Efficiency and selectivity of gold extraction from E-waste leachates by ether, amine, nitro, and nitrile-containing organic solvents

The growing demand for rare and precious metals in the fields of renewable energy and electronics is driving the search for alternative sources of the critical feedstocks. Electronic waste (e-waste) represents a promising resource, but its complex organic-inorganic composition requires robust separation methods. This study examines the selective extraction of e-waste-relevant elements, Au, Fe, Ni, Cu, Zn, and Pt, from aqueous HCl solutions using organic solvents containing ether, amine, nitro, and nitrile functionalities. Among studied solvents, decanonitrile and dibutylcarbitol exhibited the highest 99.2 % and 98.5 % Au extraction efficiency, respectively. Back-extraction with sodium thiosulfate enabled nearly quantitative Au recovery from decanonitrile or dibutylcarbitol with over 99.9 % stripping efficiency. In addition, the decanonitrile showed the best selectivity toward Au compared to other co-existing metals and was selected as the optimal solvent for Au extraction from acidic leachates of mechanically and mechano-thermally processed e-waste of printed circuit boards (PCBs). Extraction of Au from e-waste leachates by decanonitrile showed a 98.2 % extraction rate after the first extraction and > 99.9 % after the second, with other metal contents in leachates of only 4.5 %. The high selectivity and efficiency of the proposed decanonitrile extraction method, combined with a facile separation and possibility of the efficient back extraction of Au, render nitrile- solvents as promising candidates for scalable, environmentally friendly gold recovery from e-waste. • Extraction of Au from e-waste leachates by organic solvents was studied. • Ether, amine, nitro, and nitrile solvents were evaluated for extraction efficiency. • Decanonitrile and dibutylcarbitol achieved >98 % Au extraction efficiency. • Au stripping with sodium thiosulfate reached >99.9 % recovery. • Decanonitrile enabled selective Au extraction from PCB e-waste leachates.