Abstract:

The growing interest towards the sustainable recovery of metals is driven by environmental and economic limitations of conventional extraction methods. This has led to the exploration of bioleaching as a viable and promising greener alternative. The extraction of Mn from low-grade manganese ore (LGMO) is a significant challenge due to its complex ferruginous mineralogy, lower Mn and high Fe content. This study investigates the potential of biochar as a solid electron shuttle to enhance the anoxic bioleaching of manganese from LGMO using manganese reducing bacterial consortium (MRC).

Biochar, a banana peduncle based carbon composite, has been studied for its ability to transfer electrons between the bacterial consortia (MRC) and iron rich manganese oxides. The study investigated the impact of key parameters, including biochar concentration, leaching time, pulp density and the effect of agitation on the recovery of Mn. Results showed that increasing biochar concentrations up to 0.1% (w/v) led to a clear enhancement in manganese extraction, with saturation at 0.2% (w/v). The inclusion of biochar significantly accelerated the reductive dissolution of Mn from 6.71% (control) to 23.81% in 30 days of incubation without agitation, and the leaching was further enhanced upto 54.33% under similar conditions by providing agitation to the system. During the anoxic bioleaching, the specific glucose consumption rate was estimated to be 27 mg g⁻¹day⁻¹, which is significantly lower than the rates reported previously for other bioleaching methods. XRD was conducted to confirm the metal oxide phase transformation during bioleaching. The influence and interaction of MRC on biochar were confirmed using RAMAN spectroscopy and FTIR analysis.

Overall, this study demonstrates that biochar can be effectively employed as an electron shuttle to enhance the bioleaching of low-grade manganese ores, offering a greener, more efficient alternative to conventional extraction methods. This work lays the groundwork for scaling up biochar-assisted bioleaching processes, potentially revolutionizing the treatment of low-grade ores in the mining industry.

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Ms. Subhashree Sahoo