Chemical Analysis of the Output-flows of an IBA Processing Plant in Austria- The Fate of Pb and Cd

Abstract

Recovery of resources from incinerator bottom ash (IBA) is an important part of the circular economy strategy. A state-of-the-art IBA processing plant in Austria splits IBA into more than 10 output flows and yields excellent recovery of metals in coarse and fine particle size fractions. For a better understanding of the distribution of selected heavy metals among the output flows, i.e. lead and cadmium, representative samples of the output flows were taken. Laboratory samples were prepared, digested with acids, and analyzed with ICP-OES. The analyzed samples included 91% of the total mass of the processed IBA. Only coarse ferrous and non-ferrous metals >4 mm, accounting for 8% of the total mass of the processed IBA, were not analyzed and literature data were used. Unburnt material (less than 1% of the total mass of the processed IBA) was excluded from the study due to the insignificant mass flow. A substance flow analysis calculated and illustrated the distribution of lead and cadmium over the output flows. Results showed that Pb was found mainly in outputs of non-ferrous metals and to a minor extent in the mineral fraction. Cd is transferred equally to non-ferrous metals and the mineral fraction. Comparison with literature data on a model of the same IBA processing plant showed an improvement in the share of materials to be recycled after the extension of the plant. The transfer coefficients of Pb and Cd to the mineral fraction decreased due to the improvements in processing.