Designing a cost-effective and efficient system to recover valuable metals from electronic waste e-waste involves several steps, including collection, pre-processing, and chemical extraction. Here's a possible approach:1. Collection and pre-processing:- Establish a collection system for e-waste, partnering with local governments, businesses, and recycling centers.- Sort and disassemble the collected e-waste to separate components containing valuable metals, such as printed circuit boards PCBs , connectors, and wires.- Crush and grind the separated components to create a uniform particle size, which will facilitate the subsequent chemical extraction process.2. Pyrometallurgical process:- Use a pyrometallurgical process, such as smelting, to separate base metals e.g., copper from precious metals e.g., gold and silver . This involves heating the crushed e-waste at high temperatures in the presence of a reducing agent, such as carbon, and a flux, such as silica, to form a molten metal mixture.- Collect the molten metal mixture and allow it to cool and solidify. The base metals will form a separate layer from the precious metals, which can then be mechanically separated.3. Hydrometallurgical process:- Leach the precious metal-containing solid using a suitable lixiviant, such as a mixture of hydrochloric acid and nitric acid aqua regia for gold, or a solution of sodium cyanide for silver. This will dissolve the precious metals, forming a solution containing metal ions.- Separate the remaining solid residue from the metal-containing solution using filtration or sedimentation techniques.4. Metal recovery:- Recover the dissolved metals from the solution using one or more of the following methods: a. Precipitation: Add a suitable precipitating agent, such as sodium metabisulfite for gold or sodium sulfide for silver, to the solution. This will cause the metal ions to form solid particles, which can then be separated using filtration or sedimentation techniques. b. Adsorption: Pass the metal-containing solution through a column packed with a suitable adsorbent material, such as activated carbon or ion exchange resins, which will selectively bind the metal ions. The adsorbed metals can then be eluted using a concentrated solution of a suitable eluent, such as hydrochloric acid or thiourea. c. Electrolysis: Apply an electric current to the metal-containing solution using a suitable electrode setup, causing the metal ions to deposit onto the cathode as solid metal.5. Refining and purification:- Further refine and purify the recovered metals using appropriate techniques, such as electrorefining, to obtain high-purity metal products.6. Waste management:- Treat and dispose of any remaining solid and liquid waste materials in an environmentally responsible manner, in accordance with local regulations and guidelines.By following these steps, it is possible to design a cost-effective and efficient system for recovering valuable metals from electronic waste using chemical processes.