As the global production of electronic waste (e-waste) continues to surge, surpassing 53.6 million tons in 2019 and predicted to exceed 74 million tons annually by 2030, innovative solutions are imperative to manage this environmental challenge. Among the various methods proposed for e-waste management, bioleaching has emerged as a promising avenue for extracting valuable metals from diverse waste substrates, particularly printed circuit boards (PCBs), which are laden with heavy and precious metals alongside non-metal elements.
Traditional approaches for metal recovery from e-waste, such as chemical precipitation or solvent extraction, are often inefficient or environmentally detrimental. Therefore, the search for sustainable and cost-effective alternatives has led researchers to explore biosorption—a process that employs natural or waste-derived materials to selectively bind and remove metals from solutions.
A recent study conducted by researchers from 1K1-MET GmbH in Linz, Austria, and the Department of Agrobiotechnology at the University of Natural Resources and Life Sciences Vienna (BOKU), introduces an innovative biosorption approach utilising spent brewer’s yeast for selective metal recovery from polymetallic waste streams. This research addresses a critical gap in the field, as previous biosorption studies have primarily focused on single-metal solutions, neglecting the complexity of polymetallic waste streams commonly found in e-waste recycling.
The study explored various factors to optimise biosorption efficiency for individual metals—specifically aluminum, copper, zinc, and nickel—by manipulating factors such as pH, metal concentration, and yeast biomass concentration. Through systematic optimisation with single-metal solutions, the researchers achieved remarkable results, paving the way for biosorption experiments with synthetic and real-world polymetallic waste streams.
Key findings from the study include:
- Selective metal recovery: Spent brewer’s yeast demonstrates a pH-dependent biosorption capacity, enabling the selective removal of aluminum, copper, zinc, and nickel from polymetallic solutions. Over 50% of aluminum, 40% of copper, and 70% of zinc could be removed under optimised conditions.
- Real-world application: The effectiveness of the biosorption process was validated using a real polymetallic waste stream obtained from the leaching of printed circuit boards. Significant metal recovery rates were achieved, with over 50% of copper and over 90% of zinc successfully recovered.
- Reusability and sustainability: Spent brewer’s yeast biomass exhibited remarkable reusability, retaining its metal recovery capabilities through five consecutive biosorption steps with minimal loss. This underscores the sustainability and cost-effectiveness of the proposed biosorption approach.
The use of spent brewer’s yeast as a biosorbent offers several advantages, including its abundance as a by-product of the brewing industry, low cost, and eco-friendliness. Moreover, the well-described chemical composition of Saccharomyces cerevisiae facilitates understanding of the underlying mechanisms involved in metal binding, enhancing process optimisation and scalability.
This study represents a significant advancement in the field of e-waste recycling, providing a sustainable and efficient method for selectively recovering valuable metals from complex waste streams. By leveraging the unique properties of brewer’s yeast, this biosorption approach offers a promising solution to mitigate the environmental impact of e-waste while simultaneously addressing resource scarcity issues. Further research and implementation efforts in this direction hold the potential to revolutionise metal recovery practices in the electronics recycling industry.
Source
Spent brewer’s yeast as a selective biosorbent for metal recovery from polymetallic waste streams, Frontiers, 2024-03-12
Boˆreal 