# A Comprehensive Review on Mine Tailings as a Raw Material in the Alkali Activation Process
###### Abstract
Sulfidic minerals are minerals that contain sulfur combined with other elements, often including valuable metals such as copper, zinc, lead, and nickel [14]. These metals are chemically bonded to the sulfur within the minerals. In addition to sulfur, mine tailings can contain elevated levels of heavy metals, such as lead, copper, zinc, and cadmium, and metalloids such as arsenic. When the tailings are exposed to the environment, these elements can leach out and contaminate soil and water, posing serious environmental and health risks [15; 16]. The sulfur in sulfidic minerals becomes concentrated in the resulting mine tailings. When these tailings are exposed to air and water, sulfur-containing compounds can undergo oxidation reactions, producing sulfuric acid and contributing to acid mine drainage (AMD), which is a critical environmental issue associated with mine tailing management and poses significant challenges during the active mining phase and after a mine has been closed [17]. The presence of sulfidic minerals and high concentrations of heavy metals in mine tailings can hinder their recycling potential, and the effective safety management of hazardous mine tailings is essential. Improper handling or inadequate containment can result in safety risks to surrounding communities. Tailings dams, if not constructed and appropriately managed, can pose significant risks and can lead to catastrophic events. Researchers actively seek innovative solutions to mitigate the challenges associated with sulfidic minerals, heavy metals, and tailing management by developing materials and processes that can safely immobilize or utilize these components [18]. Mine tailings are typically stored in tailing storage facilities, which have specially designed areas to contain and manage these waste materials. Tailing dams are constructed to hold the tailings in place, and they are often built using earthen embankments and containment structures. Since certain mine tailings are not considered hazardous waste, the option of reusing or recycling them stands out as an appealing alternative to disposingof them in landfills [19]. Using mine tailings as a component of backfilling operations is a common approach in the mining industry. Backfilling is a technique used in mining in which voids or underground spaces created by mining activities are filled with suitable materials. This serves various purposes, providing stability to underground workings and preventing subsidence [20]. Tailings, which are often already in a slurry form due to the processing methods used during mineral extraction, can be mixed with other binding materials, such as cement, to create a paste-like substance that can be used as a backfill material in underground mining operations [21]. The final properties of paste backfill material in mining operations are influenced by a combination of factors, including the physical, chemical, and mineralogical characteristics of the tailings, the properties of the co-binder, such as cement or other binding agents, and the water content [22]. The particle size distribution, particle shape, and density of the tailings play a role in determining the overall stability and strength of the paste. Moreover, the chemical composition of the tailings, especially the presence of sulfides and heavy metals, can affect the reactivity and potential environmental impacts of the paste [23]. The types of minerals present in the tailings influence the overall behavior of the paste, including its strength, reactivity, and long-term stability. Furthermore, the choice of co-binder, often cement, affects the setting and hardening of the paste, and the amount of co-binder used in the mixture influences the mechanical properties and setting time of the paste [24]. Also, the ratio of water to solid components in the paste affects its workability, setting time, and strength when aiming to achieve the desired consistency and performance [25].