Dissertação
Recuperação seletiva de ouro de pinos de placa de circuitos impressos empregando nanofibras funcionalizadas com Cyanex 272
Fecha
2022-08-31Autor
Bernardo, Heliano Clemente
Institución
Resumen
Advances in technological development mean that the recovery of rare and strategic
metals from secondary sources has become essential, due to the high demand for these metals
in the production of electronic equipment. Contributing to this goal, the main purpose of this
work was to develop Nylon 6 nanofibers modified with the Cyanex 272 organic extractant, for
use in the selective recovery of gold present in printed circuit boards. The nanofibers were
produced by the centrifugation technique, employing the Forcespinning® system and identified
by scanning electron microscopy equipped with a secondary electron detector. The
concentration of elements present in the PCI pins was determined by atomic absorption
spectroscopy after leaching them with aqua regia. Gold concentrations in the
extraction/stripping aqueous phases were performed by atomic absorption spectroscopy. The
best extraction conditions for the separation and concentration of gold were 10% Cyanex 272,
fixed pH of 1.5, contact time of 15 min, and solid:liquid ratio (S/L) of 1/700. Gold extraction
efficiencies above 77% were achieved in this step. In the stripping step, efficiencies exceeding
85% were obtained using 1 M HCl, 1 M thiourea, S/L of 1/50, and contact time of 3 min. The
nanofibers were evaluated in terms of their adsorption capacity, stability, and capacity for reuse
in successive cycles. The results demonstrated the possibility of reuse of Nylon 6/Cyanex 272
nanofibers after at least five extraction and stripping cycles. These nanofibers provided high
selectivity in the recovery of gold when applied using real leachate solutions, in the presence
of other metals (lead, tin, zinc, and copper). The use of nanofibers modified with Cyanex 272
was shown to be an effective option for gold recovery, with lower environmental impacts,
compared to conventional liquid-liquid extraction methods that require the use of organic
solvents.