The partitioning and ionic competition of metal-chelates in the electrolyti- c foam separation process

In this study, the electrolytic foam separation process was used to treat metal-chelate solutions at varying pH values and with varying surfactant chelating agent to metal (S/M) ratios. The ionic competition characteristics of the metal-chelate systems and the partitioning of chelates during the electrolytic foam separation process were also investigated by the 1H FT-NMR method. Results of the 1H FT-NMR analysis showed that, in the Ni-citrate-NDDTC(sodium diethyl dithiocarbamate) system with an S/M ratio of 4, the Ni-NDDTC chelate formation efficiencies for pH values of 4, 7, and 10 were 87%, 100%, and 93%, respectively. These results were consistent with measurements of efficiency of Ni removal following 90 minutes of flotation including that the efficiency of Ni removal in the Ni-citrate-NDDTC system was highest at pH=7 (95%), and was lower at pH=4 (38%) and pH=10 (74%). This investigation demonstrate- s that both the pH value and the S/M ratio are critical parameters for metal removal from the metal-citrate(EDTA)-NDDTC(KEtX) system. The study also shows that the 1H FT-NMR can be used successfully to understand the nature of ionic competition and chelate partitioning in these systems.