Acid mine drainage (AMD) is a waste from mining sites, usually acidic, with high concentrations of sulfates and heavy metal ions. This study investigates the AMD neutralization process using fly ash (FA) as an alternative material. Samples of FA from coal-fired power plants in Serbia (“Nikola Tesla” (EF) and “Kostolac” (KOST)) were analyzed and used. The results were compared with the treatment efficiency of commercial neutralization agent (NaOH). The alkaline nature of FA was the basis for use in the treatment process of the extremely acid Lake Robule (pH 2.46), located in the mining areas of eastern Serbia. The optimal S/L ratio for the AMD neutralization process determined for EF was 25 wt.%, and for KOST it was 20 wt.%. The mechanism of the neutralization process was analyzed using the ANC test and PHREEQC program. The element concentrations and pH values in solutions indicated that FA samples could neutralize Lake Robule with more than 99% of Al, Fe, Cu, Zn, and more than 89% of Pb precipitated. Formation of insoluble (oxy)hydroxide forms (Fe³⁺ and Al³⁺ ions) creates favorable conditions for co-precipitation of other trace metals (Cu, Zn, Ni, Pb, and Cd) from AMD, which is further enhanced by cation adsorption on FA particles. FA proved to be a more effective neutralization agent than NaOH due to its adsorption effect, while among the FA samples, KOST was more effective due to the aging process through the carbonization reaction. Using FA as an alternative material is a promising and sustainable method for treating AMD, with economic and environmental benefits.

Electric waste from numerous devices that are put out of use every day has some form of printed circuit board that contains precious and valuable metals in their components. In order to extract these metals, the printed circuit boards were crushed and pyrolyzed into powder. The fine pyrolyzed printed circuit board (PPCB) powder was separated into fractions, and the fine metallic fraction was used as a raw material for metal leaching extraction. In order to better understand how various metal species react in leaching media, several leaching agents were used (sulfuric acid, nitric acid, glycine, and acid mine drainage-AMD) alone, and with the addition of hydrogen peroxide. Additionally, the influence of the S/L ratio and leaching temperature were investigated in sulfuric acid leaching solutions, as this is the one most widely used. In one case, the reactor was heated in a thermal bath, while in the other, it was heated in an ultrasonic bath. Lastly, several experiments were conducted with a (consecutive) two-pronged leaching approach, with and without applied pretreatment. The aim of this paper is to give a multifocal and detailed approach to how metals such as Al, Cu, Co, Zn, Sn, and Ca behave when extracted from fine PPCB powder. However, some attention is given to Nd, Pd, Pb, and Ba as well. One of the main findings is that regardless of the pretreatment or the sequence of leaching media applied, consecutive two-pronged leaching cannot be used for selective metal extraction. However, AMD was found to be suitable for selective leaching with very limited applications.

Cleavage fracture of the V and Ti-V microalloyed forging steels was investigated by the four-point bending testing of the notched specimens of Griffith-Owen’s type at −196 °C, in conjunction with the finite element analysis and the fractographic examination by scanning electron microscopy. To assess the mixed microstructure consisting mostly of the acicular ferrite, alongside proeutectoid ferrite grains and pearlite, the samples were held at 1250 °C for 30 min and subsequently cooled instill air. Cleavage fracture was initiated in the matrix under the high plastic strains near the notch root of the four-point bending specimens without the participation of the second phase particles in the process. Estimated values of the effective surface energy for the V and the Ti-V microalloyed steel of 37 Jm⁻² and 74 Jm⁻², respectively, and the related increase of local critical fracture stress were attributed to the increased content of the acicular ferrite. It was concluded that the observed increase of the local stress for cleavage crack propagation through the matrix was due to the increased number of the high angle boundaries, but also that the acicular ferrite affects the cleavage fracture mechanism by its characteristic stress–strain response with relatively low yield strength and considerable ductility at −196 °C.

Phytomining, although predominantly in its early stages on the broader scientific scope of investigation, has garnered interest in metals such as Ni, Au, or rare earth elements (REE). However, Zn pollution from mine wastes, smelters, coal ash and other anthropogenic sources has become an environmental problem. Phytoremediation by hyperaccumulating plants is one of the proposed solutions to mitigate the pollution. Therefore, a need to utilize or dispose Zn hyperaccumulating plants occurred. Since studies of certain hyperaccumulating plant species have been previously conducted in order to extract metal products, similar hydrometallurgical and pyrometallurgical techniques were tried with Zn. The hydrometallurgical route was more focused on producing crude eco catalysts for organic chemistry or separating metal hydroxides by cementation. This was achieved with acid leaching of the ash which was obtained by calcinating the aboveground plant biomass. On the other hand, the pyrometallurgical route was more focused on safe and eco-friendly disposal of combustion products such as ash or biochar, while achieving zero toxic gaseous emissions from biomass pyrolysis. Regardless of the approach further research is needed to investigate the stabilization of metals that remain in the solid fraction during combustion and lowering the metal content in produced gases. So far, none of these technologies have been brought to a semi industrial scale and there is the potential of linking those two approaches together.

Two medium-carbon microalloyed steels with a predominant acicular ferrite microstructure were investigated in this study in order to determine the initial micro-crack formation mechanism and the role of acicular ferrite structure in cleavage fracture. In order to ensure cleavage fracture, samples were investigated at −196 °C for uniaxial tension and four point bending fracture. Previous investigations have shown that cleavage fracture for steels with a predominant acicular ferrite microstructure has not been initiated by the fracture of coarse TiN particles as in ferrite-pearlite, bainite, or martensitic microalloyed steels. The average maximal thickness of cementite plates measured in this work is 0.798 µm and 0.966 µm, for V and TiV steel, respectively. The corresponding stress values required for their fracture according to Griffith’s equation are 1970 MPa and 1791 MPa, respectively. Estimated values of the effective surface energy for the V steel with an average cementite volume fraction of 3.8% range from 40 Jm⁻² to 86 Jm⁻², and for the TiV steel with an average cementite volume fraction of 18.3% range from 55 Jm⁻² to 82 Jm⁻². The fracture of coarse cementite plates was found to not to be responsible for the cleavage fracture initiation in case of both steels.

The Serbian mining sector has historically played an important role in the country’s development, but it now faces challenges related to sustainable practices. Serbia is among Europe’s leaders in mining-related material consumption and waste disposal, resulting in significant environmental costs. The technical efficiency of mining activities is very low, funding is limited, and the sector struggles to gain public trust due to weak regulation enforcement and a lack of transparency. Statistical analysis shows that Serbia ranks third in Europe for material footprint per capita, indicating a high dependence on resources without sufficient economic benefits. Penalties for overexploitation are low and do not act as a significant deterrent. Current revenues from mining account for only 3–7% of the national budget, which is insufficient to prevent overexploitation. Foreign investment in Serbian mining can generate capital and create jobs; however, it often fails to improve environmental standards or ensure a fair distribution of benefits. The growing influence of foreign investors has significantly shaped Serbia’s mining policy, highlighting the tension between economic growth and environmental responsibility. Inconsistent regulation enforcement and low mineral rents raise concerns that Serbia may attract outdated technologies with significant environmental impact. The current situation in the Serbian mining sector has failed to ensure equitable distribution of resource wealth and responsible management. Modernisation of the sector and a transition to a circular economy are crucial. Investment in raw material processing, recycling, and innovation must continue to minimise environmental impact and improve economic efficiency.