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Browsing by Author "Voelz, Jeanette"

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    Classifying Iron in Redox Reactions between Iron-Bearing Minerals and Environmental Contaminants
    (2019-08) Voelz, Jeanette
    Iron-bearing minerals are ubiquitous in the environment and are important in many reactions with environmental contaminants. The ability to classify iron in various mineral phases and in aqueous media is important for assessing iron cycling in natural processes and in processes influenced by anthropogenic activities. Presented herein is a review of iron classification by chemical dissolution and aqueous quantification methods. This review considers a breadth of dissolution studies and outlines these methods in an effort to promote accessibility and provide standards for comparisons across data sets. Solid-state characterization methods are also important for classifying iron. In the reaction of a model nitrobenzene contaminant and Fe(II) adsorbed to hematite, goethite may form as the oxidative mineral growth phase, which affects the reactivity of the mineral surface. A quantitative analysis method using X-ray diffraction and calibrated standards of goethite and hematite was developed to assess the degree of goethite formation in post-reaction solids. This formation was dependent on the distribution of Fe(II)-activated surface sites, and more goethite formed in conditions having high density of these sites. In suspensions containing organic carbon, however, the oxidative growth on hematite takes on a rough morphology and/or shrinks the domain size of the acicular goethite structures. Consequently, the change in morphology render the XRD analysis method ineffective at quantifying goethite content in post-reaction solids where organic carbon was present. Solid-state analyses and chemical dissolution methods are complimentary techniques for classifying iron in iron-bearing mineral specimens, especially for specimens of complex mineral content. Using these techniques together can help to identify promising materials as candidates for remediation reactions with environmental contaminants. A study presented herein assesses the use of iron-bearing minerals for reaction with sulfide from industrial aqueous waste streams and compares the reaction characteristics against material characteristics determined by chemical dissolution and XRD. The results of this study show that iron-bearing minerals with otherwise low economic value may have use in contaminant remediation applications.