Journal of Chemical Technology and Metallurgy

OPTIMIZATION OF ENZYMATIC HYDROLYSIS OF CASSAVA (MANIHOT ESCULENTA) STARCH CONTAINING CYANIDES

2025-04-30T10:48:53+00:00

The bitter cassava plant (Manihot esculenta), commonly referred to as bitter cassava, is a wild species that thrives in forests and gardens. The tubers of bitter cassava contain cyanogenic compounds, which are toxic due to the presence of cyanide. Cyanide removal can be achieved through extraction using water or heating at a temperature of 50 ºC. Bitter cassava starch can be converted into reducing sugars through enzymatic processes. In this study, experiments were conducted using bitter cassava starch at concentrations of 100, 200, and 300 g L^-1 (native), with added cyanide concentrations of 50, 100, and 150 mg kg^-1 as inhibitors. The effects of these variables on reducing sugar production were analysed through enzymatic hydrolysis at 30ºC. The optimization of enzymatic hydrolysis in the presence of cyanide was performed using Response Surface Methodology (RSM). The study investigated the effects of starch concentration, cyanide concentration, and hydrolysis time on reducing sugar production. RSM has been proven to be an effective and reliable tool for optimizing the process and understanding the interactive effects of the three variables involved in cassava starch hydrolysis. A highly significant quadratic regression model (R² = 0.9900, P < 0.0001) was developed. The predicted optimal conditions for hydrolysis were identified as 278.5 g L^-1 starch concentration, 51.4 mg kg^-1 cyanide concentration, and a hydrolysis time of 14.8 h, resulting in a reducing sugar concentration of 63.498 g L^-1.

EFFECT OF TIME IN THE EMULSIFICATION STEP ON THE YIELD AND QUALITY OF UREA-FORMALDEHYDE ROSE OIL MICROCAPSULES OBTAINED BY INTERFACIAL IN SITU POLYMERIZATION METHOD

2025-04-30T10:43:55+00:00

There are several parameters in the operating conditions that play a key role in the microencapsulation process by in situ polymerization. These parameters are stirring speed of the reaction mixture, temperature, time, type and concentration of emulsifier, molar ratios between components, pH, ionic strength, etc. All the mentioned characteristics determine the quality of the obtained microcapsules, which would direct us to the selection of optimal conditions for obtaining the target product. Since the emulsification step is one of the most important in the process, the present work examines the influence of the time (duration) of this step on the efficiency of microencapsulation process of rose oil and specifically on the yield, encapsulation efficiency, E% core, the size of the microcapsules obtained, the efficiency of the resin and the encapsulation factor. In this way, more complete clarity could be given on the influence of this parameter in the conditions, thus contributing to the optimization of the process in the large-scale preparation of microcapsules, particularly with rose oil.

STUDY OF THE SOLUBILITY AND RHEOLOGICAL PROPERTIES OF THE Ca(ClO3)2∙2CO(NH2)2-C4H6O5∙NH2C2H4OH-H2O SYSTEM

2025-04-30T10:35:30+00:00

To obtain the highly effective complex-acting defoliant, the Сa(ClO₃)₂∙2CO(NH₂)₂-C₄H₆O₅∙NH₂C₂H₄OH-H₂O system was studied using binary systems and ten internal sections, and the visual polythermal solubility diagram was constructed in the range of -24.2°C to 32.0°C. In the diagram, the crystallization areas of ice, Сa(ClO₃)₂∙2CO(NH₂)₂∙2H₂O and C₄H₆O₅∙NH₂C₂H₄OH were separated. This system belongs to the simple eutonic type, the components have preserved their individuality and showed good solubility in water. In the [55 % Сa(ClO₃)₂∙2CO(NH₂)₂ + 45 % H₂O]-[C₄H₆O₅∙NH₂C₂H₄OH] system, when the components are added in different proportions, the pH, crystallization temperature, refractive index, viscosity, and density changes of the solution were determined, and a “composition-property” diagram was constructed.

A COMPARATIVE STUDY FOR CHOOSING THE BEST KINETIC MODEL USING DIFFERENT ERROR METRICS

2025-04-30T10:30:26+00:00

In the present investigations, a comparison of fly ash and cow dung ash was carried out to study the adsorption kinetics of Nickel ions present in aqueous solution. Various kinetic models are evaluated during these investigations, which include pseudo-first-order, pseudo-second-order, intra-particle diffusion, fractional power, and Elovich models. These models were exhaustively evaluated and compared using eighteen different error functions. An overall performance indicator metric has also been discussed that helps in ranking the different kinetic models for estimation of adsorption capacity (qt) based on the values of different error functions. After analysing these results, it was observed that the kinetic models can be ranked from best to worst with respect to qt determination for cow dung ash and are as follows: pseudo-first order, pseudo-second order, Intra-particle diffusion, Elovich, and Fractional power. Similarly, for fly ash adsorbent, the ranking of kinetic models from best to worst was found to be: pseudo-second-order, intra-diffusion particle, fractional power, Elovich, and pseudo-first-order.

RESISTANCE TO CORROSION OF BIMETAL REINFORCING RODS RECEIVED BY EXPLOSION WELDING

2025-04-30T10:25:34+00:00

The manuscript shows the result of corrosion tests of reinforcing bimetallic rods, the core of which was made of C45 carbon steel, and the cladding layer was made of 304L steel. Bimetallic reinforcing rods were obtained by explosive welding and then subjected to hot plastic working. The corrosion tests of the rods consisted of acidified salt spray tests and polarization measurements in sulphate solutions containing chloride ions. Potentiodynamic tests confirmed the correctness of choosing 304L steel for the plating layer. To determine the influence of the production process of bimetallic reinforcing rods on the microstructure of the cladding steel and the quality of the connection between the core and the cladding layer, a microscopic analysis of cross-sections of reinforcing bimetallic rods was carried out.

SYNTHESIS OF CoFeCrMnNi/TiC-HIGH ENTROPY ALLOY COMPOSITE COATINGS BY ELECTRODEPOSITION TECHNIQUE

2025-04-30T10:17:51+00:00

CoFeCrMnNi high entropy alloys (HEA) composite coating containing various weight fractions of titanium carbide (TiC) was electrodeposited over a copper substrate using an electrodeposition technique. The current work to investigate the synthesis of HEA-TiC composite coatings through simple and convenient process. The X-ray diffraction (XRD) measurement confirms the presence of single-phase HEA/TiC composite coating comprising of FCC and BCC phase. In addition, the fabricated coating material has a rough surface with five elements and TiC uniform dispersion confirmed by scanning electron microscopy- Energy-dispersive X-ray spectroscopy (SEM-EDS). Specifically, these results revealed the better properties of HEA-TiC composite coatings were achieved within short duration and simple technique.

ADSORPTION-DESORPTION OF GOLD ONTO ACTIVATED CARBON FROM CYANIDE-GLYCINE LEACH SOLUTION OF COMPLEX GOLD ORE

2025-04-30T09:57:18+00:00

This research investigated the adsorption of gold on activated carbon from a cyanide-glycine leach solution and their desorption. The pH value varied between 9 and 11, and at each pH value, the concentration of activated carbon was changed between 5 and 20 g L^-1. The results showed that both pH and carbon concentration did not have a significant effect on gold adsorption. In all experiments, a high adsorption value of gold (above 98 %) was obtained. In all carbon concentrations, except for 5 g L^-1, the maximum gold adsorption was obtained at a pH of 10.5. The reduction of gold adsorption on activated carbon with the increase of pH to 11 can be related to the decrease of active points on the carbon surface due to the increase in the concentration of hydroxide ions. When the concentration of activated carbon was 5 g L^-1, more than 98 % of gold was adsorbed. So, a further increase in carbon concentration is not required. Elution experiments were carried out after different leaching methods; carbon in pulp (CIP) and carbon in leach (CIL). The results showed that for both leaching methods, most of the gold was dissolved in the first 6 h of the elution process and the final gold desorption for CIP and CIL were 82.89 % and 72.64 % respectively.

INFLUENCE OF MODIFIER AMOUNT ON THE SORPTION PROPERTIES OF CELLULOSIC MATERIAL

2025-04-30T09:49:51+00:00

During the study, the impact of the amination mixture consumption on the key quality indicators of cellulose filtration material, such as colour and turbidity, was analysed. Additionally, the productivity and selectivity of the material were calculated based on these parameters. Infrared (IR) spectroscopy was used to identify the active groups formed during the preparation of the amination mixture. Experimental results showed that using the modifier in an amount of up to 40 % of the absolutely dry fiber mass leads to a significant increase in the materialapos sorption properties, which substantially improves the filtration process efficiency. However, increasing the modifier amount beyond 50 % results in its deposition on the fiber surface, negatively affecting the productivity and sorption capacity of the filtration material. Such modified cellulose can be utilized in environmentally safe water purification systems, where high sorption properties and stability during filtration are key requirements. This makes modified cellulose materials promising for use in modern water treatment systems, where environmental performance and material efficiency under industrial conditions are of paramount importance.

PREPARATION AND STUDY OF RED-COLORED COPPER-CONTAINING CERAMIC GLAZE FIRED IN AN OXIDIZING ENVIRONMENT

2025-04-30T09:44:32+00:00

Red copper glazes, also known as Chinese red glazes, owe their coloration to the dispersion of colloid copper particles in the glaze and firing in a highly reducing atmosphere. The addition of some substances can be used for the reduction of copper oxide to metal nanoparticles and the glazed ceramics can be fired in an oxidation atmosphere. The colloidal copper red colouring of ceramic glazes was applied in this study. It was investigated the influence of copper oxide type (CuO or Cu₂O) added as colouring agent to a ceramic glaze and the firing temperature of the glazed for obtaining red colouring of the glaze. The samples were fired in an oxidizing atmosphere and SiC and SnO₂ were added as reductants. A structural and phase characterization of the obtained samples was done by using the XRD, DTA, FT-IR and SEM analyses. The reduction with silicon carbide when fired in an oxidizing atmosphere is more complete and the red glaze coloration is more intensive when copper is introduced as Cu₂O rather than CuO into the glaze. The best red coloration has been obtained for the composition containing 0.5 mass % Cu₂ O + 1 mass % SiC added to the glaze and fired at 1200oC.

MINERAL AND SECONDARY CLAY RAW MATERIAL RESOURCES FOR OBTAINING HIGH-ALUMINUM MASSES

2025-04-30T09:36:33+00:00

The results of a study of the chemical, mineralogical composition, as well as IR spectroscopic and optical characteristics of promising clay raw materials of Uzbekistan, in particular kaolins of the AKF - 78, AKS - 30 grades of the Angrensky and kaolins of the Alyansky and bentonites of the Kasansky deposits of the Uzbekistan are presented. The recycling of alumina-containing waste from the Shurtan gas-chemical complex as an alumina-containing component is shown. The main physicochemical characteristics of the materials under study have been established and the possibilities of using them as the main clay component for developing the composition of high-alumina ceramic masses have been shown.

CHARACTERIZATION OF CEMENT KILN DUST FROM BULGARIAN CEMENT PLANTS

2025-04-30T09:16:43+00:00

The cement production is accompanied by generation of fine dust, known as cement kiln dust (CKD), formed during the high-temperature processing of raw materials in the rotary kilns. This study focusses on characterizing CKD from Bulgarian cement plants and explore its physical and chemical properties. The study includes analysing CKD samples from three local cement plants using techniques such as laser dif fraction, XRD, XRF, FT-IR, and SEM. Variations have been observed in their physical, chemical, and mineralogical properties likely due to differences in raw materials, kiln conditions and the use of alternative fuels. This research provides valuable local data that can guide sustainable CKD management and utilization strategies, contributing to reduced waste and environmental impact in cement production.

PRODUCTION OF PORTLAND CEMENT CLINKER IN RAW MIXTURES BASED ON MINING AND METALLURGICAL PRODUCTION WASTES

2025-04-30T09:07:32+00:00

The chemical-analytical and physico-chemical properties of flotation waste generated during the enrichment of lead-zinc ores of the Almalyk MMC, steelmaking slags of Uzmetkombinat JSC, formed after the extraction of residual ferrous compounds and limestones of the Shavazsay deposit for the purpose of polishing Portland cement clinker on their basis, have been studied. As a result of experiments, a real possibility was established of obtaining Portland cement clinker of optimal mineralogical composition based on the studied waste, used as the main component in raw mixtures, under optimal firing temperature conditions.

DEPHENOLIZATION OF COAL TAR HEAVY FRACTIONS: A REAGENT - FREE METHOD FOR PHENOL RECOVERY

2025-04-30T08:56:52+00:00

The classical dephenolization process of the heavy fraction of coal tar involves alkaline washing to produce sodium phenolate, followed by carbon dioxide decomposition to yield crude phenols and a soda solution. The soda solution is causticized with lime, generating lime sludge contaminated with phenols - a significant environmental concern. This study explores phenol extraction technologies leveraging phenolic acidity and molecular polarity to address these limitations. A novel method for dephenolizing coal tar heavy fractions without alkali was developed, yielding wash oil suitable for capturing benzene hydrocarbons with a phenol content of 0.7 - 1.0 %. This process eliminates aqueous phenolate generation, producing a hydrocarbon residue with a composition resembling the phenol
fraction, achieving a reagent-free, waste-free methodology. The proposed method employs sodium phenolate solutions with optimized sodium hydroxide concentrations to ensure minimal phenol content in oil and control impurities in the phenolate solution, maintaining non-phenolic impurities at 15 - 20 %. This reduces neutral component loss and contamination, achieved by neutralizing phenols with a 27 % NaOH solution. Additionally, methyl tert - butyl ether (MTBE) was validated as a suitable organic solvent for phenol extraction from aqueous solutions. This integrated approach simplifies the technological process while aligning the composition of neutral oil with the phenolic fraction obtained during coal tar fractionation, presenting a sustainable solution for phenol recovery and wash oil purification.

IMPACT OF Mg ON DIVERSE PROPERTIES OF EUTECTIC Al - Si AUTOMOTIVE ALLOY

2025-04-30T08:49:56+00:00

Magnesium is an important element for alloying in the composition of Al - Si automotive alloy to enhance mechanical properties and ensure optimum performance. A systematic investigation has been carried out to observe its effect on various properties of this alloy. Investigations include age hardening, thermal conductivity, tensile, wear, corrosion, fracture as well as microstructural properties by developing two Al - Si automotive alloys with and without 0.5 wt. % Mg. Experimental results confirm that both alloys improve its strength during thermal ageing treatment through development of clusters and GP zones alongside metastable phases and maximum can be achieved at around 200°C for 150 min. Addition of Mg provide the different Mg-rich precipitates resulting the better strength. Mg addition in this level improves hardness but reduces the thermal conductivity of automotive alloys by approximately 15 %. Again, the tensile strength improved significantly with a reduction in ductility by 20 % mutually. These Mg - rich intermetallic precipitates improve wear properties by 30 % in dry sliding conditions but suffer 60 % in corrosive environments. Once exposed to an acidic environment, the corrosion rate is elevated by 50 %. Microstructural study confirms plate-like eutectic Si phase and the higher intermetallic created by Mg as coarsen the grain boundary. After being subjected to a temperature of 350°C for 1h, alloys achieve a totally recrystallized state. Fractography of Mg added alloy shows severe breakup occurred at its intermetallic along with a cleavage pattern featuring flat facets indicative of the Al - Si eutectic zone.

TECHNOLOGICAL POSSIBILITIES FOR THE UTILIZATION OF IRON-CONTAINING WASTE FROM METALLURGICAL INDUSTRIES

2025-04-30T08:41:49+00:00

The study presents the possibilities for processing iron-containing waste from metallurgical production. The raw material for the experiments was obtained from the tailing’s storage of a metallurgical plant in Bulgaria with the aim of obtaining a product that can be used as a raw material in blast furnace production. The test is performed in a rotary kiln at 1150°C, 1100°C, 1050°C in the presence of a reducer. Three different iron ore pellets and additionally coal grits were the raw materials for the direct reduction process. During the provided experiments, the main technological parameters of the reduction process were established, such as temperature, process time, pressure in the furnace and the composition of the exit gases from the process. Marketable iron - containing pellets were obtained and tested.

DESIGN OF ELECTROHYDROIMPULSE SHEET METAL FORMING USING LS-DYNA

2025-04-30T08:27:15+00:00

Stages of the transferring processes of electrical energy stored in the capacitor battery into the energy of plastic deformation were considered. Model of a discharge circuit with the variable part of resistance defined by electrical resistance of the discharge channel and model of formation and extension of plasma - vapour cavity during electric discharge in a liquid were presented. Using the example of manufacturing a part of complex geometry, the possibility of estimating pressure parameters in computer modelling of combined electrohydraulic sheet forming in the LS-DYNA complex is considered. An equivalent axisymmetric die model with the same volume and depth was constructed. Appearing of the pulsed and quasistatic nature of the workpiece deformation during the different stage of electrohydraulic discharge in large - volume chambers were carried out. The developed computer model of multi-digit sheet forming made it possible to evaluate the pressure parameters and determine the required changes in the parameters of the technological process.

TRACE ANALYSIS OF BRILLIANT GREEN DYE BY FLOW INJECTION TECHNIQUE

2025-04-30T08:12:57+00:00

A low-cost and high throughput flow injection analysis (FIA) system design is conducted to determine Brilliant Green (BG) dye. The research includes studying the chemical and physical variables and control of optimal conditions of the FIA system. The merging zone technique uses a homemade flow injection valve to determine BG dye. The optimum conditions are studied, such as the flow rate of the carrier, optimal dye volume, repeatability, dead volume, and dispersion coefficient. The flow rate is 3.0 mL min^-1, the optimal volume of dye is 82.425 μL, the repeatability is high for eight measurements (n = 8), and the values of dispersion coefficient are 1.41 and 1.44 for the concentrations of 4 and 7 mg L^-1, respectively. The calibration graphs have linear ranges of (0.5 - 10) mg L^-1 and (0.07 - 16) mg L^-1, with detection limits of 0.413 and 0.068 mg L^-1 for the spectrophotometric and FIA methods, respectively. The results obtained were statistically treated. FIA method successfully applied to standard solutions demonstrates its reliability and potential for further applications.

INFLUENCE OF AGING PROCESS ON UV INKJET BLACK PRINTED PVC FOIL

2025-04-30T07:59:09+00:00

During the lifespan, graphic products are exposed to various external factors. During their use, their properties
(physical, mechanical, visual, etc.) change to a greater or lesser extent. It is necessary to observe/monitor changes
and influence of external factors on their properties as soon as the product is created. The aim of this research is to
examine the impact of the aging process on the quality of inkjet printing. A different number of layers of black ink (in
10 % tonal value (TV) and 100 % TV) and a different number of varnish layers were printed on PVC foil material. The samples were exposed to xenon light (λ > 300 nm) to accelerate the ageing process over a period of 72 and 216 h. They were measured by Datacolor spectrophotometer. As expected, with longer exposure time, greater changes occurred. According to the CIE ΔE*00 formula, the differences ranged from an imperceptible to a large colour change. After 72 h, the biggest changes in colour occurred in the K10 % with one ink layer and three layers of varnish. The smallest changes were in K100 % with one ink layer and no varnish. After 216 h, the greatest changes were observed in the K10 % sample with three layers of ink and two layers of varnish. The smallest differences were K10 % sample with one ink layer and without varnish.