Unveiling the potential of Glutamicbacter nicotiana for enhanced bioleaching of nickel and valuable metals from low- and high-grade nickeline ores

This study explores the utilization of three heterotrophic bacteria, isolated from iron mine wastewater and tailings, for the bioleaching of low- and high-grade nickel-bearing arsenic ores. The objective was to assess the leaching potential of these bacteria strains in extracting nickel, cobalt, arsenic, and copper ions from nickeline samples at varying pulp densities (0.5%, 0.8%, 1.1%, and 3%). A comparative analysis was conducted to evaluate the efficiencies of these isolates, including their performance relative to each other, the supernatant (spent medium), culture, and mixed strains. Under carefully controlled experimental conditions, all the bacterial strains exhibited remarkable leaching capabilities. Notably, Glutamicbacter nicotiana emerged as the most effective strain among them. Glutamicbacter nicotiana demonstrated impressive extraction rates, reaching up to 100% for nickel, 16% for cobalt, and 73% for arsenic in the low-grade sample. Similarly, in the high-grade sample, it achieved extraction rates of up to 70% for nickel, 62% for cobalt, and 16% for arsenic. In contrast, the control leaching experiment yielded minimal dissolution of the target elements, with only 0.33% for nickel, 1.2% for cobalt, and 0.4% for arsenic. To comprehensively characterize the untreated and bioleaching residue samples, various analytical techniques were employed, including SEM-EDS, FE-SEM, and XRD. These methods enabled a thorough investigation of the samples' structural and chemical composition. Additionally, HPLC analysis detected the presence of amino acids, such as glutamic acid, which were produced by the microorganisms involved in the bioleaching process. Furthermore, the study incorporated kinetic modeling to understand the factors influencing the bioleaching of both low- and high-grade samples. The results indicated that chemical control constituted the rate-limiting factor in the bioleaching process.