| Cobalt and nickel, the important nonferrous metals, are insufficient in our country and then they are very dependent on foreign imports. While hundreds of millions of waste batteries produced annually contain large amount of cobalt and nickel metals, and the metals content in some waste batteries are even more than that of the primary ore. The hydrogen storage materials among nickel-metal hybrid battery mainly contain cobalt, nickel, and magnesium metals, and after acid leaching these metals stably exist in the form of ions in solution, these metals are separated from the production using acid phosphorus. To solve waste-water pollution brought by saponification and the cobalt and nickel extraction’ inhibition of hydrogen ions generated when phosphonic acid type extract cobalt and nickel, we use P204-N235 of compound extraction solvents to separate cobalt, nickel and magnesium.In order to explore the optimum extraction condition of composite extraction agents on extracting cobalt, nickel and magnesium, the effect factors of extraction efficiency are investigated, namely concentration of N235 and P204, oscillation time and initial pH value of aqueous phase. The experimental results demonstrated that with the increase in the concentration of P204 and vibration time,the third phase would arise and two phases separation need more time. Taking into consideration various factors, the optimum extraction conditions are chosen to be 20% volume concentration of P204, 10 min of vibration time and initial pH value of 5. The compound extraction agents have higher efficiencies for extraction of cobalt, nickel and magnesium than pure P204 under the same extraction conditions.The slopes were 3 by fitting lgD-lg[P204] spectra, which suggested that the ingredients of cobalt, nickel and magnesium extracted by compound extraction agents are CoA2(HA),Ni A2(HA) and MgA2(HA), respectively. All of the slopes of lgD-pH spectra were calculated to be 2, implying that the metals ions extraction mechanism by using compound extraction agents is the cation exchange reaction.To explore the regeneration of loaded organic phase, the effects of vibration time,ratio of phase and concentration of hydrochloric acid on reverse extraction performances are studied. The results show that Co2+, Ni2+ and Mg2+ could be reversely extracted completely at phase ratio(O/A) being 1:2 after vibrating 14 min by various concentrations hydrochloric acid being in order 5, 4 and 3 mol/L. After reverse extraction, wash the organic phase with 50℃ deionized water at the phaseratio(O/A) of 1:2 for 7~9 times then the extracted hydrochloric acid could be eluted accompanied by the pH value of washing liquid being close to neutral.The thermodynamic study of extraction cobalt and nickel by compound extraction agents at temperatures range from 288.15 to 313.15 K demonstrated that both of gibbs free energy and reaction enthalpy are less than zero meaning the extraction reaction being exothermic. Hence lower temperatures are more beneficial to the extraction of cobalt and nickel by compound extraction agents and the extraction is spontaneous.We also investigated the separation efficiencies of compound extraction agents for mixed ions of cobalt, nickel and magnesium. When the volume concentration of P204 is 30%, phase ratio(O/A) is 1.5, obviation time is 12 min and initial pH value is5, the βCo/Ni and βCo/Mg are close to 6 and 50, respectively, which manifest the effective separation mixed ions. After extraction, the loaded organic phase in separating funnel was reverse extracted by 4 mol/L hydrochloric acid, both of the reverse extraction efficiencies of nickel and magnesium were high up to 99% along with a small amount of cobalt being extracted, and then the reverse extraction solutions can be used as acid solvents to dissolve waste batteries. |
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