Polythioamide-g-C3N4 for highly efficient and selective gold recovery

Gold recovery from secondary sources is essential for sustainable supply. To develop a gold recovery approach with high efficiency and selectivity, polythioamide-functionalized carbon nitride (PTA-g-C3N4) was synthesized and applied to photo-induced gold extraction. PTA-g-C3N4 was synthesized by multicomponent polymerization of elemental sulfur, organic amines, acids and carbon nitrides. The maximum adsorption capacity of PTA-g-C3N4 reached 3668 mg·g−1, far exceeding other reported materials. Moreover, PTA-g-C3N4 enabled rapid (<3 min) and efficient gold recovery (>99%) from dilute solutions, and more importantly, the extraction for gold is highly selective in complicated wastewater and authentic e-waste leachates. High purity metallic gold with >95% content was obtained by incineration of the used material. Regeneration scheme and economic analysis further support the applicability. Mechanism studies revealed the formation of an efficient two-phase interface capable of selective adsorption and reduction of gold ions, where bifunctional PTA exhibited high affinity for AuCl4− and sacrificial behavior to accelerate photo-reduction.