Sulfur-Functionalized Single-Walled Carbon Nanotube Buckypaper/MTV-BioMetal-Organic Framework Nanocomposites for Gold Recovery.

Developing sustainable, efficient, and selective gold recovery technology is essential to implement the valorization of complementary alternative sources for this precious metal, such as spent e-waste, and to preserve the environment. The main challenge in recovering gold from liquors obtained from leached waste electronics is the low concentration of this precious metal compared to impurities. Here, we report the preparation of a novel multivariate biological metal-organic framework (MTV-BioMOF) as a potential material for the selective recovery of gold metal ions from water, even in the presence of other interfering metals. Moreover, MTV-BioMOF can be incorporated within single-walled carbon nanotube buckypapers (SWCNT-BP) to yield an MTV-BioMOF@HS-SWCNT-BP composite, which combines enhanced mechanical properties and high chemical stability. The thiol-functionalized SWCNT-BP surface and the presence of thioether groups evenly decorating the MTV-BioMOF channels shape a task-specific functional environment that boosts the interactions with gold metal ions. The efficiency of gold recovery reaches values up to 99.5% when MTV-BioMOF@SWCNT-BP is used as an adsorbent for treating Au(III) in very diluted solutions (initial concentration of 5 ppm). This high recovery efficiency, with values as high as 98.0%, is maintained even in the presence of competing metal cations, also demonstrating a noticeable selectivity. This composite material represents a promising paradigm for the selective extraction, enrichment, and purification of gold.