Sustainable Silver Recycling Developed Using Everyday Oils and Light
Finnish researchers have developed a sustainable method for recycling silver from waste, avoiding hazardous chemicals like cyanide. Their novel technique utilizes simple fatty acid molecules, similar to everyday oils, and visible light to dissolve silver and then recover it as solid metal. This breakthrough supports urban mining and a circular economy, crucial for meeting rising demand in electronics and solar panels while reducing reliance on traditional, dangerous mining practices. The process is also biocompatible and biodegradable.
Researchers at the University of Helsinki, led by Anže Zupanc, have pioneered a sustainable silver recycling method that circumvents the need for harsh chemicals like cyanide, traditionally used in metal extraction. This innovative approach addresses the growing demand for silver in electronics and solar panels, where only about one-fifth of the global supply currently comes from recycling. The technique begins by using simple organic fatty acids, similar to those found in everyday vegetable oils, along with hydrogen peroxide, to dissolve silver metal. The silver oxidizes and forms positively charged ions, creating carboxylate salts in the liquid.Subsequently, ethyl acetate is introduced to crystallize these silver compounds. The collected crystals are then subjected to visible light, emitted by compact fluorescent lamps, in a process called photoreduction. This step efficiently converts the silver ions back into fine metallic silver particles. A key advantage is the use of hydrogen peroxide as the oxidant, which breaks down into water and oxygen, preventing environmental contamination. The recovered acids can also be collected and reused, closing the recycling loop.This eco-friendly method has been successfully applied to waste materials like silver-coated keyboard plastics, demonstrating its potential to selectively extract precious metals from multi-metal substrates. The biocompatible, biodegradable, and low-acidity nature of fatty acids ensures safer working conditions compared to strong mineral acids. By supporting urban mining—recovering metals from discarded products—this technology offers a practical solution to ease supply pressures, reduce reliance on conventional mining, and foster a more circular economy for critical metals.
