Thesis (Ph. D.)--University of Wisconsin--Madison, 1981. / Typescript. Vita. Description based on print version record. Includes bibliographical references (leaves 204-210).

The leaching of goethite in solutions of perchloric, sulphuric, and hydrochloric acids and in perchloric acid in presence of sulphur dioxide has been investigated. Suspensions of goethite powder (-65, +150 mesh) were leached over a wide range of temperatures, acid concentrations and sulphur dioxide pressures. Strong solutions of hydrochloric acid leached goethite powder more rapidly than equivalent solutions of sulphuric acid, whilst at low concentrations sulphuric acid was the more active reagent. Perchloric acid was found to leach the mineral only very slowly. The rate of dissolution was found to increase with time in the early stages of leaching with all concentrations of sulphuric acid, with strong solutions of hydrochloric acid, and with perchloric acid solutions containing sulphur dioxide. This phenomenon has been correlated with changes in the surface morphology of the goethite during leaching. The rate data derived from the observed results have enabled the effects of temperature, acid type, concentration and partial pressure of sulphur dioxide on rate of leaching to be studied. A common mechanism of leaching is proposed in which protonation of the hydrated oxide surface is followed by adsorption of an anion and desorption of the ferric-anion complex. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The selective dissolution of pyrolusite (MnO₂) in presence of goethite (FeO.OH) in aqueous ammoniacal ammonium carbamate solution has been investigated; various reducing agents were studied, in particular sodium sulfite (Na₂SO₃) and hydrazine hydrate (N₂H₄.H₂O). Sodium sulfite was found to be an unsatisfactory reducing agent for both goethite and pyrolusite, for the leaching rate decreased steadily with time to an impractical level because of the limited solubility of the reactions products. Hydrazine hydrate was an effective reducing agent for pyrolusite even at low temperature, whereas goethite required much higher temperatures for any appreciable dissolution. A one hour leach at 35°C dissolved 90 per cent of the pyrolusite but only 0.1 per cent of the goethite. Additions of ammonium phosphate had no effect on the rates, there being no phosphate detected in the leach liquor. An activation energy of 17.0 K cal/mole was found for the dissolution of pyrolusite with hydrazine. A reaction mechanism for the leaching of pyrolusite with hydrazine was proposed in which a reduction reaction on the surface of the mineral was the rate-determining step. It was possible to recover manganese from solution with oxygen as an amorphous MnO₂ precipitate. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The direct dissolution of various samples of hematite and goethite in hydrochloric, sulphuric and perchloric acids using a particulate (-65, + 150 mesh) feed has been investigated. The reductive dissolution of hematite samples using acidified sulphur dioxide solutions was also investigated. Goethite and hematite leached by a common mechanism with comparable rates. The various shapes of leaching curves obtained for different hematite samples can be correlated with their grain size to particle size ratio. An increasing rate of dissolution was found for a large number of grains per particle, and an approximately constant rate was observed for particles containing relatively few grains per particle. The effect of acid concentration on the rate of dissolution for different acids has led to the modification of a previously proposed chemical mechanism dependent on the complexing power of the anion of the acid with iron. The increase in dissolution rate for a weak complexer was proportional to the acid concentration e.g. HCIO₄, and for a strong complexer, if was proportional to the acid concentration squared e.g. HCl. The rate of dissolution in the presence of sulphur dioxide was extremely rapid compared with the acid dissolution. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Thesis supervisor: Michelle M. Scherer. Includes bibliographic references (p. 168-179).

This study investigated the adsorption properties of roxarsone, an organoarsenic poultry feed additive, to goethite and kaolinite in order to determine what role mineral surfaces play in controlling the mobility of roxarsone in watersheds where poultry litter is applied. Adsorption edge experiments for goethite and kaolinite showed a dependence on pH for both As(V) and roxarsone. This pattern can be explained by the pH-dependent changes in the mineral surface charge and protonation of the aqueous arsenic species. Isotherms for As(V) and roxarsone on goethite and kaolinite show surface saturation for As(V), but not for roxarsone. The overall adsorption patterns show that As(V) and roxarsone adsorption is similar, suggesting that the arsenate functional group is the dominant control on roxarsone adsorption. However, there are some subtle differences between adsorption of As(V) and roxarsone, which can be explained by the relative sizes of the molecules, the presence of functional groups, differences in solubility, and differences in the type of adsorption (monolayer versus multilayer). Comparison of roxarsone adsorption to goethite and kaolinite reveals that at the low concentrations of roxarsone that are expected to leach from poultry litter into soil water, goethite adsorbs roxarsone more strongly then kaolinite. However, due to the abundance of kaolinite, both are important controls on roxarsone mobility. / Master of Science

Mercury is a toxic metal that has been released to the environment through numerous industrial activities. It can exist in various solid, aqueous, and gaseous forms. Volatile Hg(0) is frequently present at the source of a spill where it behaves as a dense non-aqueous phase liquid (DNAPL) contaminant that can change oxidation state and speciation via chemical or biological reactions. Mercury speciation is a key factor determining the mobility, bioavailability, and toxicity of Hg in the environment. Previous research has demonstrated that In Situ Thermal Desorption (ISTD) can be used in various modes to treat soil contaminants including Hg(0). The application of ISTD and other remediation processes must incorporate potential speciation during remediation and assess mobility of any mercury remaining in the soil post-remediation. However, research examining the impact of mercury speciation on ISTD processes is limited. The goals of this research are to investigate the fate and transport of mercury in soils from the source where concentrations are expected to be high to dilute solutions associated with down gradient groundwater, lakes, and rivers. For high concentrations of mercury, equilibrium speciation has been investigated to identify potential transformations at high temperatures consistent with those applied in ISTD processes. A model has been developed that describes mercury speciation over a range of environmental conditions. At low mercury concentrations, competitive Hg(II) adsorption on the soil minerals, goethite and gibbsite, has been evaluated over a range of experimental conditions. Models describing Hg(II) adsorption and aqueous speciation have been developed to provide a tool for predicting the fate and transport of residual mercury after thermal remediation applications. The results of these studies demonstrate that ISTD is feasible, but the off-gas speciation will depend on both the applied temperatures and the soil composition and redox conditions of the site. Pure phase mercury was predicted to be vaporized at temperatures well within the range of typical ISTD processes. The adsorption of trace levels of Hg(II) remaining after ISTD was successfully modeled on goethite and gibbsite using the 1-pK CD-MUSIC model. / text

The adsorption of oleate at the goethite-water interface has been studied. In addition, the interactions of oleate at other mineral-water interfaces were considered. / Mainly by means of a literature review, a bulk equilibrium solubility diagram for oleic acid in water was constructed, as a function of total oleate concentration and pH. The competing bulk precipitation equilibria for oleic acid mineral phases such as iron (III) oxides, barite, calcite and fluorite and the relevant metal oleates, were considered graphically. Literature, adsorption, flotation recovery, electrokinetic and infrared work was examined in the light of this bulk precipitation data. It was found that many of these studies have been carried out in pH-concentration regions where bulk equilibrium phase changes were occurring, such as precipitation of oleic acid or of metal oleates. Adsorption behaviour in these systems was obscured by the bulk precipitation effects. / Adsorption experiments were carried out with oleate in the presence of goethite, choosing pH and concentration such that bulk precipitation effects were not important. Electrostatic and hydrophobic interactions as well as chemisorption, appeared to be of importance in the adsorption process. / A new approach for surfactant adsorption, a multiple equilibrium model, was suggested to describe quantitatively, the adsorption of oleate at the goethite-water interface. This approach considers oleic acid solution equilibria. The adsorption process is represented by the reaction of neutral goethite surface sites with oleate and protons in the manner of solution equilibria. A good fit was obtained to the experimental data. The model predicts that the acid-soap species HOI2 is the most important adsorbed species.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1955. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Bibliographies: leaves 39-43, 78-80.

In situ chemical oxidation using permanganate is an increasingly employed approach to organic contaminant remediation at hazardous waste sites. Manganese dioxide (MnO2) particles form as a by-product of the reaction of permanganate with contaminants and naturally-reduced subsurface materials. These particles are of interest because they have the potential to deposit in the subsurface and impact the flow regime in/around permanganate injection, including the well screen, filter pack, and the surrounding subsurface formation. Control of these particles can allow for improved oxidant injection and transport, and contact between the oxidant and contaminants of concern. Sodium hexametaphosphate (HMP) has previously been identified as a promising aid to stabilize MnO2 in solution when included in the oxidizing solution, increasing the potential to inhibit particle deposition and impact subsurface flow. The goal of the experimental studies described herein was to investigate the ability of HMP to prevent particle deposition in transport studies using four different types of porous media. Permanganate was delivered to a contaminant source zone (trichloroethylene) located within four different media types with variations in sand, clay, organic carbon, and iron oxides (as goethite) content. Deposition of MnO2 within the columns was quantified with distance from the source zone. Experiments were repeated in replicate columns with the inclusion of HMP directly with the oxidant delivery solution, and MnO2 deposition was again quantified. While total MnO2 deposition within the 60 cm columns did not change significantly with the addition of HMP, deposition within the contaminant source zone decreased by 25-85%, depending on the specific media type. The greatest differences in deposition were observed in the goethite-containing and clay-containing columns. Columns containing these two media types experienced completely plugged flow in the oxidant-only delivery systems; however, the addition of HMP prevented this plugging within the columns, increasing the oxidant throughput.