Cascade reservoirs on the Drina River (Bosnia and Herzegovina) are heavily modified water bodies that require reliable biological tools for assessing trophic status and ecological potential. Under the Water Framework Directive (WFD), assessments of surface water ecological status and potential rely on biological quality elements, since aquatic communities integrate and respond to prevailing environmental conditions and thus serve as reliable indicators of water quality. This study aims to (i) describe phytoplankton diversity, biomass, and functional-group composition along the Drina reservoir cascade, (ii) examine monthly changes across the studied reservoirs, (iii) determine trophic status and ecological potential, and (iv) provide a preliminary estimate of total phosphorus thresholds that may support future setting of ecological potential boundaries. Phytoplankton composition and functional groups were analysed in three longitudinally connected reservoirs of the Drina River during four monthly surveys in 2024. A total of 80 phytoplankton taxa were recorded, with diatoms dominating most of the study period. The highest biomasses were recorded for Fragilaria crotonensis, Dinobryon divergens, Acanthoceras zachariasii and Sphaerocystis sp., while the dominant functional groups were P, E, A, and F. Phytoplankton assemblage structure showed moderate spatial differentiation among the reservoirs. Mean chlorophyll a and Carlson’s Trophic State Index indicated eutrophic conditions in the Višegrad Reservoir and mesotrophic conditions in the Perućac and Zvornik reservoirs, while biomass showed a pronounced summer maximum, particularly in Perućac. Ecological potential was generally classified as good or better, except for a moderate classification in the Zvornik Reservoir in late summer. The good/moderate TP boundary was estimated at 39 µg L−1, linking EQR-based ecological assessment with the onset of eutrophic conditions. Overall, this study represents the first application of the phytoplankton functional group approach in cascade reservoirs in Bosnia and Herzegovina and may provide a valuable basis for the development of a phytoplankton-based monitoring framework in lakes and reservoirs, which is currently lacking.

In this study, the possibility of using slag derived from hydrogen-plasma reduction of red mud (H 2 RMS) as a low-cost adsorbent for phosphate removal from aqueous solutions was investigated. Batch adsorption experiments were conducted to evaluate the effects of contact time, solution pH, sorbent dosage, and initial phosphate concentration under controlled laboratory conditions. Phosphate concentrations were determined spectrophotometrically using the ammonium molybdate method. These results demonstrated that phosphate adsorption onto H 2 RMS is strongly pH-dependent, with maximum removal efficiency achieved under acidic conditions (pH ≈ 2). Adsorption equilibrium was achieved after approximately 18 h of contact time. Increasing the sorbent dosage enhanced phosphate removal efficiency, although improvements became marginal beyond a dosage of 10 g/L. At optimal conditions, phosphate removal efficiency of approximately 90% was achieved. These findings indicate that H 2 RMS shows significant potential as an effective adsorbent for phosphate removal, offering a possible pathway for the valorization of metallurgical waste residues.

Fenton processes, in which hydrogen peroxide in the presence of divalent iron ions generates hydroxyl radicals (•OH), are widely used for the degradation of organic pollutants (phenols, antibiotics, dyes). In this review, red mud is analysed as a cheap source of iron ions in Fenton processes. Raw red mud can be used without additional modifications, but to increase the catalytic efficiency, its modification is required, which includes chemical reduction, carbothermal treatment or doping with metals. Particular attention is given to photo-Fenton and electro-Fenton processes, where red mud doped Cо, Sn or Cе, or in combination with reduced graphene oxide and biochar, allow the generation of not only hydroxyl radicals (•OH) but also singlet oxygen (1O2) and superoxide radicals (•O2–), achieving ≥99% pollutant removal. At the same time, the synthesised catalysts showed high stability and reusability. Based on a comparative analysis of more than 30 studies, it is concluded that red mud represents a cheap source of iron ions for heterogeneous Fenton processes, with significant potential for industrial application.Keywords: Fenton process, hydroxyl radicals, organic pollutants, red mud.

The increase in carbon dioxide (CO2) emission causes climate change, which manifests itself through global warming, so the reduction of CO2 emissions is considered an important challenge for environmental protection. Road traffic is one of the main anthropogenic sources of CO2, as well as other gases that cause the greenhouse effect, so traffic is designated as one of the main causes of global warming. This situation has led to thinking about strategies to reduce CO2 emissions from road traffic. This paper considers the impact of road traffic on CO2 emissions, including various aspects of traffic such as fuel types, vehicle types and efficiency, traffic infrastructure and strategies to reduce its emissions. For this purpose, the results of research published in the last decade were summarized and compared. Based on the presented results, it is noticeable that CO2 emission is a necessary companion of road traffic and that it increases along with the increase in the number of vehicles and the use of fossil fuels, but also that significant efforts are being made to reduce its emission. The work provides the basis for further research and development of strategies that affect the reduction of carbon dioxide emissions, which will reduce the greenhouse effect and global warming.

: This paper shows the preliminary results of an investigation into the possibility of using red mud slag (RMS) for phosphate sorption from aqueous solutions. The red mud slag was obtained from red mud treatment, specifically from carbothermal reduction at high temperatures. This process resulted in forming a metallic phase (iron) and slag enriched with other elements. The preliminary analysis of slag is performed to investigate its potential for use as a phosphate sorbent in wastewater treatment. The slag is divided into three categories. Two of them are obtained by sieving an original slag sample in the fine fraction and the coarse fraction (the slag residual after sieving). The third sample is the raw slag. After an experiment that included 24 h shaking of slag and phosphate solution, the results show potential for using red mud slag in phosphate sorption. It is an initial experiment that will be a starting point for further investigation of the sorption characteristics of red mud slag.

<p>To evaluate the surface water quality of the Drina River basin, samples were collected from the main river and its tributaries at selected monitoring sites. A total of 17 samples were collected from various locations during the years 2023 and 2024. Various physicochemical parameters and concentrations of heavy metals were analyzed. Overall, most tested samples indicated generally good water quality in terms of physicochemical indicators. However, the findings also suggest that certain human activities have a measurable influence on water quality in the basin. The results serve as an indication of existing pollution pressures and provide a basis for further investigations on the environmental status of the Drina River.</p>

Abstract Red mud, a voluminous industrial waste produced during the Bayer process in the alumina industry, has numerous application possibilities across various fields. Its potential uses are diverse, ranging from the construction industry and metallurgy to environmental protection and agriculture. There are three main aspects of red mud utilization. First, it can be analyzed from the point of view of resource utilization, where it could be applied as raw material mostly in the construction industry. Second, it could be a useful source of valuable components, such as rare earths and metals, especially iron. Third, red mud could have different environmental applications, in wastewater treatment, soil remediation, etc.The paper summarizes current data on red mud utilization methods and aims to emphasize the potential for red mud utilization in various fields.

Red mud is the main by-product of the production of alumina according to the Bayer process. It is a highly alkaline, brick-red suspension. It is characterized by a diversity of chemical and mineralogical composition. The main elements in red mud are Fe, Al, Si, Ti, Na, Ca, and they account for about 90% of the mass of the mud. In addition to these, a large number of other components can be found in minor quantities. Most elements are present in the form of oxides and hydroxides in various minerals. The demand for aluminum is constantly growing, the amount of discharged red mud is continually increasing. The annual amount of red mud produced globally, is already estimated at 200 million tons, and further growth is expected. High production rates and only minimal and sporadic utilization of red mud have resulted in the accumulation of large quantities of disposed red mud, so that the global red mud stockpile is estimated at more than 5 billion tons. In addition to financial costs, the disposal of red mud also poses certain risks to the environment. For this reason, the safe disposal of red mud is one of the main concerns of all alumina producers. Reducing the amount of red mud that is disposed of, and consequently reducing the risks and costs, requires constant efforts to find procedures for its valorization. The possibilities of valorization of red mud are diverse. It has been shown that red mud can be successfully used in many areas, such as construction, metallurgy, chemical industry, environmental protection, agriculture, etc. Analyzing the patents related to the use of red mud, it can be observed that 12% of the patents refer to the wastewater and waste treatment. The heterogeneous composition of red mud indicates the possibility of its application as a composite sorbent. The application of red mud as a low-cost sorbent has been extensively investigated, and favorable results have been obtained in the sorption of metals and metalloids, radionuclides, phosphates, nitrates, fluorides, dyes and phenols, etc. In order to increase the sorption capacity of red mud and obtain a more environmentally friendly sorbent, various treatment techniques are applied. These treatment techniques can modify the physical and chemical properties, which can lead to a change in alkalinity, specific surface area and porosity, a change in the number of active sorption sites, and its surface charge can also be changed. Modifications of red mud to remove various types of pollutants have shown promising results. Many studies have shown that red mud can be used as an efficient and low-cost sorbent for removing heavy metal cations from solutions, such as Pb2+, Cu2+, Zn2+ , Cd2+, Ni2+, Co2+, Sr2+, Cs2+, as well as for the treatment of waste water and leachate from landfills and mines. During the removal of heavy metals from solutions using red mud, various mass transfer phenomena occur: physical and chemical adsorption, surface precipitation, co-precipitation, ion exchange, precipitation, complexation, hydration, dissolution, etc. Despite the numerous possibilities of application and the benefits that arise from it, we still do not have a significant utilization of red mud.

Cobalt’s pivotal role in global development, especially in lithium-ion batteries, entails driving increased demand and strengthening global trading networks. The production of different waste solutions in metallurgical operations requires the development of an environmentally friendly research strategy. The ultrasonic spray pyrolysis and hydrogen reduction method were chosen to produce nanosized magnetic powders from waste solution based on iron and cobalt obtained during the purification process of used polycrystalline diamond blanks. With specific objectives focused on investigating the impact of reaction temperature and residence time on the morphology, chemical composition, and crystal structure of synthesized nanosized cobalt powders, our research involved 15 experimental runs using two reactors with varying residence times (7.19 s and 23 s) and distinct precursors (A, B, and C). Aerosol droplets were reduced at 600 to 900 °C with a flow rate of 3 L/min of argon and hydrogen (1:2). Characterization via scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction revealed that higher temperatures influenced the spherical particle morphology. Altering cobalt concentration in the solution impacted the particle size, with higher concentrations yielding larger particles. A short residence time (7.9 s) at 900 °C proved optimal for cobalt submicron synthesis, producing spherical particles ranging from 191.1 nm to 1222 nm. This research addresses the environmental significance of recovering magnetic particles from waste solutions, contributing to sustainable nanomaterial applications.