Behaviour of trace elements in copper smelting processes - LA-ICP-MS as a tool for sample characterisation

The rapidly increasing demand for metals used for instance in batteries, electronics and renewable energy production cannot be satisfied merely by increasing mining and primary production capacities. In order to better secure the metal supply and achieve a circular economy, metal recycling and recovery from End-of-Life (EoL) products must be significantly increased. One viable option for recycling several metals is to utilise existing primary or secondary copper smelters. Many of these smelters have been optimised for handling primary ores, which means that more research is needed in order to understand and quantify the effects of introducing secondary raw materials into the process circuits. In this thesis, the behaviour of several trace elements present in secondary raw materials (Ir, Mo, Pb, Re, Sn, Sb, Te, Ga, In, La, Nd, Li, Co, Mn) was investigated in laboratory-scale primary and secondary copper smelting experiments. The experiments were conducted in equilibrium conditions or as a function of time at 1300 °C. Different gas atmospheres were utilised for simulating the process conditions in different stages of industrial smelting operations. The phase-by-phase elemental concentrations were analysed using scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS), electron probe micro-analysis (EPMA), as well as the state-of-the-art laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) technique. A convenient way of presenting and comparing the behaviour of different trace elements is via distribution coefficients (L = wt.% metal in alloy or matte / wt.% metal in slag). Some of the obtained distribution coefficient data represents the first reported values in the literature, whereas some provide significantly more accurate results compared to earlier results. For the distributions of gallium, indium and lanthanum between copper sulphide mattes and iron silicate slags, no previous data was found in the literature. This also applies to the experimentally verified distribution coefficients of lithium and lanthanum between copper-rich alloy and high-alumina iron silicate slags. Regarding manganese, the new data indicates significantly lower distribution coefficients compared to previous data, i.e. manganese deports extremely heavily to slag. The improved accuracy and reliability in distribution data is due to the use of direct phase-by-phase analysis techniques without the need of manual phase separation, as well as the extremely low detection limits obtained with the LA-ICP-MS. The results of this thesis can be applied to industrial processes in designing, optimising, modelling and evaluating processes for industrial-scale recycling of electronic scrap and EoL batteries, for example.