A ferrocyanide-based compound called E-series is proposed as an environmentally friendly and more selectiveSelective alternative to cyanide for leachingLeaching gold (Au) from e-wasteE-waste, specifically, from printed circuit boards. E-series uses a combination of ferrocyanide and thiourea to accomplish these requirements. Experiments show that E-series can leach Au faster and copperCopper slower than cyanide, and that increasing the temperature increases both the selectivity and the leaching kinetics. The effect of changing the concentration of E-series was also investigated, and it was found that lower concentrations have a higher selectivity while having slower leaching kinetics. Overall, E-series is found to be a much safer and more effective lixiviant for leaching Au than cyanide.