Electronic waste, flash heating to recover precious metals

Electronic waste

E-waste is not just a major pollutant in landfills, but huge amounts of useful resources that are thrown away. Rice University engineers have now shown that precious metals and rare earth minerals can be recovered with flash heating and very little electricity.

The constant search for newer, better performing smartphones makes e-waste the flow of fastest growing waste in the world, with 59 million tons generated in 2019 alone. If cleaning up the environment isn't motivating enough, then perhaps the financial incentive will be. In fact, it is estimated that all discarded mobile devices contain tens of billions of dollars of precious metals such as gold, silver, copper and platinum. Unfortunately, less than 20% of the world's electronic waste is recycled, so Rice's team decided to make this process simpler and less expensive.

In previous work, researchers have demonstrated a technique called flash joule heating , which involves the use of electricity shocks lasting in the order of milliseconds, which heat materials to high temperatures. Originally the team used it to create graphene from waste products, and later converted carbon from nearly any source into graphene or diamond by alternating the flash length.

For the new study, the team has turned its attention to the problem of electronic waste. They started by grinding old discarded circuit boards into powder, then heated the mixture to 3,127 ° C. This vaporizes the metals and the vapors are then piped into a cold trap where it condenses back into solid metals. From there, common refining methods can separate specific metals for use.

The team claims that this process can recover over 60% of gold in a sample and over 80% of silver, palladium and rhodium as well as removing toxic heavy metals such as chromium, arsenic, cadmium, mercury and lead, which can pollute electronic waste landfills. Importantly, researchers say the process is also energy efficient and scalable. It consumes about 939 kWh per ton of processed material, which is one eightyth of the quantity consumed by commercial smelting and one five hundredth of that of furnaces.

---

Recycling the Middle East's e-waste in Dubai

© Provided by CNN enviroserve dubai spc intl_00014208.png

Across the globe, electronic waste is piling up. In 2019, over 53 million metric tons of electronics ended up in the trash, and that number is expected to double by 2050.

But less than 20% of used electronics are currently recycled. This means a lot of valuable resources are literally going to waste.

Among the components are bits of silver, copper, gold and steel. In total, scraps of electronic devices represented $57 billion-worth of resources in 2019, of which $47 billion-worth wasn't recycled.

Africa holds the lowest rate of formal e-waste recycling in the world -- only 1% of binned devices are redirected to recycling plants. But Enviroserve, one of the world's largest electronics recyclers, see this as an opportunity.

With e-waste on the rise globally, the company has built a plant in Dubai capable of processing 14 times more e-waste than it does today. It processes waste from 10 countries across the Middle East and Africa and can recycle up to 98% of the material from an electronic device into raw materials, which are then sold to manufacturers in the automotive, IT and construction industries.

Watch the video for the full story