Effect of Metal Speciation in Fly Ash on Environmentally Persistent Free Radical Formation

Abstract

Waste incineration and Superfund sites lead to the formation of pollutants harmful to both the environment and human health. Environmentally Persistent Free Radicals (EPFRs) are a class of newly discovered radical pollutants known to form on combustion by-products such as fly ash and particulate matter. EPFRs are rapidly gaining attention for their harmful effects on the environment and human health. Previous research has shown the formation of EPFRs through surface-mediated reactions with transition metal-oxides on particulates. The work presented in this dissertation explores the relationship between fly ash composition and EPFR formation. Fly ash production occurs from combustion systems, namely waste incinerators. Waste composition varies widely throughout the globe, which changes the composition of fly ash and its associated pollutants. In Chapter 4, the thorough characterization of real world fly ashes from municipal and medical waste incinerators is explored and includes EPFR concentrations, elemental composition and particle characterization. EPFR variability found among real world fly ashes is heavily influenced by fly ash composition. Based on the findings from the real world fly ashes, a model system was developed to further understand the role of sulfur in the formation of EPFRs and is described in Chapter 5. Sulfur species, in the form of ammonium sulfate and sulfur dioxide, have a major influence on EPFR formation. In Chapter 6, a remediation method for mining influenced water using Chitin and sulfate-reducing bacteria is presented. The work done at LSU confirmed sulfur reduction, which indicated a successful remediation of heavy metals and sulfates from the water.