Journal of Chemical Technology and Metallurgy

ANTIMICROBIAL PEPTIDES AND TEMPORIN FAMILY IN THE CONTEXT OF RISING RESISTANCE - VIEW ON CURRENT DEVELOPMENT

Dilyana Dimitrova — 2026-05-01

Antimicrobial resistance has surfaced as a gradual yet progressively significant threat to global public health, frequently overshadowed by more widely pressing issues like cancer and cardiovascular disease. Nonetheless, the rapid proliferation of multidrug-resistant pathogens has gathered worldwide attention, prompting organizations like the World Health Organization to classify it as one of the most urgent challenges that modern medicine must face. The reduced efficacy of conventional antibiotics has led to increasing treatment failures, prolonged hospitalizations, and elevated mortality rates, highlighting the urgent need for novel therapeutic approaches. In response to this, there is an increasing interest in overcoming the limitations of conventional antibiotics by developing novel treatment alternatives. Among these alternatives, antimicrobial peptides have attracted considerable attention due to their broad-spectrum efficacy, which includes antibacterial, antiviral, antitumour activities, alongside a unique mechanism of action, coupled with reduced likelihood of inducing resistance. The Temporin family is one of the groups in this category. It was originally isolated from amphibian skin secretions and has shown significant potential as a new source of antibacterial, antiviral, and antifungal agents. Temporins show strong antibacterial properties, particularly against Gram-positive bacteria. Their simple structures make them attractive candidates for enhancement and therapeutic applications. Ongoing research on temporins and other AMPs holds great promise for finding a solution to the global problem of antimicrobial resistance and for shaping the next generation of infection-fighting therapeutics.

A MICROWAVE-ASSISTED ACID HYDROLYSIS OF CORNCOB: RAPID FURFURAL PRODUCTION AND ITS KINETIC

Rinna Juwita — 2026-05-01

The microwave-assisted hydrolysis of corncob was successfully performed using H2SO4 as an acid catalyst for rapid furfural production. The influences of reaction time and the catalyst amount on the yield of furfural production were discussed comparatively. The hydrolysate obtained from the reaction was characterized by an aniline-acetate test and FT-IR to confirm furfural generation. The degradation of the cell wall structure of corncobs during the reaction was investigated by SEM and FT-IR analysis of the solid before and after the reaction. The results showed that hemicelluloses were released from the cell wall to be converted into furfural. The highest yield of furfural was reached after a 5 min reaction under microwave irradiation, which was 9-fold faster than a reaction with conventional heating methods for the same amount of furfural (a 45 min reaction). It signifies that the chemical reaction could be
performed efficiently using microwave irradiation which provides better heating distribution, faster heating, and a more controllable heating mechanism compared to conventional heating methods.

ANALYTICAL METHOD FOR DETERMINATION OF AVERMECTINS IN MILK BY LIQUID CHROMATOGRAPHY WITH FLUORESCENCE DETECTION

Milena Peycheva — 2026-05-01

A fast, sensitive and selective method has been developed for quantitative determination of residues of six avermectins - abamectin, doramectin, moxidectin, ivermectin, eprinomectin and emamectin in milk by liquid chromatography with fluorescence detection (HPLC - FLD). Nemadectin is used as an internal standard (IS). Avermectins are used as antiparasitic agents in veterinary medicine. They have maximum residue limits (MRLs) in accordance with Commission Regulation (EU) No 37/2010 in foodstuffs of animal origin. The substances are extracted by liquid extraction with acetonitrile, followed by clean up step using solid - phase extraction (SPE) with
Strata C18 - E cartridges and derivatization with trifluoroacetic acid anhydride (TFAA), 1 - methylimidazole and the addition of 100 % acetic acid and triethylamine (TEA), to enable fluorescence detection. Chromatographic separation is achieved using Agilent Eclipse XDB - C18 (150 x 4.6 mm, 5 μm) column, equipped with a guard column of the same packing in 15 min. Gradient elution is applied with mobile phase A (acetonitrile) and mobile phase B (water) and a fluorescence detector works with wavelengths at λex = 365 nm and λem = 460 nm. The analytical method is validated according to the requirements of Commission Implementing Regulation (EU) 2021/808. The method has been implemented, and it is used as routine method for control of residues of Avermectins in Central Laboratory of
Veterinary Control and Ecology (CLVCE).

STUDYING THE SOLUBILITY OF THE ZINC SULFATE - AMMONIUM NITRATE - WATER SYSTEM

Dilnoza Ne’matjon qizi Makhkamova — 2026-05-01

The solubility of the components in the ZnSO₄ - NH₄NO₃ - H₂O system was studied by the visual-polythermal method in the temperature range from -19.4°С to +13.0°С. The phase diagram delimits the fields of ice crystallization, NH₄NO₃, NH₄NO₃·ZnSO₄·3H₂O, and ZnSO₄. A solubility diagram was constructed, and a new compound NH₄NO₃·ZnSO₄·3H₂O was separated. The new compound was identified by scanning electron microscopy (SEM), chemical, X-ray phase, and IR spectroscopic analysis.

GREEN SYNTHESIS OF GOLD NANOPARTICLES USING MENTHA SPICATA L. AND ITS APPLICATION AS A CATALYST FOR OXIDATION NADH TO NAD+

Rafah M. Thyab — 2026-05-01

Due to their high biocompatibility, stability, and unique characteristics, gold nanoparticles (AuNPs) have numerous applications in the medical and biological fields. Plant-based nanoparticle synthesis is beneficial over other biological processes because it can be scaled up to an industrial scale. The electrochemical measurement of dihydronicotinamide adenine dinucleotide (NADH) is crucial because it serves as a required coenzyme for several dehydrogenases. NADH is the final electron donor molecule in the mitochondrial electron transport pathway. This study examined the catalytic role of AuNPs produced using Mentha spicata L. in the oxidation of NADH to
nicotinamide adenine dinucleotide (NAD+). AuNPs reduced NADH fluorescence intensity. As the quantity of AuNPs increased, the intensity of the 260 nm NAD+ band increased, while that of the 340 nm NADH band decreased. The surface plasmon absorbance band of AuNPs at 520 nm increased in intensity due to the presence of NADH. This study provides significant evidence that the AuNPs surface catalyzes the oxidation of NADH to NAD+. The catalyst characteristic of this crucial reaction may have significant potential applications in the biological and medicinal fields.

OPTIMIZING THE COMPOSITION OF UNPLASTICIZED POLYVINYL CHLORIDE PROFILES BY ADDING CHLORINATED POLYETHYLENE

Petranka Naydenova-Marinova — 2026-05-01

The synergistic effect of partial replacement of acrylic modifier with chlorinated polyethylene on the performance properties of extruded profiles made of rigid polyvinyl chloride was studied. Five dryblend formulations with different ratios of chlorinated polyethylene and acrylic modifier were prepared. Profiles with identical geometry (five-chamber frame) were extruded from them. Test specimens were prepared from the surface of the profiles. Tests were conducted and the physicomechanical properties of the tested samples were analysed. Based on this, the optimal content of chlorinated polyethylene in the dryblend composition was established. The impact and cold resistance, linear expansion, strength of the weld (thermally sealed corner), gloss and whiteness of the products were studied on the modified profiles. The aim of the present work is to improve the performance properties and reduce the cost of the final products by modifying the composition of the dryblend to produce profiles made of unplasticized polyvinyl chloride.

OPTIMIZATION AND THERMODYNAMIC CHARACTERISTICS OF COPPER CORROSION INHIBITION BY EXPIRED TOPLEX SYRUP IN SULFURIC ACID

Boumediene Kheroubi — 2026-05-01

This study investigates the effectiveness of expired Toplex syrup as a sustainable and eco-friendly corrosion inhibitor for copper in 0.5 M sulfuric acid (H₂SO₄), using weight loss measurements to assess its performance. The influence of critical parameters inhibitor concentration (0.1 - 0.4 % v/v), temperature (293 - 323 K), and immersion time (0.5 - 1.5 h)-on corrosion rate and inhibition efficiency were comprehensively examined. Experimental results revealed a direct correlation between inhibition efficiency and both Toplex concentration and temperature, with peak efficiency (95.55 %) was achieved at 0.385 % v/v, 322.5 K, and 1 h of immersion. Optimization using Response Surface Methodology (RSM) with a central composite design yielded a statistically robust and predictive model (R2 = 0.994, Q² = 0.946). Adsorption behaviour followed both the Langmuir and Temkin isotherms, while thermodynamic analysis confirmed a spontaneous physisorption mechanism, as evidenced by negative Gibbs free energy values (ΔGads = - 11.69 to - 17.46 kJ mol⁻¹). Activation energy calculations indicated an endothermic corrosion process, with significantly higher energy barriers observed in the presence of the inhibitor supporting a predominantly physical adsorption mechanism. Furthermore, Scanning Electron Microscopy (SEM) revealed the formation of a uniform and protective film on the copper surface, confirming the role of Toplex syrup in mitigating
acid-induced degradation. These findings highlight the potential of expired Toplex syrup as an effective, low-cost, and environmentally benign corrosion inhibitor for copper in acidic environments, with promising implications for industrial applications.

ECOLOGICAL CHEMICAL METHOD FOR PREPARATION OF A ZINCATE ELECTROLYTE FOR ELECTRODEPOSITION OF LOW-ALLOYED Zn-Fe ALLOYS

Daniela Lilova — 2026-05-01

An ecological chemical method was developed to obtain a non-toxic zincate electrolyte for the electrodeposition of low-alloy Zn-Fe (< 1 wt. % Fe) alloys. The self-dissolution parameters of zinc in 120 g L^-1 NaOH from alternative sources - self-dissolution rate (V) and full removal time (tfrc), were compared for three zinc sources: hot-dip galvanized steel (A-Zn), galvanic industry waste (B-Zn), and battery waste (C-Zn). Optimal conditions for the dissolution of zinc from A-Zn were selected: concentration of the activating additive hydrogen peroxide (50 mL L^-1 50 % H2O2), temperature (50 - 55°C), and solution saturation time (10 - 15 min). A procedure is proposed for the preparation of the final alkaline zincate electrolyte for deposition of low-alloy Zn-Fe (< 1 wt. % Fe) alloys, including preparation of basic solutions of the primary ions-zinc from chemical dissolution of A-Zn and an alkaline iron concentrate derived from spent hydrochloric pickling solutions for carbon steel, containing two Fe-complexing ligands. By controlling the solution composition and the reflectivity of the Zn-Fe coatings, a design for an alkaline zincate electrolyte has been proposed, enabling the production of high-quality alloys.

EVALUATION AND PARAMETERS AFFECTING OF HYBRID ACTIVE CARBONE-ETHANOL SOLAR ADSORPTION REFRIGERATOR

Adnan G.T. Al-Hasnawi — 2026-05-01

The development of environmentally acceptable refrigerants and the use of solar energy and low-grade waste heat made adsorption refrigerators more appealing. However, more study is required to optimize these methods further as they do not yet match the performance and commercial application of typical vapor compression systems. This article illustrates the thermal response of adsorption systems under varying operating circumstances by simulating the pressure effect on temperature distribution in a porous adsorbent bed using ANSYS Fluent. Although heat transfer in porous media has been studied in the past, little is known about the precise function that pressure plays in influencing thermal behaviour. According to simulation studies, ethanol desorption efficiency is increased by greater inlet pressures because they provide more consistent and raised temperature distributions. varied x-positions (2.9125 mm, 5.825 mm, and 11.65 mm) exhibit varied temperature profiles, which correspond to localized flow and pressure conditions. The results provide important insights into improving the design and functionality of adsorption-based cooling and separation systems by highlighting the predominant roles of heat conduction and vapor transport in determining thermal gradients.

ZINC DIPHOSPHATE Zn2P2O7 GLASS: ELABORATION, CHARACTERIZATION, AND DFT STUDY

Abdelahad El Addali — 2026-05-01

Zinc diphosphate glass Zn₂P₂O₇ has been synthesized using the conventional melt quenching process and investigated through various techniques. These analyses include X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR), and Raman spectroscopy. Besides confirming the glassy nature of this material, the different phosphate groups within the glass structure have been identified and their vibration frequencies have been assigned. The study aims to propose three distinct short-range structural models for the Zn₂P₂O₇ glass compound: IVZn, VZn, and VIZn. These buildings underwent optimization and a detailed theoretical analysis using the Density Functional Theory (DFT) method. By examining the global reactivity indices of these clusters, we were able to identify the most stable structural configuration for this compound. The results of the investigation confirm a strong agreement between the experimental observations and theoretical predictions, enhancing our understanding of the material’s structure.

SOL-GEL PROCESSING AND PROPERTIES OF Eu3+ DOPED SiO2 - B2O3 GLASSES

Hristo Lalkovski — 2026-05-01

Eu³⁺ doped glasses from the SiO0₂ - _B2O3 system containing up to 20 mol % _B2O3 have been synthesized. To obtain a homogeneous glass, it was determined that a certain degree of hydrolysis of Si(OC₂H₅)₄ was essential before B(OC₂H₅)₃ could be incorporated. These glasses have been characterized by X - ray diffraction, DTA and IR spectroscopy. According to the XRD method, amorphous gels have been obtained. IR spectra exhibited bands in the 1700 - 620 cm^-1 range which could be related to the vibrations of SiO₄ and BO₃ inorganic structural units. Characteristic emission peaks of Eu³⁺ ions were detected in the luminescence spectra. The obtained results confirmed that Eu³⁺ doped glasses are useful for optical applications.

GLASS-FORMING REGION IN THE GeSe2-In2Te3-GeTe SYSTEM AND SOME PHYSICOCHEMICAL PROPERTIES OF GLASSY ALLOYS

Lilia Aljihmani — 2026-05-01

For the first time, chalcogenide glasses from the GeSe₂-In 2Te₃-GeTe system are synthesized. Visual, X-ray diffraction, and electron microscopic investigations identify the glass-forming area, primarily located in the GeSe₂-rich region.
Differential thermal analysis determines the characteristic temperatures of phase transformations, including the glass transition temperature (T_g), crystallization temperature (T_cr), and melting temperature (T_m). Hruby’s criterion is used to estimate the glass-forming ability (K_G). The chalcogenide glasses’ density (d) and microhardness (HV) are measured. Compactness, elasticity modulus, and thermomechanical characteristics (micro-void volume (V_h) and formation energy (E_h)) are computed using the acquired properties. A thorough discussion and link between the glasses’ properties and composition are established.

PHYSICAL-CHEMICAL CHARACTERIZATION OF INDUSTRIAL WASTE FROM SUNFLOWER HUSK COMBUSTION FOR POTENTIAL GREEN APPLICATIONS

Katerina Mihaylova — 2026-05-01

The industrial ash used in this study is a residue from the combustion of plant biomass - sunflower husks. The increasing generation of this type of waste and the need for implementation of sustainable practices warrant the investigation of its possible green applications.
The study presents the results on the chemical and phase composition of two series of fly ash samples obtained from the industrial combustion of sunflower husks using wavelength-dispersive X - ray fluorescence analysis, powder X - ray diffraction, and Fourier transform infrared spectroscopy. The chemical data of the samples show high contents of biogenic and nutritional oxides such as K (34 - 39 % wt.), S (5 - 11 % wt.), and Са (3 - 8 % wt.), with no detectable contamination with toxic or radioactive elements. The phase composition of the samples includes synthetic analogues of arcanite, K₂CO₃, sylvite, calcite, spurrite, and gypsum. The data obtained demonstrate that this waste material has high potential for use in the production of fertilizer components, activators, or improvers for soils and soil fertility.

MECHANICAL PROPERTIES OF ALUMINIUM METAL MATRIX COMPOSITES REINFORCED WITH MILLSCALE AND ALUMINA

Adeolu A. Adediran — 2026-05-01

The present investigation examines the mechanical properties of aluminium metal matrix composites (AMCs) that are reinforced with millscale and alumina. The composite materials were produced through a stir casting technique and analysed for density, porosity, hardness, tensile strength, yield strength, specific strength, percentage elongation and fracture toughness. The microstructure of the produced composites and the fractured surfaces of the composites were examined using a scanning electron microscope (SEM). The findings demonstrate that the addition of millscale and alumina improves the mechanical properties of the composites. The mechanical testing reveals a gradual increase in tensile strength with a higher weight ratio of alumina, resulting in a maximum ultimate tensile
strength of 124.73 MPa for sample D. Moreover, hardness increases slightly with higher weight ratios of alumina, with sample D exhibiting the highest hardness value of 94.6 BHN. Fracture toughness varies with composition, and sample D displays a fracture toughness of 7.6 MPa m^0.5. The incorporation of alumina enhances hardness, yield strength, and tensile strength. Whereas the presence of millscale leads to improved hardness and tensile strength. The incorporation of millscale and alumina markedly improves the specific strength of the composites. The analysis of the microstructure demonstrates the distribution and bonding properties of the reinforcement particles in the aluminium matrix. The findings indicate the potential of millscale and alumina as reinforcing materials for AMCs, providing a sustainable and cost-effective solution for diverse engineering applications.

COMPUTER MODELING AND RESEARCH OF THE ASYMMETRIC ROLLING OF A WORKPIECE WITH A GRADIENT DISTRIBUTION OF MECHANICAL PROPERTIES

Abdrakhman Nizabekov — 2026-05-01

The paper presents the results of finite-element modelling of asymmetric rolling of a workpiece with a gradient distribution of mechanical properties. To create a gradient distribution of properties, the workpiece was pre-loaded and Vickers microhardness was evaluated. The resulting workpiece model had a microhardness distribution that was close to the experimental values. The workpiece was subjected to both symmetric rolling and asymmetric rolling with an asymmetry coefficient of 1.5, which was achieved by varying the roll speeds (90 and 60 rpm) in two scenarios (90/60 and 60/90). The parameters of the stress-strain state and the rolling force were analyzed. The results showed that asymmetric rolling of a workpiece with a gradient distribution of mechanical properties had only minor differences from symmetric rolling. When the asymmetry coefficient exceeds 3, this factor begins to have a significant impact
on the processing unevenness.

SYSTEMATIC APPROACH TO DESCRIBING STEEL REFINING PROCESSES IN A LADLE FURNACE

Daria Togobitska — 2026-05-01

This work presents a systematic approach to describing the physicochemical processes occurring in the metal-slag system during steel refining in a ladle furnace. The aim of the study was to develop methods for predicting the distribution of main and impurity elements based on a comprehensive analysis of the initial and final melts of metal and slag. Industrial data on the chemical composition of SAE1006 grade steel and the corresponding slag were used as the input. Based on the methodological framework of the Directed Chemical Bonding Concept (DCBC) and mathematical processing of multivariate data, the applicability of interatomic interaction parameters and technological regime indicators as model parameters was substantiated. Complex indicators for the metal-slag and metal-additive systems were constructed using Harrington’s desirability function, which enables integration of multidimensional parameters into a single generalized index. Analytical dependencies were developed for calculating the distribution coefficients of sulphur (S), silicon (Si), manganese (Mn), and aluminium (Al), considering both the composition of metallurgical phases and the smelting conditions. The proposed approach provides a quantitative assessment of the distribution coefficients of elements as variable quantities, which fundamentally distinguishes it from traditional methods. The results obtained form the basis for developing algorithms to predict the chemical composition of the final melt and for creating practical recommendations on the selection of optimal additives and slag-forming mixtures aimed at improving steel quality and reducing production costs.

EFFECT OF DEFORMATION ROUTES ON THE EFFICIENCY OF THE RADIAL-SHEAR ROLLING PROCESS

Sergey Lezhnev — 2026-05-01

The paper presents the simulation of the radial-shear rolling process in two technological routes. The direct route involved the repeated rolling of the workpiece in the second pass. In the reverse route, the rolls were rotated in the opposite direction in the second pass, and the workpiece was captured at the exit from the rolls. The analysis of the shape change showed that the reverse rolling process resulted in the complete rolling over of the helical surface formed in the first pass. The analysis of the stress-strain state and the microstructure evolution revealed that the direct rolling process resulted in a gradient structure with fine grains on the bar surface and elongated grains in the axial zone, while the reverse rolling process allowed for a more uniform distribution of grain size across the cross-section. Additionally, it was found that the reverse rolling route allowed for a greater processing of the axial zone due to the
deeper penetration of plastic deformation into the workpiece. The final choice of the deformation route will depend on the desired outcome, whether it is a uniform or gradient structure across the bar.

GENUINE ECOTOURISM VS GREEN MASS TOURISM FOR EFFECTIVELY DELIVERING EU GREEN DEAL TARGETS RELATED TO TOURISM

Petya Romanova — 2026-05-01

This paper aims to examine and distinguish the concepts of ecotourism and green mass tourism in the context of EU’s environmental framework and their suitability to contribute towards delivering EU Green Deal targets in tourism, including 55 % emissions reduction by 2030, Natura 2000 biodiversity protection, and circular economy principles. Through systematic policy analysis of EU legislation, strategic frameworks, and case studies (EU4Prespa versus Interreg Euro-MED Ecolabel programme), ecotourism demonstrates superior alignment via binding LIFE funding instrument, density caps and multi-level governance. Green mass tourism achieves operational efficiency, but structural volume growth undermines achieving absolute environmental targets. SWOT analysis reveals that
ecotourism is better aligned to the EU Green Deal but it falls short on scalability. Policy recommendations include binding conservation KPIs for Ecolabels, dedicated funding and multilevel governance to meet 2030 climate neutrality targets.