Estudo da remoção de metais pesados de placas de circuito impresso por eletrodeposição utilizando eletrodos de cobre

Abstract

Electronic waste is becoming one of the most serious environmental and social problems today. To take aware of the problem, we need to discuss disposal and recycling alternatives. In this thesis, a new methodology for the removal of metals from printed circuit boards (PCB) is presented. This methodology contributes to the minimization of environmental impacts by recovering metallic elements of PCB, which reduces the exploitation of mineral deposits. The process of recycling of the PCB presented in this thesis consisted of the application of chemical and physical technologies, involving the leaching stage in acidic (nitric and hydrochloric) environments and the removal of copper, silver and tin by electrodeposition using copper electrodes. The initial electrodeposition reactions were performed in three current conditions (0.5 - 1.0 - 1.5 A) and time variations (15 - 30 - 60 - 90 and 120 min), respectively, with the original solution. For all conditions, the process was accomplished out without mechanical stirring and with mechanical agitation at 550 rpm. In another stage of reactions, the solution was diluted in 1: 3 and 1: 7 proportions, and electroplating tests were carried out under the same current conditions, with and without stirring and a constant time of 60 minutes. The electrodeposition of copper has been shown to be efficient at all applied times and currents, removing up 98%. For silver, the best deposition rates occurred at a current density of 0.022 A / cm2 and time of 60 minutes, removing up 7%. For the tin, the best removals proceeded in the process without agitation, with the diluted solution, presenting rates of removal in current of 1.5 A and without agitation of about 99%. The concentrations of silver and tin, at the end of each process, were analyzed by X-Ray Fluorescence (FRX), Atomic Absorption Spectroscopy (EAA), X-Ray Diffraction. The morphology of the deposits, analyzed by Scanning Electron Microscopy (SEM) coupled to the Dispersive Energy Spectroscopy.