IMPACT OF ENGINEERED TITANIUM DIOXIDE AND ZERO-VALENT IRON NANOPARTICLES ON CARBON DIOXIDE FIXATION BY AN AQUATIC MICROBIAL COMMUNITY: EFFECT AT ENVIRONMENTALLY RELEVANT CONCENTRATIONS

Author

Pratima Adhikari, Southern Illinois University CarbondaleFollow

Date of Award

9-1-2021

Degree Name

Master of Science

Department

Civil Engineering

First Advisor

Liu, Jia

Abstract

AN ABSTRACT OF THE THESIS OFPratima Adhikari, for the Master of Science degree in Civil Engineering, presented on June 30, 2021, at Southern Illinois University Carbondale.TITLE: IMPACT OF ENGINEERED TITANIUM DIOXIDE AND ZERO-VALENT IRON NANOPARTICLES ON CARBON DIOXIDE FIXATION BY AN AQUATIC MICROBIAL COMMUNITY: EFFECT AT ENVIRONMENTALLY RELEVANT CONCENTRATIONSMAJOR PROFESSOR: Dr. Jia LiuThe purpose of this study is to investigate the effect of engineered nanoparticles (ENPs) on carbon dioxide reduction by aquatic microbial communities. Titanium dioxide (TiO2) nanoparticles and nanoscale zero-valent iron (nZVI) of different concentrations (10, 1, 0.1, 0.01, 0.001 mg/L and control), both environment-relevant and higher than the environmental concentrations as prediction for future concentrations, were selected. An anaerobic microbial community from the campus lake of Southern Illinois University Carbondale was studied. Different humic acid concentrations (100, 10, and 1 mg/L) were considered under pH 6.0 - 9.0. The research was conducted in two phases: 1) Transformation of TiO2 and nZVI nanomaterials in simulated environmental conditions, and 2) Inoculation of microbial community to the pristine nZVI nanoparticles as well as environmentally transformed nanoparticles, i.e. TiO2 and nZVI, to study their impacts on carbon dioxide reduction. The nanoparticles were suspended in a medium that simulates the aqueous environment for the growth of anaerobic bacteria. The nanoparticle suspension was kept in the simulated medium for 12 h light and 12 h dark for a period of one month and the transformed nanoparticles were then used for the study in its interaction with the microbial community. When the microbial community was inoculated, carbon dioxide gas was purged inside the vials to ensure no oxygen present in the vials. These samples were then monitored for a period of 2-3 weeks to see the carbon dioxide reduction. The results showed that the transformed nZVI had significant impact on the reduction of carbon dioxide concentration, whereas pristine nZVI and transformed TiO2 nanoparticles did not have significant impact on the reduction of carbon dioxide concentrations in the vials. The spearman correlation coefficient value showed that there is a somewhat monotonic relation between the reduction of carbon-dioxide and organic carbon formation for transformed TiO2 nanoparticles, however, for the transformed nZVI no such correlation was found. From this study, we can state that certain microbial communities can increase the rate of carbon dioxide fixation when exposed to the transformed zerovalent iron nanoparticles. This study can provide guidance on the industrial usage and environmental release of ENPs that are related to carbon fixation.