Intensified bioleaching of chalcopyrite concentrate using adapted mesophilic culture in continuous stirred tank reactors

Abstract

The bioleaching of chalcopyrite concentrate, intensified by the adapted mesophilic culture in the continuous stirred tank reactors (CSTR) was investigated. The cumulative bioleaching efficiency of copper was found to be increased from 34.8% to 49.3% in CSTR-1, 40.3% to 71.2% in CSTR-2, and 44.3% to 73.8% in CSTR-3, while the temperature was elevated from 30 to 37 °C, respectively; whereas, the pulp density (10%, w/v), agitation speed (350 rpm), aeration (400 cc/min), and retention time (7 days across the three reactors) were also optimized to keep constant. Further, the activation energy calculated for copper dissolution under the continuous flow indicated that the surface-diffusion was the overall rate-limiting step for the bioleaching process. Instrumental analysis of solid samples could reveal the degradation pathways of chalcopyrite bioleaching as: CuFeS₂ → Cu₂S → Cu_0.3333Fe_0.6667S → H₉Fe₃O₁₈S₈. It follows a complex mechanism that includes the occurrence of polysulfide and cooperative mechanism along with the passivation onto mineral surfaces.

Keywords: Bioleaching mechanism; Chalcopyrite; Continuous stirred tank reactors; Mesophilic consortia; Microbial intensified leaching; Rate-limiting step.