Date of Award

2024

Document Type

Open 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

Kyle Griffin

Committee Member 2

Stephen M. Techtmann

Committee Member 3

Lei Pan

Abstract

Manganese extraction by biological methods is a green and economical way to produce manganese from low as well as high grade manganese ores. This is especially important for US ores, which are primarily either small in extent, low-grade with a high iron content, or both. They are therefore not suitable for conventional mining, which is very capital-intensive and requires a large up-front investment and are therefore imported at high costs. The goal is therefore to develop a process that can be applied at small scales, with minimal startup costs, and low equipment and labor requirements. It is also critical to minimize environmental impacts, and so it is desirable to use minimal excavation and little or no toxic chemicals.

Manganese extraction requires a reduction of manganese in its naturally occurring low-solubility oxidation states (+3, +4) to its higher-solubility +2-oxidation state. Once the manganese is reduced, it can be selectively dissolved and isolated from the ores. Many microorganisms have been known to reduce manganese from ores and there are still more that are being investigated. These microorganisms have been found to reduce manganese in aerobic as well as in anaerobic conditions.

This dissertation will first review the various methods that have been studied thus far to make biological manganese extraction viable to be commercialized. This includes investigation of the form of reduction that took place, that is, direct or indirect; the parameters affecting the reduction process, such as pH, nutrient media, ore size, and inoculum size; and the microorganisms involved in the process.

Next, the potential for a low-impact bioleaching process will be examined. Studies in this paper include the use of native microorganisms found in the Keweenaw peninsula of Michigan, USA, to extract manganese from high and low grade ores. Decomposing cattails (Typha latifolia) provide a natural food source for microorganisms. Parameters such as nutrient media type, ore size, flowrate, and pH, which affect efficiency of manganese extraction are studied. Key findings include elimination of carbon dioxide interaction with dissolved manganese ions by increasing flowrate, reducing manganese carbonate formation and increasing manganese production efficiency.

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