This M.A.Sc. work focuses on the development of a sensor to operate at industrially relevant conditions, directly in autoclaves, to generate accurate online free acidity estimates. The main goal is to obtain accurate (within 5% from titrated) free acid estimates at leach temperature while compensating for various metals in solution at high solid loadings. The electrodeless conductivity sensor and calibration technique that were developed in previous work have been improved upon for operation in slurry systems. The sensor operates at temperature on the basis of induction currents and is suitable for very concentrated solutions containing solid dispersions. Three systems have been investigated: limonitic feeds, limonite-saprolite blends, and a converter slag feed. Up to 40 wt.% solids were tested with investigation carried out from 25°C to 260°C. High quality estimates of acidity were produced for all systems studied, with the average difference between measured and titrated acidities being within 5%.

This M.A.Sc. work focuses on the development of a sensor to operate at industrially relevant conditions, directly in autoclaves, to generate accurate online free acidity estimates. The main goal is to obtain accurate (within 5% from titrated) free acid estimates at leach temperature while compensating for various metals in solution at high solid loadings. The electrodeless conductivity sensor and calibration technique that were developed in previous work have been improved upon for operation in slurry systems. The sensor operates at temperature on the basis of induction currents and is suitable for very concentrated solutions containing solid dispersions. Three systems have been investigated: limonitic feeds, limonite-saprolite blends, and a converter slag feed. Up to 40 wt.% solids were tested with investigation carried out from 25°C to 260°C. High quality estimates of acidity were produced for all systems studied, with the average difference between measured and titrated acidities being within 5%.

In the production of base metals by smelting of sulphide ore concentrates, large amounts of iron are rejected with iron silicate slags. These slags contain Ni, Cu and Co in concentrations up to several percent units. Extraction of the entrapped base metals using high pressure oxidative acid leaching (HPOXAL) was investigated in this work. Crystalline slags containing fayalite (Fe2SiO4), magnetite (Fe3O4), silica (SiO2) and matte (MeSn<1) were found to be highly amenable to leaching at 250°C, 90 psi (6.2 bar) O2 partial pressure and 70 g/L initial H2SO4. Extractions of Ni, Co and Cu exceeded 90% within 15-20 min and arrived at 95-97% after 45 min. The residues of leaching were identified as aggregates of crystalline hematite (Fe2O3) and amorphous silica. Dissolution of fayalite and magnetite was shown to be acid driven. Since HPOXAL operates with substoichiometric additions of sulphuric acid (10-20% of the stoichiometric requirement), acid regeneration facilitated by iron oxidation and hydrolysis is crucial to high rates of leaching. Low acidities (<10 g/L) were shown to cause precipitation of ferrous sulphate, slowing acid regeneration and slag dissolution. Elevated acidities (>70 g/L) result in excessive concentrations of Fe(III) in the leach solution, complicating downstream processing. The use of pyrrhotite tailings, an environmentally hazardous waste, as a substitute of sulphuric acid in slag leaching was investigated. Oxidative co-leaching of pyrrhotite tailings with naturally cooled converter slag at 250°C, 90 psi (6.2 bar) O2, 68 g/L equivalent H2SO4 was shown to have kinetics comparable to adding sulphuric acid with final extractions reaching 95-97% in 45 min. Granulation of slag melt can produce an amorphous solid solution of SiO2 and metal oxides. Amorphous slag is not amenable to HPOXAL due to the formation of a passive layer of silica. Leaching of amorphous slag at low temperatures was shown to proceed nearly to completion. The difference in the leachability of amorphous slag at high and low temperatures is explained in terms of the rate of silicic acid re-polymerization leading to closure of pores in the leached layer.

In the production of base metals by smelting of sulphide ore concentrates, large amounts of iron are rejected with iron silicate slags. These slags contain Ni, Cu and Co in concentrations up to several percent units. Extraction of the entrapped base metals using high pressure oxidative acid leaching (HPOXAL) was investigated in this work. Crystalline slags containing fayalite (Fe2SiO4), magnetite (Fe3O4), silica (SiO2) and matte (MeSn<1) were found to be highly amenable to leaching at 250°C, 90 psi (6.2 bar) O2 partial pressure and 70 g/L initial H2SO4. Extractions of Ni, Co and Cu exceeded 90% within 15-20 min and arrived at 95-97% after 45 min. The residues of leaching were identified as aggregates of crystalline hematite (Fe2O3) and amorphous silica. Dissolution of fayalite and magnetite was shown to be acid driven. Since HPOXAL operates with substoichiometric additions of sulphuric acid (10-20% of the stoichiometric requirement), acid regeneration facilitated by iron oxidation and hydrolysis is crucial to high rates of leaching. Low acidities (<10 g/L) were shown to cause precipitation of ferrous sulphate, slowing acid regeneration and slag dissolution. Elevated acidities (>70 g/L) result in excessive concentrations of Fe(III) in the leach solution, complicating downstream processing. The use of pyrrhotite tailings, an environmentally hazardous waste, as a substitute of sulphuric acid in slag leaching was investigated. Oxidative co-leaching of pyrrhotite tailings with naturally cooled converter slag at 250°C, 90 psi (6.2 bar) O2, 68 g/L equivalent H2SO4 was shown to have kinetics comparable to adding sulphuric acid with final extractions reaching 95-97% in 45 min. Granulation of slag melt can produce an amorphous solid solution of SiO2 and metal oxides. Amorphous slag is not amenable to HPOXAL due to the formation of a passive layer of silica. Leaching of amorphous slag at low temperatures was shown to proceed nearly to completion. The difference in the leachability of amorphous slag at high and low temperatures is explained in terms of the rate of silicic acid re-polymerization leading to closure of pores in the leached layer.

This study investigated the effects of high intensity interval training (HIIT) and β-hydroxy-β-methylbutyric free acid (HMBFA) on the onset of neuromuscular fatigue in healthy young men and women. Thirty-seven subjects (22 men and 15 women; mean ± SD age = 22.8 ± 3.4yrs) completed an incremental cycle ergometer test (GXT) to exhaustion. During the GXT, electromyography (EMG) signals from the right vastus lateralis were recorded to determine the power output at the onset of neuromuscular fatigue (PWCFT), and peak wattage was used to assign individual training loads. After baseline testing (PRE), subjects were randomly assigned to one of three groups: control (C, n = 9), training with placebo (P, n = 14), or training with supplementation (S, n = 14). Subjects assigned to P and S completed 12 HIIT sessions over 4 weeks while subjects assigned to C were asked to maintain their normal diet and activity patterns. After 4 weeks, subjects returned for post-testing (POST). The PWCFT values (W) were determined using a DMAX method. The EMG amplitude root mean square (µVrms) values were used to generate a third-order polynomial regression (3PR) representing the increase in µVrms versus time of the GXT. The onset of fatigue (TF) was defined as the x-value (time, s) of the point on the 3PR that measured the maximal perpendicular distance from the line between the first and last data points. TF was used to estimate PWCFT according to the equation: PWCFT = PO + a · (n/N), where PO is the power output of the stage in which TF occurred, a is the increment in power output between GXT stages (25W), n is the difference (s) between TF and the beginning of the stage during which TF occurred, and N is the duration of a stage (120s). A two-way repeated measures ANOVA was used to identify group × time interaction for PWCFT. If a significant interaction occurred, one-way factorial ANOVAs were used. Fisher's least significant difference post hoc comparisons were performed between groups. If a significant main effect occurred, dependent samples t-tests with Bonferroni corrections (p = [0.05/3] = 0.017) were performed across time for each group. The two-way ANOVA resulted in a significant interaction (F = 6.69, p = 0.004). Follow-up analysis with one-way ANOVA resulted in no difference among groups at PRE (F = 0.87, p = 0.43), however a significant difference was shown for POST values (F = 5.46, p = 0.009). Post-hoc analysis among POST values showed significant differences between S and both P (p = 0.034) and C (p = 0.003). No differences (p = 0.226) were noted between P and C. Paired samples t-tests detected significant changes following HIIT for S (p < 0.001) and P (p = 0.016), but no change in C (p = 0.473). Results of this study indicate that HIIT was effective in delaying the onset of fatigue, but supplementation with HMBFA in conjunction with HIIT was more effective than HIIT alone. An increase in PWCFT represents an increase in the maximal power output an individual can sustain without eliciting fatigue. Therefore, HIIT can be used to improve performance in both endurance activities as well as intermittent sports. In addition, HMBFA supplementation is a simple method that can be used to maximize the benefits of HIIT. Acknowledgments: Metabolic Technologies, Inc. provided the supplement and funding for this study.