Nora Schreithofer

Effect of calcium and thiosulfate ions on flotation selectivity of nickel-copper ores

Abstract Effect of calcium and thiosulfate ions on flotation of a Ni–Cu ore was investigated. The ions improved the flotability of sulfides at the normal process pH after grinding in steel mill. Calcium activated especially nickel and copper sulfides when the galvanic effect of mill iron was effective. The UV/Vis measurements showed that calcium ions increased xanthate adsorption on the sulfides. The effect of thiosulfate was different. It was concluded that thiosulfate reduced the effect of hydrophilic compounds on sulfide particles, and in that way improved their flotation.

Effect of some process variables on flotability of sulfide nickel ores

The influence of grinding media, process water ions (calcium and thiosulfate) and pulp oxidation on flotability of sulfides nickel ores was investigated. Bench scale flotation experiments were carried out with Enonkoski ore using ethyl xanthate as collector. The results showed that the galvanic effect of mill iron controls the separation selectivity of pentlandite from pyrrhotite. Calcium and thiosulfate ions activated the flotation of sulfides with xanthate after using a steel mill for grinding. The ions improved also the selectivity of nickel separation. After grinding in ceramic mill, the ions depressed sulfide flotation but increased the selectivity of nickel flotation in the presence of a collector. Pulp oxidation improved both the flotability of sulfides and the selectivity of nickel flotation with both grinding methods.

Impedance Spectroscopy Structural Analysis: Ca-Dopant Segregation in (Pb0.75Ba0.25)(Zr0.70Ti0.30)O3

In this paper we address the hitherto unreported structural dependence of the electrical properties of lead–barium–zirconate–titanate (PBZT) solid solution associated with Ca-dopant segregation. Our research takes into account the already well-known fact that the physical properties of metal oxides are affected by the oxygen partial pressure in the atmosphere, and indicates the necessity of the thorough correction of experimental data obtained so far by ex situ measurements in high vacuum. In contrast, impedance spectroscopy (IS) offers in situ structure examination under ambient conditions. IS is shown to be an efficient method capable of detecting the contributions of the resistances of grains and grain boundaries resistance to the complex impedance of a compound, accurately estimating its electrical conductivity as well as its corresponding activation energies and conclude on its structural properties. This is demonstrated for the case of calcium segregation in the grain boundaries of PBZT. The obtained values have additionally been verified by microstructural investigations of this material by microscopic observations and composition analysis [energy-dispersive X-ray (EDX) and atomic force microscopy (AFM)].