Dejan Todorović

The technological performance of bentonite in foundry applications is strongly influenced by the nature of its exchangeable interlayer cations, with sodium bentonites generally exhibiting superior swelling, plasticity, and bonding properties compared with calcium bentonites. Given the limited availability of natural sodium bentonite, upgrading abundant calcium-rich bentonite resources holds significant industrial interest. In this study, a natural Ca-rich bentonite from the Bijelo Polje deposit (Bar, Montenegro) was upgraded by alkali activation using Na₂CO₃ and evaluated as a binder for green sand foundry molds. The raw bentonite was characterized by physicochemical, mineralogical, and structural analyses, confirming its Ca-type character and suitability for sodium activation. Activation was performed using 2–6 wt.% Na₂CO₃, with the optimum treatment achieved at 5 wt.% Na₂CO₃. The activated bentonite was subsequently characterized using structural, textural, thermal, and physicochemical methods. Alkali activation significantly improved the key technological properties of the material, increasing the free swelling capacity from 7 to 20 cm³, the specific surface area from 27.4 to 45.8 m² g⁻¹, the cation exchange capacity from 74.6 to 89.5 meq/100 g, and the plasticity index from 79.6% to 193.4%. XRD, ATR–FTIR, and thermal analyses confirmed successful sodium activation while preserving the fundamental montmorillonite structure. Evaluation of foundry-relevant properties, including refractoriness, methylene blue adsorption, gas permeability, thermal stability, and bonding strength, demonstrated that the activated bentonite satisfies the technological requirements for green sand molding of both ferrous and non-ferrous alloys. These findings demonstrate that Na₂CO₃ activation is an effective and resource-efficient approach for converting natural Ca-rich bentonite into a high-performance foundry binder.

Although countless hours are devoted to process development, engineering of appropriate equipment, and the selection of optimal suppliers, one often overlooked yet extremely important aspect of a successful production line is the recycle loop (circulating batch, recycling loop). This topic is particularly significant when dealing with the processing of bulk solid materials. Plants for processing bulk solids do not operate as linear processes but rather as dynamic circulating systems, with the recycle loop being the key element that governs this circulation. Whether it involves fertilizer granulation, catalyst pelletization, or limestone drying, the integration and design of the recycle loop have a significant impact on process efficiency and yield. In these systems, the recycle loop is not merely a means of returning out-of-spec material-it is a mechanism that enables consistent, high-yield production.

Mineral comminution is the largest energy consumer in the mining industry, accounting for up to 50% of total site energy consumption. Over the past decade, High-Pressure Grinding Rolls (HPGR) and Vertical Roller Mills (VRM) have emerged as key alternatives to traditional grinding circuits, particularly in dry processing applications that reduce water consumption and support decarbonization efforts. This review paper compares HPGR and VRM technologies, focusing on energy efficiency (kWh/t), mineral liberation degrees, and applicability in dry conditions for copper, iron, Lithium, and nickel ores. Based on data from installations and pilot tests conducted between 2020 and 2026, HPGR demonstrates energy savings of 30-40% in the primary stages of hard rock processing. Meanwhile, VRM excels in flexibility for finer grinding and integrated classification, offering potential energy savings of 40-45%. The paper further analyzes operational constraints (wear, dust) and emerging trends (hybrid systems, AI optimization), providing recommendations for application in the mining sector of Serbia and the surrounding region, where dry processing is becoming increasingly critical due to limited water resources.

Coating is a surface modification technique frequently applied to agglomerates to improve performance, handling, appearance, and integrity. The process involves applying a thin layer of material to pellets or granules, offering benefits such as reduced dust formation, improved flowability, moisture resistance, and controlled solubility. This paper discusses the key advantages of coating, the selection of appropriate coating materials, and equipment used for application, with reference to industry practices and relevant literature.

Comminution, which includes crushing and grinding, is one of the most energy-intensive processes in the mining industry, accounting for up to 50% of total energy consumption in mineral processing plants. Recent technological advancements have introduced more efficient, cost-effective, and environmentally friendly comminution equipment. This paper reviews the latest innovations in crushing and grinding technologies, including high-pressure grinding rolls (HPGR), vertical roller mills (VRM), and advanced cone crushers with real-time optimization systems. The study evaluates the energy efficiency, operational performance, and economic feasibility of these devices compared to traditional equipment such as ball mills and jaw crushers. The findings suggest that adopting modern comminution technologies can significantly reduce energy consumption, improve particle size distribution, and lower operational costs. These advancements contribute to more sustainable mining operations by minimizing environmental impact and optimizing resource utilization.

In this study, two samples of flotation tailings from the "Rudnik" Mine (one from boreholes and one from the surface) were examined. Various physical and chemical properties were analyzed, including gross and hygroscopic moisture, specific mass, bulk density in both loose and compacted states, and specific weight. Additionally, granulometric and chemical compositions were determined. A qualitative mineralogical analysis was conducted using X-ray diffraction (XRD), along with the preparation of polished sections for optical and SEM microscopy. Comprehensive physicochemical and mineralogical tests were performed to define all parameters necessary for the valorization and recycling of flotation tailings from the "Rudnik" Mine.

This study was conducted to examine the potential harmful effects of zeolite consumption in daily supplementation. The research focused on the acid stability of zeolite in HCl solution at pH values ranging from 1.5 to 3, corresponding to gastric pH levels. The initial zeolite sample, as well as the samples subjected to acidic treatment, were characterized using X-ray diffraction (XRD) method, and their chemical composition was analyzed. The results obtained indicate that the crystalline structure of zeolite was not disrupted during the treatment. At a pH of 1.5, up to 2% of aluminum leached into the solution, while at higher pH values, no aluminum leaching was observed. These findings underscore the need for cautious consideration of zeolite supplementation due to potential aluminum release in highly acidic environments.

In this study, two samples of "TA-Nb" ore from Congo (MMR-1 and MMR-2) were analyzed. Various physical and chemical properties were determined for these samples, including gross and hygroscopic moisture, specific gravity, granulometric composition of the initial samples and after each level of crushing, bulk density of the initial samples and after each crushing stage, and chemical composition. Qualitative mineralogical analysis was conducted using X-ray diffraction (XRD), while polished sections were prepared for optical microscopy, scanning electron microscopy (SEM), and mineralogical analysis by particle size classes. Detailed physicochemical and mineralogical tests were carried out on the MMR-1 and MMR-2 samples to comprehensively define the parameters necessary as a foundation for further technological testing of "TA-Nb" ore from Congo. The results showed that the examined samples have appropriate characteristics for further technological tests.

The presented work offers an innovative process scheme for valorizing Pb-Zn slag, which involves crushing, grinding, and separation techniques to concentrate valuable components (non-ferrous metals). This methodology could have a significant impact on the global beneficiation of metallurgical slags since it is significantly more simple, environmentally friendly, and cost-effective than standard pyro- and hydrometallurgical procedures. According to previous physicochemical and mineralogical studies, Pb-Zn slag is a valuable secondary raw material. This inhomogeneous technogenic resource contains substantial amounts of non-ferrous metals (Pb, Zn, Cu, and Ag). However, laboratory tests have indicated that the Pb-Zn slag contains highly uneven amounts of valuable metals, ranging from several g/ton to tens of g/ton. The main issue is that traditional metallurgical procedures for releasing beneficial elements are not commercially viable since the elements are “trapped” within the amorphous aluminosilicates or intergrowths of alloy grains and glassy phases. Gravity concentration (Wilfley 13 shaking table) and magnetic separation (Davis separator and disk separator) were used to obtain the final concentrate following comminution and grindability testing. The gravity concentration proved more effective. Namely, magnetic separators could not process nor adequately separate beneficial non-ferrous elements because they were merged together with iron-bearing minerals and aluminosilicates in amorphous Pb-Zn slag grains. With the gravity concentration approach, 12.99% of the processed slag belonged to ∆T fraction (concentration of non-ferrous metal alloys), while remaining 87% corresponded to the tailings fraction (∆L). The total amounts of recovered Pb, Zn, Cu, and Ag from ∆T and ∆L fractions were 5.28%, 6.69%, 0.58%, and 76.12 ppm and 1.22%, 6.05%, 0.43%, and 15.26 ppm, respectively. This streamlined approach to valorizing Pb-Zn slag can reduce the need for hazardous chemicals used in hydrometallurgical refinement operations, as well as the extremely high temperatures required for pyrometallurgical processing. This is the first study to investigate the viability of this novel methodology, which involves the direct examinations of the Pb-Zn slag feed with various alternative technologies for separation and concentration. After extracting the valuable metals, the amorphous aluminosilicate part of the Pb-Zn slag can be reapplied as an alternative raw material in the building sector, adding to the circularity of the suggested approach.

The presented work offers a novel process scheme for valorizing historical Pb-Zn slag, which involves crushing, grinding, and then using separation techniques to concentrate valuable components (nonferrous metals). This methodology could have a significant impact on the global beneficiation of metallurgical slags since, in theory, it is significantly more simple, environmentally friendly, and cost-effective than standard pyrometallurgical or hydrometallurgical procedures. According to previous physicochemical and mineralogical studies, Pb-Zn slag from "Topilnica" Veles is a valuable secondary raw material. This inhomogeneous technogenic resource contains substantial amounts of nonferrous metals (Pb, Zn, Cu, and Ag). However, laboratory tests have indicated that the Pb-Zn slag contains a very uneven valuable metals amounts, ranging from several g/ton to several tens of g/ton. The main issue is that traditional metallurgical procedures for releasing beneficial elements are not commercially viable since the valuable elements are "trapped" within amorphous aluminosilicates or intergrowths of alloy grains and glassy phases. Gravity concentration (Wilfley 13 shaking table) and magnetic separation (Davis separator and disk separator) were used to obtain the final concentrate following comminution and grindability testing. The gravity concentration proved more effective. This streamlined approach of valorizing Pb-Zn slag can reduce the need for hazardous chemicals used in hydrometallurgical refinement operations, as well as the extremely high temperatures required for pyrometallurgical processing. This is the first investigation into the feasibility of this novel approach, which includes direct investigations of the Pb-Zn slag feed using these alternative technologies. After extracting the valuable metals, the amorphous aluminosilicate part of the Pb-Zn slag can be reapplied as an alternative raw material in the building sector, adding to the circularity of the suggested approach..