Preliminary Bioleaching Experiment of E-Waste

Abstract

Nowadays, we can hardly imagine our life without the achievements of modern technology, such as refrigerators, televisions, computers, or smartphones. Producers are pushing consumers to buy newer, more modern appliances instead of repairing the original ones. However, all the devices represent a huge amount of waste. E-waste is one of the fastest growing types of waste, and only less than a half of it is recycled. Its disposal poses a great challenge for the population and constitutes a huge burden for the environment. In the research described in this article, we focused on individual techniques for metals recovery from e-waste. In the experimental part, we deal with the recycling of electronic waste by bioleaching, using microorganisms Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. Compared to conventional techniques, bioleaching is a more environmentally friendly and economical alternative of metals recovery from e-waste.

Two-Step Bio-Dissolution of Metals from Printed Circuit Boards Using Acidophilic Iron- and Sulfur-Oxidizing Mesophiles

“…However, a significant decrease was witnessed with a PS of 500-700 µm where an ORP of 400 mV on the last day of the experiment occurred, from an ORP of 720 mV. These findings are not peculiar to this study as they were also witnessed by other authors [4,25]. These findings demonstrated that the PS has an impact on microbial activity.…”

“…The pH of the medium was corrected, when necessary, by adding droplets of 98 v/v% H 2 SO 4 to reduce the alkalinity and the formation of jarosite participates that is caused by a pH above 2 [26]. This increase in pH was also observed in various studies [2,4,27]. The ORP profile also showed a decrease when the e-waste was added, and this decrease varied depending on the PS.…”

“…The nutrients from the 9K media were dissolved in 700 mL of distillate water, and the pH was adjusted to 1.8 with 98% v/v stock sulfuric acid (H 2 SO 4 ). After that, 44.22 g of FeSO 4 •7H 2 O was dissolved in 300 mL of distillate water, and the pH was also adjusted to 1.8 [4]. Thereafter, two solutions were mixed to remove any formation of undesired precipitation, and the pH was re-measured to ensure that the 1 L pH medium was still at the pH of 1.8; if not, the solution was readjusted to 1.8.…”

“…A two-step bioleaching approach was followed as described by Kucmanová et al [4]. The first step involved the bio-oxidation of ferrous iron (Fe 2+ ) to ferric iron (Fe 3+ ) using the non-adapted microorganisms.…”

“…Printed circuit boards (PCBs) have been noted as one of the e-waste materials that contain valuable metal content, where 28-30% is the metallic portion, and 70-72% is the non-metallic portion, such as polymers, ceramics, plastics, fiberglass, brominated flame retardants, etc. Therefore, PCBs can serve as alternative secondary sources of base, precious, and rare earth metals (REMs) [4]. It is worth mentioning that the element contents deposited on PCBs are ten to a hundred times higher than those of mined natural ores [5].…”