Date of Award

2025

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy in Chemical Engineering (PhD)

Administrative Home Department

Department of Chemical Engineering

Advisor 1

Timothy C. Eisele

Committee Member 1

S. Komar Kawatra

Committee Member 2

Lei Pan

Committee Member 3

Snehamoy Chatterjee

Committee Member 4

Stephen Techtmann

Abstract

Manganese is critical in the steel and battery industries, but the United States has not produced it since 1974. While potential manganese ore deposits are available in the US, mining them with the current technology does not result in a competitive product. This dissertation explores the development and evaluation of a novel in-situ bioleaching process that uses anaerobic organisms and biomass-derived reagents to extract manganese from low-grade ore bodies without the use of purchased toxic chemicals.

The research begins with a literature review of in-situ manganese bioleaching, addressing biological dissolution mechanisms, manganese-reducing organisms, nutrient sources, manganese precipitation methods, and challenges in field-scale implementation. It then extends previous work at Michigan Technological University that demonstrated that microorganisms could dissolve manganese at laboratory scale.

A pilot plant study demonstrated successful manganese extraction using a mixed-culture of manganese-reducing organisms and fen with organics produced by decomposition of biomass from Typha latifolia, which was fermented to generate organic acids. The resulting manganese-rich leachate was treated using electrolytic oxidation for the recovery of high-purity manganese oxide. This approach achieved over 90% product purity with minimum iron contamination. In addition to manganese, the same anaerobic organisms were used to evaluate their potential for extracting iron from iron ore tailings, when manganese is not present.

Direct leaching of manganese by microorganisms leads to loss of manganese as manganese carbonate. To overcome the challenge of manganese carbonate formation, a two-stage bioleaching strategy was developed using bio-solubilized iron as a reductant. In this approach, metal-reducing organisms were first used to dissolve iron, producing a Fe2+ rich solution. This iron-bearing solution was then used to reduce and solubilize manganese oxides. The two-stage method significantly enhanced manganese dissolution while effectively preventing manganese carbonate precipitation.

A techno-economic analysis based on pilot-scale investigations demonstrated that the in-situ bioleaching process is both technically scalable and economically competitive with conventional extraction methods. Low capital and operating costs, along with strong financial performance metrics, demonstrate that the process is well-suited for industrial-scale implementation. Overall, this research demonstrates that in-situ bioleaching is a technically feasible, economically viable, and scalable method for extracting manganese from low-grade ores.

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