Sustainable urban mining of silver with fatty acids

Recycling silver from waste materials is becoming increasingly important to secure its supply. The design of new sustainable separative recycling strategies is highly desired to replace current, environmentally burdensome processes. Herein, we disclose a novel sustainable recycling concept for Ag. It includes the facile dissolution of silver using the most common fatty acids – oleic, linoleic and linolenic acid – that reaches 4.6 % of silver per fatty acid weight and high dissolution rates of up to 1.62 mol/m²h calculated from the wire mass loss during dissolution. The addition of ethyl acetate to the reaction mixture separates silver carboxylates − analyzed by NMR, IR, EDS and CHN combustion analysis − from the unreacted acids that can be recycled. As also introduced here, the light-enabled reduction in a reactor consisting of two 30 W 6700 K CFL lights with wavelengths of 400–650 nm is a powerful and safe method to bring silver back to its easily separable elemental form, determined by SEM-EDS. The protocol uses 30 % aqueous hydrogen peroxide as a green oxidant under benign conditions and can be applied to urban mining from waste silver-plated keyboard connection plastics and for the notable separation of silver from other metals.