The most efficient solvent extraction method to recover valuable metals such as gold and silver from electronic waste using a continuous-flow system is the combination of leaching and solvent extraction processes. This method involves the following steps:1. Pre-treatment: The electronic waste is first mechanically processed to separate and concentrate the metal-bearing components. This may involve shredding, grinding, or crushing the waste to expose the metals.2. Leaching: The concentrated metal-bearing components are then subjected to a leaching process, where they are mixed with a suitable leaching agent, such as aqua regia a mixture of nitric acid and hydrochloric acid or cyanide solution. This step dissolves the metals, including gold and silver, into the solution.3. Solvent extraction: The leach solution containing the dissolved metals is then subjected to a solvent extraction process. In this step, an organic solvent, such as an extractant like diisobutyl ketone DIBK or dibutyl carbitol DBC , is mixed with the leach solution. The extractant selectively binds to the gold and silver ions, forming a metal-organic complex that can be easily separated from the aqueous phase.4. Stripping: The metal-organic complex is then separated from the organic solvent by a stripping process, typically using an acidic solution. This step recovers the gold and silver in a concentrated form, which can be further refined and purified.5. Recycling and regeneration: The organic solvent and leaching agents can be regenerated and recycled for reuse in the process, minimizing waste and reducing the overall environmental impact.This continuous-flow system allows for the efficient recovery of gold and silver from electronic waste, with the potential for high metal recovery rates and minimal environmental impact. However, it is essential to optimize the process parameters, such as the choice of leaching agent, solvent, and operating conditions, to maximize efficiency and minimize costs.