Agnieszka Kramek

Excessive blood loss is a leading cause of mortality among soldiers and accident victims. The wound healing process typically ranges from three weeks to several months, with disruptions in healing stages potentially prolonging recovery time. Chronic wounds may persist for years, creating a favorable environment for microbial growth. Chitosan, a derivative of chitin—the second most abundant biopolymer in nature—is obtained through deacetylation and exhibits mucoadhesive, analgesic, antioxidant, biodegradable, non-toxic, and biocompatible properties. Due to its hemostatic and regenerative support capabilities, chitosan is widely applied in the food, cosmetic, and agricultural industries; environmental protection; and as a key component in dressings for chronic wound healing. Notably, its antibacterial properties make it a promising candidate for novel biomaterials to replace traditional antibiotics and prevent the emergence of drug-resistant strains. The primary aim of this study was the chemical cross-linking of chitosan with the amino acids L-aspartic and L-glutamic acid in the presence of periclase (magnesium oxide) under microwave radiation conditions. Subsequent research stages involved the analysis of the samples’ physicochemical properties using SEM, FT-IR, XPS, atomic absorption spectrometry, swelling behavior (in water, SBF, and blood), porosity, and density. Biological assessments included biodegradation, cytotoxicity, and antibacterial activity against Escherichia coli and Staphylococcus aureus. The obtained results confirmed the high potential of the newly developed hemostatic agents for effective hemorrhage management under non-sterile conditions.

The influence of different solvents, including aqueous and nonaqueous types, on the physicochemical properties of V₂O₅ nanostructures was thoroughly investigated. Various characterization techniques, such as XRD, XPS, FTIR, Raman spectroscopy, UV-vis DRS, SEM, TEM, and BET, were employed to analyze the obtained materials. Additionally, the adsorption properties of the synthesized V₂O₅ nanostructures for methylene blue were examined, and kinetic parameters of adsorption were calculated. The results demonstrate that the morphology of the obtained crystals can be finely controlled by manipulating water concentration in the solution, showcasing its profound impact on both the structural characteristics and adsorption properties of the nanostructures. Furthermore, the structural changes of the resulting V₂O₅ material induced by solvents show strong impacts on its photocatalytic properties, making it a promising photocatalyst.

Laser-induced graphene (LIG) has emerged as a promising solvent-free strategy for producing highly porous, 3D graphene structures, particularly for electrochemical applications. However, the unique character of LIG and hydrogel membrane (HM) coated LIG requires accounting for the specific conditions of its charge transfer process. This study investigates electron transfer kinetics and the electroactive surface area of LIG electrodes, finding efficient kinetics for the [Fe(CN)6]3-/4- redox process, with a high rate constant of 4.12 x 10-3 cm/s and an electroactive area 28 times higher than the geometric area. The impact of polysaccharide HM coatings (cationic chitosan, neutral agarose and anionic sodium alginate) on LIG's charge transfer behavior is elucidated, considering factors like Ohmic drop across porous LIG and Coulombic interactions/permeability affecting diffusion coefficients, estimated from amperometry. Experimental findings are supported by ab-initio calculations showing a electrostatic potential map’s negative charge distribution upon chitosan chain protonation, having an effect in over a two-fold redox current increase upon switching the pH from 7.48 to 1.73. This feature is absent for other studied HMs. It was also revealed that the chitosan's band gap was reduced to 3.07 eV upon acetylation, due to the introduction of a new LUMO state. This study summarizes the operating conditions enhanced by HM presence, impacting redox process kinetics and presenting unique challenges for prospective LIG/HM systems’ electrochemical applications.

In this study, conversion coatings were produced on the AM50 magnesium alloy by a plasma electrolytic oxidation (PEO) process in alkaline-silicate electrolyte with the addition of potassium hexafluorophosphate, using a unipolar pulse power source. The coating microstructure and its composition were determined using scanning electron microscopy (SEM) and an X-ray photoelectron spectroscopy (XPS). The corrosion resistance of the conversion coatings was evaluated by means of potentiodynamic polarization tests (PDP) and electrochemical impedance spectroscopy (EIS) in a dilute Harrison solution (DHS). It has been found that the properties (microstructure, composition, and coating thickness) of the obtained layer and, therefore, their anticorrosive resistance strongly depend on the electrolyte composition. The best anticorrosive properties were observed in the layers obtained in the presence of 2.5 g/L KPF₆. It was found that the conversion coating produced with the addition of hexafluorophosphate is characterized by a different morphology (sponge-like) and better anticorrosion properties, in comparison to the coating obtained with the addition of fluoride and orthophosphate salts commonly used in PEO synthesis. The sponge-like structure, which is similar to bone structure in combination with the presence of phosphates in the layer, can increase the biocompatibility and the possibility of self-healing of this coating. However, neither Mg(PF₆)₂, nor any other compounds containing PF₆⁻, have been found in the layers produced.

The paper presents new reactive materials, namely marl and travertine, and their thermal modifications and the Polonite^® material, analyzing their phosphorus removal from water and wastewater by sorption. Based on the experimental data, an analysis of the factors influencing the sorption capacity of the materials, such as the material dose, pH of the initial solution, process temperature, surface structure, and morphology, was performed. Adsorption isotherms and maximum sorption capacities were determined with the use of the Langmuir, Freundlich, Langmuir–Freundlich, Tóth, Radke–Praunitz, and Marczewski–Jaroniec models. The kinetics of the phosphorus sorption process of the tested materials were described using reversible and irreversible pseudo-first order, pseudo-second order, and mixed models. The natural materials were the most sensitive to changes in the process conditions, such as temperature and pH. The thermal treatment process stabilizes the marl and travertine towards materials with a more homogeneous surface in terms of energy and structure. The fitted models of the adsorption isotherms and kinetic models allowed for an indication of a possible phosphorus-binding mechanism, as well as the maximum amount of this element that can be retained on the materials’ surface under given conditions—raw marl (43.89 mg P/g), raw travertine (140.48 mg P/g), heated marl (80.44 mg P/g), heated travertine (282.34 mg P/g), and Polonite^® (54.33 mg P/g).

The article presents research on the possibility of using troublesome waste such as: sewage sludge, mineral fraction of municipal waste <10 mm, stabilizer after mechanical-biological processing (MBP), carbon waste, glass - as a flux in the production of new light ceramic materials. Clay was used as the basis of the material. In order to determine the possibility of using individual materials to produce a ceramic material, the oxide composition of individual components was examined using the XRF method. XRF analysis showed the presence of quartz and aluminosilicates in the materials, which makes it possible to use these wastes to produce new materials. Then the waste was ground in a ball mill and mixed in different proportions by adding water and three different materials were obtained. Material A: clay, sewage sludge, waste water, glass. Material B: clay, mineral fraction of waste <10 mm, flotation waste, glass. Material C: clay, stabilizer after mechanical-biological processing, post-mining waste, glass. The materials were subjected to strength and absorbability tests. The most stable was Material B. The highest variability of properties was observed in Material A. On the other hand, a high heterogeneity was observed in Material C. The bulk density for all materials was 658kg/m3 on average.