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1

Effect of the type of ion-exchange resin on Mn2+ adsorption in the presence of competing cations

Amengol Bruna P. C., Pires Renata. C., Leão Versiane A.

Physicochemical Problems of Mineral Processing

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2024

|

Vol. 60, iss. 2

art. no. 187844

EN

Present in soils, ground and surface waters, manganese is among the most common metals in Earth crust. It is also an essential trace element to the functioning of several enzymes in the human body. However, exposure to high manganese concentrations can also be harmful to humans with psychiatric and motor effects and therefore, manganese concentrations in drinking water and also industrial effluents are regulated. In the current work, the adsorption of Ca2+, Mg2+ and Mn2+ on three different ion-exchange resins: (i) aminophosphonic acid - chelating (Purolite S950), (ii) polyacrylic weak acid cation (Purolite C104E) and (iii) polystyrene strong acid cation (Purolite C100) was investigated. The results revealed that Purolite S950 had the highest Mn2+ uptake (37.9 mg/mL-resin or 0.69 mmol/mLresin) as compared to Ca2+ (3.2 mg/mL-resin or 0.08 mmol/mL-resin) and Mg2+ (~0 mg/mL-resin) and was selected for further kinetics and equilibrium studies. The results indicated Purolite S950 as particularly suited to be applied in the treatment of neutral mine waters with high Mg/Mn ratios. Additionally, Purolite S950 showed a small affinity for Ca2+ and therefore an efficient Mn2+ removal will depend on the Ca/Mn ratio of the mine water under treatment. According to the kinetic analysis, manganese sorption on Purolite S950 was described by the pseudo-second order model (r2 > 0.98) with an activation energy of 6.34 kJ/mol and thus pore-difussion was the rate controlling step of the process. In terms of equilibrium studies, manganese sorption on Purolite S950 followed the Langmuir model with maximum loadings of up to 41.5 mg/mL-resin. The thermodynamic modelling indicated an exothermic process (-85.0 kJ/mol, as standard enthalpy) with a standard entropy of -274 J/mol×K, which was ascribed to the release of two adsorbed H+ ions for each Mn2+ ion taken up from solution.

2

Rozkład nadtlenku wodoru podczas katalitycznego epoksydowania propylenu

Lina Wang, Cheng Shen, Yingfeng Duan, Wei Du, Yagang Zhang, Wenying Li

Przemysł Chemiczny

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2023

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T. 102, nr 10

1018--1021

PL

Jako katalizator epoksydowania propylenu za pomocą nadtlenku wodoru w wodnym roztworze metanolu zastosowano sito molekularne TS-1 (krzemian tytanu). Zbadano szybkość samoistnego rozkładu nadtlenku wodoru wtemp. 30-50°C. Znaleziono optymalne warunki (temp. reakcji 43°C, stężenie nadtlenku wodoru 10,3% mas., zawartość metanolu 65% mas.). Ustalono, że rozkład nadtlenku wodoru jest reakcją pierwszego rzędu. Wyznaczono stałą szybkości tej reakcji i jej energię aktywacji.

EN

Ti silicalite mol. sieve (TS-1) was used as catalyst for propylene epoxidation with H₂O₂ in aq. MeOH soln. The H₂O₂ self-decompn. rate at 30-50°C was studied. The optimum conditions were found (reaction temp. 43°C, H₂O₂ concn. 10.3% by mass, MeOH concn. 65% by mass). The H₂O₂ selfdecompn. was the first-order reaction. Its reaction rate const. and activation energy were detd.

3

Stagnation-point flow of Williamson fluid along a stretched plate with convective thermal condition and activation energy

Salawu S. O.

International Journal of Applied Mechanics and Engineering

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2023

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Vol. 28, no. 3

101--111

EN

The implication of a stagnation-point flow together with the influence of activation energy in a Williamson fluid, which consists of tiny particles, over an expansive plate is analyzed numerically. Conditions of convective heat and mass motion with features of irregular movement and thermal-migration of particles influenced by viscous dissipation and convective heat surface condition are checked in the study. The conversion of the model equations from the initially formulated partial derivatives to ordinary ones is implemented by similarity transformations while an unconditionally stable Runge-Kutta-Fehlberg integration plus shooting technique are then used to complete the integration. Various interesting effects of the physical parameters are demonstrated graphically and explained appropriately in order to make accurate predictions. Moreover, the accuracy of the solution is verified by comparing the values of the skin friction factor with earlier reported ones in literature under limiting constraints. It is worth mentioning that the velocity profiles flatten down as the magnitude of the magnetic field factors expands but this causes a boost in the fluid’s temperature. The concentration field also appreciates with activation energy but depreciates with chemical reaction and Schmidt number.

4

Austenite-grain-growth kinetics and mechanism in type 347H alloy steel for boiler tubes

Huda Zainul, Zaharinie Tuan, Aniszulaikha Ireen, Almitani Khalid

Advances in Materials Science

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2023

|

Vol. 23, nr 3(77)

79--97

EN

The research material (type 347H alloy steel) has been characterized using optical microscopy and an EDS/SEM system. Annealing experiments have been conducted at temperatures range of 600–1050°C for 30 min–20 h by using an atmosphere-controlled furnace. Normal grain growth with intermediate grain size has been related to the favouring of creep resistance to recommend the material suitable for boiler tubes at operating temperatures up to 750oC for long duration. The kinetics of grain growth in the 347H has been shown to behave similar to a pure metal in the initial stage of annealing in the range of 0–30 min, beyond which the grain-growth process was found to be suppressed due to second-phase (NbC) particle-pinning and solute drag effects. The grain-growth exponent n is computed to be in the range of 0.117–0.313; the deviation from ideal kinetic behavior (n=0.5) has been scientifically justified. The activation energy for grain growth Qg, for the investigated alloy, has been graphically computed and validated.

5

Energia aktywacji utworów warstw menilitowych i jej implikacje dla procesu generowania węglowodorów w Karpatach

Spunda Karol, Słoczyński Tomasz

Nafta-Gaz

|

2022

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R. 78, nr 5

327--335

PL

W artykule zaprezentowano procedurę obliczeń energii aktywacji kerogenu utworów warstw menilitowych oraz implikacje wynikające z jej zróżnicowania dla przebiegu procesu generowania węglowodorów w karpackim systemie naftowym. Powstawanie węglowodorów w skałach następuje w wyniku rozpadu złożonych związków organicznych (głównie związków węgla, wodoru i tlenu) budujących kerogen na cięższe i lżejsze węglowodory frakcji olejowej i gazowej. Proces jest reakcją termokatalityczną, której dynamika determinowana jest między innymi przez energię aktywacji kerogenu. Energia aktywacji jest jednym z podstawowych parametrów wejściowych implementowanych do numerycznych modeli systemów naftowych, dlatego jej oznaczenie jest bardzo istotne dla rzetelnego odtworzenia tego procesu, zachodzącego w naturalnych warunkach geologicznych i w skali czasu geologicznego. Obliczeń energii aktywacji dokonano na podstawie wyników oznaczeń parametrów kinetycznych reakcji krakingu kerogenu, który to kraking przeprowadzono w kontrolowanych warunkach laboratoryjnych przy użyciu analizatora pirolitycznego Rock-Eval. Eksperyment polegał na nieizotermicznej pirolizie skał zawierających kerogen i rejestrowaniu szybkości reakcji (tempa generowania węglowodorów) w całym zakresie temperaturowym pirolizy. Energię aktywacji (Ea) i stałą Arrheniusa (A) obliczano z równania Arrheniusa, opisującego zależność stałych szybkości reakcji od temperatury. Do obliczeń wykorzystano model dyskretnej dystrybucji energii aktywacji (Ea) ze stałą wartością stałej Arrheniusa (A). Rozkład optymalizowano iteracyjnie metodą regresji liniowej i nieliniowej. Dla każdego z reagentów, o początkowej masie x0i, obliczono dyskretną wartość energii aktywacji (Eai). W tym przypadku i-ta reakcja równoległa odpowiadała wiązaniom chemicznym, które muszą zostać rozbite energią aktywacji (Eai) w cząsteczkach kerogenu. Optymalizacji rozkładu energii aktywacji dokonano przy użyciu oprogramowania Kinetics2015.

EN

The article presents the procedure for calculating the kerogen activation energy of rock of the Menilite Beds which are considered the main source rock of the Carpathian petroleum system. The formation of hydrocarbons in rocks occurs as a result of breakdown of complex organic compounds (mainly carbon, hydrogen and oxygen compounds) which build kerogen into heavier and lighter oil and gas hydrocarbons. This process is a thermocatalytic reaction, the dynamics of which is determined, inter alia, by the kerogen activation energy. The activation energy is one of the basic input parameters implemented into numerical models of petroleum systems. For this reason, the determination of the activation energy is very important for a reliable reconstruction of the hydrocarbon generation process in natural geological conditions and on the geological time scale. Activation energy calculations were made on the basis of the results of measurements of kinetic parameters of the kerogen cracking reaction, which (kerogen cracking) was carried out under controlled laboratory conditions using a Rock-Eval pyrolyser. The experiment consisted in non-isothermal pyrolysis of rocks containing kerogen and recording the rate of reaction (rate of hydrocarbon generation) over the entire temperature range of pyrolysis. The activation energy (Ea) and pre-exponential factor (A) were calculated using the Arrhenius equation describing the dependence of the reaction rate constants on the temperature. Discrete distribution of activation energies (Ea) model with a constant value of the pre-exponential factor (A) was used for the calculations. The energy distribution was optimized by iterative linear and non-linear regression. The discrete activation energy (Eai) was calculated for each reactant with an initial mass x0i. In this case, the “i-th” parallel reaction corresponds to chemical bonds that must be broken with an energy equal to Eai in the kerogen molecules. The activation energy distribution was optimized using the Kinetics2015 software.

6

Electrical characteristics of dry cement – based composites modified with coconut husk ash nanomaterial

Robert Ubong Williams, Etuk Sunday Edet, Ekong Sylvester Andrew, Agbasi Okechukwu Ebuka, Ekpenyong Nsikak Edet, Akpan Samuel Sunday, Umana Eme Aniefiok

Advances in Materials Science

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2022

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Vol. 22, nr 2(72)

64--77

EN

Coconut husk is generated yearly as waste in large quantities but majorly under-utilized. Also, as a result of high embodied carbon, cement production is one of the largest contributors to construction sector carbon footprint. Since accumulation of unmanaged agro-waste like coconut husk has an increased environmental concern due to its pollution effect, recycling it into sustainable construction materials is a viable solution for future generation. In this study, experiments were performed to investigate the influence of coconut husk ash nanomaterial (CHAN) inclusion on electrical characteristics of plain cement paste (BCP) and mortar (CSM) samples at curing ages of 7 and 28 days. The results showed increase in electrical resistivity, thermal constant, and activation energy with curing duration for heating and cooling cycles of BCP and CSM. With inclusion of CHAN, the developed cement paste (CAP) and mortar (CASM) possessed lower values in all cases compared to their counterparts. Also, during heating at 28 days, both the CAP and CASM exhibited decrease in thermal constant. Though electrical resistance of all the samples varied inversely with temperature, CAP and CASM were found to possess greater potentials to make building structures intrinsically smart. Hence, in addition to solving disposal problems, utilization of coconut husks as described herein could enhance development of safe, inexpensive, and sustainable buildings that have large temperature sensing volume.

7

Study of thermal stability and energy of activation of epoxy composites with particles of synthesised powder mixture for increasing reliability of vehicles

Komsta Henryk, Vitenko Tetiana, Buketov Аndrii, Syzonenko Оlha, Bezbakh Оleh, Torpakov Andrii, Kruglyj Dmytro, Appazov Eduard, Popovych Pavlo, Rybicka Iwona

Zeszyty Naukowe. Transport / Politechnika Śląska

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2021

|

z. 110

73--86

EN

The prospective of the application of new materials on a polymer base is shown in this work. Given that developed composites can be efficiently used for protection of equipment that is operated at elevated temperatures, the impact of the nature and content of powder mixture, synthesised by high voltage electric discharge, on the thermophysical properties of epoxy composites were studied. Epoxy diane oligomer was chosen as the main component of the binder during the formation of the composites. Polyethylene polyamine hardener was used for cross-linking of epoxy composites, which allows hardening of materials at room temperatures. The selection of powder mixture, synthesised by high voltage electric discharge, for increase of thermophysical properties of developed materials was justified. More so, thermal stability and activation energy of epoxy composites were studied. Permissible limits of the temperature, at which developed materials can be used, were established based on the conducted tests of thermophysical properties of materials, filled by powder mixture, synthesised by high voltage electric discharge.

8

A study on the dissolution kinetics of iron oxide leaching from clays by oxalic acid

Arslan Volkan

Physicochemical Problems of Mineral Processing

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2021

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Vol. 57, iss. 3

97--111

EN

Clay is widely used in a number of industries due to its special properties like fine particle size, brightness and whiteness, chemical inertness, platy structure, etc. In this study, the general characteristics of clays have been investigated by XRF, XRD, FT-IR, TG-DTA and SEM. The presence of iron as an impurity decreases its commercial value due to giving unwanted colors to clay mineral. Therefore, the dissolution capacity of clay ore was investigated by oxalic acid leaching. Under optimized leaching conditions (0.8 M oxalic acid concentration, 85°C reaction temperature, 1.75 ambient pH, 106+75 µm particle size, 15% w/v solids concentration and 150 min. leaching time) with 250 rpm stirring, 83.90% of Fe2O3 was removed. The amount of iron oxide, the main impurity in the clay, has been reduced from 2.70 to 0.40%. The iron dissolution kinetics was mainly controlled by internal diffusion control of shrinking core model and activation energy, Ea, of 26.29 kJ/mol was obtained for the process. The results also showed that the studied clays have adequate characteristics for ceramics industry, earthenware and porcelain production.

9

Determination of the activation energy of a gasless pyrotechnic composition

Zakusylo Daryna

Materiały Wysokoenergetyczne

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2021

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T. 13

96--100

EN

This article presents the determining of some parameters of a gasless pyrotechnic composition. Thermo-analytical studies have been carried out. The activation energy of the gasless pyrotechnic composition was determined experimentally and by calculation. The flashpoint was 100 °C. The value of the activation energy of the pyrotechnic composition was 369.39 kJ/mol, which exceeds the activation energy of standard solid and liquid explosives by 2.4-2.8 times and makes it more stable. The change in the mass of the pyrotechnic composition during heating did not exceed 1%.

PL

Artykuł dotyczy zagadnień wyznaczania niektórych parametrów bezgazowej kompozycji pirotechnicznej. Przeprowadzono badania derywatograficzne. Energię aktywacji bezgazowej kompozycji pirotechnicznej wyznaczono doświadczalnie i obliczeniowo. Temperatura zapłonu wynosiła 100 °C. Wartość energii aktywacji kompozycji pirotechnicznej wyniosła 369,39 kJ/mol, co przewyższa energię aktywacji standardowych materiałów wybuchowych stałych i ciekłych 2,4-2,8 razy i czyni ją bardziej stabilną. Zmiany masy kompozycji pirotechnicznej pod wpływem temperatury nie przekraczają 1%.

10

Hydrothermal Carbonization Kinetics of Lignocellulosic Municipal Solid Waste

Putra Herlian Eriska, Djaenudin Djaenudin, Damanhuri Enri, Dewi Kania, Pasek Ari Darmawan

Journal of Ecological Engineering

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2021

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Vol. 22, nr 3

188--198

EN

Hydrothermal carbonization (HTC) is known as a thermochemical converting of wet biomass into a coal-like solid fuel (hydrochar). Hydrochar is easily crumbled. Because of hydrophobic properties, hydrochar is difficult to degrade by microorganisms. It has a calorific value comparable to lignite coal. In this study, hydrochar was made via converting the organic fraction of municipal solid waste through HTC at 190, 210, and 230°C for 30 min with feed to water ratio (FWR) 0.1, 0.2, 0.3. The feedstock processed includes food waste, paper, and wood waste, represented as a pseudo-component of the organic fraction of MSW. The high heating value (HHV), FTIR, as well as proximate and ultimate analyses were applied both to feedstock and hydrochar. The results showed that the energy density of hydrochar was elevated with increasing HTC temperature. The energy densification ratio and heating value increased by approximately 1.0–1.32 and 30%, respectively compared to raw feedstock. The lower yields of hydrochar were obtained at higher temperature. The typical char yields for lignocellulosic material range between 62–63 wt% at 190 °C and reduce to 54–57 wt% at 230 °C. Furthermore, a preliminary study of kinetic model for lignocellulose decomposition was conducted. This model was based on the mass loss rate of the lignocellulose compound in HTC of MSW. Three first-order reactions were given to illustrate the hydrochar yield at of 190, 210, and 230°C. The activation energy of lignocellulose decomposition was 76.26 kJ/mol, 51.86 kJ/mol, 12,23 kJ/mol for lignin, cellulose, and hemicellulose decomposition, respectively.

11

The activation energies and optimum temperatures of olive oil hydrolysis by lipase porcine pancreas

Miłek Justyna

Ecological Chemistry and Engineering. S

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2021

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Vol. 28, nr 3

389--398

EN

Lipase activity is a perfect indicator for the monitoring of processes of bioremediation of degraded soils. Lipase is also used in the processes of oil hydrolysis in wastewater treatment. To be able to predict and model processes with used lipase in environmental operations, knowledge of the kinetic parameters of the process are required. The paper presents the determined values of activation energies and optimum temperatures for porcine pancreas lipase. The parameters were estimated based on the literature of the activity curves vs. temperature for hydrolysis of olive oil by lipase. It was noticed that concentration of gum arabic added as an emulsifier during lipase activity measurements influences on the obtained values of determined parameters. A mathematical model describing the effect of temperature on porcine pancreas lipase activity was used. Based on the comparison analysis, the optimum temperature Topt were obtained in the range from 313.30 ±0.56 to 319.62 ±0.96 K, activation energies Ea were from 51 ±10 to 82.6 ±9.9 kJ/mol, and values of deactivation energies Ed were in the range from 122.7 ±4.0 to 150.9 ±5.8 kJ/mol.

12

The effect of pH on determination of activation energies and the optimum temperatures of hydrolysis of olive oil by lipase from porcine pancreas

Miłek Justyna

Acta of Bioengineering and Biomechanics

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2021

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Vol. 23, no. 3

25--31

EN

Purpose: The present paper reports the determination of the activation energies and the optimum temperatures of olive oil hydrolysis by porcine pancreas lipase with simultaneous effect of pH. Methods: The parameters were estimated based on the literature data on the activity curves versus temperature for olive oil hydrolysis by lipase obtained from porcine pancreas. It was assumed that both the hydrolysis reaction process and the deactivation process of lipase were first-order reactions by the enzyme concentration. A mathematical model describing the effect of temperature on porcine pancreas lipase activity was used. Results: The determinate activation energies Ea were from 31.37 ± 5.38 kJ/mol to 61.60 ± 11.46 kJ/mol, the optimum temperatures Topt were obtained in the range from 305.46 ± 1.26 K to 313.23 ± 1.18 K and the values of deactivation energies Ed were in the range from 65.18 ± 3.19 kJ/mol to 109.27 ± 6.79 kJ/mol. Conclusions: The obtained results (Ea, Ed, Topt) might find application in research on the prognosis of pancreatic cancer.

13

Wyznaczanie energii aktywacji oraz optymalnej temperatury dla reakcji hydrolizy skrobi katalizowanej przez α-amylazę z Bacillus licheniformis

Miłek Justyna

Przemysł Chemiczny

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2020

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T. 99, nr 6

880--881

PL

Na podstawie modelu matematycznego opisującego wpływ temperatury na aktywność α-amylazy z Bacillus licheniformis wyznaczono energię aktywacji i dezaktywacji oraz optymalną temperaturę procesu hydrolizy skrobi. Wartości te wynosiły odpowiednio 27,16 ± 6,89 kJ/mol, 143,54 ± 13,31 kJ/mol i 339,76 ± 0,95 K. Założono, że reakcja hydrolizy skrobi katalizowana przez α-amylazę przebiega zgodnie z kinetyką pierwszego rzędu ze względu na stężenie enzymu.

EN

Exptl. data on the temp. relationship of α-amylase from Bacillus licheniformis activity published by Haq et al.¹⁾, were used to calc. the optimal temp., activation energy and deactivation energy of the starch hydrolysis according a resp. math. model of the reaction. The calc. values were 339.76 ± 0.95 K, 27.16 ± 6.89 kJ/mol, 143.54 ± 13.31 kJ/mol, resp.

14

Study of thermal degradation behavior and kinetics of ABS/PC blend

Bano Saira, Ramzan Naveed, Iqbal Tanveer, Mahmood Hamayoun, Saeed Farhan

Polish Journal of Chemical Technology

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2020

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Vol. 22, nr 3

64--69

EN

This work investigated kinetics and thermal degradation of acrylonitrile butadiene styrene and polycarbonate (ABS/PC) blend using thermogravimetric analysis in the range of 25 to 520°C. For thermal degradation of blend, activation energy (Ea) and pre-exponential factor (A) were calculated under various heating rates as 5, 10, 15 and 20°C/min using iso-conversional model-free methods (Kissinger, Flynn-Wall- Ozawa and Friedman). Mass loss of the blend as a function of temperature was plotted as thermogravimetric curve (TG) while derivative values of mass loss were drawn as derivative thermogravimetric (DTG) curve. Using Kissinger method, Ea was 51.4 kJ/mol, while values calculated from FWO and Friedman method were 86–161 and 30–251 kJ/mol respectively. Results showed increasing trend of Ea with higher conversion values indicating different degradation mechanisms at the initial and final stages of the experiment. Thermodynamic parameters such as enthalpy change (ΔH), Gibbs free energy (ΔG) and entropy change (ΔS) were also calculated.

15

Evaluation of alkali processing for the recycling of rare earth values from spent fluorescent lamps

Shukla Neha, Tanvar Himanshu, Dhawan Nikhil

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 4

710--722

EN

Phosphor samples collected after crushing and sieving of discarded fluorescent lamps comprise approximately 31 % rare earth elements in the form of Y1.90Eu0.10O3, Al11Ce0.67MgO19Tb0.33, and Al10.09Ba0.96Mg0.91O17: Eu2+ phase. Direct leaching and mechanical activation assisted leaching are incapable of recovering Ce, Tb values from the Al11Ce0.67MgO19Tb0.33 phase. Heat treatment with NaOH was found successful for dissociation of Ce, Tb phase via substitution of rare-earth ion by Na+ ion to form rare earth oxide and water-soluble NaAlO2. Y, Eu, Ce, and Tb values were recovered from heattreated mass in a two-step leaching process followed by recovery from the leach solution by oxalic acid precipitation. Over 95 % extraction rate was attained after heat treatment at 400 °C with 150 wt-% NaOH for 1 h. It was found that Y, Eu containing phase does not take part in the heat treatment process whereas the Ce, Tb phase undergoes a solid-state chemical reaction with NaOH via product layer diffusion model with 41.5 kJ/mol activation energy. Approximately 15 g mixed oxide (purity >95 %) of Y (79 %), Eu (7 %), Ce (5 %), and Tb (4 %) could be recovered from 100 units of discarded FLs. Microwave treatment of phosphor and NaOH (50 wt-%) yielded approximately 42 % Y, 100 % Eu, 65 % Ce, and 70 % Tb recovery in just 5 min. Approximately 9 g of REO and 5 g of cerium enriched leach residue were recovered from the microwave route within 5 min and depicted high microwave potential application in the recovery of Ce and Tb values from waste phosphor sample.

16

A procedure of Arrhenius activation energy determination for salt flotation of particles in the vicinity of one molar salt aqueous solutions

Ratajczak Tomasz, Kurkiewicz Szymon, Drzymala Jan

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 6

1--5

EN

A modified Arrhenius equation, in which thermal energy is replaced with chemical (Gibbs) potential, and a special calculation procedure were used to evaluate the flotation activation energy for salt solutions in the one molar range of concentrations. The proposed formula overcomes the difficulties of calculating the salt flotation activation energy caused by mathematical problems of finding 1/(ln(c/c o)) for the standard salt concentration c o=1 M (1 kmol/m3 and when the applied salt concentration c is in the vicinity of 1 M. The salt flotation activation energy was calculated for flotation of copper-bearing carbonaceous shale in the 0.25, 0.50, 1.00 and 2.00 M NaCl solutions performed in a laboratory machine as equal to 1.9 RT for standard salt solution equal to 1 M.

17

Surface diffusion and cluster formation of gold on the silicon (111)

Plechystyy V., Shtablavyi I., Rybacki K., Winczewski S., Mudry S., Rybicki J.

Journal of Achievements in Materials and Manufacturing Engineering

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2020

|

Vol. 101, nr 2

49--59

EN

Purpose: Investigation of the gold atoms behaviour on the surface of silicon by molecular dynamics simulation method. The studies were performed for the case of one, two and four atoms, as well as incomplete and complete filling of gold atoms on the silicon surface. Design/methodology/approach: Investigations were performed by the method of molecular dynamics simulation using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). MEAM potential of interatomic interaction was used for modelling. Molecular dynamic simulations were carried out in isothermal-isobaric ensemble (NpT) with a timestep 1.0 fs. Findings: As a result of studies, the preferred interaction between gold atoms and the formation of clusters at temperatures up to 800 K was revealed. Analysis of the temperature dependences of the number of large jumps of atoms made it possible to calculate the activation energy of a single jump. It was found that activation energy of single atomic displacement decreases with increasing number of gold atoms. Research limitations/implications: Only a limited number of sets of atoms were used in the study. It is possible that for another combination of atoms and a larger substrate surface, the formation of gold nanoislands on the silicon surface can be observed, which requires further research. Practical implications: The research results can be used to select the modes of gold sputtering to create gold nanoislands or nanopillars on the silicon surface. Originality/value: Computer modelling of the behaviour of gold atoms on the surface of silicon with the possibility of their self-organization and cluster formation was performed for the first time.

18

Changes in the spontaneous combustion tendency of humic coals according to their petrographic composition and physico-chemical properties

Bielowicz Barbara

Gospodarka Surowcami Mineralnymi

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2020

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T. 36, z. 2

197--218

EN

The article presents the analysis of the correlation between the self-ignition parameters and the ultimate and proximate analysis, as well as the petrographic properties of Polish lignite, sub-bituminous coal, bituminous coal and anthracite. The following coal properties were determined: the moisture, ash content, volatile matter and sulfur content, gross calorific value, net calorific value, C, O, N and H contents, total porosity, ash oxide composition, rates of spontaneous combustion in 237°C and 190°C, and activation energy. During the petrographic analysis, maceral composition and random reflectance were determined. To determine the linear correlation between the self-ignition parameters and the analyzed coal properties, the Pearson correlation coefficient was calculated. The results show that there is no strong linear correlation between the lignite tendency to self-ignition and its petrographic properties. However, a strong negative correlation between the rate of spontaneous combustion and moisture and volatile matter content was observed. In the case of bituminous coal, strong correlations between self-combustion parameters and various coal properties were confirmed. The most noteworthy are the correlations between self-ignition parameters and the maceral composition, that is, between the content of macerals of the inertinite group in coal and content of macerals of the huminite/vitrinite group. The obtained results suggest that the spontaneous combustion tendency of coal increases with the increasing content of semifusinite and liptinite.

PL

W artykule przedstawiono analizę korelacji między parametrami samozapłonu a analizą technologiczną i chemiczną oraz właściwościami petrograficznymi polskiego węgla brunatnego, węgla kamiennego i antracytu. Określono następujące właściwości węgla: wilgotność, zawartość popiołu, zawartość części lotnych i siarki, wartość opałową, ciepło spalania, zawartość C, O, N i H, całkowitą porowatość, skład tlenkowy popiołu, wskaźniki samozapłonu w temperaturach 237 i 190°C oraz energię aktywacji. Podczas analizy petrograficznej określono skład petrograficzny i współczynnik odbicia. W celu określenia liniowej korelacji między parametrami samozapłonu a analizowanymi właściwościami węgla obliczono współczynnik korelacji Pearsona. Uzyskane wyniki pokazują, że nie ma silnej korelacji liniowej między tendencją węgla do samozapłonu a jego właściwościami petrograficznymi. Zaobserwowano jednak silną ujemną korelację między samozapłonem a wilgotnością i zawartością substancji lotnych. W przypadku węgla kamiennego potwierdzono silne korelacje między parametrami samozapłonu a różnymi właściwościami węgla. Najbardziej godne uwagi są korelacje między parametrami samozapłonu a składem petrograficznym, tj. pomiędzy zawartością macerałów grupy inertynitu w węglu oraz zawartością macerałów grupy huminitu/witrynitu w węglu. Uzyskane wyniki sugerują, że tendencja do samozapłonu węgla rośnie wraz ze wzrostem zawartości semifuzynitu i liptynitu.

19

Determination of optimum temperatures and activationenergies of inulin hydrolysis by endo-inulinase Aspergillus Niger

Miłek Justyna

Chemical and Process Engineering

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2020

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Vol. 41, nr 3

229-–236

EN

The paper presents a comparative analysis to determine the optimal temperatures and the activationenergies for various origin endo-inulinases fromAspergillus niger. The parameters were estimatedbased on the literature of the activity curves vs. temperature for hydrolysis of inulin. It was assumedthat both the hydrolysis reaction process and the deactivation process of endo-inulinase were first-orderreactions by the enzyme concentration. A mathematical model describing the effect of temperature onendo-inulinases fromAspergillus nigeractivity was used. Based on the comparison analysis, valuesof the activation energies Ea were in the range from23:53+/-3:20kJ/mol to50:66+/-3:61kJ/mol, thedeactivation energies Ed were in the range from88:42+/-5:03kJ/mol to142:87+/-2:75kJ/mol andthe optimum temperatures Topt were obtained in the range from317:12+/-0:83K to332:55+/-0:72forendo-inulinase A. niger.

20

Kinetic Studies of Pt(IV) Chloride Complex Ions Reduction Reaction Using Potassium Formate

Wojnicki M., Żabiński P., Csapó Edit

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 3

1135--1140

EN

In this paper, the kinetics of the platinum(IV) chloride complex ions reduction reaction was studied. It was shown that the mechanism exhibits autocatalytic character. The presence of metallic platinum in the system significantly increases the reaction rate. The influence of the initial concentration of precursor, reductant, ionic strength, initial concentration of the chloride ions as well as the temperature on the process rate was investigated. The activation energy was determined and is equal to 93.57 kJ/mol. Moreover, the obtained metallic phase was analyzed, and it was observed that it has a micrometric size.