Selective Extraction of Gold by Niacin

Abstract

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 ∼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.

Highly efficient and selective extraction of gold by reduced graphene oxide

“…In comparison to the reported novel gold adsorbents, though some showed reductive adsorption, other physi-and chemi-sorptions were also significant. That is, gold extracted by these adsorbents was a mixture of ionic and metallic gold 4,[12][13][14][15]19,[27][28][29] , therefore, it would require energy-and cost-intensive post-processing, for example, elution and precipitation to desorb and reduce the ionic gold, so that a full adsorption capacity can be achieved 30,31 . In contrast, as >95% extracted Au ions were reduced to metallic gold by rGO, it allowed direct isolation of metallic gold from rGO surface without further post-adsorption processing, providing an extra advantage of rGO for gold extraction.…”

Rapid Dissolution of Noble Metals in Organic Solvents

“…Various kinds of metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) were also exploited in gold capture from aqueous solutions [9–11] . The simple pyridine‐carboxylic acid, niacin was also used to precipitate gold halides selectively from mixed‐metal acidic solutions [12] . Love and co‐workers developed a simple primary amide and showed that gold was recovered selectively from a mixture of metals representative of e‐waste by solvent extraction [13] .…”

“…[ 9 , 10 , 11 ] The simple pyridine‐carboxylic acid, niacin was also used to precipitate gold halides selectively from mixed‐metal acidic solutions. [12] Love and co‐workers developed a simple primary amide and showed that gold was recovered selectively from a mixture of metals representative of e‐waste by solvent extraction. [13] Following on from this work, a method was developed for the selective precipitation of Au and Pt using a simple diamide.…”

Tuneable separation of gold by selective precipitation using a simple and recyclable diamide

“…Supramolecular interactions between acyclic durene diamides and HAuCl 4 resulted in gold precipitation as extended networks, although in these cases no selectivity for gold over other metals was explored 32 . Extended supramolecular network structures were also formed upon selective precipitation of HAuCl 4 from acidic solutions comprising Au, Ni, Cu, Zn, alkali-, and alkaline-earth metals by the biomolecule niacin, a pyridine carboxylic acid 33 .…”