What is it about?

The separation of Co(II) and Li(I) from simulated solution of lithium ion battery (LIB) industry wastes has been studied by a supported liquid membrane (SLM) process. The synergistic effect of mixture of the extractants Cyanex 272 and DP-8R on the permeation rate and separation factor of Co(II) and Li(I) from dilute aqueous sulfate media using a supported liquid membrane (SLM) technique has been examined. A microporous hydrophobic PVDF film was used as the solid support for the liquid membrane. The extractants Cyanex 272 and DP-8R and mixture of those were used as mobile carriers. The effects of different parameter such as stirring speed, pH of the feed solution, extractant concentration in the membrane phase, Co(II)/Li(I) concentration in the feed solution, and H2SO4 strip acid concentration, on Co(II) flux (JCo(II)) and Li(I) flux (JLi(I)) have been studied and compared. For all of the systems studied, Co/Li are optimally separated in the acidic pH region of 5.06.0. The best separation factor of 496.99 was achieved at pH 5.00 using a mixture of Cyanex 272 and DP-8R at a concentration of 750 mol/m3 in the membrane phase, a strip acid concentration of 100 mol/m3, and a stirring speed of 350 rpm. The separation factors for all three systems under the respective optimum experimental conditions have been calculated and compared. Qualitatively, they follow the order: mixed-extractant system > Cyanex 272 > DP-8R. This sequence may be quantitatively expressed as: mixed-extractant system ≈ 3  Cyanex 272 ≈ 15  DP-8R.

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Why is it important?

The separation of Co(II) and Li(I) from simulated solution of lithium ion battery (LIB) industry wastes has been studied by a supported liquid membrane (SLM) process. The synergistic effect of mixture of the extractants Cyanex 272 and DP-8R on the permeation rate and separation factor of Co(II) and Li(I) from dilute aqueous sulfate media using a supported liquid membrane (SLM) technique has been examined. A microporous hydrophobic PVDF film was used as the solid support for the liquid membrane. The extractants Cyanex 272 and DP-8R and mixture of those were used as mobile carriers. The effects of different parameter such as stirring speed, pH of the feed solution, extractant concentration in the membrane phase, Co(II)/Li(I) concentration in the feed solution, and H2SO4 strip acid concentration, on Co(II) flux (JCo(II)) and Li(I) flux (JLi(I)) have been studied and compared. For all of the systems studied, Co/Li are optimally separated in the acidic pH region of 5.06.0. The best separation factor of 496.99 was achieved at pH 5.00 using a mixture of Cyanex 272 and DP-8R at a concentration of 750 mol/m3 in the membrane phase, a strip acid concentration of 100 mol/m3, and a stirring speed of 350 rpm. The separation factors for all three systems under the respective optimum experimental conditions have been calculated and compared. Qualitatively, they follow the order: mixed-extractant system > Cyanex 272 > DP-8R. This sequence may be quantitatively expressed as: mixed-extractant system ≈ 3  Cyanex 272 ≈ 15  DP-8R.

Perspectives

The separation of Co(II)/Li(I) by the SLM technique has been thoroughly investigated using Cyanex 272, DP-8R, and mixtures thereof as mobile carriers. The following conclusions have been drawn: 1) With all of the studied system, Co and Li are optimally separated in the lower acidity range of pH 5.0 to 6.0. At higher acidities, such as below pH 3.00, the separation of Co and Li is not possible since there is no possibility of a metal-extractant complexation reaction. Hence, the leach LIB leach liquor has to be adjusted to the required pH to separate Co(II)/Li(I) by the SLM process using a mixed-extractant of Cyanex 272 and DP-8R. 2) In all of our studies of the various experimental parameters, although the JCo(II) values were comparable, in the case of the mixed-extractant system the JLi(I) values decreased. Consequently, the separation factor was synergistically enhanced, which meets the requirements for better separation and the production of highly pure Co(II) solution. 3) Under the optimal experimental conditions, the separation factors qualitatively conform to the following order: mixed-extractant of Cyanex 272 and DP-8R > Cyanex 272 > DP-8R. This sequence can be quantitatively expressed as: mixed-extractant of Cyanex 272 and DP-8R ≈ 3  Cyanex 272 ≈ 15  DP-8R. 4) Quantitative separation of Co(II)/Li(I) with the required purity is possible by the SLM process using a mixed-extractant of Cyanex 272 and DP-8R as the mobile carrier. This eliminates the problems of higher solvent demand, scrubbing difficulties, and multistage extraction. 5) Judicious combination of cheaper and expensive extractants under suitable conditions and in an appropriate ratio can help to reduce costs in comparison with a single extractant SLM system.

Dr Basudev Swain
Institute for Advanced Engineering (IAE)

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This page is a summary of: Synergistic separation of Co(II)/Li(I) for the recycling of LIB industry wastes by supported liquid membrane using Cyanex 272 and DR-8R, Hydrometallurgy, February 2010, Elsevier,
DOI: 10.1016/j.hydromet.2009.11.012.
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