Our addiction to tech is producing vast amounts of e-waste – 45 million tonnes (50 million US tons) of it to be precise, according to a 2016 UN survey. To put this into perspective, that is roughly the same weight as 4,500 Eiffel Towers. Rising incomes, falling prices, and a growing demand for gadgets, gizmos, and other electrical goods means we can only expect the figure to keep going up, which is good news for tech companies but bad news for the environment.
Currently, only 20 percent of that waste is being recycled. However, a new method outlined in the journal Small could make the practice of recycling metal-coated SIM cards and other electronics a whole lot easier and more affordable. The technique makes use of ultrasound and a process called cavitation, when sound is pumped through a liquid to produce tiny bubbles.
First, an extremely fine layer of a cheap surfactant is used to cover the SIM card. The team then repeats the process with a second type of surfactant before submerging the SIM in water. Surfactants help to lower the surface tension between two substances so that when ultrasonic waves are introduced, microscopic bubbles are released, raising pressure and temperatures (which can reach highs of 4700°C), and causing microjets of gold particles to expel from the SIM and get caught in the liquids. Later, the gold can be collected and recycled.
Methods currently used to extract metals involve toxic solvents and cremation and, therefore, release harmful substances into the atmosphere. In contrast, Dale Huber of Sandia National Laboratories in Albuquerque, New Mexico, who worked on the paper, has said this new process is low-cost, has very little impact on the environment, and can be used to help tackle the growing problem of wasted metal in discarded electronics.
In 2016, more than $20 billion worth of gold was simply chucked away as e-waste. Other precious metals such as silver, copper, platinum, and palladium are also being thrown away. The researchers hope this new method could help limit the amount of raw metal waste in future – and even, possibly, reduce the amount currently sitting in landfills.
“It could be applied to reclaim some of the $3.5 billion-worth of palladium waste, and while requiring further investigation, it should be applicable to rare-earth metals, the next target we’ll investigate in detail,” added Huber, speaking to New Scientist.