Dragan Radulović

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.

Aflatoxin B1 (AFB1) is one of the most toxic mycotoxins contaminating animal feed, and bentonite clays are widely used as adsorbents to reduce its bioavailability. This study introduces and characterizes a new, previously unexplored bentonite deposit from Bijelo Polje (Bar, Montenegro), with ~55% montmorillonite in the raw material. Size fractions (w/v adsorbent) simulated monogastric gastrointestinal conditions. Progressive size reduction increased smectite content (from ~55% to 91%), CEC (44–70 meq/100 g), purity, and BET specific surface area (26.5–50.8 m²/g), while reducing impurities and heavy metals to undetectable levels. The finest fraction (q_max ≈ 240 mg/g), attributed to enhanced surface homogeneity and site accessibility, significantly outperforming coarser fractions and most unmodified natural bentonites. Only the 90% binding, low quartz/calcite). These results demonstrate that simple mechanical fractionation can yield exceptional performance in a novel natural raw material, offering a cost-effective, sustainable alternative to chemical modification for mycotoxin mitigation.

The production route for cement clinker, including the clinkerization protocol and temperature, is highly dependent on the selection of raw materials. Natural resource reserves used in cement manufacturing are steadily declining due to rapid urbanization and the growing demand for building materials. Consequently, there is an urgent need to identify alternative resources, potentially from cost-effective primary raw materials or waste products. This study aims to evaluate the feasibility of incorporating recycled concrete as construction and demolition waste (C&DW) with unconventional clayey materials (bentonite and zeolite) into clinker synthesis at a reduced temperature of 1300 °C. The effect of mechanical pretreatment of the clinker raw meal, applied for durations of 10 to 30 min, was investigated. Mix designs combining traditional and alternative raw materials, along with different mechanical pretreatment durations, were systematically tested to assess their impact on raw meal clinkerization and the resulting cement mechanical properties. Despite variations in raw meal composition, the produced clinkers consistently exhibited phase compositions comprising C₃S, C₂S, C₃A, and C₄AF, as confirmed by XRD, FTIR, and SEM/EDS analyses. Among the studied raw materials, clayey components played a dominant role in controlling the formation of the main cement minerals, demonstrating that zeolite and bentonite can effectively substitute standard clays. Additionally, C&DW did not impede clinkerization; rather, it functioned as a silica source, replacing quartz sand. Short mechanical pretreatments (10 min) enhanced the content of cement minerals, whereas longer treatments adversely affected clinkerization. This study offers new insights into cement clinker production at reduced temperatures through the use of C&DW combined with unconventional clayey materials. The clinkerization temperature was reduced by approximately 100 °C from the conventional 1400–1450 °C, while still producing cements with mechanical performance comparable to ordinary Portland cement (OPC). The resulting zeolite- and bentonite-based cements, either mechanically untreated or subjected to short pretreatment, are potentially suitable for structural concrete applications, while cements produced with longer mechanical pretreatments may be more appropriate for lower-demand or non-structural uses.

The incorporation into use of the widest possible range of semi-finished products and industrial wastes represents a fundamental task of the circular economy. The formation of crystalline graphite during the process of obtaining pig iron from ore materials has been known for more than a hundred years, yet it is still largely disposed of as hazardous industrial waste. The high degree of structural perfection of this type of graphite and its strong similarity to natural graphite are noteworthy, suggesting the possibility of replacing scarce natural graphite in a significant number of applications with graphite concentrates obtained by purifying waste graphite from steel production. Therefore, investigating the characteristics of the input raw material represents an important step toward solving the problem of utilizing this type of metallurgical waste. This paper presents the results of the physicochemical characterization of a waste graphite sample from an exhaust gas suction system, kindly provided by the HBIS steel plant in Smederevo. The chemical, phase, and granulometric composition of the material were determined, providing important information for the development of methods for its beneficiation to achieve commercially viable graphite concentrate quality.

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.

The paper concisely presents the results of many years of geological research conducted within the Adriatic-Ionian geotectonic unit and provides an assessment of the potential of Upper Cretaceous limestones as carbonate raw materials from the perspective of architectural-construction (decorative) and technical-construction stone, as well as the possibility of their use as carbonate fillers in various industrial sectors. As a result of this research, the reserves of all deposits of architectural-construction (decorative) and technical-construction stone in this area are presented, along with the quality of limestones in terms of their application in construction for the production of aggregates of various fractions. Special attention is given to the results of limestone testing from individual locations in order to assess the potential of carbonate raw materials for their use in other industrial sectors as well.

Aflatoxin B1 is one of the most toxic mycotoxins contaminating animal feed, and bentonite clays are widely used as adsorbents to reduce its bioavailability. The influence of particle size on bentonite adsorption performance, particularly regarding cost-effectiveness of fine fractionation, remains underexplored. This study investigated natural bentonite from the Bijelo Polje deposit (Montenegro) containing ~55% montmorillonite and its size fractions: <0.200 mm (~72% smectite), <0.037 mm (~75% smectite), and 90% at 4 mg/L). The finest <0.005 mm fraction exhibited the highest maximum adsorption capacity (qmax ≈ 240 mg/g) due to superior specific surface area and site accessibility. However, only the 90% binding), as coarser fractions retain excess quartz and calcite. Extensive fractionation, despite higher costs, is essential for regulatory-compliant, high-performance natural bentonite adsorbents.

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.