Spectroanalytical method for evaluating the technological elements composition of magnets from computer hard disks

摘要

In this study, inductively coupled plasma optical emission spectrometry (ICP OES) was used for the development of an analytical procedure for elemental analysis of hard disks (HDs). More than 50 samples were acquired and separated according to the manufacturers. Both magnets were used, namely, the actuator (a) and the spindle (s) motor. The samples were heated to remove magnetism, ground in a knife mill and sieved. Different digestion procedures were performed with a block digester and microwave, and three acid concentrations were employed. Due to the lack of certified materials or references from HDs, tests of standard addition and recovery were performed to verify the accuracy of the proposed method. Hyperspectral image and principal component analysis were also used to assist in the data treatment related to the Ni layer. For both magnets, the best analytical procedure was 100 mg of sample, 7 mol L-1 nitric acid and a digester block. The elements observed in the highest concentrations were Fe followed by Nd and Pr. This procedure was simpler than others were and prioritized the principles of green chemistry.