Estudo exploratório da lixiviação simulada de Cd e Pb presentes em bijuterias

Abstract

The aim of this work was to evaluate the leaching of metals in jewelry in different extractive solutions using spectrometric techniques. The inductively coupled plasma mass spectrometry (ICP-MS) technique was initially used to scan the extracts of four solutions to verify the metals being leached. The 23 full factorial design with triplicate at the central point was carried to study the leaching parameters. The parameters chosen were temperature (26 ° C), time of 24 h, pH 5.0 (solution 3) and pH 7.5 (solution 1). After this, the chosen parameters were applied to the leaching of Cd and Pb in five samples of jewelry. Samples of jewelry from the same batch were also digested for determination of the total Cd and Pb content. The solutions resulting from the leaching and digestion of the five jewelry samples were analyzed using the graphite furnace atomic absorption spectrometry (GF AAS). The leached extracts contained from 9.96 x 10-8 to 1.48 x 10 -6 % m/m of cadmium and < LD to 8.65 x 10-6 % m/m of lead. The samples of digested jewelry contained from 1.96 x 10 -6 to 3.74 x 10-6 a % m/m of cadmium and 1.24 x 10-6 to 1.60 x 10-6 % m/m of lead. The limits of detection were 2.9 x 10-11 % m/m for cadmium and 1.2 x 10-10 % m/m for lead in inductively coupled plasma mass spectrometry (ICP-MS), 5.5 x 10-6 % m/m for cadmium and 1.9 x 10-5 % m/m for lead (F AAS) and 2.5 x 10-8 % m/m for cadmium and 3.2 x 10-7 % m/m for lead in the graphite furnace atomic absorption spectrometry (GF AAS). The curve in aqueous medium was suitable for the analyses, which was evaluated with addition and recovery studies, where values varied between 84-100% and 75-81% for cadmium and lead, respectively. The results obtained by standard addition were similar with those obtained by the calibration curve in 6 % for cadmium and 0.5 and 1.3 % for lead in samples A and E. Among the analyzed analytes, the Cd was the one more leached and the solution that leached more metals was solution 1, indicating that this metal was in the most available form and the possibility of leaching occurred in solutions with pH between 6-8.