The valorization of tailings includes the utilization of the mineral matrix, as it contains mainly silica, and the recovery of residual metals, containing metals such as iron, copper, titanium, and many others
[5]. Depending on the ore and the process used to treat it, it is possible to recover valuable elements from mine tailings. For example, copper sulfide ores are treated by flotation to recover copper, so the produced tailings contain mainly silicon oxide and a variety of metals
[6]. In this regard, tailings may contain minerals such as quartz, orthoclase, magnetite, hematite, pyrite, and chalcopyrite, among others. Additionally, the total iron grade may be around 19%, due to their origin in the north of Chile
[7][8]. In addition, given that tailings have already been mined and crushed, the treatment costs are considerably lower than primary ores, turning tailings into an economic raw material
[5]. Therefore, studies have been made to use tailings as a construction material such as cement and to recover valuable elements such as iron through magnetic concentration and copper through bioleaching
[7][9][10]. This reprocessing of mine tailings by different technologies is being explored to make mining operations more sustainable
[11]. Acid leaching is widely used in mineral extraction and the recycling of valuable metals
[12]. Sulfuric acid is the best-known and most conventionally used leaching agent; however, some studies recommend hydrochloric acid since the presence of chloride ions is advantageous for copper extraction
[9][13][14]. In addition, many studies are focused on copper recovery from slags. Dimitrijević et al. worked with hydrochloric acid concentration below 2 M and combined it with hydrogen peroxide on copper slag samples
[15]. Chen et al. performed a similar study using, also with copper slag, an 11 M concentration of hydrochloric acid at temperatures above 80 °C
[13].
Chilean researches have carried out the characterization of an iron-rich tailing and the extraction of metals through leaching
[16]. They obtained the tailing sample from a tailing dam placed in the north of Chile. Specifically, the sample was taken from the wall of the tailing dam using the trial pits technique. Their results showed that 80% of the sample is approximately below an ASTM 60 mesh, corresponding to 250 µm, meaning that the particle size distribution is fine. The tailing particles are irregular, and the composition is based on silicates and iron oxides. The composition was mainly quartz, magnetite, orthoclase, and albite. They determined that the tailing contains a total iron grade of 19%, which is a high concentration of iron. They focused on some interesting elements such as copper, aluminum, calcium and magnesium. They found that if the tailing is submitted to acid treatment with hydrochloric acid (HCl), a liquid solution and an insoluble solid are generated. Both phases (liquid and solid) represent an opportunity to produce valuable secondary species
[17][18]. Regarding the acid solution, it is rich in a variety of metals, specially iron. As for the insoluble solid, the samples had an irregular morphology composed mainly of silica, having mainly orthoclase, quartz, and albite.