Sludges produced in the pickling line in a steel company were applied to the soil as a secondary source of nutrients. In the experiments, the addition of two types of sludge, namely neutralization sludge (NS) and phosphatization sludge (PS), was evaluated. The listed sludges are defined as non-hazardous waste and contain elements such as iron, phosphorus, zinc, and others in minor quantities. The primary motivation for using these sludges in the soil is their phosphorus content, as phosphorus is a crucial mineral nutrient. Leaf lettuce was used as a test object. The quality of the soil in which it grew can be seen from the appearance of its leaves. The period of monitoring the growth of leaf lettuce was 35 days, while the length of the leaves was measured on different days (Days 7, 14, 21, 28, and 35). Different ratios of sludge to soil were chosen (1:2, 1:1, and 2:1) for the experiments. The comparative sample for evaluation of sludge addition was leaf lettuce that grew in soil without any presence of the sludge. The application of NS to the soil in all proportions significantly accelerated the growth of the lettuce, whereas the application of PS to the soil had a negative effect on the growth. Various analytical techniques, such as SEM, EDX, XRD, HR CS FAAS, and leachability tests, were used to analyze samples of the sludges.

This study details the sustainable synthesis and characterization of electrospun zinc oxide nanofibers, uniquely derived from industrial waste streams. Our approach leverages diverse industrial byproducts—specifically sal ammoniac skimming from hot-dip galvanizing, electric arc furnace dust, and galvanization flue dust—as sustainable raw materials. Following hydrometallurgical treatment with various leaching agents (HCl, (NH₄)₂CO₃, or H₂SO₄) to obtain zinc-rich leachates, electrospinning solutions were formulated. The resulting fibers were subsequently calcined, yielding three distinct ZnO-based materials. Comprehensive characterization by XRD, SEM-EDX, and TEM revealed that the choice of leaching strategy significantly influenced the resultant fibers’ morphology and chemical composition. To demonstrate the potential applicability of these waste-derived materials, their photocatalytic activity was assessed through the degradation of methylene blue dye under UVA irradiation. ZnO fibers derived from HCl leaching exhibited remarkable photodegradation capabilities, achieving nearly complete dye removal within 690 min at optimal catalyst-to-dye ratios. Conversely, the H₂SO₄-prepared sample displayed impaired efficiency, primarily due to the formation of an undesirable Al₂ZnO₄ phase stemming from high aluminum content in the input waste, a critical consideration for waste-to-product strategies. The results showed that the cost-effective ZnO fibers obtained by electrospinning from industrial waste products have potential for applications in photocatalytic water treatment.

This work focuses on the production of ceramic nanofibers from waste materials, which represents a significant contribution to the sustainable use of resources and innovative solutions in the field of nanotechnology. The research builds on existing knowledge of nanofiber production, with a specific focus on the use of zinc galvanizing flue dust. The main objective of the study is to explore the possibilities of converting zinc-containing waste materials into ceramic nanofibers, introducing a new direction in nanotechnology. Laboratory experiments involved leaching processes and electrostatic spinning processes of zinc solutions. From the obtained results, it can be concluded that ZnO ceramic nanofibers produced from both synthetic and real solutions exhibit similar fiber structures. Therefore, it can be stated that both acids (HCl and H₂SO₄) are suitable for preparation. Among them, 0.5 M HCl is the most ideal, resulting in oval fibers with a rough and coarse surface, while 0.5 M H₂SO₄ produces fibers with a different morphology in the form of hollow ribbons, which are presumed to have a higher specific surface area. Thus, it can be concluded that the production of ceramic nanofibers from zinc galvanizing flue dust is feasible and effective, with electrostatic spinning proving to be a low-waste technology. The study also examines the influence of contaminants from real waste solutions on the production of ceramic nanofibers and compares their properties with nanofibers obtained from synthetic solutions. Experimental results suggest that contaminants in real solutions did not have a negative impact on the morphology of the prepared ZnO nanofibers. In conclusion, the production of ZnO ceramic nanofibers from waste offers a promising approach for the future development of nanotechnology, combining innovation with sustainability and efficient resource utilization.

The research investigates the utilization of zinc galvanizing flue dust as a secondary resource for the preparation of ZnO ceramic nanofibers. The applied methodology combined acidic leaching with electrospinning of the obtained zinc solutions, with emphasis on the effect of leaching agents and waste-derived impurities on fiber morphology. Results revealed that 0.5 M HCl produced coarse oval fibers, whereas 0.5 M H2SO4 generated hollow ribbon-like nanostructures with increased surface area. Importantly, the presence of impurities in real waste solutions did not adversely affect fiber formation. The study confirms that electrospinning is a viable and low-waste approach for converting industrial zinc residues into advanced ceramic nanomaterials, providing a sustainable pathway for nanotechnology development.

One of the environmental aspects of processing electronic waste using hydrometallurgical methods is the generation of waste solutions. Solutions after leaching and recovery of target metals are destined for disposal and contain valuable non-ferrous metals such as Cu, Sn, Ni, and others. Their disposal leads to wasting their material potential. The aim of this work is to propose a method by which selected non-ferrous metals can be selectively recovered from these solutions prior to disposal. The results of the experimental work show that the combination of pH adjustment with sodium hydroxide followed by cementation with iron is a suitable procedure for copper displacement from the solution. The cemented copper contains impurities. Removal of these impurities is possible by washing in sulfuric acid. pH adjustment can also be achieved using waste material containing copper. The results confirm that copper can be selectively recovered from waste solutions.