Browsing by Subject "POWERFUL REAGENTS"

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  • Räisänen, Minna; Heliövaara, Eeva; Al-Qaisi, Feda'a; Muuronen, Mikko; Eronen, Aleksi; Liljeqvist, Henri; Nieger, Martin; Kemell, Marianna; Moslova, Karina; Hämäläinen, Jani; Lagerblom, Kalle; Repo, Timo (2018)
    Dissolution of elemental gold in organic solutions is a contemporary approach to lower the environmental burden associated with gold recycling. Herein, we describe fundamental studies on a highly efficient method for the dissolution of elemental Au that is based on DMF solutions containing pyridine-4-thiol (4-PSH) as a reactive ligand and hydrogen peroxide as an oxidant. Dissolution of Au proceeds through several elementary steps: isomerization of 4-PSH to pyridine-4-thione (4-PS), coordination with Au-0, and then oxidation of the Au-0 thione species to Au-I simultaneously with oxidation of free pyridine thione to elemental sulfur and further to sulfuric acid. The final dissolution product is a Au-I complex bearing two 4-PS ligands and SO42- as a counterion. The ligand is crucial as it assists the oxidation process and stabilizes and solubilizes the formed Au cations.