Method:
1. Take the old mobile phone apart, take out the motherboard and put it in a beaker.
2. Pour concentrated nitric acid and wait for a while.
3. Because the chemical properties of gold are very stable, it can't react with concentrated nitric acid, while other metals can react with concentrated nitric acid. After the reaction, the residue was filtered out.
Note: concentrated nitric acid is very dangerous, please don't try it easily.
Usually, about 5 grams of gold can be extracted by mining one ton of gold sand. But do you know that under the same weight, a ton of used mobile phones can extract 400 grams of gold, 2.3 kilograms of silver, 172 kilograms of copper and so on. Xu He, a professor at the School of Environmental Science and Engineering of Shanghai Jiaotong University, and his team have developed electronic waste sorting technology and equipment with independent intellectual property rights, making it possible to find gold in urban mines.