Identification of Major Species in Industrial Metal-Refining Solutions with Raman Spectroscopy

Abstract

Raman and resonance Raman spectroscopies were used to characterize industrial metal-refining solutions containing nitrogen, sulfur, and Ni, Co, Zn, and Cu ammine complex species. To identify the species present in these solutions, 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 plant solutions. We roughly estimate that Raman can determine cobalt at the 0.3 g Co/L level, nickel at the ∼5 g Ni/L level, and copper at the 2–3 g Cu/L level in these solutions. Also, sulfate and sulfamate can be detected at the 1 g/L level with Raman spectroscopy. Finally, the Raman spectrum can be used to determine bound ammonia with detection limits of about 20 g/L. The detection of free ammonia depends on the concentration ratio of free to bound ammonia because of their overlapping vibrational bands and the weaker intensity of free ammonia Raman scattering.