Determination Of Activation Energy Research Articles

Eco-Innovation in Energy: Solid Degradation Kinetics of Rejected Red Macroalgae (Kappaphycopsis cottonii) for Bio-Oil and Biochar Production

In the pursuit of renewable energy sources, biomass conversion into biofuels has garnered attention as a sustainable alternative to fossil fuels. This research focuses on the pyrolytic conversion of red macroalgae, specifically rejected Kappaphycus cottonii, an underutilized biomass in Indonesia, into valuable bio-energy carriers, while analyzing the solid degradation kinetics involved. The dried K. cottonii underwent slow pyrolysis at varying temperatures (400‒600 °C) and time intervals (10‒50 min). The impact of these variables on the yield of bio-oil and biochar, alongside the thermogravimetric profiles indicating mass loss, was thoroughly assessed. The study also explores the chemical kinetics of the decomposition process, utilizing the first-order reaction model to analyze the solid biomass conversion rate, activation energy, and frequency factor. Key findings demonstrate that the optimal pyrolysis temperature for maximizing bio-oil yield was precisely 500 °C, beyond which thermal cracking led to yield reductions. Reaction times also greatly affect yield, highlighting the importance of optimized pyrolysis conditions. The determined activation energy and frequency factor, based on the Arrhenius equation, highlighted K. cottonii's lower decomposition energy barrier relative to terrestrial biomass. This distinction is largely ascribed to its unique chemical makeup, notably a lower lignin content, positioning K. cottonii as an advantageous feedstock for biofuel production through pyrolysis.

A Study toward the Model Independence of Various Heating Rates Method in Thermoluminescence Glow Curve Analysis

This study analyzes thermoluminescence (TL) glow curves simulated in general order kinetics (GOK), one trap one recombination center (OTOR), and non‐interactive multi‐trap system (NMTS) models using various heating rates (VHR) method in linear heating scheme to extract the activation energy. A theoretical analysis to determine activation energy from TL curves using OTOR and NMTS models in an iterative manner, where the TL intensity is determined by using the Lambert‐W function, is proposed with its limitations. It is established that the activation energies in OTOR and NMTS models consist of the relevant GOK term and a respective correction term. Systematic analysis is carried out to study the improvement of the accuracy of activation energy derived from OTOR and NMTS model TL curves over the GOK model calculation. A quantitative analysis of the quasi‐equilibrium (QE) approximations is carried out for choosing appropriate system parameters. The validity of QE conditions are determined by studying variations of full width at half maximum as well as area under the curve as a function of heating rate. The present method is applied on some experimental data to estimate activation energies. This investigation reveals that the activation energy derived in VHR method has negligible dependence on the underlying theoretical models, i.e., the activation energy derived from GOK model calculation is significantly accurate for experimental scenario.

Deep‐bed drying kinetics and thermodynamic parameters of high‐moisture parboiled paddy (ASD‐16) in a reversible airflow fixed bed dryer

AbstractReversible airflow fixed bed dryer (RAFBD) is an energy‐efficient, cost‐effective, and dependable dryer for using renewable energy sources in parboiling mills. In this study, a medium‐sized and high‐moisture parboiled paddy, ASD‐16, was dried in the RAFBD to determine its deep drying characteristics and thermodynamic properties. The chosen paddy variety is a commonly cultivated paddy in the southern region of Tamil Nadu, India. The RAFBD experimental setup was designed to dry 30 kg of parboiled paddy. For the statistical analysis, the experimental data for the deep‐bed drying at hot air temperatures 50–80°C and velocities of 0.1 and 0.15 m/s were used at constant specific humidity. To predict drying characteristics, 12 drying models were compared. Based on their statistical parameters, the Midilli et al. model was selected. For the tested conditions, the coefficients for effective moisture diffusion, heat transfer, and mass transfer were between 9.82 × 10−8 and 2.13 × 10−7 m2/s, 0.3802 and 1.325 W/m2 K, and 0.375 × 10−4 and 1.26 × 10−4 m/s, respectively. Furthermore, the determined activation energy ranged from 20.4964 to 20.4390 kJ/mol.Practical ApplicationsASD‐16 is one of the popular paddy varieties cultivated and used in parboiling mills in the study region. The outcome of this research can contribute to the application of a cost‐effective dryer for drying high‐moisture paddy. Furthermore, the drying time and bed height proposed in this work can reduce the drying time in the mills and improve energy efficiency. The drying kinetics and suitability of the models found in this study will contribute to the design and development of low‐cost dryers for the local parboiling industries. As rice husk, which is a waste from paddy processing, is used for the heating process, industries can reduce the cost of energy for closed‐roof drying. This study provides a clear insight to the researchers and designers in standardizing the capacity of the dryer, drying temperature, and airflow rate for any similar kind of paddy variety.

Synergistic effects of the mixing factor on the kinetics and products obtained by co-pyrolysis of Rosa rubiginosa rosehip seed and husk wastes

The aim of this work was to study the potential synergistic effects of the mixing factor on the kinetics parameters and products obtained through co-pyrolysis of two wastes from Rosa rubiginosa rosehip, and further co-gasification with CO2 of the remaining biochar. Thermogravimetric analysis showed that 6 different processes occur by slow pyrolysis (heating rates of 5, 10, and 20 °C/min), associated with the decomposition of hemicelluloses, cellulose, lignin, and CaCO3 from the ashes. Isoconversional methods determined activation energies of 84.68–223.42, 230.11–270.85, 187.58–303.37, and 400.11–421.71 kJ/mol for hemicellulose, cellulose, lignin, and CaCO3 decomposition, respectively. In most cases, the activation energy from co-pyrolysis was higher for the blends than for the pure wastes, which means that the blends are less reactive to pyrolysis. Gas and tar analyses showed that the blend with 75 % husk waste and 25 % seed waste produced the most hydrogen (5.639 mmol/g biomass), while the blend with 25 % husk waste and 75 % seed waste produced the most carbon monoxide (3.642 mmol/g biomass). The biochar produced by the blends and pure wastes were thermally treated with CO2 to compare reactivity to gasification. It was concluded that the addition of husk waste to the blend increases the reactivity of the biochar obtained, mainly due to its higher ash content.

Efficient hydrogen evolution from NaBH4 using bimetallic nanoparticles (Ni–Co) supported on recycled Zn–C battery electrolyte paste

Electrolytic paste (EP) from used batteries was innovatively utilized as a support for Ni–Co nanoparticles (Ni–Co NPs) to catalyze hydrogen evolution from NaBH4. The materials exhibited a porous and heterogeneous morphology, characterized by a ZnMn2O4 interplanar distance of 0.34 nm, as confirmed by SAED analysis. Elemental analysis identified carbon, nitrogen, hydrogen, and sulfur, while ICP-MS quantified zinc, manganese, and iron. XRD unveiled an amorphous broad peak at 2θ = 13.3–39.8°, with additional phases identified as ZnO, graphite, simonkolleite, manganese oxides, and hetaerolite. Raman spectroscopy showcased characteristic bands typical of carbonaceous materials. FTIR detected functional groups alongside Ni–O, Co–O, and Zn–O bonds. Various Ni/Co ratios were assessed, and the 25:75 and 20:80 (w/w) ratios showed optimal performance, yielding hydrogen at rates of 238.1 and 278.0 mL H2 gcatalyst−1 min−1, respectively. The determined activation energy was 32.76 kJ mol−1. The turnover frequency reached 1823.93 mL H2 gcatalyst−1 min−1 (328.15 K), and the catalyst exhibited satisfactory performance over 16 reuse cycles.

Machine learning-based modeling of malachite green adsorption on hydrochar derived from hydrothermal fulvification of wheat straw

This study investigated the efficiency of hydrochar derived from hydrothermal fulvification of wheat straw in adsorbing malachite green (MG) dye. The characterizations of the hydrochar samples were determined using various analytical techniques like SEM, EDX, FTIR, X-ray spectroscopy, BET surface area analysis, ICP-OES for the determination of inorganic elements, elemental analysis through ultimate analysis, and HPLC for the content of sugars, organic acids, and aromatics. Adsorption experiments demonstrated that hydrochar exhibited superior removal efficiency compared to feedstock. The removal efficiency of 91 % was obtained when a hydrochar dosage of 2 g L−1 was used for 20 mg L−1 of dye concentration in a period of 90 min. The results showed that the study data followed the Freundlich isotherms as well as the pseudo-second order kinetic model. Moreover, the determined activation energy of 7.9 kJ mol−1 indicated that the MG adsorption was a physical and endothermic process that increased at elevated temperatures. The study also employed an artificial neural network (ANN), a machine learning approach that achieved remarkable R2 (0.98 and 0.99) for training and validation dataset, indicating high accuracy in simulating MG adsorption by hydrochar. The model's sensitivity analysis demonstrated that the adsorbent dosage exerted the most substantial influence on the adsorption process, with MG concentration, pH, and time following in decreasing order of impact.

Solution polymerization mechanisms and kinetics of bismaleimide with trithiocyanuric acid

Solution polymerization mechanisms and kinetics of 4,4′-bismaleimidodiphenylmethane (BMI) with trithiocyanuric acid (TCA) in n-methyl-2-pyrrolidone (NMP) were investigated. A competition between the aza-Michael addition reaction and free radical polymerization occurred, and the reaction system competed with the predominant aza-Michael addition reaction. Model-free in differential form method was used to determine activation energy along fractional conversion. In addition, the model-fitting approach was adopted to assess compensation effect parameters for the activation energy and pre-exponential factor. Then, triplet kinetic parameters were achieved. The average activation energy and frequency factor were approx. 94 kJ mol−1 and 1.45 × 1012 min−1, respectively, in the fractional conversion (α) range 0.1–0.9, and the reaction-order model, f(α) = (1 − α)0.81, was of choice. Importantly, these triplet kinetic parameters could effectively predict kinetic curves for the isothermal reaction BMI and TCA.

Fast method for calibrated self-discharge measurement of lithium-ion batteries including temperature effects and comparison to modelling

The self-discharge rate is an important parameter to assess the quality of lithium-ion batteries (LIBs). This paper presents an accurate, efficient, and comprehensive method for measuring and understanding the self-discharge behaviour of LiB cells, considering factors such as temperature and cell to cell variability, as well as underlying electrochemical mechanisms. A method for precise potentiostatic self-discharge measurement (SDM) is demonstrated that is validated by measuring 21 commercial cylindrical 4.7 Ah cells at a state of charge (SoC) of 30%. The self-discharge current ranges between 3 and 6 μA at 23 °C, with an experimental noise level of 0.25 μA. At higher temperatures of 40 °C the self-discharge current increases to 97 μA. The temperature coefficient of voltage (TCV) is experimentally obtained by exposing the cells to a temperature profile with positive and negative step polarities and following the open circuit voltage (OCV) response. Observed TCVs range from +180 µV/K at 40% SoC to −320 µV/K at 0% SoC. For SDM temperature experiments, the cells were set to an SoC with a minimum TCV. From the SDM currents at different temperatures the Arrhenius kinetics and the electrochemical activation energy barrier is determined as 0.94 ± 0.14 eV, indicating chemical side reactions as source of self-discharge. For SDM modelling the electrochemical processes are coupled with a 3D temperature finite element model (FEM) and an electric circuit model resulting in a good overlap with the dynamics and time-constants of the experimental self-discharge curves. The primary challenges addressed are accurately measuring microampere (µA) discharge currents of high-quality cells, reducing measurement time, understanding the temperature dependence of self-discharge, determining activation energy, and demonstrating the applicability and generalization of SDM.

High thermal stability of warm white emitting single phase GdPO4: Dy3+/ Sm3+ phosphor for UV excited wLEDs

Highly thermally stable warm white light emission has been obtained from a single component phosphor; GdPO4: Dy3+/Sm3+. A series of GdPO4: Sm3+ (1%)/Dy3+ (x%) (x = 0.1, 0.5, 1 and 2) phosphors have been synthesized by the co-precipitation method. The crystal structure and phase purity of the samples obtained were verified by X-ray diffraction. Photoluminescence spectra, luminescence lifetimes are used to study the effect of Dy3+ concentration and the energy transfer from Dy3+ to Sm3+ as a function of excitation wavelength. The nearest-neighbor contributed to the non-radiative energy transfer from Dy3+ to Sm3+ in GdPO4, under 273 and 363 nm excitation. A warm white light was obtained from all phosphors excited at 273 nm and for 1 and 2% of Dy3+ in GdPO4:Sm3+ under 363 nm excitation. Temperature-dependent luminescence properties are determined for GdPO4: Sm3+ (1%), Dy3+ (1%) under 273 nm and 363 nm excitation. The studied phosphor has a good luminescence thermal stability and the determined activation energy for thermal quenching is 1.26 and 0.75 eV for 273 nm and 363 nm excitation wavelengths, respectively. The effect of the Dy3+ concentration as an activator ion responsible for the white emission light, at a fixed concentration of Sm3+ as a red emission compensator in the Dy3+ emission spectrum, was discussed. The low color temperature and high thermal stability indicate that the studied material is a promising solid-state emitting phosphors for the UV chip excited warm wLED applications.

Comparative pyrolysis characteristics and kinetics of agricultural food grains by thermogravimetric analysis

Pyrolysis precedes the development of smouldering or flaming fires in storage and processing facilities. Understanding this process and determining the parameters that characterise it is essential for controlling fires. This study analysed the pyrolysis of African food grains that are important for food security but historically have received limited attention. Cowpeas, lentils, millet, soybeans, unshelled peanuts, flax, sunflowers, shelled peanuts, and sesame were subjected to thermogravimetry in a nitrogen atmosphere at heating rates of 5, 10, 20, and 40 °C/min from ambient to 600 °C. All grains were completely dehydrated at 170 °C and started decomposing at about 180 °C. The decomposition patterns varied with the relative proportion of hemicellulose, cellulose, protein and, particularly, lipids (oil content). Pyrolysis rates peaked at lower temperatures of about 300 °C for non-oil grains but at higher temperatures of 400 °C for oil grains. Friedman and Coats-Redfern methods were used to determine activation energies (130–355 kJ/mol), preexponential factors (8.1 × 107–1.0 × 1031 s−1) and the numerical values of the complex, multistep reaction models. Oil grains (or their powder) generally have lower activation energies, are thus more reactive than non-oil grains, and therefore constitute critical consideration for fire safety in processing facilities. The work is important for developing fire engineering solutions for food facilities based on quantitative fire behaviour data.

Hot deformation behavior and flow stress modeling of coarse-grain nickel-base GH4151 superalloy ingot materials in cogging

Due to the high deformation resistance and poor thermal ductility of the new cast GH4151 alloy ingots, cracks are easy to occur during cogging process. For clarifying the effects of deformation parameters on microstructural evolution and dynamic recrystallization (DRX) nucleation mechanisms. In this work, the causes of crack formation and extension were first investigated using SEM and EBSD. The study revealed that the reasons for crack formation and propagation are the MC carbides at the original grain boundaries, large-size γ′ phase, residual eutectic phases, and tiny pores near the grain boundaries. Subsequently, a series of hot compression tests were performed using a Thermecamastor-Z thermo-mechanical simulator at temperatures ranging from 1080 °C to 1160 °C and a strain rate range of 0.01–10 s−1. The constitutive equation of the Arrhenius model and the hot working map was established, determining activation energy(Q) of 1086.58 kJ·mol−1. Large-size γ′ is coherent with the matrix. For the γ+γ′ dual-phase region, heterogeneous strain-induced dynamic recrystallization (HDRX) occurs, and discontinuous dynamic recrystallization (DDRX) is the main nucleation mechanism for DRX. However, for γ single-phase region, DDRX plays a more significant role. Furthermore, the MC phase (>1 μm) has different crystal orientations with the γ matrix and acts as sites for recrystallization through particle-stimulated nucleation (PSN). Finally, a fine and uniform grain structure can be obtained in the temperature range of 1120–1135 °C and the strain rate range of 0.1 s−1 to 1 s−1.

Thermogravimetric analysis (TGA) and determination of activation energies of waste paper products

Tetra Pak® paper and PE (polyethylene) wastes were evaluated to obtain a new composite material with awareness of environmental responsibility. Fillers and coupling agents were used for this joining process. Calcite (CaCO3), boric acid (H3BO3), SPT (Sodium Perborate Tetrahydrate / NaBO3.4H2O), titanate, MAPE (maleic anhydride grafted polyethylene, and vinyltriethoxysilane (C8H18O) composites were produced in 30 × 30 cm plates. A total of 30 samples were prepared as 5 mg flour for thermogravimetric analysis (TGA). Samples were observed in a thermal analyzer at 10, 15, or 20 °C/min heating rate in nitrogen atmosphere. Graphs were obtained as a result of TGA, and the activation energies were calculated using these graphs. The activation energy was calculated using the Flynn-Wall-Ozawa method. The determined activation energies of the composites were close to each other for each temperature group. In the samples using calcite and vinyltriethoxysilane, relatively higher activation energies were observed in comparison to the samples with boric acid and MAPE.

Investigation of the thermal behavior of Ca(NO3)2·4H2O and its application for the regeneration of HNO3 and CaO

Nitric acid pressure leaching has great potential in treating limonitic laterite. A new method is designed to improve the downstream process. The resulting calcium nitrate solution is concentrated/crystallized/pyrolyzed to achieve the regeneration of nitric acid and calcium oxide. Calcium nitrate pyrolysis is the core process to realize the new method, but the dynamic analysis of this process is relatively lacking and the pyrolysis mechanism is controversial. In this paper, TG-DSC, TG-MS and XRD were applied to systematically study the thermodynamics and phase evolution of calcium nitrate tetrahydrate. It is found that pyrolysis of calcium nitrate tetrahydrate can be divided into four stages: removing free water and part of crystal water, removing residual crystal water, stable existence of anhydrous calcium nitrate, and its decomposition after melting. Calcium nitrite and nitrogen are absent in the process of calcium nitrate pyrolysis. Three iso-conversion methods, including Flynn-Wall-Ozawa method, Kissinger-Akahira-Sunose method and Starink method, were applied to determine activation energies of calcium nitrate pyrolysis as 224.4 kJ/mol, 221.8 kJ/mol and 222.2 kJ/mol. The kinetic mechanism model of calcium nitrate pyrolysis determined by Melak method is closer to An model, which is the random nucleation and growth reaction. Calcium nitrate pyrolysis process further expands the industrial application of nitric acid pressure leaching.

Reliability evaluation of DC power optimizers for photovoltaic systems: Accelerated testing at high temperatures with fixed and cyclic power stresses

This paper presents a long-term and large-scale time-to-failure reliability study to determine the acceleration factor and field-use lifetime for dc optimizers. Forty optimizers were tested at two high static temperatures (85 °C and 95 °C) and two input power profiles (fixed power and cyclic power) over a period of 6400 h. For degradation analysis, continuous electrical and thermal data were collected. On average, the dc optimizer units degraded by about 1%, while no hard failures occurred over 6400 h of high-temperature stress testing. Using the Arrhenius life-stress model along with average field measured temperature, it is predicted that the dc optimizers should be able to survive for 39–73 years in field operating conditions with a reliability of 79%, having a lower one-sided confidence bound of 90%, demonstrating similar or even exceeding the lifetime of the associated PV modules. Nevertheless, with the determined activation energy of 0.33 eV, derived from the observed degradation percentage in cyclic power profiles, the projected lifespan for dc optimizers is significantly curtailed. Under field conditions, our estimations suggest a service life ranging between 9 and 12 years. Furthermore, the cyclic power profile at higher stress temperature demonstrated higher levels of degradation compared to the fixed power profile. This implies the cyclic thermal mechanisms at higher stress temperature (which are not captured in the Arrhenius equation) account for a higher contribution to degradation. This has been confirmed through the use of Weibull distribution model where the analysis indicates that the estimated lifetime for dc optimizer can significantly decrease based on a higher stress temperature along with the power cycling of the units.

Determination of Pyrolysis and Kinetics Characteristics of Chicken Manure Using Thermogravimetric Analysis Coupled with Particle Swarm Optimization

The valorization of chicken manure via pyrolysis can give biowaste a second life to generate value and contribute to the circular economy. In the present study, the thermal degradation and pyrolysis characteristics of chicken manure pyrolysis were investigated via thermogravimetric analyses (TGA) coupled with optimization methods. Thermogravimetric data were obtained for the samples at five heating rates of 5, 10, 20, 30 and 50 °C/min over a range of temperature under inert conditions. The manure devolatilization process was initiated at between 328 and 367 °C to overcome the global activation energy barrier. The determined activation energy of the manure via Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), Friedman and Kissinger methods was in the range of 167.5–213.9 kJ/mol. By using the particle swarm optimization (PSO) method, the pyrolytic kinetic parameters of the individual component present in the manure were calculated, in which the activation energy for cellulose (227.8 kJ/mol) was found to be higher than that of hemicellulose (119 kJ/mol) and lignin (134.3 kJ/mol). Based on intrinsic transition-state theory, the pre-exponential factor and activation energy of the manure can be correlated through a linear equation ln Aα = 0.2006 Eα − 1.2847. The devolatilization characteristics of the chicken manure were elucidated via the optimization process, paving the way for the design of thermochemical conversion reactors and processes.

Activation energies and evolved gas analysis for Argonne premium coals

ABSTRACT A set of eight coals from the premium Argonne coal sample program were studied using thermogravimetric and evolved gas analysis. Gaseous combustion products were analyzed using an FTIR spectrometer and a chemiluminescence analyzer. Additionally, modulated thermogravimetric experiments were carried out to determine activation energies associated with the combustion of each sample. The exhaust from the thermogravimetric analyzer was directed to the gas analyzers for detecting and quantifying CO, CO2, and NO. Evolved gas analysis was conducted at a ramp rate of 5°C for CO, CO2 evolution, and 20°C per minute for nitric oxide evolution, with the furnace temperature varying between 20°C–750°C. Modulated thermogravimetric analysis experiments were carried out in the same temperature range. The temperature was increased at a rate of 2°C per minute for the modulated experiments. Each test had a superposed temperature modulation with amplitude ±5°C and a period of 200 seconds. The experiments provide valuable information on the combustion kinetics and emission characteristics of selected American coals.

Influence of Mg on the Li ion mobility in Li4-2xMgxP2S6.

Aliovalent substitution of Li in salts by Mg can generate Li vacancies and thus in principle improve the ionic conductivity. In fact the influence of substitution on ionic conductivity is far more complex. Here the impact of Mg substitution on Li ion mobility is studied in the example of Li4P2S6 by a combination of nuclear magnetic resonance experiments on 31P and 7Li at variable temperatures, impedance spectroscopy and X-ray powder diffraction to elucidate the relationship with structural changes and the effect on mobility on different length scales. It is found that substituting Li ions with Mg ions in Li4-2xMgxP2S6 with 0 ≤ x ≤ 0.2 increases the local Li ion mobility up to a certain concentration at which a phase transition induces a different structural realignment of the P2S64- units. The determined activation energies can be assigned to vacancy hopping processes by comparison with nudged elastic band calculations at the density functional level of theory, which shows not only the possibilities but also limitations of substituting Li with Mg.

A kinetic study of thermal degradation of non-metallic part of printed circuit boards for the combined effect of particle size and catalyst

ABSTRACT After the successful removal of metals from printed circuit boards either through a physical or chemical process, epoxy resins are thermosetting plastics left over for landfilling. To overcome landfilling, thermal degradation of this resin was done under different particle sizes with varying catalyst concentrations. A series of thermogravimetric experiments were carried out using ZSM-5 as the catalyst. To study kinetics parameters’ mass loss with temperature was divided into 3 zones 120–240°C, 240–360°C and 360–650°C. To determine activation energy and the order of reaction, the Coats and Redfern method was used. Experimental data in all three zones were found in agreement with the Coats and Redfern method. ZSM-5 was found to be reducing activation energy and the order of reaction in zone 2. The average activation energy was in the range of 150–200 kJ/mol and the order of reaction was 1.5–2 in zone 2 for different experiments. Coarser particles were found to have less decomposition than finer particles due to heat transfer limitation within the particle. However, the effect of increasing catalyst concentration was found ineffective in the mass transfer of more volatiles from PCB.

The application of selective leaching and complex anion exchange in a novel aqueous process to produce pure indium from waste liquid crystal display panels

By studying the leaching kinetics of indium from waste liquid crystal displays (LCD), it was pointed out, that recoveries of > 90 % are possible with 0.5 M HCl at 80 °C or 2 M HCl at 55 °C. The anion-exchange sorption of indium was found practically negligible from sulphate solutions, however, in chloride solutions of 2 mol/dm3 HCl (or NaCl) indium was moderately sorbed (log D = 0.83), and a further increase of the distribution coefficient (log D = 1.1) was found until 6 mol/dm3 Cl- ion concentration. Based on the determined activation energies, at low (< 1 M) HCl concentrations, the process is controlled by the formation of the complex species, while above, diffusion and transport processes are more important. The devised chromatographic separation in an anion-exchange column was able to eliminate virtually all the practical impurities. After loading the leachate of 5 mol/dm3 chloride ion concentration, the non-sorbed alkali, alkaline earth and some transition metals can be removed by rinsing the resin bed with a solution of 2 mol/dm3 chloride ion concentration. Indium can be eluted by reducing the chloride ion concentration in the influent to 0.25 mol/dm3. The still retained elements (Zn, Sn, Bi) can be removed with 1 M NaOH solution. The pure solution was used to electrowon indium metal, which was analysed by SEM-EDS and - after dissolution – with ICP – OES. The purity of the metallic indium product was found to be 99.9997 %.

Lithium and boron diffusivity and isotopic fractionation in hydrated rhyolitic melts

Lithium and boron are trace components of magmas, released during exsolution of a gas phase during volcanic activity. In this study, we determine the diffusivity and isotopic fractionation of Li and B in hydrous silicate melts. Two glasses were synthesized with the same rhyolitic composition (4.2 wt% water), having different Li and B contents; these were studied in diffusion-couple experiments that were performed using an internally heated pressure vessel, operated at 300 MPa in the temperature range 700–1250 °C for durations from 0 s to 24 h. From this we determined activation energies for Li and B diffusion of 57 ± 4 kJ/mol and 152 ± 15 kJ/mol with pre-exponential factors of 1.53 × 10–7 m2/s and 3.80 × 10–8 m2/s, respectively. Lithium isotopic fractionation during diffusion gave β values between 0.15 and 0.20, whereas B showed no clear isotopic fractionation. Our Li diffusivities and isotopic fractionation results differ somewhat from earlier published values, but overall confirm that Li diffusivity increases with water content. Our results on B diffusion show that similarly to Li, B mobility increases in the presence of water. By applying the Eyring relation, we confirm that B diffusivity is limited by viscous flow in silicate melts. Our results on Li and B diffusion present a new tool for understanding degassing-related processes, offering a potential geospeedometer to measure volcanic ascent rates.