Marija Stojmenović

This study presents, for the first time, an assessment of the dual role of waste enamels from heating device production in asphalt mixtures, as additives to modify euro bitumen (50/70) and as fillers, with a detailed analysis of their influence on properties of asphalt mixtures. Three types of enamels were investigated—premix (WEP), classic (WETM), and acid-resistant (WEART). Different characterization methods confirmed that these materials possess a borosilicate matrix enriched with various elements, including heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn). Although classified as hazardous by-products, enamels replaced 100% of conventional stone dust filler, with confirmed leaching test. Their role in bitumen modification was interpreted through a structure–property approach: bitumen (4–6 wt.%) acts as a viscoelastic polymer-like matrix, while enamel particles serve as micro-scale reinforcements that govern binder–filler interactions. The results demonstrate that, despite their hazardous nature, waste enamels are compatible with asphalt technology containing 5 wt.% bitumen, achieving satisfactory stability, acceptable deformation response, and favorable volumetric characteristics. By valorizing industrial waste in this novel way, this study opens a sustainable pathway for transforming hazardous materials into functional components for the asphalt industry.

In this study, phenol adsorption from aqueous solutions was investigated using a carbonized adsorbent derived from a 1:1:1 mixture of banana, carrot, and potato peels, representing a major fraction of municipal bio-waste in Serbia. The material (CARB_BCP) was characterized by pH_pzc, SEM, FTIR, and BET analyses. The results indicated a highly porous structure with developed micro- and mesoporosity and a high specific surface area (S_BET = 483 m²/g). FTIR confirmed the formation of a stable aromatic carbon structure, while the high pH_pzc value (10.55) suggested a limited role of electrostatic interactions. Adsorption experiments performed at an initial phenol concentration of 1858 mg/L, room temperature, and an adsorbent dose of 0.1 g achieved a removal efficiency of 20.5%. The Langmuir model provided the best fit, indicating monolayer adsorption, with good agreement between theoretical (≈187 mg/g) and experimental (≈190 mg/g) capacities. Kinetic analysis followed the pseudo-second-order model, suggesting chemisorption as the rate-controlling step. The adsorption mechanism was mainly governed by π–π interactions, hydrophobic effects, and hydrogen bonding. These results demonstrate that CARB_BCP, derived from biodegradable waste, is a promising low-cost adsorbent for wastewater treatment.

This study demonstrates the complete transformation of almond shell waste into a high-performance carbon material for carbon paste electrode (CPE) fabrication. The biocarbon was synthesized via carbonization at 800 °C and subsequently activated with CO₂, resulting in a semicrystalline structure rich in carbonyl groups—consistent with its lignocellulosic origin (34.25% cellulose, 13.48% hemicellulose, 48.03% lignin). Carbonization increased the total pore volume of carbonized almond (CAR_ALD) by nearly 13-fold and the specific surface area by over two orders of magnitude compared to raw almond (RAW_ALD), while CO₂ activation further enhanced activated almond’s (ACT_ALD) surface area (~19%) and pore volume (~35%). To improve electrochemical performance, Bi₂O₃ doped with Sm was applied as a surface modifier. Comprehensive characterization (N₂ physisorption X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopic Analysis (FTIR), X-Ray Photoelectron Spectroscopic Analysis (XPS), Thermogravimetric and Differential Thermal Analysis (TG-DTA), Cyclic voltammetry (CV), Electrochemical impedance spectroscopy (EIS)) confirmed the material’s structural integrity, graphitic features, and successful modifier incorporation. Electrochemical testing revealed the highest current response (48 µA) for the CPE fabricated from CAR_ALD/Bi₂O₃-Sm, indicating superior electrocatalytic activity and reduced charge transfer resistance. Notably, this is the first report of a fully functional CPE working electrode fabricated entirely from waste material.

Nowadays, there is increasing global demand for activated carbon considering its wide usage as an adsorbent of environmental pollutants. Biowaste rich in lignocellulose, like the cone-like flowers of black alder (A_AC), shows promise as a precursor for novel materials. Building upon previous research and this material’s established applicability for removing cyanobacteria cells and cyanotoxins from water, this study investigates the CNOHS composition of A_AC and its potential to inhibit biofilm formation. A comprehensive CNOHS analysis showed the material composition as 64.5%, 1.77%, 28.83%, 2.05%, and 0.12% for C, N, O, H, and S respectively. The material’s efficacy in inhibiting biofilm formation across eight selected bacterial strains was evaluated. The results showed biofilm formation rates of 62.6%, 22.1%, 73.8%, 12.1%, 40.9%, 24.2%, 9.2%, and 7.6% for Escherichia coli, Pseudomonas aeruginosa, Enterobacter cloacae, Salmonella Typhimurium, Proteus mirabilis, Klebsiella pneumoniae, Acinetobacter baumannii, and Enterococcus faecalis, respectively. Biofilm formation is influenced by biotic and abiotic factors, especially the physicochemical properties of the substrate. This study offers insights into the potential of black-alder-derived activated carbon to prevent biofilm formation, highlighting its role in water purification and environmental protection.

This paper presents the results of the application of hazardous waste slag generated by lignite combustion for the adsorption of ethyl xanthate anions (EX) from aqueous solutions. The starting material (RWS) was washed (WWS) and modified (MWS) and then characterized in detail by using different chemical and physical–chemical techniques (determination of chemical composition and content of heavy metals, X-ray diffraction (XRD), infrared spectroscopy (FTIR), determination of textural properties and point of zero charge). Besides the chemical stability of EX, the influence of the initial pH, mass of the adsorbent, initial concentration, and time on the EX anion removal was tested. The characterization results showed that applied waste slag is a hazardous material with complex mineral and structural properties but with good buffer properties and pH stability, which is also characteristic of the MWS sample. The adsorption experiments showed that modification with Cu(NO₃)₂ and Fe(NO₃)₃ significantly increases the adsorption capacity of the starting slag. Under applied experimental conditions, the maximal adsorbed amount of EX anions on the MWS was 210 mg/g, while equilibrium was obtained after 700 min. The Freundlich model and pseudo-second-order model best fit the results, suggesting the complex mechanism of EX removal by the MWS sample.

Harmful cyanobacteria blooms and the escalating impact of cyanotoxins necessitates the effective removal of cyanobacteria from water ecosystems before they release cyanotoxins. In this study, cyanobacteria removal from water samples taken from the eutrophic Aleksandrovac Lake (southern Serbia) was investigated. For that purpose, novel activated carbons derived from waste biomass—date palm leaf stalk (P_AC), black alder cone-like flowers (A_AC), and commercial activated carbon from coconut shell (C_AC) as a reference were used. To define the best adsorption conditions and explain the adsorption mechanism, the influence of contact time, reaction volume, and adsorbent mass, as well as FTIR analysis of the adsorbents before and after cyanobacteria removal, were studied. The removal efficiency of P_AC and A_AC achieved for the applied concentration of 10 mg/mL after 15 min was ~99%, while for C_AC after 24 h was only ~92% for the same concentration. To check the safety of the applied materials for human health and the environment, the concentrations of potentially toxic elements (PTEs), the health impact (HI) after water purification, and the toxicity (MTT and Comet assay) of the materials were evaluated. Although the P_AC and A_AC achieved much better removal properties in comparison with the C_AC, considering the demonstrated genotoxicity and cytotoxicity of the P_AC and the higher HI value for the C_AC, only the A_AC was further investigated. Results of the kinetics, FTIR analysis, and examination of the A_AC mass influence on removal efficiency indicated dominance of the physisorption mechanism. Initially, the findings highlighted the superior performance of A_AC, with great potential to be globally commercialized as an effective cyanobacteria cell adsorbent.

This research presented, for the first time, the results of the successful application of the waste press sludges, WSLP (plant for lacquer and paint) and WSEP (powdery enamel plant), from a wastewater treatment plant generated during heating device production in the construction industry. The results of WSEP characterization and its influence on cement paste, mortar, and concrete properties showed that this material could be used as a cement replacement (with a maximum replacement amount of 20%) in producing mortar and concrete. Although waste WSLP sludge does not possess pozzolanic properties and does not meet the criteria prescribed by the standards for application in mortar and concrete due to its chemical inertness and fineness, as well as its extended setting time, it can be used as a replacement for stone filler or other powdered mineral admixture in the production of self-compacting concrete (SCC) in amounts up to 100%, with a maximum quantity of up to 100 kg/m³. The obtained results indicate that with the appropriate conversion, waste sludges, despite representing hazardous waste, can be used as safe products in the construction industry; i.e., the waste material can become a useful and valuable raw material by applying (respecting) all of the principles of the green economy.

The possibility of using waste tailings produced by flotation in the lead and zinc mine of Grot, Serbia as a potential source of secondary mineral raw materials was examined. The aim of the research was primarily to carry out a detailed characterization in order to determine the dominant minerals, and, for the first time, to trace the changes occurring in the unit cells of the minerals present in that deposit. There was also a need to determine the exact proportions of the present mineral phases for their further application and utilization as natural resources in environmental protection. Samples were taken from three different sections of tailings: the crest of dam (JKB), outlet pipe of the flotation facility (JOF) and hydrocyclone overflow (JHC). Granulometric separation was performed to facilitate the extraction of certain minerals from waste. The results showed that all samples mainly contained quartz, clinochlore, calcite, albite, pyrite and biotite, but their ratios in each sample varied significantly. After characterization, samples were separated into different fractions and their mineralogical compositions were determined. Depending on the fraction, the mineralogical compositions also changed. Mineralogy and geochemical analysis indicate that waste tailings can be used as a secondary mineral raw materials source applicable in various industries.

In recent years, the interest of the scientific community has become focused on the integration of circular economy principles by eliminating end-of-life concepts and forming zero-waste strategies. The present paper suggests the possible application of innovative, eco-friendly, cost-effective, and highly efficient ceramic materials with the partial implementation of aluminosilicate-based waste in the form of wastewater sludge in advanced technology solutions. The specific objective was to demonstrate the effective utilization of the investigated waste in the production of refractory adhesives and/or sealants for Intermediate-Temperature Solid-Oxide Fuel Cells (IT-SOFCs). Different physical–mechanical and chemical properties were determined along with the performance of leaching tests, the thermal cycling procedure, and leakage tests in a single cell. Based on the maintenance of mechanical integrity after thermal cycling and satisfying crystal and microstructural stability after high-temperature treatment, it was concluded that the investigated materials may be considered promising candidates for application as heat-resistant adhesives for connecting components in heating systems. However, they were not found to be applicable as sealants for IT-SOFCs in raw form according to the failure of testing in a single cell. Still, requirements for this purpose could be met after certain modifications of the composition and synthesis methodology, which presents the major initiative for our further research in this field.

Waste vitreous enamels from the heating device production process were used for partial replacement of cement in the mortar and concrete production industry. This waste, due to the high content of heavy metals, is classified as hazardous waste. At the same time, waste vitreous enamels possess pozzolanic activity and belong to class 15 (WEP—generated during the production process of heating devices, premix technology), that is 5 (WETM—generated during the production process of heating devices, classic technology) of pozzolanic materials. The purpose of this research was to develop new composites from these wastes to reduce the deposition of the toxic compounds and reduce their environmental impact. The chemical and physical-chemical characterization and pozzolanic activity of the raw waste materials were studied by a mixture of complementary methods, as well as physical-mechanical characterization and a leaching test of mortar and concrete composites. The results indicate that the replacement of cement with WEP up to 30%, or with WETM up to 20% does not significantly affect the quality of concrete in comparison to the quality of the reference concrete prepared with 100% cement. The leaching test showed no significant release of toxic elements for both obtained composites.