Identification of major species in industrial metal-refining solutions with Raman spectroscopy

Raman and resonance Raman spectroscopies were used to characterize industri al metal-refining solutions containing nitrogen, sulfur, and Ni, Co, Zn, an d Cu ammine complex species. To identify the species present in these solut ions, we also recorded Raman spectra of model compounds in similar matrices . The results indicate that clearly resolved diagnostic bands in the Raman spectrum can be used to identify and discriminate free ammonia, metal-bound ammonia, sulfate, sulfamate, and metal species in industrially relevant pl ant solutions. We roughly estimate that Raman can determine cobalt at the 0 .3 g Co/L level, nickel at the similar to 5 g Ni/L level, and copper at the 2-3 g Cu/L level in these solutions. Also, sulfate and sulfamate can be de tected at the 1 g/L level with Raman spectroscopy. Finally, the Raman spect rum can be used to determine bound ammonia with detection limits of about 2 0 g/L. The detection of free ammonia depends on the concentration ratio of free to bound ammonia because of their overlapping vibrational bands and th e weaker intensity of free ammonia Raman scattering.