D.R. Nagaraj

SIMS study of adsorption of collectors on pyrite

Abstract Adsorption of sulfide collectors such as xanthate on pyrite has been studied extensively over several decades using a wide variety of techniques. In spite of this, there are unanswered questions as to the identity of adsorbed species on pyrite surfaces—dixanthogen vs. iron xanthate complexes. Far less is known in non-xanthate collector systems. We have used Secondary Ion Mass Spectroscopy (SIMS) successfully in the past to obtain direct evidence for the identity of the adsorbed collector species on copper sulfides, galena and Cu-activated quartz. The present study is an extension of the SIMS analysis to investigate the adsorption of xanthate, dithiophosphate, dithiocarbamate, and modified thionocarbamates and thioureas on pyrite. Adsorption of these collectors on chalcocite was also studied for comparison. An attempt was also made to obtain SIMS spectra for pure dixanthogens at room temperature. The collector molecular ion was detected for pure amyl dixanthogen, but only dixanthogen fragments were observed for the isobutyl and ethyl homologues. Only in the case of dithiocarbamate (DTC) was there direct evidence for the presence of not only the collector dimer, but also iron–DTC complexes. On chalcocite, only the copper–DTC complexes were detected (no dimer). In the case of xanthate, the collector molecular ion and its S adduct—which are possible fragments from dixanthogen—were detected on pyrite, along with a fragment peak suggesting Fe2X. For dithiophosphate, the collector molecular ion and Fe(DTP)(OH) complex were detected (no dimer). For modified thionocarbamate and thiourea, adsorption on pyrite was negligible. SIMS results obtained in this study imply that one cannot subscribe only to collector dimers as the predominant species on pyrite under practical flotation conditions and rule out the formation of Fe-collector complexes for the adsorption of collectors on pyrite.

Practical aspects of oxide copper recovery with alkyl hydroxamates

Abstract Alkyl hydroxamates are well known collectors for oxide copper minerals as evidenced by the large amount of published literature. Our studies on a wide variety of copper ores from around the world have shown that alkyl hydroxamates will recover most of the “floatable” oxide copper minerals from an ore. They are available commercially, and they offer many advantages over alternative technologies for oxide copper recovery. In spite of this, the full potential of hydroxamates has not been exploited in the industry. The objective of this paper is to provide relevant practical aspects and guidelines to facilitate successful application of hydroxamates in operating plants. A critical analysis of the available information and data, based on several case studies, flotation testing, and microscopic analysis indicates that alkyl hydroxamates can effectively recover well-defined oxide minerals of copper, but not copper occurrences such as Cu-bearing goethite (often misidentified as cuprite) which report as Acid Soluble copper in chemical assays. Prior to any flotation testing with hydroxamates, it is necessary to assess the various modes of occurrence of Acid Soluble copper using microscopic and microprobe analysis.

The use of a factorial experimental design to study collector properties of N-allyl-O-alkyl thionocarbamate collector in the flotation of a copper ore

Abstract A three-factor, three-level, face centered cubic (FCC) experimental design was used to study the effect of important chemical variables—collector chain length, collector concentration and frother type—on the collector properties of the recently developed N-allyl-O-alkyl thionocarbamates (ATC) in copper flotation from a porphyry ore. The objectives of this study were to exploit the advantages of using experimental designs to evaluate multivariable effects and interactions, and to develop fundamental applications knowledge that is currently lacking for the ATC collectors. The effects of these process variables on copper recovery, copper concentrate grade, iron recovery, and particle size of the flotation concentrate were determined and the best process conditions were identified. The flotation efficiency of the ATC was compared with that of two better-known collectors, the O-alkyl-N-ethoxycarbonyl thionocarbamate (ECTC) and the N-alkyl-N-ethoxycarbonyl thiourea (ECTU).

The Translational and Rotational Dynamics of a Colloid Moving Along the Air-Liquid Interface of a Thin Film

This study examines the translation and rotation of a spherical colloid straddling the (upper) air/liquid interface of a thin, planar, liquid film bounded from below by either a solid or a gas/liquid interface. The goal is to obtain numerical solutions for the hydrodynamic flow in order to understand the influence of the film thickness and the lower interface boundary condition. When the colloid translates on a film above a solid, the viscous resistance increases significantly as the film thickness decreases due to the fluid-solid interaction, while on a free lamella, the drag decreases due to the proximity to the free (gas/liquid) surface. When the colloid rotates, the contact line of the interface moves relative to the colloid surface. If no-slip is assumed, the stress becomes infinite and prevents the rotation. Here finite slip is used to resolve the singularity, and for small values of the slip coefficient, the rotational viscous resistance is dominated by the contact line stress and is surprisingly less dependent on the film thickness and the lower interface boundary condition. For a colloid rotating on a semi-infinite liquid layer, the rotational resistance is largest when the colloid just breaches the interface from the liquid side.