Fundamental Research for Extractive Removal of Interfering Anions Using Secondary Diamide Compounds with Different Spacer Length And Their Application to Microreactor System

Copper anode slime in hydrometallurgical purification process of copper contains a variety of anions. For recovery of platinum group metals, removal of coexisting and interfering toxic anions is of importance. Secondary diamide reagents providing d +nature of N-H hydrogen atoms with different spacer length have been prepared to investigate extractive removal of chloride and nitrate ions in two different solvents as fundamental study for removal of interfering toxic anions from platinum group metals. All secondary diamide reagents examined exhibited preferable extraction for NO3-as an oxoanion over Cl-as a simple anion, probably due to plural affinities between N-H hydrogen atoms and N-O oxygen atoms. However, obvious evidence that distance between two N-H hydrogen atoms affects the selectivity of a certain size of anion. It may be caused by extremely weak d +nature of N-H hydrogen atoms, that is, affinity between N-H hydrogen atoms and anion is extremely weak and would be affected by intermolecular hydrogen bonds and solvation. It means that the affinity was also affected by type and polarity of solvent. The extraction equilibrium constants (Kex), the separation factors (β), of Cl-and NO3-with three secondary diamide reagents were estimated. The extraction of Cl-and NO3-with three secondary diamide reagents were also investigated in microreactor system. The extraction in microreactor system was extremely fast compared with that in batch-wise system, and immediately (on the second time scale) reached steady-state.