Iron: From Synthesis, Characterization, and Application of Sulfide Green Rust to Viability in Arsenic Water Treatment
Colvin, Vicki L.
Doctor of Philosophy
Iron chemistry plays an important role in our world. At the nanoscale, iron oxide nanoparticles (nanomagnetite) have many inherent physical or chemical characteristics that drive potential solutions to real-world problems; appropriation of nanomagnetite’s properties as a “scaffold” for chemistry would further enhance its effectiveness in applications. In an effort to make use of nanomagnetite’s physical properties, a new “Sulfide Green Rust” (sGR) has been synthesized from magnetic iron nanoparticles. The material is crystalline, reactive due to high iron(II) content, and dissolves in the aqueous phase. Nanomagnetite’s magnetic properties were also observed to persist after sGR synthesis. X-ray absorption spectroscopy (XAS) confirmed the synthesis of this new FeS2-like material. The crystallinity, composition, and various physical characteristics were examined using a host of techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Mössbauer spectroscopy, CRYO-TEM, Raman spectroscopy, and ultraviolet-to-visible (UV-Vis) spectroscopy. To demonstrate its use, the material was then subjected to a test of its reactive potential, namely water remediation of an orange dye contaminant. Iron serves a function at the macroscale as well regarding water treatment, since iron coagulation-filtration is the industry standard for arsenic treatment. Determining a technology’s merit as a solution goes beyond technical concern, however, as environmental and economic aspects also play important roles. Life Cycle Analysis, or LCA, methodology works to holistically compare each of these facets from cradle to grave. To address the current arsenic drinking water requirements at a case setting in Hungary, the LCA technique was applied on two example arsenic removal technologies, both coagulation-filtration and adsorption. 9 out of 10 considered impact categories tended to favour coagulation-filtration in this small municipality study, however realistic variations in water chemistry and product characteristics led to some overlap of their environmental impact. Electricity did not have a large direct impact, regeneration of the adsorption technology was very costly, and adsorption’s hazardous waste was not reduced compared to coagulation-filtration. Coagulation-filtration is also the cheaper of the two technologies; its highest cost is that of waste disposal, while the highest single expense modeled is that of adsorption media cost.