SEES Fellows: Sustainable Nanosilicon Production through the Electrochemical Reduction of Diatoms and Integration into Wastewater Remediation and Biofuel Industries PI: Steven N. Girard, University of Wisconsin Madison
Nanostructures of abundant and non-toxic silicon can serve a significant role in various renewable energy technologies, including solar cells, Li-ion batteries, and thermoelectric materials. To realize the potential of nanosilicon for renewable energy applications, mass quantities must be economically and sustainably produced. Current silicon production relies on an energy- and material- consuming carbothermal reduction process, in which the reaction between carbon and sand (silica) at very high temperatures yields metallurgical silicon and carbon dioxide. Metallurgical silicon is subsequently dissolved, refined, and recrystallized in multiple energy- and material-consuming steps to generate nanosilicon for renewable energy applications. For nanosilicon to be used for renewable energy, the large scale production of silicon must be redesigned from a sustainability perspective. I propose to develop an altogether new process of direct electrochemical conversion of nanosilica-to-nanosilicon that will be energy and material efficient, and therefore inexpensive and sustainable. In collaboration with industrial partner AlgaXperts, we will also analyze the scalability and feasibility of this approach through the integration into existing wastewater remediation and algae-for-biofuel industries by essentially recycling the nanostructured diatoms (silica) from these processes.
Intellectual Merit. A novel process of sustainable and direct nanosilicon production through the electrochemical reduction of nanostructured silica frustules of diatoms will be developed. The naturally nanostructured silica microshells of diatoms (unicellular algae) are inexpensive and easily obtained either from mined diatomaceous earth deposits or from diatom algal cultures. Under host mentor Prof. Song Jin, Department of Chemistry at UW-Madison, the proposed research seeks to develop electrochemical reduction of nanosilica within novel eutectic salt electrolytes, which will enable single-step nanosilicon production at very low temperatures, consuming considerably less energy. If the starting nanomorphologies can be retained following conversion to silicon, this process will represent the most sustainable means of nanosilicon production to date.
Broader Impact. The proposed research will be immediately useful for a variety of industrial applications and expose the SEES fellow new chemical techniques. We further propose harvesting specific diatom genera from industrial-scale algal cultures used for the bioremediation of wastewater effluent and production of lipids for biofuels. Obtaining specific diatom genera allow control over the types of nanostructures obtained. In collaboration with partner mentor Jun Yoshitani, President of AlgaXperts LLC, we will analyze the feasibility of the integration of these approaches at a Midwestern water treatment facility. Furthermore, this collaborative research will involve chemical analysis of the wastewater effluent nutrients, selectivity of specific genera in industrial-scale cultures, and analysis of the associated costs. The SEES fellow will gain a better understanding of the industrial considerations connected to implementing large-scale sustainability technologies.
Educational Outreach. In collaboration with Prof. Greg Nemet, Nelson Institute of Environmental Studies at UW-Madison, and Dr. Andrew Greenberg, Director of REU programs at UW-Madison, a highly interdisciplinary summer practicum focusing on public policy and sustainability science will be designed and implemented. Lessons learned in the primary research will be integrated into the REU summer practicum. In collaboration with Dr. Greenberg, underrepresented minority undergraduate researchers will be mentored by the SEES fellow in summer research projects related to the proposed research. The SEES fellow will gain experience in sustainability policy, teaching, course design, integration of teaching and research, and undergraduate mentoring.
