James Vaughan

Corrosion of Titanium and Its Alloys in Sulfuric Acid in the Presence of Chlorides

Titanium alloys (ASTM Grades 1, 2, 7, 12, and 18) are employed as the liner and internal components of autoclaves during the high-pressure acid leaching (HPAL) of nickel laterite ores. This paper summarizes the corrosion behavior of these alloys in sulfuric acid and the effect of the addition of chlorides (NaCl). New thermodynamic Eh–pH diagrams for the Ti–H2O, Ti-SO4–H2O, and Ti–Cl–H2O systems are presented. Micrographs are also presented and the corrosion morphology is discussed. Long-term immersion tests were carried out to determine corrosion rates. Electrochemical techniques were used to provide insight into the corrosion chemistry. The shortcomings of accelerated corrosion testing of Ti alloys are addressed. Pd enrichment on the surface of Ti-18 was confirmed by a combination of open-circuit potential measurements and chronoamperometric measurements.

Electrodeposition of Aluminum from Aluminum Chloride–Trihexyl(tetradecyl) Phosphonium Chloride

Ionic liquids (ILs) are solvents of interest for applications such as electroplating, winning, and refining of metals. In this study, the conductivity of the AlCl3–trihexyl(tetradecyl) phosphonium chloride ([P14,6,6,6]Cl) system was characterized over a wide range of AlCl3 concentration and temperature. Cyclic voltammetry was used to determine the electrochemical window of the neat IL using a Pt substrate. The anodic and cathodic potentiodynamic polarization behavior of Al was measured in AlCl3–[P14,6,6,6]Cl at an AlCl3 concentration of 0.67 mol fraction (XAlCl3). Aluminum was electrodeposited at a constant potential over a range of potentials (0.3–0.75 V); the deposit morphology, current efficiency, and power consumption are provided. The presence and effects of impurities such as H2O and HCl in the ionic liquid are also addressed.

Density, viscosity and conductivity of tetraalkyl phosphonium ionic liquids

The density, viscosity and conductivity of nine commercially available terra-alkyl phosphonium ionic liquids (ILs) are presented. The effect of cation volume and symmetry, anion volume, and temperature are observed. The Vogel-Tamman-Fulcher (VTF) equation is used to calculate the theoretical glass transition temperature (To) and the activation energy of conductivity E a,A . The conductivity of three halo-aluminate ionic liquid systems for mole fractions up to 0.7 AlCl 3 is reported.

Processing of bio-ore to products

Hyperaccumulator plants may contain valuable metals at concentrations comparable to those of conventional metal ore and can be significantly upgraded by incineration. There is an incentive to recover these metals as products to partially counter-balance the cost of disposing the contaminated biomass from contaminated soils, mine tailings, and processing wastes. Metal recovery is included in the agromining chain, which has been developed over the past two decades for Ni and Au. More than 450 Ni-hyperaccumulator species are currently known and some grow quickly providing a high farming yield. Nickel recovery involves an extraction step, ashing and/or leaching of the dry biomass, followed by a refining step using pyro- or hydrometallurgy. The final products are ferronickel, Ni metal, Ni salts or Ni catalysts, all being widely used in various industrial sectors and in everyday life. Gold can be recovered from mine tailings using a number of plant species, typically aided by a timed addition of an Au-chelating extractant to the soil. Dry biomass is ashed and smelted. This approach enables the treatment of resources that could not be effectively processed using conventional methods. In addition to nickel and gold, the recovery of other metals or elements (e.g. Cd, Zn, Mn, REEs) has been investigated. Further effort is required to improve process efficiency and to discover new options tailored to the unique characteristics of hyperaccumulator plant biomass.

Improved Copper Smelter and Converter Productivity Through the Use of a Novel High-Grade Feed

Copper sulphide processing technologies face increasing pressures associated with decreasing concentrate grade leading to increasing thermal inefficiency and lower productivity. Impurity concentrations are on average increasing, creating potential environmental risk and additional treatment costs. In copper flash smelters dust, partially oxidised materials and fume formed from the condensation of volatile impurities, are routinely recycled to the feed. In the converting stage the heat balance is maintained by charging anode reverts and other inert materials. In both cases, the thermal energy available from sulphide oxidation is not fully utilised or optimised. The productivities of both smelter and converter stages can be potentially increased through the addition of a high copper, low iron, low impurity precipitated copper product. Calculations are carried out for fayalite smelter and calcium ferrite converter slags using an optimised FactSage thermodynamic database. The potential for significant increases in smelter and converter productivities using existing technologies are predicted.

The Synergistic Copper Process concept

ABSTRACT A new process concept is proposed, one that combines the inherent advantages of conventional hydro- and pyro-metallurgical processes to provide opportunities for significant increases in resource utilisation and smelter productivity. The process involves first leaching copper minerals in aqueous solution, separation of undesirable impurity elements from the solution using conventional hydrometallurgical technologies, and then preparation of a precipitated solid copper compound product. The product can then be used directly as a high-copper, low-iron feedstock in the smelting and/or converting stages of pyrometallurgical copper production. The solid precipitated copper product can be transported to the smelter and used as a separate feed, or can be used to enhance copper concentrations in sulphide concentrate blends. This new tradeable copper product provides an effective way of increasing copper concentrate grades, and the opportunity to more efficiently utilise the excess enthalpy available from the sulphide mineral oxidation reactions in current copper matte smelting and converting process technologies.

Ionic liquid electrodeposition of reactive metals

Abstract Ionic liquids are solvents of interest for applications such as electroplating, winning and refining of metals. Of particular interest is the possibility of processing reactive metals such as aluminium, magnesium and titanium that cannot be deposited from aqueous solutions. Aluminium has been electrodeposited from AlCl3: ionic liquid mixtures at low temperatures relative to conventional Hall–Héroult smelting. Imidazolium ionic liquids have been used in the past due to their relatively high ionic conductivity and cation stability. The less studied and less expensive phosphonium ionic liquids systems may provide a viable alternative to imidazolium ionic liquids for certain applications. New information regarding the physical properties and electrochemical behaviour of phosphonium ionic liquid systems is presented.

Scandium Loading on Chelating and Solvent Impregnated Resin from Sulfate Solution

ABSTRACT Adsorption of Sc onto two chelating resins, aminomethyl phosphonic (TP 260) and iminodiacetate (TP 209), and one solvent impregnated resin with bis(2,4,4-trimethylpentyl) phosphinic acid (TP 272) was investigated. Resin capacities, ion selectivity, adsorption kinetics, and equilibrium isotherms were measured. Sc speciation was predicted using chemical thermodynamic data. The kinetic data were fit to empirical models. The adsorption behavior was established by fitting equilibrium data to Langmuir and Freudlinch isotherms. Process variables such as pH, sulfate concentration, and temperature were considered. This new information will be used for hydrometallurgical process selection for Sc recovery.

Australian Hydrometallurgy Research and Development

Australia is a major miner of ore that requires hydrometallurgical processing. According to the 2016 US Geological Survey Minerals Commodities Summaries, the country is 1st for aluminium (bauxite) and lithium, 2nd for gold, zinc and cobalt, 4th for nickel and silver, and 6th for copper mining, not to mention its wealth in coal and iron ore. In this paper, examples of recent Australian hydrometallurgical activities are summarised. Then, selected research projects from the University of Queensland hydrometallurgy research group are profiled. The projects profiled are related to fundamental aspects of processing bauxite with organics and reactive silica as well as the development of a synergistic hydro- and pyrometallurgical process for copper. The process context and motivation for the research is introduced, key results are highlighted with the associated relevant references.

Potentiodynamic Polarization of Platinum and Aluminum in AlCl3-[P14,6,6,6]Cl Melts

Ionic liquids (ILs) are being considered for a wide range of applications including as a medium for the electrowinning and refining of reactive metals such as aluminium. The electrochemical characteristics of the aluminum chloride - trihexyl(tetradecyl) phosphonium chloride (AlCl3-[P14,6,6,6]Cl) system are explored in this paper. Cyclic voltammograms using a platinum working electrode are presented over a wide range of AlCl3 concentrations (XAlCl3 = 0, 0.3, 0.5, 0.6, 0.67 mole fraction). The potentiodynamic polarization of aluminum were measured in the XAlCl3 = 0.67 melt at 323, 355, 375, 402 and 423 K. The [P14,6,6,6]Cl used was of commercial purity; one of the main impurities is HCl. The presence of HCl in the melt detracts from the current efficiency of aluminum electrodeposition.