Validation and setting up quality control for characterization of aluminum alloys in non-ferrous fraction of auto-shredders

Abstract

The improvement of recycling rates of metal waste, namely those of end-of life vehicles, is nowadays becoming imperative. Aluminum and its alloys are the main metal components in non-ferrous fraction of auto-shredders separated out after sampling. Silicon, Mg, Cu, Zn, Mn, Ti, Fe and Cr are alloying elements, which allowed the identification and differentiation of Al alloys. Flame Atomic Absorption Spectrometry was used for quantification after HCl-HNO3 digestion, with the exception of Si, where HCl–HNO3–HF–H3BO3 digestion was used. Performance characteristics of measurement procedures, namely analytical dynamic ranges, limits of detection and quantification, precision and trueness were evaluated and measurement uncertainty estimated by applying an approach based on precision and trueness validation studies and quality control data. Target values, for repeatability, intermediate precision, trueness (recovery) and measurement uncertainty, were specified to differentiate Al alloys based on their own fit-for-purpose. Metrological traceability of the measurements results of the alloying elements was established by using certified values of British Chemical Standard (BCS) of Al alloys, BCS no 181/1, BCS No 268. BCS No 300 and Standard Reference Material of Al-base alloy, SRM 87. The quantification of Si, Mg, Cu, Zn, Mn, Ti, Fe and Cr in aluminum alloys from the non-ferrous fraction of automatic crushers was determined successfully through the validated procedures.