A strategy for the efficient recovery of highly pure copper and antimony metals from electronic waste (e-waste) was implemented by the combination of hydrometallurgical and electrochemical processes. The focus is on copper recovery as the main component in the leached solution, whereas the antimony recovery process was established as a purification step in order to achieve a highly pure copper deposit. The strategy includes mechanical methods to reduce the size of the wasted printed circuit boards to enhance the efficiency of antimony and copper lixiviation via ferric chloride in acidic media (0.5 M HCl) followed by an electrowinning process. In order to establish the best parameters for copper electrowinning, the leached solution was characterized by cyclic voltammetry and cathodic polarization. Then, an electrochemical reactor with a rotating cylinder electrode was used to evaluate the copper concentration decay, the cathodic current efficiency, the specific energy consumption, and mass-transfer coefficient. Furthermore, antimony was recovered via precipitation by a pH modification in accordance with the Pourbaix diagram. Under this methodology, two valuable products from the e-waste were recovered: a 96 wt % pure copper deposit and 81 wt % pure antimony precipitate. The strategy for recovery of other metal ions, such as lead, present in the e-waste at high concentrations will be reported in further works.
The anodic dissolution of gold in chloride medium is a well-known phenomenon in many practical electrochemical applications. However, from the theoretical point of view, there is still a lack in the comprehension of how this process takes place. This work is a fundamental and deep study about the electrochemical stages involved in the gold dissolution process when chloride and perchloric ions are present in the electrode-electrolyte interface. The effect of chloride ion's concentration and the anodic polarized potential is extensively evaluated by cyclic voltammetry and electrochemical impedance spectroscopy. Here, we present four possible equivalent circuits where two of them are statistical and phenomenological valid to describe the adsorption process in absence and presence of charge transfer as well as the fundamental stages involved in the charge and mass transfer over the gold electrodissolution process. An extensively discussion concerning these processes and the phenomena associated to them are presented. The results satisfactorily complement previous knowledge acquired by others studies in where the electrochemical impedance spectroscopy was not applied.
The aim of this study
is to design and develop an efficient leaching
process based on a fundamental and theoretical thermodynamic analysis
and the optimization of the operation parameters via the response
surface methodology (RSM). Using this methodology, the design of a
leaching process for the recovery of copper, silver, and lead from
highly metal-concentrated fractions of e-waste is presented. Thermodynamic
predictions were performed through the construction and analysis of
Pourbaix diagrams for the specific conditions of the leaching system.
From this analysis, it was possible to determine the values of potential
(
E
vs NHE) and pH at which the leaching reactions
occur spontaneously. Additionally, RSM was useful to deduce a quadratic
semiempirical model that predicts the copper leaching efficiencies
as a function of two parameters involved in the leaching procedure,
the stirring speed and the solid/liquid ratio, by which the response
variable, the leaching efficiency, can be optimized.
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