Electronic waste (e-waste) is the fastest-growing waste stream globally, with 62 billion kilograms generated in 2022 according to the Global E-Waste Monitor. Among the many valuable metals found in e-waste, tin plays a particularly crucial role. Tin is primarily used in the solder that connects components on printed circuit boards (PCBs). In fact, on average PCBs contain around 3% tin.
The demand for tin is set to grow as it is increasingly used in new technologies, such as batteries, solar panels, and water treatment solutions. As demand for tin grows, aiding primary tin sources with secondary recycling methods is key.
The process of recovering tin from e-waste involves several stages, starting with collection and sorting. Advanced technologies, such as X-ray fluorescence (XRF) spectroscopy, can be used to identify and separate e-waste based on elemental composition making the recovery process more efficient.
Once e-waste materials are sorted, specific methods can be implemented to isolate and recover desired elements. In the case of tin, methods such as thermal and chemical depopulation can be used. Thermal depopulation uses heat to melt solder, while chemical depopulation dissolves solder using acids such as hydrochloric acid (HCl) often combined with oxidants to enhance the process.
Alternative hydrometallurgical technologies such as deep eutectic solvents (DES) and bioleaching can be used to recover tin from PCBs. DES are often derived from plants, for example oxalic acid found in spinach has been shown to selectively leach tin from PCBs. Bioleaching, on the other hand, uses bacteria to leach and recover tin from PCBs.
Pyrometallurgical methods such as smelting and flash joule heating (FJH) also play an important role in tin recovery. These methods use high temperatures to separate metals quickly and efficiently. Flash joule heating, for example, uses rapid electric discharges to heat e-waste in milliseconds, making it an energy-efficient method for metal extraction.
As the demand for tin continues to rise, particularly in sectors like renewable energy, recovering tin from e-waste is becoming increasingly essential. A comprehensive summary of the various methods for tin recovery from e-waste can be found inside our Tin Valley lounge.
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