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In Slovakia, around 200 environmental burdens that contain a significant amount of usable raw materials were created by the extraction of ores or the dumping of industrial waste. In this research, the hydrometallurgical metal recovery method from a metal-bearing environmental landfill in Sereď was investigated. The analysis of a representative sample of waste obtained from this landfill proved the presence of significant amounts of metals (43.45% Fe; 1.3% Cr; 0.09% Co, and 0.23% Ni). A thermodynamic study of the metals' (Fe, Cr, Ni, and Co) leaching probability confirmed the possibility of metal extraction in an acidic environment. Subsequently, the effect of the most important factors on the leaching process (stirring intensity, temperature, liquid-to-solid phase ratio, and acid concentration) was experimentally tested. The analysis of the results determined the optimal leaching conditions. The extraction of 90.35% Fe and 59.62% Cr was ensured at a stirring intensity of 400 rpm, a leaching temperature of 80 °C, a liquid-to-solid phase ratio of 40, and a H2SO4 concentration of 3 mol/dm3. Various techniques, including SEM, EDX, XRD, Eh-pH diagrams, and AAS analysis, were used to analyze samples and products after leaching. The possibility of precipitating metals/compounds from the leachate to obtain a marketable product was theoretically proposed and proven. [ABSTRACT FROM AUTHOR]

The research aimed to observe the influence of the storage conditions of silver colloidal solutions prepared by biological (green) and chemical methods on their long-term stability. Green methods for reducing and stabilizing silver nanoparticles (AgNPs) use natural substances. The rosemary leaf extract was used for AgNPs synthesis, and prepared nanoparticles were spherical (average size of 12 nm). In the chemical method, commercial chemicals (NaBH4, TSC, PVP, and H2O2) were used, and two colloids were prepared; the first contained spherical nanoparticles with an average size of 8 nm, and the second triangular prisms with an average size of 35 nm. The prepared colloids were stored under four conditions: at room temperature in the light and the dark, and at a temperature of 5 °C (refrigerator) in the light and the dark. The results confirmed the influence of storage conditions on the stability of nanoparticles. Colloids stored at 5 °C in the dark show the best stability. However, differences in stability dependent on the shape of nanoparticles prepared by chemical method were also observed; triangular nanoparticles showed the least stability. Methods such as UV–vis spectrophotometry, TEM, and EDX were used to analyze the nanoparticles before and after storage. [ABSTRACT FROM AUTHOR]

The article presents the results of a survey on the use of methods and tools of the Lean Manufacturing (LM) concept by middle management in an automotive industry company in Poland. The conducted study will allow to assess the management's awareness in terms of knowledge of LM solutions, their use in everyday work, the impact of LM tools on improving the organization of production and occupational health and safety, and involvement in improvement projects. Knowledge, commitment, and support for employees are important factors in shaping the Lean culture in the company. The middle management, who manages the work in individual departments of this company, through appropriate attitudes and behavior builds the awareness of the entire team. The article ends with conclusions that can be treated as a form of guidance for top management to take improvement actions. Design/methodology/approach: The study of employees' awareness of the use of methods and tools of the LM concept was carried out using the survey method. The research group consisted of middle management in the automotive industry company in Poland (respondents indicated by top management). To achieve the assumed goal, a four-stage research methodology was developed. In the first stage, a questionnaire was developed, which concerned three areas: OSH, LM methods and tools, and implemented management systems. For the purposes of the study and the assumed goal, one research area was taken into account, related to the use of LM methods and tools and the awareness of the middle management staff in this area. In the second stage of the research, the research sample was characterized. In the third stage, the minimum number of respondents was determined (using the PQStat tool). In the fourth stage, the results obtained were analyzed and conclusions were formulated, which may serve as guidelines for managers responsible for continuous improvement of processes in this company. Findings: The conducted research made it possible to assess the awareness of the middle management regarding the use of LM solutions in the enterprise. The assessment of awareness was a subjective assessment resulting from the analysis of each survey question. Based on the conducted research, it was found that the vast majority of middle management has knowledge and high awareness in the field of continuous improvement, in the form of using the methods and tools of the LM concept in everyday work. Employees are aware of the impact of these solutions on various areas of activity (quality, safety, organization of production), engage in improvement projects, and identify and solve problems, but also see the difficulties associated with the implementation of LM methods and tools. The knowledge and awareness of middle management translate into the attitudes and behavior of production employees, which affects the culture of continuous improvement of the company. Based on the research results, areas requiring improvement were also identified. Research limitations/implications: The conducted survey research was limited to assessing the awareness of a specific group of respondents, i.e. middle management. The direction of further research should focus on assessing the awareness of production employees to obtain more complete information related to shaping the Lean culture in this company. Practical implications: The conducted research may provide important information for the management staff on the awareness of middle management in the application of solutions of the LM concept in this company. The research results also allow to identify areas requiring improvement actions. Social implications: The article discusses issues related to the awareness and involvement of employees that shape the culture of continuous improvement in organizations. Originality/value: The analysis of the literature for the years 2018-2023 showed that there is a research gap regarding the assessment of awareness of the LM concept among employees of automotive companies. Therefore, the article refers to the study of the awareness of middle management in the use of LM methods and tools in the automotive industry - in a large company in Poland. [ABSTRACT FROM AUTHOR]

In this work, we aimed to analyze the impact of extracts prepared from dried Lavandula angustifolia (lavender) flowers and leaves on the synthesis of silver nanoparticles (AgNPs) (wherein the shape and size of AgNPs and the efficiency of the process were analyzed) and to prove the possibility of transferring the AgNPs' properties into a polymer matrix. An ex situ method was used to incorporate AgNPs and prepare polymer matrix composite (PVP-AgNPs) films (via casting) and fibers (via electrospinning). We used UV-vis absorption spectrophotometry, Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM) to analyze and characterize the AgNPs and prepared composites. The results of FTIR analysis confirmed the presence of phytochemicals that can reduce silver ions from Ag+ to Ag0 in both extracts. The presence of spherical nanoparticles was confirmed via TEM regardless of the type of extract used. However, leaf extract caused the formation of AgNPs with a narrower size interval (an average size of 20 nm), and with higher efficiency, compared to the nanoparticles prepared using the flower extract. The nanoparticles prepared using the leaf extract were then incorporated into the polymer matrix, and thin polymer composite films and fibers were successfully prepared. The anti-biofilm activity of AgNPs colloids and prepared polymer nanocomposites against green algae Chlorella kessleri was studied. The anti-biofilm properties of the AgNPs were proved, along with the efficient transfer of their toxic properties into nontoxic polymer. [ABSTRACT FROM AUTHOR]

Bioleaching processes were used to solubilize metals (Cu, Ni, Zn and Al) from printed circuit boards (PCBs). In this study, a PCBs-adapted pure culture of Acidithiobacillus ferrooxidans, pure culture of Acidithiobacillus thiooxidans and PCBs-adapted mixed culture of A. ferrooxidans and A. thiooxidans were used for recovery of the metals. The study showed that the mixed bacterial culture has the greatest potential to dissolve metals. The maximum metal bioleaching efficiencies were found to be 100, 92, 89 and 20% of Cu, Ni, Zn and Al, respectively. The mixed culture revealed higher bacterial stability. The main factor responsible for high metal recovery was the ability of the mixed culture to maintain the low pH during the whole process. The pure culture of A. thiooxidans had no significant effect on metal bioleaching from PCBs.

Byline: Michal Besterci, Oksana Velgosova, Ladislav Pesek Using a Depth Sensing Indentation technique (DSI), the Martens hardness HM, indentation modulus EIT and deformation work W for Al matrix and Al4C3 particles have been measured. It has been shown that the hardness of Al4C3 particles is 5-7 times higher than the hardness of matrix. The change in fracture for the Al-12Al4C3 system was investigated and analysed at different temperatures and strain rates. With increasing tensile load, local cracks are formed by rupture of large particles and by decohesion of smaller particles from the matrix. Further increase of load leads to the crack growth by coalescence of cavities.

Byline: Michal Besterci, Frantisek Lofaj, Oksana Velgosova Deformation of the AlAl4C3 composites with different volume fraction of Al4C3 phase was investigated at different temperatures (293723 K) and different strain rates (2.5 o 10-5 s-1 1 o 10-1 s-1). At temperatures 673723 K and at the highest strain rate of 10-1 s-1, a significant ductility increase was observed. TEM analysis suggests that it is the result of dynamic grain polygonisation, grain slip and rotation, partial recrystallisation and dislocation creep in the tested system, which is known as strain induced dynamic recovery. Increase of the volume fraction of secondary phase in the studied composite resulted in a shift in the deformation mechanism from more slip on grain boundaries to more grain rotation.

This article focuses on the eco-friendly (green) synthesis of silver nanoparticles (AgNPs) and their incorporation into a polymer matrix. For AgNPs synthesis, Lavandula angustifolia (lavender) leaf extract was used as a reducing and stabilizing agent, and as a silver precursor, AgNO 3 solution with different concentrations of silver (50, 100, 250, and 500 mg/L) was used. Prepared AgNPs colloids were characterized using UV-vis spectrophotometry, transmission electron microscopy (TEM), and X-ray diffraction (XRD). The spherical morphology of AgNPs with an average size of 20 nm was confirmed across all samples. Further, the antimicrobial properties of the AgNPs were evaluated using the disk diffusion method on algae ( Chlorella kessleri ) and the well diffusion method on bacteria ( Staphylococcus chromogenes , Staphylococcus aureus , and Streptococcus uberis ), along with root growth inhibition tests on white mustard ( Sinapis alba ). Polymer composite (PVA-AgNPs) was prepared by incorporation of AgNPs into the polymer matrix. Subsequently, non-woven textiles and thin foils were prepared. The distribution of AgNPs within the nanocomposites was observed by scanning electron microscopy (SEM). Antibacterial properties of PVA-AgNPs composites were analyzed on bacteria Streptococcus uberis . It was found that not only AgNPs showed good antimicrobial properties, but toxic properties were also transferred to the PVA-AgNPs nanocomposite.