Synthesis and Binding Studies of a Novel Highly Selective Ag(I) Ligand
Ligands bearing <i>S</i>- and <i>N</i>- donors are an important class of extractants with demonstrated efficiency and selectivity for Ag<sup>+</sup> extraction over metals with similar chemistries. However, the synthesis of some of these ligands can be complicated and low yielding. Here, we report the synthesis of a novel ligand - <i>N</i>-(2-((4-vinylbenzyl)thio)ethyl)acetamide, over two simple steps and in a good yield. The extractant was observed to demonstrate excellent selectivity for Ag<sup>+</sup>, extracting only Ag<sup>+</sup> from an aqueous solution also containing Cu<sup>2+</sup> and Pb<sup>2+</sup>. Moderate extraction efficiencies of 36 % for Ag<sup>+</sup> and 0% each for Cu<sup>2+</sup> and Pb<sup>2+</sup> were observed. From mass spectrometry and proton NMR titration data, the extractant was found to form both the 1:1 and 1:2 (Ag<sup>+</sup>:ligand) complexes with Ag<sup>+ </sup>indicating that ligand forms bent linear and tetrahedral coordination complexes with Ag<sup>+</sup>. Overall, the results indicate that the novel amide-based ligand is highly selective for Ag<sup>+</sup> removal from aqueous solutions containing Cu<sup>2+</sup> and Pb<sup>2+</sup>. These results indicate the ligand could be easily synthesized and applied for selective silver recovery from low grade ores.