Selective Extraction Of Gold By Niacin

Gold recovery using a sustainable and inexpensive method has tremendous environmental and economic implications. We developed a highly cost-effective and sustainable method of gold extraction in which aqueous Au3+ is precipitated selectively as it is complex with the biomolecule niacin, having an overall formula, [AuCl4](-)[2Niacin + H](+), abbreviated as I. This selective precipitation occurs from mixtures of Au3+ with Ni2+, Cu2+, and Zn2+ along with commonly occurring alkali (Na+/K+) and alkaline earth (Mg2+/Ca2+) metal ions. From single-crystal studies, it was confirmed that electrostatic attraction and supramolecular interactions are the reasons for such co-precipitation, which was also confirmed by spectroscopy. Using the method, about 96.5% of gold was extracted in 2 min from electronic waste composed of Au, Cu, and Ni. This method was also employed to extract gold from nanomaterial waste generated in laboratories. Niacin, being inexpensive and renewable, costing similar to US$ 6000 per ton in the local market, the method may be used for cost-effective, selective and sustainable extraction of gold from diverse raw materials.