Lithium ion adsorption–desorption properties on spinel Li4Mn5O12 and pH-dependent ion-exchange model

• A pH-dependent isotherm model was built.
• Li+ adsorption capacity and selectivity of the ion-sieve was tested using the Qarhan brine as the feed.
• 55 cycle’s adsorption–desorption experimental result indicating the ion-sieve was stable.
• An easy method was used to synthesize Li4Mn5O12.

A spinel-type Li4Mn5O12 precursor was synthesized by solid-phase reaction using inexpensive manganese and lithium salts as raw materials, where the two-step calcination procedure (at 543 K for 2 h and 673 K for 24 h) was adopted. The synthesized Li4Mn5O12 precursor was characterized using X-ray powder diffraction, scanning electron microscope, transmission electron microscopy, and micromeritics ASAP-2010C adsorption apparatus. Spherical MnO2⋅0.4H2O ion sieve was used to adsorb Li+ from Qarhan brine with a Mg2+/Li+ ratio of 746, after desorption the ratio was reduced to less than 1. Li+ adsorption capacity of the spherical ion sieve was studied by 55 cycle’s adsorption–desorption experiment, the adsorption capacity was ∼0.4 mmol g−1 and kept constant. Furthermore, a pH-dependent ion-exchange equilibrium model for Li+ adsorption was built for further optimization of the cyclic adsorption–desorption process to recover the Li+ from Qarhan brine.

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