Journal of Chemical Technology and Metallurgy

KINETIC AND MECHANISTIC STUDIES ON THE RUTHENIUM (III) CATALYSED OXIDATION OF DL-ASPARTIC ACID WITH CERIUM (IV)

2025-03-06T23:25:04+00:00

Kinetics of oxidation of DL-aspartic acid (Asp) was carried out at 30oC with cerium (IV) in sulphuric acid medium in presence of ruthenium (III) catalyst to elucidate its mechanism of oxidation. The reaction is first order with respect to [cerium (IV)] and [DL-aspartic acid], and the rate was determined to be independent of [H+] and [bisulphate]. A suitable mechanism was proposed involving the protonated form of DL-aspartic acid and cerium (IV).

CONCENTRATION OF WET PROCESS PHOSPHORIC ACID FROM WASHED THERMO CONCENTRATE OF PHOSPHORITES CENTRAL KYZYLKUM AND ITS RHEOLOGICAL PROPERTIES

2025-03-06T23:18:26+00:00

The process of purification and concentration of wet process phosphoric acid (WPA) creates the possibility of obtaining more concentrated phosphorus - containing products, such as ammonium dihydrogen phosphate and ammonium hydrogen phosphate, calcium dihydrogen phosphate and calcium dihydrogen phosphate, liquid complex fertilizers for drip irrigation. WPA from the washed thermo concentrate (WTC), although low concentrated (≥ 20 % Р₂О₅ ), contains alone 0.3 - 0.5 % MgO and is suitable for concentration by evaporation. To obtain concentrated phosphoric acid, it is necessary to carry out the processes of desulfurization and evaporation of the Kyzylkums WPA.

STUDY OF THE POLYTHERMAL SOLUBILITY AND RHEOLOGICAL PROPERTIES OF THE SULFOSALICYLIC ACID DIHYDRATE - MONOETHANOLAMINE - WATER SYSTEM

2025-03-06T23:00:43+00:00

In this work, the polythermal solubility of the three-component system containing C₇H₆ O₆S∙2H₂ O - NH₂C₂H₄OH - H₂O was studied in the visual polythermic method based on binary systems and internal sections in the temperature range from -50.2°C to 42.0°C, and the diagram was constructed. In the solubility diagram, based on the phase-separating binary and ternary points the table was created, and the projection was drawn. In the diagram, the crystallization areas of ice, C₇H₆O₆S, C₇H₆O₆S∙2H₂O, NH₂C₂H₄OH∙2H₂O, NH₂C₂H₄OH∙H₂O, NH₂C₂H₄OH, and a new chemical compound C₇H₆O₆S∙NH₂C₂H₄OH were separated. A new phase formed during the study of the C₇H₆O₆S∙2H₂O - NH₂C₂H₄OH - H₂O system was separated, and the separated phase was analysed using chemical, physico-chemical methods and the presence of a new chemical compound (C₇H₆O₆S ∙ NH₂C₂H₄OH) was confirmed.

PRACTICAL ASPECTS OF OBTAINING DEFORMED BLANKS FOR THE PRODUCTION OF BIODEGRADABLE IMPLANTS OF INCREASED QUALITY

2025-03-06T22:53:39+00:00

This work investigates the possibility of improving the structure and properties of a cast magnesium alloy in the Mg-Nd-Zr-Ag system due to its plastic deformation. The optimal ones have been selected as modes of plastic deformation of cast blanks for the manufacture of high-quality implants. It has been shown that plastic deformation of the MC10 alloy makes it possible to significantly refine its structure by 10 times and increase the level of its mechanical properties by 3 or 5 times. Bacteriological studies of MC10 alloy blanks have shown its high antimicrobial properties, which makes it a promising material for the manufacture of implants.

CLINICAL TRIALS FOR COVID-19 TREATMENT - VIEW ON A PERIOD 2020-2022

2025-03-06T22:49:17+00:00

The purpose of the article is to provide an overview of the dynamics of clinical trials for the COVID-19 treatment. We have therefore created a database from the Register of Authorized Clinical Trials, Bulgarian Drug Agency and from the European Union Drug Regulating Authorities Clinical Trials Databases, European Medicines Agency. We studied all 27 clinical trials authorized for conduction in Bulgaria in the search of a COVID-19 treatment during the pandemic (2020-2022).
The results of the article reveal the share and impact of the Bulgarian trial sites in the search for treatment of COVID-19. The pandemic has fundamentally changed clinical trials themselves and diverted attention from diseases other than COVID-19. Competent authority databases include clinical trials with therapeutic areas of impact close to the coronavirus, the results of which would be a benefactor for the accelerated launch of COVID-19 treatment, which motivated us to overview all clinical trials during the pandemic.

COMPARATIVE EVALUATION OF THE POLYPHENOLIC CONTENT AND THE RESULTING ANTIOXIDANT ACTIVITY OF SEVERAL COMMON ALLIUM SPECIES

2025-03-06T22:44:15+00:00

The Allium genus representatives are recognized as valuable nutrients, widely used in various national cuisines all over the World due to their specific taste. Besides, their evinced antioxidant properties, these species possess some pharmaceutic abilities. That is why these plants are the object of growing research interest. Thus, the present study provides data, regarding the polyphenolic compound contents, especially flavonoids, the resulting antioxidant activity and the functional groups of their molecules. The research activities included garlic, leek, shallot, red, white and yellow onions. These species were submitted to comparative analysis, by UV-Vis spectrophotometry, and Fourier Transform Infrared Spectroscopy (FT-IR). The former method was applied to four procedures on powder extracts for determination of to determine: (i) the total polyphenols and particularly (ii) flavonoids, followed by (iii) ferric reducing antioxidant power (FRAP) and (iv) free radical scavenging activity (also known as “DPPH-method”).
The analysis of the results showed that the yellow onion samples contained the highest amount of polyphenolic compounds, whereas the highest content of flavonoids was registered for the shallot. The results for antioxidant activities of the studied cultivars showed similar trends, completely coinciding with the data for the flavonoid contents. Hence, according to the obtained data, the antioxidant activity and flavonoid content decreased in the following order: shallot > yellow onion > red onion > white onion > leek > garlic.

AMMONIA REMOVAL FROM WATER USING CATIONIC MATERIALS KU-2-8 AND DOWEX MAC-3

2025-03-06T22:38:05+00:00

In this work, it is shown that theareighest efficiency of ammonium extraction from water using cationites KU-2-8 and DOWEX MAC-3 is achieved when they are used in their acidic form. It has been established that hardness ions, namely calcium and magnesium ions, complicate the process of ion-exchange ammonium extraction, since these cationites have a higher selectivity for hardness ions. The highest level of regeneration of cationite KU-2-8 was found by using acid solutions compared to sodium chloride solutions. The use of phosphoric and nitric acid solutions for regeneration will allow further use of regeneration solutions for fertiliser production.

SURFACE STRUCTURE AND CHEMICAL COMPOSITION OF COCONUT SHELL CHARCOAL USING NIRA AREN (Arenga pinnata) ACID ACTIVATION

2025-03-06T22:29:16+00:00

Coconut shell is a waste of copra manufactured in North Sulawesi, Indonesia. Pyrolysis coconut shell charcoal is potentially a raw material for bio-adsorbent for health. Bio-adsorbent activated carbon is produced from coconut shells using an acetic acid activator from palm sap (Arenga pinnata). Coconut shell pyrolysis was carried out at a temperature of 400 - 600^oC and an acetic acid activator was obtained by fermenting the palm for six months. The results of the FT-IR analysis of coconut shell charcoal activated with CH₃COOH 3 M and CH₃COOH fermented palm sap showed a decrease or removal of impurity functional groups and an increase in coconut shell charcoal functional groups. The results of SEM-EDS analysis of coconut shell charcoal with CH₃COOH activator fermented
palm sap has a larger average pore diameter of 7.82 μm. The elemental content of carbon C is 87.88 % by mass. Thus, coconut shell charcoal activated using CH₃COOH resulting from palm sap fermentation has potential as an adsorbent for industrial liquid waste.

ESTIMATION OF MINERALOGICAL, MORPHOLOGICAL, AND MAGNETIC PROPERTIES OF THE MINERAL SEDIMENTS OF GUANO CAVES IN THE KARST AREA

2025-03-06T22:14:37+00:00

Guano sediments can record environmental changes in caves and be investigated through the magnetic mineral properties contained therein. The properties of magnetic guano depend on the type, concentration, shape and size of the magnetic mineral grains. These properties can provide clues to the cave-forming environment, both lithogenic and anthropogenic influences. Therefore, this study aims to analyse the magnetic properties, mineralogy, and magnetic mineral morphology of guano sediments in caves in the karst region of Maros, Indonesia, especially Bat caves and Dream caves. Guano samples were taken according to the condition of the cave floor. Magnetic susceptibility measurements are used to analyse the magnetic properties of guano sediments. X - Ray Diffraction (XRD) and Scanning Electron Microscopy - Energy Dispersive Spectroscopy (SEM - EDS) measurements were used to analyze the mineralogy and morphology of the magnetic mineral guano sediments, respectively. The results show that the magnetic susceptibility value at low frequencies ranges from (0.072 - 1.476) x 10^-6 m³ kg^-1 for Bat cave guano. The χLF value of Dream cave guano ranged from (2.867 - 85.507) x 10^-6 m³ kg^-1. The χFD (%) of Bat cave guano samples (2.78 - 8.70) %, while χFD (%) of Dream cave guano samples (0 - 4.18) %. The analysis of magnetic susceptibility, mineralogy, and magnetic mineral morphology showed that the guano samples from both caves tended to be affected by the ferrimagnetic mineral of the iron-titanium oxide group, namely magnetite (Fe₃O₄). The grain hapes
of the guano samples from the two caves are similar; they are oval and irregular, and there are also fractures and heterogeneous grain distribution. Thus, the magnetic mineral sources in Bat cave and Dream cave guano tend to come from magnetic minerals controlled by lithogenic and anthropogenic components.

PREPARATION AND CHARACTERIZATION OF ACTIVATED CARBON BASED ON ACACIA LIGNOCELLULOSIC BIOMASS

2025-03-06T22:08:13+00:00

The aim of our study is to investigate the correlation between the porous texture, chemical nature, and the sorption capacity of activated carbons based on acacia lignocellulosic biomass. Two samples with different ratios of active carbon and chemical activating agent were examined. For this purpose, a two-stage laboratory technology was used - carbonization and chemical activation with potassium hydroxide. The data obtained from the conducted analyses show that the adsorbents based on this type of carbon material have a high surface area and good textural characteristics. They can be used in water purification, catalyst carriers, and other applications.

DEVELOPMENT AND CHARACTERIZATION OF NEW ART AND DECORATIVE ENAMELS

2025-03-06T22:02:59+00:00

The application of enamels on metals has many advantages as improving chemical, corrosion, antibacterial resistance and artistic and aesthetic value. The enamel and the substrate must have good adhesion and close coefficients of thermal expansion. In this study, new enamels based on glasses with a melting temperature of up to 1150°C for jewelry brass-coated steel and copper plates were developed. The theoretical properties as the coefficient of thermal expansion, firing temperature, density, compressive strength, tensile strength of the obtained enamels was calculated with the help of the additive constants of Winkelmann & Schott and Mayer & Havas. A good adhesion of the vitreous enamels to the metal substrates of brass-coated steel and to the copper plates was found. After firing at 800 - 820^oC for 5 min at maximum temperature the resulting enamels are transparent (compositions 2, 4, 5, 6, 7 and 8), semi-transparent (composition 4) and opaque white (composition 1). Coloured enamels in yellow (with 1 mass % Fe₂O₃), turquoise blue (with 1 mass % CuO) and dark brown (with 1 mass % NiO) have been obtained. The new developed enamels can be used for the decoration of metals and for jewelry.

EXPLORING THE EFFECTS OF PILOT INJECTION TIMING ON CRDI ENGINE OPERATION UNDER VARYING LOADS

2025-03-06T21:53:56+00:00

In this study, a single-cylinder CRDI engine running on 20MEWCO (20 % Methyl Esters of Waste Cooking
Oil + 80 % diesel) fuel was used to test various pilot injection timing modifications, including 34°, 36°, and 38° bTDC with a dwell period of 15° and 10 % pilot mass at a pressure of 500 bar. The analysis focused on cylinder pressure, heat release rate, fuel consumption, brake thermal efficiency, and emissions of carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and smoke. As a result of advanced pilot injection timings, at 38° bTDC, the cylinder pressure, heat release rate, and brake thermal efficiency were 63.73 bar, 34.04 J/°CA, and 30.74 %, respectively. Emissions of HC, CO, and smoke increased significantly, while NOx emissions were significantly reduced. Advanced pilot injection timing at maximum load caused a decrease in ignition delay, while shorter combustion duration resulted in more efficient combustion.

HYDRO-DISTILLATION VERSUS STEAM DISTILLATION FOR CLOVE OIL PRODUCTION

2025-03-06T21:41:33+00:00

The production of clove essential oil by hydro distillation and steam distillation has been experimentally investigated. The density of the oil was determined to be ρ ≈ 1.0648 g cm^-3. By means of hydro-distillation, a higher yield of 9.714 mass % was obtained compared to the steam distillation - 4.986 mass %. This is due to the formation of a hard-to-break emulsion in the distillate when using the steam distillation technique. Liquid-liquid extraction and gravity sedimentation were independently applied for the aim of separating the essential oil from the obtained distillate. The obtained yield of clove oil per distillate unit using liquid-liquid extraction was 9.714 mass % and its higher than that found by gravity sedimentation - 4.95 mass % using the same production method. However, considering the final cost per unit of produced oil and its intended use in foods, cosmetics and medicines, separation of the oil by gravity settling is more suitable.

ABRASIVE WEAR RESISTANCE OF STEEL M390P AFTER HEAT TREATMENT

2025-03-06T21:34:55+00:00

In present work abrasive wear resistance after heat treatment of a powder steel M390P with composition 1.9 % C, 0.7 % Si, 0.3 % Mn, 20.0 % Cr, 1.0 % Mo, 4 % V and 0.6 % W was investigated. Machine used for laboratory wear tests is a device that allows to imitate friction conditions in the exploataion of objects. Heat treatment consisting of quenching from 1070ºC in oil and tempering at 450ºC provides maximum hardness of HRC 59 units and suitable for details working at cutting and grinding without high impact load conditions. Quenching from 1150ºC with subsequent twice high temperature tempering at 550ºC achieves hardness of HRC 61. This heat treatment is good for abrasion wear resistance working blades. Hardening at 1070ºC and tempering at 450ºC show wear rate V = 3.6.10^-5 g m^-1 and E = 27778 m g^-1 for abrasive wear resistance. The best parameter values are respectively V = 1.82.10^-5 g m^-1 and E = 54745 m g-1 after high temperature quenching at 1150^oC and subsequent twice tempering at 550^oC.

ELECTRICAL WIRE PRODUCTION FROM Al - Ce - La ALLOY RODS AFTER ELECTROMAGNETIC MOLD AND COMBINED ROLLING ‑ EXTRUSION

2025-03-06T21:16:09+00:00

The paper presents the results of the power parameters when producing rods and wires with Ø 2 mm from them and the mechanical and electrical properties of the resulting semi - finished products from an alloy of the Al - Ce - La system with a rare earth metal content of 1 %. The wire is produced using the method of combined rolling-extrusion (CRE) from the billet Ø 12 mm after electromagnetic mold (EMM), and further drawing. The results of experimental studies of the process of producing longish deformed semi-finished products from the Al - 1 % REM alloy using the CRE-200 combined processing unit are presented. Data were obtained on the mechanical properties of hot - extruded rods Ø 5 mm and Ø 9 mm, as well as wire Ø 2 mm obtained from these rods after implementing the combined processes of rolling - extrusion. It was found that the proposed processing modes make it possible to obtain rods with Ø 9 mm and Ø 5 mm using a combined rolling - extrusion method from workpieces after EMM with diameter 12 mm. The forces on the rolls and die were measured during the implementation of the investigated combined processes. The plasticity of the resulting rods Ø 5 and 9 mm after the CRE method was quite high (elongation to failure reached 14 - 26 %). When drawing wire up to Ø 2 mm, no intermediate annealing was required. The values of electrical resistance do not exceed 0.0271 Ω mm2 m-1 for rods and from 0.0301 Ω mm2 m-1 for wire with a diameter of 2 mm, depending on the processing modes. At all stages of the experimental studies, the structure of the metal was studied and the patterns of change in physical and mechanical properties depending on the processing modes were established.

STUDY OF STRAIN STATE AND FORCE PARAMETERS IN A WIRE DURING DEFORMATION BY A NEW COMBINED TECHNOLOGY

2025-03-06T21:06:36+00:00

In this article, the influence of a new copper wire processing technology on the equivalent strain change was investigated. This technology consists in the wire deforming in a rotating equal-channel step matrix and subsequent drawing. The matrix rotates around the axis of the wire and thereby creates tension due to equal-channel angular broaching and twisting in the matrix. Deformation modelling was carried out at ambient temperature. To assess the effect of the twisting degree on the strain distribution, the rotation speed of the matrix was changed within 6, 18 and 30 rpm. The distance between the two deforming tools was also changed in the range of 100, 200 and 300 mm. The simulation results showed that an increase in the distance between the tools and the rotation speed of the matrix leads to an increase in the twisting angle and the total accumulated strain.

STUDY OF THE EFFECT OF EQUAL-CHANNEL ANGULAR PRESSING ON THE CLOSURE OF CASTING DEFECTS IN ZIRCONIUM ALLOYS

2025-03-06T20:57:21+00:00

In this study, the effectiveness of the Equal Channel Angular Pressing (ECAP) method for closure of casting defects in the zirconium alloy Zr - 1 % Nb, widely used in nuclear power engineering, was studied. A FEM simulation of ECAP processing of a workpiece with an artificially created through defect with a diameter of 5 mm in matrices from different angles of the junction of the die channels was carried out (45°, 90°, 135°). The simulation was verified on a 135° die. The results showed that after two passes, the defect was practically eliminated, the remaining residual crack had a width of only 10 - 25 mm, which indicates the high efficiency of the method. Microstructural analysis revealed a significant grinding of grains to sizes 1 - 8 mm and an increase in the hardness of the material from 145 HV to 171.5 HV. The data obtained confirm the potential of the ECAP method for improving the microstructure and mechanical properties of zirconium alloy ingots.

SIMULATION-DRIVEN CALIBRATION OF MHD SENSORS CONSIDERING VARIATIONS IN REYNOLDS NUMBER, TEMPERATURE, AND MAGNETIC FIELD STRENGTH

2025-03-06T20:39:07+00:00

Liquid metal flow measurement is a challenging task in nuclear and metallurgical industries, due to the high-temperature corrosive environment. Magneto-hydrodynamic (MHD) flow meters are a good choice for such applications, due to their inherent safety, less pressure drop, bi-directional, and accurate flow measurements. In this study, sodium metal flow measurement is investigated in a circular pipe at different temperatures (T) and Reynolds number (Re), using the computational fluid dynamics tool (ANSYS Fluent®) with the MHD module, to benchmark the calibration for flow meters. Simulations are performed for T = 150 to 450°C up to Re 400, for various magnetic field strengths (B) (i.e., 0.05 to 0.4 T). It is noted that the M-shaped velocity profile develops at B ≥ 0.2 T and the
maximum velocity decreases with increasing T, at a given Re and B, and it increases with increasing Re, at a given T and B. Moreover, a systematic parametric study for Re, T, and B is performed in which it is found that the voltage and Lorentz force, increases with increasing Re and decreases with increasing T, at a given B. Our results suggest that the optimum window of operation for the magnetic sensor is at T ≤ 300 and Re ≥ 200 for better performance.