Abstract
Overcoming the slow-leaching kinetics of refractory primary copper sulfides is crucial to secure future copper sources. Here, the effect of carbon was investigated as a catalyst for a bioleaching reaction. First, the mechanism of carbon-assisted bioleaching was elucidated using the model chalcopyrite mineral, under specified low-redox potentials, by considering the concept of Enormal. The carbon catalyst effectively controlled the Eh level in bioleaching liquors, which would otherwise exceed its optimal range (0 ≤ Enormal ≤ 1) due to active regeneration of Fe3+ by microbes. Additionally, Enormal of ~0.3 was shown to maximize the carbon-assisted bioleaching of the model chalcopyrite mineral. Secondly, carbon-assisted bioleaching was tested for three types of chalcopyrite/enargite-bearing complex concentrates. A trend was found that the optimal Eh level for a maximum Cu solubilization increases in response to the decreasing chalcopyrite/enargite ratio in the concentrate: When chalcopyrite dominates over enargite, the optimal Eh was found to satisfy 0 ≤ Enormal ≤ 1. As enargite becomes more abundant than chalcopyrite, the optimal Eh for the greatest Cu dissolution was shifted to higher values. Overall, modifying the Eh level by adjusting AC doses to maximize Cu solubilization from the concentrate of complex mineralogy was shown to be useful.
Highlights
To satisfy the world’s increasing copper demand, refractory primary copper sulfides, represented by chalcopyrite (CuFeS2), are considered a critical copper source
Ahead of the present study on chalcopyrite, we have reported the catalytic mechanism of Activated Carbon (AC)-assisted bioleaching of enargite concentrate (37.4% enargite and 47.3% pyrite) with moderately thermophilic microorganisms at 45 ◦C [25]
By controlling at Eh < 700 mV, the pyrite dissolution was largely suppressed, which in turn enabled a steady and continuous dissolution of enargite [25]. By combining these findings on the AC-assisted enargite bioleaching mechanism [25], the second objective of the present study was set to test three types of chalcopyrite/enargite-bearing complex concentrates for the AC-assisted bioleaching in order to compare and clarify their leachability with regard to the Eh profile
Summary
To satisfy the world’s increasing copper demand, refractory primary copper sulfides, represented by chalcopyrite (CuFeS2), are considered a critical copper source. Chalcopyrite constitutes a dominant component of porphyry copper deposits and accounts for approx. On the one hand, such surface passivation layers were suggested to hinder chalcopyrite chemical leaching (e.g., [3,4,5]). It was suggested that porous S0 layers do not impede the leaching efficiencies [4,6,7,8]. It is generally recognized that one of the most critical factors ruling the chalcopyrite leaching efficiency is the solution redox potential (Eh)
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