The municipal sewage sludge (MSS) was hydrolyzed at 230 °C for 60 min to obtain an organic-rich aqueous phase (AQ). The effects of the volume ratio of AQ on the structural characteristics and electrochemical performance of nitrogen-doped porous carbon materials (A-BCs), prepared by co-HTC with cellulose were investigated. Elemental analysis and XPS results indicated that both the yield and the nitrogen content of the A-BCs increased proportionally with the amount of AQ added. The optimal AQ fraction (20 v%) effectively synergized with KOH activation, significantly increasing the specific surface area of the resulting A-BC-0.2 to 2279.20 m2/g. The A-BC-0.2 electrode exhibited a specific capacitance of 298.65 F/g at a current density of 1.0 A/g in a three-electrode system with a 6 M KOH electrolyte, which was 30.4% greater than that of the sample without AQ (A-BC-0). Moreover, excessive AQ addition (>20 v%) inhibited pore development and induced the formation of an aliphatic carbon structure, thereby decreasing the SSA of A-BC-1.0 to 952.15 m2/g. This study provides a theoretical basis for the preparation of high-performance supercapacitor electrode materials on the basis of the resource utilization of sewage sludge.
In this study, sewage sludge (SS) was mixed with chicken manure (ChM), swine manure (SM), and cow manure (CM) for cohydrothermal carbonization (co-HTC) to evaluate their synergistic effects on hydrochar properties and reaction mechanisms. The experiments were conducted with different mass ratios of SS to manure (1:3, 1:1, and 3:1) at 240 degrees C for 1 h. The elemental composition, yield, and physicochemical structure of the produced hydrochars were analyzed. These results demonstrated a significant synergistic effect on the co-HTC of SS with SM, and the synergistic effect was most prominent at the 1:3 SS to SM ratio, with the maximum values of hydrochar yield (58.63%), energy yield (56.98%), and C and N retention ratio (56.45% and 36.41%, respectively) achieved. The synergistic cohydrothermal effect resulted in increased hydrochar yield, energy yield, and C and N retention rates. The enhancement can be attributed to intensified cross-linking reactions, such as the Maillard reaction, which promoted the formation of stable C-N and C-O bonds and facilitated the incorporation of nitrogen, primarily pyrrole-N (>70%). In contrast, mixtures with ChM and CM had antagonistic effects, particularly at relatively high SS ratios, leading to decarboxylation and nitrogen loss through gasification or leaching into the liquid phase. Overall, co-HTC of SS and SM at a 1:3 mass ratio represents a promising approach for resource recovery, enabling the production of nutrient-rich, high-quality hydrochar, which has the potential to be used as a solid recovery fuel, soil conditioner, and supercapacitor material.
The main source of radon penetrating buildings is the ground. Both the concentration of natural radioactive nuclides and the physical properties of soil and rock, which facilitate the migration of radon, are important. In the Upper Silesian Coal Basin (Poland), many years of mining activity have caused the disintegration of the geological environment, hydrological disturbances, and damage to buildings located within continuous and discontinuous deformation areas. These phenomena may facilitate the transport and penetration of radon into residential and workplace premises. This paper presents a risk assessment of elevated radon activity concentrations based on a multifactorial analysis, taking into account hazards caused by mining activities, as well as natural and technical factors. A set of criteria and an assessment of the significance of each criterion were proposed, adopting ranges of values and limits established by regulations or determined arbitrarily. The model was calibrated and subsequently validated using a series of in situ measurements demonstrated an overall classification accuracy of 67%, with a low false negative rate (6%), which is particularly important for environmental risk assessment. In addition, the Cohen's kappa coefficient increased from 0.12 to 0.36 after model calibration, indicating improved agreement between theoretical predictions and field measurements. The proposed approach can therefore be used as a preliminary screening tool for identifying radon-prone areas in mining and post-mining regions and for supporting the planning of targeted in situ radon measurements.
Coatings are often applied in the materials industry to impart hydrophobic properties to the produced materials. Commonly used coatings contain plastics as well as perfluorinated compounds, which pose challenges for environmental sustainability due to their persistence and end-of-life impacts. Coatings based on natural wax, such as rapeseed, soy, palm or beeswax, constitute a key bio-based and more sustainable alternative. These waxes exhibit high hydrophobicity while also being biodegradable, offering opportunities to replace fossil-derived coatings within circular-economy material systems. Wax coating constitutes a protective layer that undergoes biodegradation after a certain amount of time. This paper presents the results of studies concerning the development of a wax coating characterized by a coarse microstructure that increases water resistance, and an appropriate susceptibility to biodegradation. It was revealed that all the analysed coatings were susceptible to biodegradation, although their rates varied markedly depending on wax type and form. The biodegradation of palm wax in bulk form and as a thick layer was 17% and 80%, respectively, after 180 days. Palm wax exhibited a pronounced ability to bind inorganic and organic matter deposits, which reduced the degradation rate. When applied as a thin coating, palm wax did not form such a barrier. Palm wax significantly influences coating durability because its surface undergoes morphic changes induced by bio-surfactants secreted by microorganisms. These changes the adhesion of organic and inorganic matter particles, and the layer thus established limits the diffusion of oxygen, enzymes and microorganisms to the wax coating. The tests demonstrated that the addition of palm wax to wax mixtures allows the degradation rate to be controlled, and that its inhibitory effect is strongly dependent on the geometry of the material.
Urban sprawl and limited access to green spaces are critical challenges in post-industrial cities, affecting public health and environmental resilience. This study aims to (1) characterize brownfields in the urban core of the Górnośląsko-Zagłębiowska Metropolis (GZM) in southern Poland and (2) identify which of these sites offer the greatest potential for conversion into accessible green spaces. Using GIS analysis and a 1 km2 hexagonal grid framework, 301 brownfield sites across 13 interconnected cities were assessed based on criteria such as size, ownership, planning status, and existing structures. Population density and green space availability were analyzed in each hexagon to determine local deficits in greenery, benchmarked against WHO standards. Results show that 46 brownfields meet all transformation criteria, and greening 71 sites could significantly improve access to green space in 24 underserved zones. The study underscores the importance of strategic, data-informed brownfield re-greening to strengthen urban social and ecological resilience. The applied methodology offers a scalable planning tool that can inform sustainable redevelopment in other post-industrial regions facing similar spatial challenges.
