Extraction of platinum from aqueous solutions using tetraalkylammonium dicyanamides

Ionic liquids (IL) based on tetrahexyl-, tetraheptyl-, and tetraoctylammonium cations and dicyanamide anion were obtained as a result of the chemical interaction of ammonium bromides with dicyanamide salts. The purity of IL synthesized (>98%) was confirmed by atomic absorption spectrometry and ionic chromatography. The influence of such factors as solution acidity, extraction, temperature, and duration, the ratio of organic and aqueous phase volumes on the recovery of platinum ions was studied. It was shown, that ionic liquids with longer alkyl chains exhibit higher efficiency due to their improved hydrophobic properties. Spectroscopic analysis of the extracted systems revealed that the mechanism of platinum extraction is associated with the formation of stable ion pairs between metal halogen complexes and tetraalkylammonium cations. This interaction causes a hypsochromic shift in the absorption spectra (λ max = 261 nm), confirming the nature of the formed compounds. Ionic liquids demonstrated stability and low solubility in the aqueous phase, which makes them reliable extractants. The application of the proposed eco-friendly approach can be useful for recycling secondary platinum sources, cleaning industrial wastewater and minimizing environmental pollution.