Copper Extraction from Black Copper Ores through Modification of the Solution Potential in the Irrigation Solution

Abstract

This article presented the behavior of ores containing black copper under acid leaching. The solution potential was modified by adding agents, and five leaching conditions were evaluated, one as a control based on sulfuric acid leaching (conventional), and the others by changing the solution potential with: ferrous sulfate (FeSO4), white metal (Cu2S), sulfur dioxide (SO2), and ozone (O3). Leaching behavior was evaluated with laboratory bottle (ISO-pH) and column leaching tests. Two ores samples from the Lomas Bayas mine were used. The samples, identified as low (LG) and high grade (HG), were characterized as 0.13–0.25% Cu and 0.15–0.38% Mn, respectively. The mineralogical analysis indicated that black copper represented around 20% of total Cu (0.05% Cu). The results of the bottle tests indicated that the solution potential decreased with the addition of reducing agents, while the copper extraction rate with the HG sample increased to 83.7%, which exceeded the extraction rate obtained by conventional acid leaching by 25%. Ozone did not favor the extraction of Mn and Cu extraction when the solution potential increased. Cu and Mn extraction were directly related. The results of the column leaching tests showed that it was possible to maintain the solution potential at values below 600 mV (SHE) with the addition of white metal and sulfur dioxide while obtaining the highest copper extraction rate of approximately 60%, which was 18% higher than the rate obtained with conventional leaching. Sulfuric acid consumption was 11 kg/t over 45 days of leaching.

Comparative Study of MnO2 Dissolution from Black Copper Minerals and Manganese Nodules in an Acid Medium

“…The authors found that when an Fe 3 O 4 /MnO 2 ratio of 2/1 or higher is used, other variables (H 2 SO 4 concentration, particle size, agitation speed, leaching time) are irrelevant when obtaining Mn dissolutions of around 80%. There are few studies on black copper minerals, and recent studies report Cu and Mn recovery when Fe-reducing agents are added [3,20,24]. Benavente et al [24] added ferrous ions to acid in order to reduce leaching of black copper minerals and found that the dissolution of MnO2 immediately promoted Cu dissolution in black copper minerals.…”

“…There are few studies on black copper minerals, and recent studies report Cu and Mn recovery when Fe-reducing agents are added [3,20,24]. Benavente et al [24] added ferrous ions to acid in order to reduce leaching of black copper minerals and found that the dissolution of MnO2 immediately promoted Cu dissolution in black copper minerals. Pérez et al [20] proved that the Fe 3 O 4 in tailings can be an efficient reducing agent of MnO 2 in black copper minerals when working with high concentrations, but showed lower dissolution kinetics regarding ferrous ions.…”

Treatment of black copper with the use of iron scrap - part I

“…There are few studies that investigated leaching of black copper minerals [16][17][18][19]. In the investigations carried out by Benavente et al, [18] and Pérez et al, [16] it was discovered that working in an acid-reducing leaching favors dissolution of MnO2, thus favoring the extraction of copper.…”

Dissolution of Black Copper Oxides from a Leaching Residue

“…Exotic deposits can be found in northern Chile near copper porphyry systems from the Paleogene period, such as Huanquintipa (Collahuasi), Quebrada Ichuco (El Abra), Mina Sur (Chuquicamata), and Damiana (El Salvador) [9,10]. Black copper appears in "wad" or "pitch" form in compact earthy botryoidal masses, or filling fractures and cementing gravel [11]. When it appears alone in an earthy state, it is called wad, while when it is associated with chrysocolla, it is called pitch or black chrysocolla [12,13].…”

“…Some reducing agents proposed for dissolving refractory minerals under conventional conditions are white metal (Cu 2 S) [11], sulfur dioxide (SO 2 ) [6,11,[18][19][20][21][22], ferrous sulfate (FeSO 4 ) [23][24][25], sponge iron [26], hydrogen peroxide [27,28], and even pyrite [29], several of which have been evaluated for industrial application as treatment alternatives. The SO 2 and Cu 2 S present better performance, although the use of SO 2 is complex from the safety and environment point of view and Cu 2 S availability is limited for small-scale mining; the reagent to be evaluated is FeSO 4 , which is easy to access and manage.…”