Aleksandar N. Nikoloski

Review of the Application of Ion Exchange Resins for the Recovery of Platinum-Group Metals From Hydrochloric Acid Solutions

Platinum-group metals (PGMs) have become one of the most sought after rare metals in this modern age of science and they will continue to increase in importance as a result of their advantageous use in clean-air technology. Due to the scarcity of these precious metals, the application of ion exchange processes to recover PGM ions from relatively uncontaminated aqueous solutions, such as produced by the leaching of secondary sources including used automotive catalytic converters and electronic scrap, is becoming an increasingly cost-effective option and hence an important topic for the PGM production industry. This paper provides a general overview of the basic principles and theories relevant to the hydrometallurgical recovery of PGMs using ion exchange resins, along with a review and discussion of the most important factors that affect the separation and purification of PGMs present initially in predominantly ionic state in an aqueous hydrochloric acid solution. It is shown that in these acidic chloride solutions, the current system of choice for the leaching of PGMs, the adsorption behavior of the PGM ions onto chelating ion exchange resins is strongly dependent on the anionic PGM chloro-complex species present. In addition, it is revealed that the main factors affecting this complexation are (i) acidity and chloride ion concentration of the contacting aqueous chloride solution, (ii) “ageing” of the solution, and (iii) temperature of the solution.

Addition of Cobalt to Lead Anodes Used for Oxygen Evolution—A Literature Review

A review of the literature dealing with the effect of cobalt on lead-based anodes for oxygen evolution during electrolysis of sulfuric acid solutions verifies that the presence of cobalt at the anode–electrolyte interface, either as constituent of the anode material or as ions in the electrolyte, catalyzes the evolution of oxygen and reduces the corrosion of the anodes and the contamination by lead of metal cathodes produced during electrowinning. However, due to harmful effects of cobalt ions on the cathodic reaction in some processes, these benefits are limited to the electrowinning of copper. Efforts to develop a way of introducing cobalt at the anode–electrolyte interface without interfering with the cathodic reactions are reviewed in this paper. The use of lead–cobalt alloy anodes has had limited success due to issues arising from the low solubility of cobalt in lead, segregation during casting of the alloys, and nonuniform distribution of cobalt which affects the integrity of the anodes. This has been overcome in part lately by inclusion of cobalt into only the surface layer of a lead or lead alloy substrate, by thermal treatment of a cobalt salt to form a catalytic cobalt oxide surface species, or by electrodeposition of composite lead–cobalt oxide anodes. The last approach in particular has been actively investigated by several groups, but to our knowledge it is yet to find application in the industry. The review also critically examines the likely reaction mechanisms involved.

Effect of cobalt ions on the performance of lead anodes used for the electrowinning of Copper-A literature review

The effect of cobalt ions in the electrolyte on the performance of lead alloy anodes used for oxygen evolution during electrolysis of copper/sulfuric acid solutions has been studied extensively over the past 90 years. A review of the literature has confirmed that cobalt both as constituent of the anode material and present as ions in the electrolyte reduces the rate of corrosion of the anodes, lowers the overpotential for the evolution of oxygen, and reduces lead contamination of the copper cathodes. Despite the fact that these effects have been developed into widespread applications in the electrowinning industry, a fundamental understanding of the mechanism of the action of cobalt ions remains a point of debate. A selection of the most relevant literature on this phenomenon has been reviewed and the data and proposed mechanisms critically evaluated.

The Electrochemistry of the Leaching Reactions in the Caron Process. I. Anodic Processes

The Caron process involves the oxidative dissolution of pre-reduced iron alloys containing nickel, cobalt and copper in ammoniacal carbonate solutions. This study has demonstrated that passivation is exhibited by nickel and cobalt at higher potentials than previously established for iron. It is shown that alloys of iron with nickel and cobalt also undergo passivation at low potentials resulting in inhibition of the dissolution of the valuable metals. The potential regions of active dissolution of each of these metals in ammonia-ammonium carbonate solutions have been established. The effect of thiosulphate and cobaltammine complex ions on the dissolution of iron and nickel was found to be significant in that thiosulphate appears to partially prevent the passivation of nickel while the presence of cobaltammine ions leads to lower apparent anodic current densities. Possible mechanisms for the passivation processes and for the effects of thiosulfate and cobaltammines on the dissolution are presented.

Adverse Effects of Fluoride on Hydrometallurgical Operations

This review addresses the detrimental effects of fluoride on the various steps which constitute any hydrometallurgical operation. It focuses on the specific examples of apatite flotation, copper bioleaching, zinc electrowinning, and the manufacture of phosphoric acid. The presence of fluoride modifies the surface characteristics of minerals altering their effective flotation. Toxicity of fluoride to bacteria directly affects the mechanisms of bioleaching. Fluoride can interfere with the adhesion of metals to cathodes and affect deposit morphology during electrodeposition. In phosphoric acid synthesis from phosphate ores, fluoride affects production efficiency by altering the crystal morphology of the gypsum by-product.

Recent developments in the application of microwave energy in process metallurgy at KUST

ABSTRACT Kunming University of Science and Technology (KUST) has successfully developed, designed, fabricated and installed industrial microwave units for (i) removal of halides, (ii) activation of carbon, (iii) heating of dust laden air in electrostatic precipitators, (iv) drying of water based paints, and (v) heating of the HF pickling solution for cold rolled titanium alloy coils. This review article provides a summary of these process metallurgy applications. It is found that the use of microwave energy can increase the process efficiency, giving advantages, such as lower reaction temperature and shorter reaction time compared to traditional processes. 可显著降低反应温度、缩短时间，具有强化作用