Reciclagem de placas de circuito impresso de computadores desktops obsoletos através de processos hidrometalúrgicos

Abstract

Currently, waste electrical and electronic equipment (WEEE) has become an environmental problem that must be managed responsibly, as well as an economic resource that must be exploited in a viable way. For example, printed circuit boards (PCBs), which form part of most WEEE, are made up of hazardous materials such as heavy metals and flame retardants, as well as valuable materials such as base and precision metals, so they must be treated properly. In view of this, the scientific community has dedicated itself to the recovery of this residue. Therefore, the objective of this work is to study the recycling of PCBs from obsolete desktop computers through hydrometallurgical processes, more precisely the modeling and optimization of copper leaching with nitric acid and depolymerization with benzyl alcohol and potassium hydroxide through an experimental design composed central. Therefore, the PCBs were initially pre-treated (dismantled, cut, milled and sieved) to obtain a pulverized material with a granulometry smaller than 2 mm. After that, the pulverized PCBs were characterized through different analyzes (granulometric classification, incineration, digestion in aqua regia and XRF). The first study evaluated the effects of acid concentration (from 0.2 to 4.2 mol/L), temperature (from 30 to 90 °C), solid/liquid ratio (from 10 to 90 g/ L of PCI/solution) and time (from 30 to 150 minutes) on the copper leaching efficiency that was determined by molecular absorption spectroscopy analyzes in the visible region. The second study evaluated the effects of hydroxide concentration (from 0.10 to 0.90 mol/L), PCI mass (from 1 to 9 g) and temperature (from 50 to 150 °C) on the efficiency of depolymerization in benzyl alcohol determined by mass balance. The adjusted statistical models for both processes proved to be significant and predictive (R² close to or greater than 0.9) and their optimization resulted in complete extraction of the copper and polymeric fraction presente in the PCI. Finally, the present study contributed to the development of two viable hydrometallurgical routes for PCB recycling.