive (2 and 5 wt.%) in a high-energy ball mill on composite desorption properties were examined. The influence of microstructure on the dehydration temperature and hydrogen desorption kinetics was monitored. Morphological and microstructural studies of the synthesized sample were performed by X-ray diffraction (XRD), laser particle size distribution (PSD), and scanning electron microscopy (SEM) methods, while differential scanning calorimetry (DSC) determined thermal properties. To further access amorph species in the milling blend, the absorption spectra were obtained by FTIR-ATR analysis (Fourier transform infrared spectroscopy attenuated total reflection). The results show lower apparent activation energy (Eapp) and H2 desorption temperature are obtained for milling bland with 5 wt.% added vanadium. The best explanation of hydrogen desorption reaction shows the Avrami-Erofeev model for parameter n = 4. Since the obtained value of apparent activation energy is close to the Mg-H bond-breaking energy, one can conclude that breaking this bond would be the rate-limiting step of the process.

Oxygen release and reduction kinetics of La0.35Sr0.35Ba0.3Fe1-xCoxO3 as oxygen carriers for chemical looping dry reforming of methane

Chemical looping dry reforming of methane (CL-DRM) is a viable technology by converting CH4 and CO2 to various value-added products to achieve carbon neutrality. However, it is vital for the technology to find suitable oxygen carriers with high oxygen capacity and activity. La0.35Sr0.35Ba0.3Fe1-xCoxO3 perovskite-type oxides were proposed as oxygen carriers for CL-DRM. The oxygen (O2) release property and the kinetics of La0.35Sr0.35Ba0.3Fe1-xCoxO3 reduction by CH4 were investigated via thermogravimetric analysis, O2-temperature programmed desorption and then in a fixed-bed reactor. The O2 release process of La0.35Sr0.35Ba0.3Fe1-xCoxO3 OCs can be divided into two phases. The O2 release process and corresponding rate of OCs were facilitated due to the substitution of Fe with Co in B-site. The total amounts of O2 release for these OCs were enhanced about 1.5 times from 0.445 mmol/gOC to 0.706 mmol/gOC as Co atomic fraction in B-site changes from 0 to 1. The linear correlation for high temperature phase and a volcano-curve for low temperature phase was found for the correlations among total O2 release and Co content during the O2 release process. The reduction kinetics of CH4 over OCs was described using the Avrami–Erofe'ev model (A1.5 or A2). The values of apparent activation energy (Ea) for all OCs were obtained. The results indicated the best substitution proportion of Co in La0.35Sr0.35Ba0.3Fe1-xCoxO3 OCs can be set in the range of 0.2–0.4 to emerge the excellent redox performance. The kinetics models and parameters offer valuable information for CL-DRM reactor design and further development of OCs with different A or/and B-site modifications.

Study of the basic laws of dissolution of gold and copper in solutions with an ultra-low concentration of sodium cyanide

The work sets out to study the basic physicochemical dissolution patterns of gold, copper, and natural copper-containing minerals (chalcopyrite, bornite and azurite) in solutions with an ultra-low concentration of sodium cyanide (from 0.102∙10-3 to 4.08∙10-3 mol/L). The influence of various factors on the rate of dissolution of Au and Cu in solutions with ultra-low NaCN concentrations was studied by the rotating disk method; for natural copper minerals, the powder diffraction method was used. The concentration of gold and copper in solutions was determined by atomic absorption analysis. The chemical composition of the studied copper minerals was determined using the X-ray phase method, while the specific surface of the minerals was detected using a laser granulometer. The process of gold dissolution is shown to proceed in both diffusion and kinetic regions. In the diffusion region, the rate constant was 0.334∙10-6 L∙cm-2∙s-1/2∙rad-1/2; in the kinetic region – 0.919∙10-6 L∙cm-2∙s-1/2. The calculated value of the apparent activation energy for the diffusion region was 22.5 kJ/mol; for the kinetic region – 40.1 kJ/mol. The addition of glycine to a solution with an ultra-low concentration of sodium cyanide is shown to increase the specific dissolution rate of gold by 1.2 times: from 0.692∙10-9 to 0.82∙10-9 mol/cm2∙s. The process of copper dissolution is shown to take place in the diffusion r egion. The rate constant was 0.496∙ 10-6 L∙cm-2∙s-1/2∙rad-1/2 at an activation energy of 17.0 kJ/mol. With a fractional supply of sodium cyanide, the dissolution rate of copper minerals is reduced by 10–30% compared to a single load. The calculated apparent activation energy values for chalcopyrite, bornite, and azurite were 22.03, 24.2, and 24.1 kJ/mol, respectively. Thus, the use of ultra-low concentrations of NaCN in the process of cyanidation of gold and copper has a positive effect, which can be used i n the processing of gold-copper raw materials to significantly reduce the consumption of sodium cyanide.

Thermal decomposition features of micro-nano rice husk/polylactic acid blends for 3D printing

The thermal decomposition process of 3D printed filament made from micro-nano rice husk (MNRH)/polylactic acid (PLA) blends was studied by dynamic thermogravimetric analysis. The characteristic temperatures and apparent activation energies of unmodified, single modified, and double modified RH/PLA composites were calculated by Friedman (FD), Flynn-Wall-Ozawa (FWO), Coats-Redfern (CR), and Kissinger (KS) kinetic models. With the modification of MNRH and PLA in the composites, the initial thermal decomposition temperature of the composite increased from 236.3°C to 244°C. At the same time, the thermal degradation degree decreased and the transition temperature interval increased. The apparent activation energy (AAE) values of different modified composites ranged from 90 to 120 kJ/mol, depending on the modification method and calculation method of the material. These four kinetic models provide methods to analyze the thermal stability of composites. It is helpful to known the thermal decomposition behavior of MNRH/PLA composites, and it will contribute to the development of MNRH/PLA filament for 3D printing in the application of automotive interior parts production.

Weak Metal-Support Interaction over CuO/TiO2 Catalyst Governed Low-Temperature Toluene Oxidation.

Regulating the metal-support interaction is essential for obtaining highly efficient catalysts for the catalytic oxidation of volatile organic compounds (VOCs). In this work, CuO-TiO2(coll) and CuO/TiO2(imp) with different metal-support interactions were prepared via colloidal and impregnation methods, respectively. The results demonstrated that CuO/TiO2(imp) has higher low-temperature catalytic activity, with a 50% removal of toluene at 170 °C compared to CuO-TiO2(coll). Additionally, the normalized reaction rate (6.4 × 10-6 mol·g-1·s-1) at 160 °C over CuO/TiO2(imp) was almost four-fold higher than that over CuO-TiO2(coll) (1.5 × 10-6 mol·g-1·s-1), and the apparent activation energy value (27.9 ± 2.9 kJ·mol-1) was lower. Systematic structure and surface analysis results disclosed that abundant Cu2+ active species and numerous small CuO particles were presented over CuO/TiO2(imp). Owing to the weak interaction of CuO and TiO2 in this optimized catalyst, the concentration of reducible oxygen species associated with the superior redox property could be enhanced, thus significantly contributing to its low-temperature catalytic activity for toluene oxidation. This work is helpful in exploring the influence of metal-support interaction on the catalytic oxidation of VOCs and developing low-temperature catalysts for VOCs catalytic oxidation.