Leaching of Cu, Zn, and Pb from Sulfidic Tailings Under the Use of Sulfuric Acid and Chloride Solutions

Abstract

The imbalance between raw materials of high economic importance and their supply has increased the search for new approaches to obtain valuable elements from mining tailings. In this study, the extraction of copper, zinc, and lead from sulfidic tailing in sulfate–chloride media was investigated. A 33 Box–Behnken design was applied to evaluate three variables over a 4-h testing period: sulfuric acid concentration (0.01–1.0 mol/L H2SO4), sodium chloride (10–60 g/L NaCl), and temperature (20–70 °C). The design showed two optimum working regions: a combination of a high NaCl level, low H2SO4 level, and medium temperature level for lead leaching, while for copper and zinc, a combination of a medium–high H2SO4 level and a high temperature level. The concentration of NaCl had only a slight impact on their leaching. Based on these results, two-stage leaching was performed. The first stage was carried out under an experimental condition that favored the leaching of lead (60 g/L NaCl, 0.01 mol/L H2SO4, 45 °C, 1 h, 10:1 liquid-to-solid ratio), whereas the second stage maximized the leaching of copper and zinc (60 g/L NaCl, 0.5 mol/L H2SO4, 70 °C, 24 h, 10:1 liquid-to-solid ratio). The global leaching rate was 66.8 ± 3.0% copper, 84.1 ± 5.2% zinc, and 93.9 ± 3.2% lead. The iron and arsenic content were also leached by about 20 and 50% at the end of the second stage. The study demonstrated that the use of sulfate–chloride media in a two-stage leaching considerably improved the extraction of the desired metals and was, therefore, suitable for their recovery. Graphical Abstract

Preface to the Thematic Section: Mine Tailings: Problem or Opportunity? Towards a Combined Remediation and Resource Recovery Approach

“…Six papers of the thematic section are dedicated to different aspects of the characterization, metal extraction, and valorization of the mineral fraction of the Neves Corvo extractive waste [6][7][8][9][10][11][12]. Neves Corvo is an underground Cu-Zn mine located in Southern Portugal.…”

“…While pure minerals were used in the current study, in a next step, the technique will be applied to sulfidic tailings. Schueler et al (this issue) apply sulfuric acid and chloride leaching for the recovery of copper, zinc, and lead [8]. Everaert et al (this issue) apply an alternative method to recover target metals: they explore a roasting process followed by ammoniacal leaching [9].…”

The Development of Innovated Complex Process for Treatment of Old Flotation Tailings of Copper-Zinc Sulfide Ore

“…At the same time, some of the leaching procedures performed required the application of high concentrations of leaching agents, as well as high temperatures, which suggests the low economic efficiency of some processes proposed [8]. In the works [22,23,26], high rates of Pb, Cu, and Zn extraction from the samples of flotation tailings, as well as high selectivity of metal extraction, were reached using leaching with NaCl and CuCl 2 . Despite the methods proposed providing high metal extraction, they require high consumption of reagents, as well as providing pregnant solutions with high chloride content, which may impede liquid metal extraction and result in equipment corrosion.…”

“…The reserves of metals contained in flotation tailing in some sites may be estimated as significant due to the large volumes of wastes accumulated from decades of exploitation of some mineral deposits [15,17,21]. Therefore, investigations have been carried out in recent decades to estimate the possibility of metal extraction from old sulfide-containing tailings using different approaches, which include hydrometallurgical techniques (acid leaching (with sulfuric, organic, hydrochloric leaching), leaching with sodium chloride, cupric chloride, ammonium salts, different oxidants, cyanidation, column and stirred tank reactor bioleaching [2,8,18,[21][22][23][24][25][26][27][28][29], roasting [30] and flotation [3], as well as treatment of AMD formed in tailing disposal areas as source of metals [16]. The results of these studies suggest that valuable metals can be successfully extracted from these wastes and high levels of extraction can be reached, while the specific chemical and mineral composition and high iron content (in the form of pyrite and oxide minerals) result in difficulties in base metal extraction.…”

A comprehensive evaluation on leaching of non-ferrous metals from polymetallic tailings

“…The calcination of copper-zinc sul de concentrate followed by leaching with H 2 SO 4 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 sul de tailings. The results showed that the extraction of lead was dependent on NaCl concentration, and temperature positively affected the extraction e ciency of Cu and Pb.…”