Capture of copper cyanide complex ions based on self-assembly of ionic liquids actuation and application to cyanide wastewater

The tetrabutylammonium bis (2-ethylhexyl) phosphate [N4444][P204] ionic liquid (IL) was synthesized, which was applied to extract copper cyanide complex ions in cyanide tailing liquid stream pressure filtration. In the extraction process, macroscopic layered solids rich in copper cyanide complex ions were formed at the phase interface, which was based on self-assembly of ionic liquids actuation. The solid samples can be obtained by simple filtration. Meanwhile, the extraction behaviors were investigated in detail. The [N4444][P204] ionic liquid exhibited excellent extraction efficiency for copper cyanide complex ions. More than 90% of copper cyanide complex ions were extracted at pH 13.4 and enriched as self-assembly solids in the process of one-step extraction and solidification. Notably, the extraction efficiency of copper cyanide complex ions can still reach more than 75% after three cycles of organic phase with fresh aqueous phase. Furthermore, the analyses of the SEM, EDS, XPS, FTIR, and ESI-MS for self-assembly sample implied that the potential mechanism of extraction for copper cyanide complex ions is coordination reaction. It is worthy of note that the extraction system of [N4444][P204] IL has no extraction effect on iron cyanide complex ions. In the end, the proposed strategy may be further expanded to the separation of other metal cyanide complex ions by designing the ionic liquids.