The Independent reported that scientists have developed a new technology to extract valuable metals from electronic waste. This technology uses 500 times less energy than existing methods, reducing the need for raw material mining and preventing environmental damage to the waste generated. "The largest source of waste has become a treasure." The technology is based on the "Flash Joule Heating Method," an innovative method for producing graphene from carbon sources such as wood and plastic. A research team at Rice University in Texas has modified the "Flash Joule Heating Method" to recover materials such as rhodium, palladium, gold, and silver from waste for reuse. The new technology works by rapidly heating waste to 3400K (3124°C) with an electric current, vaporizing the metals into gases for separation, storage, or disposal. The research team stated that "Flash Joule Heating" removes residual highly toxic heavy metals such as chromium, arsenic, cadmium, mercury, and lead from the material, leaving behind byproducts with extremely low metal content. With more than 40 million tons of e-waste generated globally each year, this new form of "urban mining" has enormous potential, offering tech companies the opportunity to avoid sourcing raw materials from countries and regions with security, corruption, and conflict issues. "Here, the largest source of waste is transformed into a treasure," said Professor James Tour of Rice University. "This could reduce the need to mine ore, dig up the ground, and use vast quantities of water in remote and dangerous areas around the world... The treasure is right in our trash cans." Tour said the increasing rate of replacement of personal devices, such as mobile phones, has led to a rapid increase in e-waste worldwide. Currently, only about 20% of waste is recycled. "We've found a way to recover precious metals and turn e-waste into a sustainable resource, while also removing toxic metals to protect the environment." The flash evaporation process, which takes less than a second, also reduces the concentration of toxic metals. The research team said that flash evaporation of e-waste requires some preparation. Led by Dr. Bing Deng, a postdoctoral researcher at Rice University and lead author of the study, the researchers ground the circuit boards they were testing into powder and added special additives, such as Teflon or salt, as well as a small amount of carbon black to improve recovery. The flash evaporation process focuses on the "evaporative separation" of metal vapors. Under vacuum, the vapors are transferred from the flash chamber to another container, where they condense into the raw metals. "The metal mixture recovered in the collector can be further purified into individual metals using established refining methods," Dr. Deng said. The researchers report that a single flash Joule reaction reduced the lead concentration in the remaining carbon to below 0.05 ppm, a level generally considered safe for agricultural soil. As the number of flashes increased, the levels of arsenic, mercury, and chromium further decreased. "Because each flash takes less than a second, it's easily achievable," said Professor Tour. The researchers report that the new technology consumes approximately 939 kilowatt-hours of electricity per ton of material processed, which is 80 times less than a commercial smelting furnace and 500 times less than a laboratory tubular furnace. It also eliminates the lengthy purification steps involved in smelting and leaching. Source: Environmental Information Center (https://e-info.org.tw/node/232500)
