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Surface spectroscopic techniques have been applied to facets of the flotation beneficiation and hydrometallurgical extraction of sulfide minerals to enhance the fundamental understanding of these industrially important processes. As a precursor to the determination of surface chemical composition, the sub-surface properties of some sulfide minerals that have not previously been fully characterised were also investigated. The electronic properties of ??-NiS and ??-NiS (millerite), Ni3S2 (heazlewoodite), (Ni,Fe)9S8 (pentlandite), CuFe2S3 (cubanite), CuFeS2 (chalcopyrite), Cu5FeS4 (bornite) and CuS (covellite) were investigated by conventional and synchrotron X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy augmented by ab initio density of state calculations and NEXAFS spectral simulations. Particular aspects studied included the relationship between sulfur coordination number and core electron binding energies, the higher than expected core electron binding energies for the sulfur in the metal-excess nickel sulfides, and the formal oxidation states of the Cu and Fe in Cu-Fe sulfides. It was concluded that the binding energy dependence on coordination number was less than previously believed, that Ni-Ni bonding was the most likely explanation for the unusual properties of the Ni sulfides, and that there was no convincing evidence for Cu(II) in sulfides as had been claimed. Most of the NEXAFS spectra simulated by the FEFF8 and WIEN2k ab initio codes agreed well with experimental spectra, and the calculated densities of states were useful in rationalising the observed properties. XPS, static secondary ion mass spectrometry (SIMS) and NEXAFS spectroscopy were used to investigate thiol flotation collector adsorption on several sulfides in order to determine the way in which the collector chemisorbs to the mineral surface, to differentiate monolayer from multilayer coverage, and to characterise the multilayer species. It was found that static SIMS alone was able to differentiate monolayer from multilayer coverage, and together with angle-resolved NEXAFS spectroscopy, was also able to confirm that 2-mercaptobenzothiazole interacted through both its N and exocyclic S atoms. The altered layers formed on chalcopyrite and heazlewoodite during acid leaching were examined primarily by means of threshold S KLL Auger electron spectroscopy, but no evidence for buried interfacial species was obtained.

The aim of this work was to determine whether a mechanism exists for bacterial oxidation of covellite (CuS) other than that involving cyclic reduction and oxidation of soluble iron, and to describe any such mechanism.It was thought likely that mechanisms of bacterial attack on CuS would also apply to other metal sulphides. High purity covellite was synthesized by the thermal reaction of sulphur and copper. Thiobacillus cultures were obtained from other workers and from the natural environment, and enriched for sulphide oxidizing capability. Oxygen consumption was monitored polarographically. Soluble copper, sulphate and total iron were assayed by Atomic Absorption Spectrophotometry while ferrous ion was determind spectrophotometrically as a complex with orthophenanthroline. By rapid specific inhibition of biological activity during sulphide oxidation, the contribution of bacteria to the stoichiometry of oxidation was determined. At pH 2.5 the product of either biological (Thiobaccillus ferrooxidans) or non-biological oxidation was CuSO4, the biological rate exceeding the non-biological rate about a hundredfold. At pH 4.5 T.thioparus was incapable of oxidizing CuS itself but catalysed attack by oxygen (about fivefold) by oxidizing a sulphur passivation film which formed by reaction of CuS with oxygen. The nett result was again CuSO4 production. At pH 2.5 three strains of T. ferrooxidans oxidized CuS itself without the aid of ferric ion; a fourth strain (BJR-V-1) was completely dependent on ferric ion or dissolved oxygen to oxidize CuS to sulphur. In situations where dissolved oxygen initiated the oxidation of CuS, the oxidation rate was approximately first order with respect to dissolved oxygen, while zero order kinetics were observed when other mechanisms predominated. In dilution experiments designed to demonstrate the dependence of sulphide oxidation (to sulphate) on physical contact between bacteria and mineral surfaces, no dependence was observed. It was concluded that water soluble intermediate were involved in CuS oxidation by T. ferrooxidans and in sulphur transport to the cells of T. ferrooxidans and T. thioparus. Arguments were advanced suggesting that the intermediates were inorganic and the concentration of intermediates was estimated from experimental results and the theory if diffusion. The process of CuS passivation was studied; consumption of oxygen and acid, and production of cupric ion and sulphate were measured, the results indicating that passivation resulted from the accumulation of approximately 30 micromole of elemental sulphur per square metre of CuS. Oxygen consumed during depassivation by thiobacilli supported this conclusion. Assuming an even distribution of sulphur over the surface, the film was calculated to be one or two atoms thick. From consideration of the results of this study it was proposed that polythionates may be involved both in CuS oxidation by bacteria and in transport of sulphur into bacterial cells. The role of iron was investigated. Chemically synthesized ferric ion was less effective in CuS oxidation than was ferric ion produced by T. ferrooxidans strain BJR-V-1 through oxidation of ferrous ion. The half saturation ferrous ion concentration with respect to oxidation by each of the T. ferrooxidans strains was approximately 10-5 molar, in contrast to values of 10-2 molar reported by others. Further ferrous oxidation kinetic experiments with strain BJR-V-1 indicated that the major substrate for the rate limiting reaction in ferrous oxidation was a ferrous phosphate complex; a sulphate complex also played a part.

Twenty-four crossbred steer calves (235 + 6 kg initial BW) were weaned, adapted to a growing diet, trained to use Calan feeders and assigned to one of four treatments in a 2 x 2 factorial arrangement as follows: (1) no transit stress and saline injection, (2) no transit stress and trace mineral and vitamin E (TM/VitE) injections, (3) transit stress and saline injection and (4) transit stress and TM/VitE injection. TM/VitE injections consisted of MultiminTM to provide 0.3, 0.6, 0.15 and 0.6 mg of Cu, Mn, Se, and Zn/kg BW, respectively, and Vita ETM to provide 9 IU of VitE/kg BW on d 0 and 21 of the study. On d 24, transit-stressed steers were subjected to a three-d, 2000-km, transportation period. During the 56-d experiment, liver and serum samples were assayed to assess trace mineral status, antibody titers to keyhole limpet hemocyanin (KLH) measured to assess humoral immunity and phytohemagglutinin(PHA)- and ovalbumin(OVA)-induced skin swelling and lymphocyte proliferation measured to assess cellular immunity. TM/VitE-injected steers grew slower (P < 0.05) over the first 24 d of the experiment and tended (P = 0.10) to grow slower after transit. TM/VitE injections increased (P < 0.05) liver Cu and Zn concentrations 135 and 21 % by d 30, respectively. TM/VitE-injected steers had increased (P < 0.05) serum Cu on d 24 and 26, but decreased (P < 0.05) serum Zn and whole blood Se compared to saline-injected steers on d 24 and 56. TM/VitE injections increased serum α-tocopherol concentrations. TM/VitE injections did not affect humoral immunity, but decreased (P < 0.05) skin-swelling responses to PHA on d 21, and decreased (P < 0.05) lymphocyte proliferation to OVA and KLH. Transit-stressed steers had higher (P < 0.05) serum Cu on d 26, and higher (P < 0.05) liver Cu concentrations on d 56 than non-transit-stressed steers. Transit stress did not affect serum Zn or whole blood Se concentrations. Injections of TM/VitE increased Cu, Zn and vitamin E, but not Se status. The TM/VitE treatment suppressed growth and cellular immune function suggesting that levels of trace minerals used in this study were too high.

The formation of Fe oxides is influenced by pedogenic factors including ionic environments However, the surface chemistry of Fe oxides formed under different ionic conditions remains obscure Tins study reveals the impact of the structural chemistry of the Fe oxides formed under the influence of low-molecular-weight organic acids and inorganic ligands on their surface chemistry. The selected ligands at optimal ligand/Fe(II) molar ratios (MRs) promoted the crystallization of the Fe oxides formed and decreased their specific surface area through fundamental structural changes. At relatively high ligand/Fe(II) MRS, the ligands inhibited the crystallization of the Fe oxides formed, resulting in the development of micropores, the increase in their surface roughness and irregularity as revealed by atomic force microscopy, as well as the increase in their specific surface area. The net negative surface charge of the Fe oxides consistently increased as the ligand/Fe(II) MR increased. The ligands altering the surfaceproperties of the Fe oxides generally followed the order of the stability constants of the Fe-ligand complexes: silicic acid > citrate > tartrate > oxalate > sulfate > carbonate. The kinetics and mechanisms of adsorption/desorption of P and Ph on the Fe oxides formed at various citrate/Fe(II) MRs were investigated by conventional batch method, pressure-jump relaxation spectrometry and differential Fourier transform infrared spectroscopy. The apparent rate constants, intrinsic rate and equilibrium constants, activation energies, pre-exponential factor values of P and Ph adsorption by the Fe oxides formed and the coordination of P and Ph on the Fe oxide surfaces greatly varied with the amount of the citrate ligands coprecipitated with Fe and their surface properties. The mechanistic rate laws of P and Pb adsorption by the Fe oxides formed at the citrate/Fe(II) MRs of 0 and 0.001 were different. The P adsorption occurred in two sequential reactions whereas the Pb adsorption included two parallel reactions. The role of organic and inorganic ligands in influencing the surface properties of Fe oxides through their effect on crystallization is profound. The subsequent impact on the dynamics of nutrients and pollutants in terrestrial and aquatic environments merits close attention.

Twenty-four crossbred steer calves (235 + 6 kg initial BW) were weaned, adapted to a growing diet, trained to use Calan feeders and assigned to one of four treatments in a 2 x 2 factorial arrangement as follows: (1) no transit stress and saline injection, (2) no transit stress and trace mineral and vitamin E (TM/VitE) injections, (3) transit stress and saline injection and (4) transit stress and TM/VitE injection. TM/VitE injections consisted of MultiminTM to provide 0.3, 0.6, 0.15 and 0.6 mg of Cu, Mn, Se, and Zn/kg BW, respectively, and Vita ETM to provide 9 IU of VitE/kg BW on d 0 and 21 of the study. On d 24, transit-stressed steers were subjected to a three-d, 2000-km, transportation period. During the 56-d experiment, liver and serum samples were assayed to assess trace mineral status, antibody titers to keyhole limpet hemocyanin (KLH) measured to assess humoral immunity and phytohemagglutinin(PHA)- and ovalbumin(OVA)-induced skin swelling and lymphocyte proliferation measured to assess cellular immunity. TM/VitE-injected steers grew slower (P < 0.05) over the first 24 d of the experiment and tended (P = 0.10) to grow slower after transit. TM/VitE injections increased (P < 0.05) liver Cu and Zn concentrations 135 and 21 % by d 30, respectively. TM/VitE-injected steers had increased (P < 0.05) serum Cu on d 24 and 26, but decreased (P < 0.05) serum Zn and whole blood Se compared to saline-injected steers on d 24 and 56. TM/VitE injections increased serum &#945;-tocopherol concentrations. TM/VitE injections did not affect humoral immunity, but decreased (P < 0.05) skin-swelling responses to PHA on d 21, and decreased (P < 0.05) lymphocyte proliferation to OVA and KLH. Transit-stressed steers had higher (P < 0.05) serum Cu on d 26, and higher (P < 0.05) liver Cu concentrations on d 56 than non-transit-stressed steers. Transit stress did not affect serum Zn or whole blood Se concentrations. Injections of TM/VitE increased Cu, Zn and vitamin E, but not Se status. The TM/VitE treatment suppressed growth and cellular immune function suggesting that levels of trace minerals used in this study were too high.

Blood-borne biochemical markers were used to track comparative rates of bone turnover in horses fed differing amounts of Ca, P and Mg. Bone turnover was tracked by serum osteocalcin, bone resorption by the carboxyterminal telopeptide of type I collagen (ICTP), and bone formation by the carboxyterminal propeptide of type I procollagen (PICP). Twenty-four long-yearling Quarter Horses were blocked by gender and age, randomly assigned to one of four diets and subjected to 128 d of race training. Horses entered the study at approximately 20 months of age. The study was conducted in 32-d periods, each consisting of 28 d of race training followed by a 4-d fecal and urine collection, or a 4-d rest period. Blood samples were taken weekly during the training period. Serum and plasma samples were analyzed for concentrations of osteocalcin, the carboxyterminal telopeptide of type I collagen (ICTP) and the carboxyterminal propeptide of type I procollagen (PICP). Urine was collected for analysis of deoxypyridinoline (DPD) and creatinine. Onset of training resulted in elevated concentrations of ICTP, PICP and osteocalcin. Horses consuming the highest levels of Ca, P and Mg exhibited higher concentrations of PICP and lower concentrations of ICTP indicating greater bone formation coupled with lesser amounts of bone resorption. Further, ICTP, PICP and osteocalcin concentrations decreased dramatically following 4-d of confinement and relative inactivity. Therefore it appears that feeding minerals at levels greater than current NRC recommendations provided a protective effect on the developing skeleton of the young racehorse. Additionally, the biochemical markers used in this study were sensitive enough to track daily changes in bone activity resulting from daily changes in stress to the skeleton.