Tracer 4 sd

Experimental studies were carried out with 10 kg of mobile phone PCBs supplied by a WEEE recycling plant that had previously removed all the electronic components like capacitors, cables, resistors, etc. The sample was firstly crushed by a Retsch SM 2000 cutting (Haan, Germany) mill up to −4 mm after various steps of comminution, reducing the size of the output grid after each step. This product was further ground with a Fritsch pulverisette 9 vibratory steel ring mill for 10 min. The resulting powder was sieved with a 0.5 mm screen and the +0.5 mm and −0.5 mm fractions were obtained. The +0.5 mm fraction was analysed with X-ray fluorescence by using a Bruker-Tracer IV SD (Billerica, MA, USA). The −0.5 mm fraction was subjected to an automatic sampling with PT 100—Retsch to obtain representative samples for chemical analyses and leaching tests. Chemical analyses of this fraction were carried out on six 1 g portions of the powder that were dissolved with 1:3 nitric acid and hydrochloric acid (aqua regia) at 90 °C for 3 h. The cooled digestion solution was filtered to remove plastics and ceramics and analysed for the main constituents and precious metals by flame atomic absorption spectroscopy (AAS).

Sediment source samples were sieved to < 63 µm in the field to facilitate direct comparison to the target sediment samples^{29 (link),105} . Sediment source samples were air-dried and ground for further analysis (Fig. 6c). All sediment samples (sources and target) were analysed in the laboratory for their chemical properties, including total carbon (TC) and total nitrogen (TN) content^{21 ,106 (link)} and major and minor elemental geochemical constituents^{32 (link),106 (link)} as potential sediment tracers. For TC and TN concentration a sub-sample of 15 mg was wrapped in tin capsules and combusted in an elemental micro-analyser (Elementar vario MICRO Cube, Elementar Analysensysteme GmbH, Langenselbold, Germany) at 950 °C. A handheld XRF spectrometer (Bruker Tracer IV-SD, Bruker, Kennewick, WA USA) that uses energy dispersive X-ray fluorescence (EDXRF) was employed to determine the following major elements: Al₂O₃, CaO, Fe₂O₃, K₂O, MgO, Na₂O, P₂O₅, SiO₂ and TiO₂ and trace elements: Ba, Cr, Cu, Mn₂O₃, Nb, Ni, Pb, Rb, Sr, Y, Zn and Zr. For this analysis, a sub-sample of 500 mg was placed onto a thin film to measure trace elements at a setting of 40 kV and 15.7 µA and major elements at an excitation of 15 kV and 35 µA under vacuum with Helium gas. For each sample the mean of three replicates was used for further analysis (Fig. 6d).