The global demand has been significantly increased for critical and valuable metals; on the other hand, a 50-year period is estimated to be sufficient to deplete Cu, Pb, Mn, Ag, Sn, and Zn [1–3]. Therefore, the need for new resources like polymetallic ores and efficient processing methods attracts much attention [4–7]. Utilization of this kind of ores may support the sustainable development of metals industries. Although oxide minerals have been treated historically by the hydrometallurgy method [8–10], the extraction of metals from complex or polymetallic ores has been developed recently. An appropriate lixiviant is required to leach ore to produce metal through hydrometallurgical treatment. In order to extract valuable metals from multi-metal ores, aqueous solutions of ammonia [11–14], sulfuric acid [6, 15–17], organic acids[18], and bioleaching[2, 7, 19, 20] have been used as solvents. Sulfuric Acid (H2SO4) is the most common chemical reagent that is used for the leaching of various minerals, including copper; however, during the leaching process, in addition to copper, other metals in the matrix of the ore can be dissolved by this acid. Iron is the critical impurities that influence the final product’s quality as well as the current efficiency of the electrolytic process [21, 22]. Therefore, the acid concentration should be low to limit the leaching of undesirable metals in the matrix of the ore. Thus, it may be advantageous to work on the essential leaching factors such as concentration of the reagent, pulp density, temperature, and time.
The leaching of polymetallic ores has been the subject of many studies. For example, the leaching process of non-ferrous metals from flotation tailings of copper converter slag using H2SO4 as a leaching agent was studied by Muravyov et al. [23], and the effect of different factors on the leaching process was investigated. They found that 81.6% of copper and 37.7% of zinc can be dissolved under optimal conditions, while the iron recovery was only 26.2%. Cao et al. [24] examined the factors controlling zinc and copper leaching rates for extracting valuable metals from the residue of zinc refineries. According to the results, under the optimum conditions, zinc and copper leaching rates were found to be 98.1% and 98.7%, respectively. Xiao-bo et al. [25] proposed a three-step process for extracting iron and zinc from leaching tailings. As a result, concentrates containing 52% zinc and 32% iron were obtained in the flotation and magnetite separation processes.
Jamali et al. [26] developed a process to leach a copper flue dust with 20% copper, 21% iron, and 3% zinc via a hydrometallurgical route. They found that 96% of zinc and 76.7% of copper have been transferred into PLS under the optimum conditions, whereas iron has dissolved at only 23.92%. The application of ionic liquids in the extraction of metals was investigated by Kilicarslan et al. [27]. Their findings revealed that by using a convenient leaching agent, almost all of the zinc and more than 80% of copper were leached from the solution. An innovative method comprising roasting process, beneficiation and leaching had been developed by Zhuo-yue et al. [28]. By utilizing this procedure, they extracted copper and zinc from a low-grade ore with recoveries of 86% and 69%, respectively.
Some studies applied a two-step leaching process to extract selectively non-ferrous metals, including copper and zinc, from the tailings of the flotation process, in which Zn &Cu was dissolved in the first stage, and iron was transferred into the solution in the second stage of leaching with H2SO4 agent [29]. Calcination prior to the leaching process was another way used by Ferron and Cuyper [30]. The calcination of copper-zinc sulfide concentrate followed by leaching with H2SO4 could recover 99% and 95% of copper and zinc, respectively. A mixture of lixiviants like sulfuric acid and chloride solution was used by Schueler et al. [31] for the extraction of Cu, Zn, and Pb from sulfide tailings. The results showed that the extraction of lead was dependent on NaCl concentration, and temperature positively affected the extraction efficiency of Cu and Pb. The leaching rates of copper, lead, and zinc were obtained as 94, 84 and 67%, respectively. Using direct reduction and magnetic separation as a processing method for obtaining valuable metals from jarosite residues was used by Wang et al. [32]. More than 90% of lead and zinc, and 50% of iron were recovered under the optimum conditions. Top [33] conducted a two-step study and recovered almost 90% of manganese and 57% of iron through leaching and magnetic separation.
Although the leaching of non-ferrous metals such as copper, zinc, lead, and iron by microbial leaching is quite promising, this process suffers from a low extraction rate. Contic et al. [19] worked on a polymetallic sulfide concentrate to extract copper, lead, and iron. The bioleaching efficiency was obtained at 68%, 83%, and 89% for iron, copper, and zinc, respectively. Muravyov [34] utilized bio-hydrometallurgy process to extract metals from pyritic wastes. Under the optimum oxidation conditions, more than 60% of copper and zinc and 85% of gold content was recovered from the tailings. Kovarikova et al. [35] showed that 47% of aluminum, 54% of iron, and 28% of Cu with the bioleaching method could be extracted from a polymetallic ore. Experiments on silver-bearing copper ore conducted by K.Zhappar et al. [36] demonstrated that bioleaching had higher extraction yield compared to conventional leaching method.
Several studies, such as Xi et al. [37], also applied the pressure oxidation process. They found that 98% copper and 99% zinc in the low-grade polymetallic chalcopyrite ore can be dissolved in the optimum condition while lead and iron remained in the residue. Karimo et al. [38] have studied the autoclave leaching of furnace electric filter dust to extract non-ferrous metals and analyze arsenic behavior. Oxidative leaching with sulfuric acid in an autoclave led to the extraction rate of 89 and 92 percent for copper and zinc, respectively. Copper and zinc leaching from a polymetallic concentrate was reported by Patel et al. [39] where 81% of copper and 54% of zinc can be extracted within a contact time of 30 and 90 minutes respectively.
The focus of this work is on the extraction of metals from a polymetallic ore that was historically lie in waste ores at the mine site because efficient metal extraction technologies were not available and at the same time the smelters impose financial penalties on copper concentrate because of the presence of certain impurities. As a result, further research is still necessary to effectively extract ores of this type. In this paper, to establish a leaching process, various conditions were examined to determine the leaching efficiency for copper extraction from multi-metal oxide ores.