Utilization of Coal Through Microbial Electrolysis Cell (MEC) Systems And Bioleaching Approach

Author

Zeying Zhu, Southern Illinois University CarbondaleFollow

Date of Award

8-1-2018

Degree Name

Master of Science

Department

Civil Engineering

First Advisor

Liang, Yanna

Abstract

Coal is becoming more important both as an energy source and as the source of organic chemical feedstock in the 21st century. Combustion of coal certainly generates electricity; however, it is not sustainable for the current global energy crisis. More eco-friendly, sustainable ways of utilizing coal, need to be investigated. This study focuses mainly on biochemical conversion and bioleaching approaches. Burning coal will release toxic chemicals to impact the environment. It has greatly increased the level of carbon dioxide (CO2) in the air. Due to increasing concern of CO2, the first part of this thesis is focused on applying Microbial Electrolysis Cell (MEC) systems. These systems utilize coal and reduce CO2 at the same time, thus protecting the environment. To set up a two-chamber reactor, bacteria are used to degrade coal to CO2 in the anode chamber, and archaea uses CO2 to produce methane with an electron donor in the cathode chamber. Enriched communities were developed separately from whole microbial community driven from coal mine formation water. The bacteria community was enriched by adding 2-bromoethanesulphonate (BES) to inhibit methanogens’ growth. Archaea community was enriched by providing electrical potential and eliminating organic carbon source in the medium. Based on the next generation 16S rRNA sequencing results, the bacterial community was fully enriched with 100% bacteria species dominated by romboutsia lituseburensis (50.41%). Archaea community was enriched with the methane production species, which were electroactive and capable of using CO2. Only two species survived with exposure to defined medium. They were methanobacterium sp. (81.40%), and methanoculleus sp. (18.60%) within the archaea kingdom. With the coming age of 3D printing, this project aimed to utilize 3D printed technology in the MEC application. Non-toxicity of 3D printed reactors was confirmed in the experiments. In addition to that, printed bottles yielded to higher methane production with lower cost relative to glass bottles. Coal also contains a lot of valuable mineral and metal sources. The next part of this thesis dedicated to bioleaching method, especially recovery of Rare Earth Elements (REEs). Unlike traditional chemical leaching process, Candida bombicoca was used as the functioning microorganisms due to its high leaching efficiency. Feasibility of coal direct leaching was tested with comparison of different rankings of coal and coal fly ash. Among different rankings of coal, bituminous coal had higher mineral loss either treated or untreated, which were 71.56% and 49.82% respectively. However, with comparison to coal fly ash, coal fly ash had much higher mineral loss rate. According to ICP-MS quantifications, treated coal had higher leaching efficiency than untreated coal. Overall, this thesis study established two feasible, environmentally friendly and sustainable approaches to utilize coal. Further study and investigations are strongly encouraged in the form of two-chamber MEC application with the communities developed. More ICP-MS quantifications of REEs for more solids, liquids, and even cell residual samples could be studied for better leaching efficiency calculations.