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Transformation of iron oxide and hydroxide phases and its effects on contaminant mobility
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| Title: | Transformation of iron oxide and hydroxide phases and its effects on contaminant mobility |
| Other Titles: | 鉄酸化物および水酸化物の相変換と汚染物質の移行に対する影響 |
| Authors: | Francisco, Paul Clarence Magdael Browse this author |
| Issue Date: | 26-Sep-2016 |
| Publisher: | Hokkaido University |
| Abstract: | Iron oxides and hydroxides [iron (hydro)oxides] are one of the most common phases in the earth'scrust. Due to their ubiquity in the natural environment, they have long been recognized for their ability toregulate the concentrations of hazardous elements in nature. Furthermore, the relative ease with which theycan be synthesized under controlled conditions has made them attractive materials for industrial applicationslike water-treatment and contaminant remediation. The feasibility of iron (hydro)oxides as long-term sinksfor contaminants both in nature and in engineered environments depend on their behavior during phasetransformation. In this work, the effects of foreign ligands on the transformation behavior of iron(hydro)oxides as well as on the behavior of contaminants were investigated.Chapter 1 reviews the literature on the general properties of iron (hydro)oxides, their distributions,recognized applications as well as current knowledge on transformation mechanisms. In this chapter, thefactors governing iron (hydro)oxide transformation and contaminant transport are identified.Chapter 2 focuses on the effects of Si, one of the most common ligands present in the naturalenvironment on the transformation kinetics of ferrihydrite. In this work, it was observed that even a smallamount of Si significantly retards the crystallization of both goethite and hematite. This work provides newinsights on the impacts of Si on ferrihydrite solubility as well as on the morphology of goethite and hematite.New quantitative data on transformation rates as well as activation energies are also presented in this chapter,which may be useful in predicting the crystallization behavior of goethite and hematite in alkalineenvironments (e.g. high-level waste disposal repositories).Chapter 3 focuses on the behavior of selenite taken up by ferrihydrite during the crystallization ofgoethite and hematite, a contaminant originating from weathering of sedimentary rocks as well as from highlevelwastes. In this work, a fraction of the selenite co-precipitated with ferrihydrite was released duringtransformation, with another fraction becoming immobilized within the crystalline phases. A combination ofchemical extraction experiments as well as diffraction and spectroscopic studies show that the retentionmechanism involves the incorporation of selenite within the crystalline phases. The findings presented in thischapter provides insights that can be used to predict the behavior of selenite or other contaminants during theevolution of iron (hydro)oxide sorption substrates.iiDrawing from the insights presented in Chapters 2 and 3, Chapter 4 focuses on the effect of Si on thebehavior of selenite during ferrihydrite transformation. The retardation of transformation by Si results in theretardation of selenite release back into solution. Furthermore, the presence of Si results in the release ofmore selenite back into solution. These observations are attributed to the competitive effect of Si for uptakesites on iron (hydro)oxide surfaces.This work presents important insights on the stability of iron (hydro)oxides and their capability toretain contaminants in the presence of other elements. These findings may be useful in a broad range ofcontexts, such as on the behavior of iron (hydro)oxides in nature and in engineered environments. |
| Conffering University: | 北海道大学 |
| Degree Report Number: | 甲第12468号 |
| Degree Level: | 博士 |
| Degree Discipline: | 工学 |
| Examination Committee Members: | (主査) 教授 佐藤 努, 教授 五十嵐 敏文, 教授 廣吉 直樹, 准教授 東條 安匡, 准教授 大竹 翼 |
| Degree Affiliation: | 工学院（環境循環システム専攻） |
| Type: | theses (doctoral) |
| URI: | http://hdl.handle.net/2115/63437 |
| Appears in Collections: | 課程博士 (Doctorate by way of Advanced Course) > 工学院(Graduate School of Engineering)
学位論文 (Theses) > 博士 （工学）
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