Joseph Hamuyuni

High-temperature phase equilibria of Cu–O–Al2O3 system in air

Phase equilibria of Cu–O–Al2O3 system were experimentally investigated in a temperature range of 1100–1400°C under 0.21 atm oxygen pressure. The experiments were conducted employing a high-temperature equilibration and quenching method. Microstructures of the quenched samples were observed with scanning electron microscope. The phase compositions in the samples were analysed with electron probe microanalysis technique. Measured solubility of Al2O3 into the molten oxide ranged from 0.0 to 1.8 wt-%. A small solubility of Cu2O into Al2O3 was also observed ranging from 1.20 to 1.58 wt-%.

Selective reductive leaching of cobalt and lithium from industrially crushed waste Li-ion batteries in sulfuric acid system

Recycling of valuable metals from secondary resources such as waste Li-ion batteries (LIBs) has recently attracted significant attention due to the depletion of high-grade natural resources and increasing interest in the circular economy of metals. In this article, the sulfuric acid leaching of industrially produced waste LIBs scraps with 23.6% cobalt (Co), 3.6% lithium (Li) and 6.2% copper (Cu) was investigated. The industrially produced LIBs scraps were shown to provide higher Li and Co leaching extractions compared to dissolution of corresponding amount of pure LiCoO2. In addition, with the addition of ascorbic acid as reducing agent, copper extraction showed decrease, opposite to Co and Li. Based on this, we propose a new method for the selective leaching of battery metals Co and Li from the industrially crushed LIBs waste at high solid/liquid ratio (S/L) that leaves impurities like Cu in the solid residue. Using ascorbic acid (C6H8O6) as reductant, the optimum conditions for LIBs leaching were found to be T = 80 °C, t = 90 min, [H2SO4] = 2 M, [C6H8O6] = 0.11 M and S/L = 200 g/L. This resulted in leaching efficiencies of 95.7% for Li and 93.8% for Co, whereas in contrast, Cu extraction was only 0.7%. Consequently, the proposed leaching method produces a pregnant leach solution (PLS) with high Li (7.0 g/L) and Co (44.4 g/L) concentration as well as a leach residue rich in Cu (up to 12 wt%) that is suitable as a feed fraction for primary or secondary copper production.

Valuable Metals and Energy Recovery from Electronic Waste Streams

E-waste management through traditional methods such as disposing in landfills, burning in incinerators or exporting abroad for disposal are no longer options due to the strict environmental regulations. Fortunately, the presence of valuable metals in the e-waste and increasing demand for the metals as well as complexities of the currently available primary raw materials make recycling an attractive and viable option both environmentally and economically. Moreover, it is efficient in terms of resource management by closing the loop of metals. Consequently, urban mining such as the recovery of precious metals from e-waste streams through sustainable recycling processes have emerged. The sustainable recycling practices address the scarcity of primary resources and reduce consumption of energy for metals production while managing environmental issues related to hazardous materials from the e-waste streams. In this paper, valuable metals recoveries from e-waste streams through pyrometallurgical and hydrometallurgical processes are critically reviewed. And, innovative ideas for different steps of the thermochemical processes in the valuable metals and energy recovery from the e-waste streams are discussed.

A Sustainable Methodology for Recycling Electric Arc Furnace Dust

In a race to save the planet of its rapidly depleting natural resources, the use of Secondary Raw Materials (SRMs) as replacements in several processes is currently intensively pursued. In fact, this is currently one of the European Union (EU)’s mandates. Valorization of SRMs is consistent with circular economy, where resource efficiency is maximized for the benefit of both businesses and the environment. In line with this mandate, this paper focuses on investigating process phenomena related to hydrometallurgical recycling of Electric Arc Furnace (EAF) dust. In the experimental study, selective dissolution of zinc and other metals is investigated to acquire a recyclable leach residue. Based on the experimental and theoretical investigations, zinc could be extracted from the EAF dust and a recyclable leach residue produced, having chemical composition suitable as a feed material into electric arc furnace.

Thermodynamic Stability of Condensed Phases in the Ternary System CaO–Cu–O by the EMF Method

The standard thermodynamic properties of the compound Ca2CuO3 were determined electrochemically by the Electromotive Force (EMF) method. The ternary phase Ca2CuO3 was synthesized from the pure oxides CaO and CuO at CaO saturation using a ceramic route. The EMF measurements were performed over a temperature range 973 ≤ T/K ≤ 1124. The standard Gibbs energy of formation of the ternary compound Ca2CuO3 was determined using the EMF technique as:

Liquidus in System Cu2O − CaO -Al2O3 at 1250°C

\Delta _{{{\text{f}}({\text{ox}})}} {\text{G}}^\circ_{\text{Ca2CuO3}} = 2 1. 8 8 4{-} 2 2. 9 2\cdot 10^{ - 3} \cdot {\text{T}}.

Measurement of surface tension of molten matte phases by an improved sessile drop method

(1)

Experimental determination of the liquidus of the binary system (Cu2O+CaO) in air at temperature from (1050 to 1500 C)

Solubilities of CaO and Al2O3 in copper rich molten oxide phases have wide industrial applications in various copper smelting and refining operations producing copper matte or blister copper. However, experimentally determined solubility data on these simple systems are still scarce even after a long spell of industrial copper making. In this experimental study, these solubilities have been quantified by a static equilibration technique at 1250 °C in an inert atmosphere of purified argon gas. The compositions of condensed molten phases and all solids in equilibrium have been analyzed and quantified using Electron Probe Micro-Analyzer (EPMA).