## 1 Introduction  
Industrial development has contributed to the growth of the global economy, but on the other side, it has led to environmental degradation. In developed countries, problems related to environmental degradation have been mainly solved by introducing new technologies and strict regulations. However, due to the increased demand for natural resources, their exploitation is still active and related environmental problems are present. In contrast to developed countries, in developing countries, more environmental problems exist whose resolution has not even begun, and which are mainly related to unresolved historical pollution or the generation of waste polluted by different hazardous chemicals and materials. Mining is always followed by the production of waste which is deposited in nature in the form of tailings. The waste materials are often very noticeable, located near water resources, underinsured, or in areas with tourist or agricultural potential. Mining is one of the most significant industries in Serbia. Of the total gross domestic production in the Republic of Serbia, metallurgy accounts for 10% of the total manufacture of basic metals and metal products [1]. The Grot Mine is one of the biggest and most significant, located in southeastern Serbia and mainly exploiting lead and zinc ones. The total content of lead and zinc in the ore is about 10.5 wt %, which indicates that about 90 wt % is waste material. The flotation process has generated around 5.5 million tons of waste material until now, mostly in a state of biological vacuum [2]. The area around the Grot Mine is mostly composed of crystalline shales, predominantly of the Early Paleozoic and, to a lesser extent, of the Proterozoic age, with larger and smaller masses of Paleozoic and Triassic granitoid rocks and large Surdulic Paleogene granodiorite plutons. The Grot Mine represents a geo-economic unit within the Paleozoic metamorphic shale complex of the Serbian-Macedonian mass, located on the eastern perimeter of the Surdulian granodiorite. The minefield is located in a crystalline nucleus, located between the Carpatho-Balkanids in the east and the Vardar zone in the west [3]. In the Metallogenic Region of Besna Kobila, the ore deposits are related to Neogene volcanic-plutonic complexes. Mineral associations consist of sulfides of lead and zinc, locally copper and/or molybdenum. In the morphod structural sense, the deposits are of the quadruple/impregnation type, hydrothermal-wire, lens-plate, metasomatic and wire-impregnation types [4]. The deposits were formed by metasomatic alteration of marble and calcschist under the influence of hydrothermal solutions rich in Pb, Zn and Cu. Vertical mineralization intervals are over 400 m [5]. Based on hydrogeological features, this granodiorite massif is characterized by a large area of open cracks and medium water permeability [6]. The landscape surrounding the Grot tailings is mostly mountainous. Environmental protection in the area that surrounds the locality where tailings are placed represents a significant problem. A possible solution may be given based on determining the geochemical properties of the waste materials and finding their potential application. Namely, although it is well known that this kind of waste poses a negative influence on the environment [7], it can contain a significant number of different valuable elements and minerals [8]. Thus, reprocessing of tailings reduces dependence on reserve extraction [9] and can provide economic and environmental benefits, which is completely in agreement with the circular economy and the Sustainable Development Goals [10,11]. In general, the area of the Western Balkans is rich in lead, zinc and copper ones, which is why there are a large number of mines in this area, both abandoned and active, and consequently leading to the generation of millions of tons of waste.