Remoção de metais em placas de circuito impresso de computadores utilizando o processo de biolixiviação

Abstract

The generation of electronic waste grows in parallel with technological development. The presence of toxic substances and the restricted disposal of these wastes represent environmental pollution and public health problems with global impacts. Printed circuit boards (PCBs) are very common components in electronic waste. These plates have high concentrations of metals, including both heavy metals for human health and valuable metals. This characteristic gives this material fundamental importance in the context of sustainability, as it stands out as a valuable secondary resource. In this scenario, several techniques are used to recover the metals present in PCBs, among them, bioleaching stands out, which promotes the mobilization of metals from solid substances to aqueous solutions and catalyzes this process by leaching agents produced from the metabolic activity of microorganisms. In this context, the present work aims to analyze the efficiency of removing lead (Pb), copper (Cu) and zinc (Zn) metals from printed circuit boards through bioleaching using the bacteria Acidithiobacillus ferrooxidans and a combination of A. ferrooxidans and Penicillium oxalicum. In this study, PCBs were collected and subjected to manual separation into Sample I (Boards) and II (Electronic components), which were designated in terms of metal content by X-ray Flourescence Spectroscopy. Experiments were carried out using A. ferrooxidans and a combination of A. ferrooxidans and Penicillium oxalicum with different initial inoculum proportions. The experiments were carried out for seven days with daily monitoring. With the leachate obtained in the process, pH determination, analysis of microorganism concentration and concentration of metals Cu, Pb and Zn were carried out. The results showed that sample I presented 4.31% Cu, 0.4% Pb and 0.05% Zn, while sample II presented 6.21% Cu, 0.26% Pb and 1. 19% Zn in its composition. Scanning Electron Microscopy (SEM) analyzes revealed similar surface morphologies in samples I and II, highlighting the presence of particles, tubular structures, and crystalline forms. Regarding pH, the results showed that during the first 24 hours of the experiment there was a sharp drop in pH values in all treatments, with evident variations depending on the amount of stock culture added. For the removal results, the behavior was observed of an increase in the percentage of metals removed over time. The ideal condition for total removal of Cu, Pb and Zn for both samples was with a final pH equal to 1.6 and a proportion of 35% (v/v) of inoculum. The removal of metals occurs through the bioleaching mechanism through the metabolic activity of microorganisms that mobilize metals from solid material to aqueous solutions and catalyzes this process through leaching agents such as organic acids.