New compounds dissolve gold at room temperature

Extracting gold from electronics

The electrical contacts of memories, processors, and various other components used in computers, cell phones and other electronic devices are made of gold to ensure accurate operation and corrosion protection that could make these devices stop working quickly if other metals were used , which are susceptible to oxidation.

With so much junk being accumulated around the world , there has been a growing interest in "mining" this precious metal in scrap heaps.

Efforts in this area were mainly focused on biomineration , which uses bacteria and fungi to extract metals, including printed circuit boards .

The problem is that it consumes a lot of energy because all the electronic waste should be melted or frozen so that its components are extracted.


The good news is that everything can be done more simply from now on thanks to the work of Sebastian Riedel of the Free University of Berlin, Germany.

Riedel synthesized two new poly-pseudohalogen compounds that had the unusual property of dissolving gold at room temperature just as water dissolves the sugar.

The discovery promises to enable the creation of safer chemicals not only to recover and recycle the noble metal from junk, but also to be used in the leaching of gold and other noble metals from the mined ore - gold mining today uses a process based on cyanide, an extremely toxic compound.

The chemistry of polyhalogens has been the subject of great interest in recent years. However, due to their high instability, volatility and problematic synthesis, much less attention has been paid to poly-pseudohalogens, which are pseudohalogen compounds that essentially mimic the halogens in their chemistry, while also possessing poly- halogen - they belong to the class of ionic liquids .

Leaching of gold

Riedel was able to synthesize and characterize two new anions capable of dissolving gold - [PNP] [Br (BrCN)] and [PNP] [Br (BrCN) 3]. Although they can not be called environmentally friendly, the two compounds are 10 times less volatile than their precursor and gold leaching works at ambient conditions.

"With our new compounds, it may be possible to simplify the gold leaching process using ionic liquids at room temperature," said Benjamin Schmidt, member of the team.


From Polyhalides to Polypseudohalides: Chemistry Based on Cyanogen Bromide
Sebastian Hasenstab-Riedel, Benjamin Schmidt, Benjamin Schröder, Karsten Sonnenberg, Simon Steinhauer
Angewandte Chemie
DOI: 10.1002 / ange.201903539

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