Al and F ions co-modified Li1.6Mn1.6O4 with obviously enhanced Li+ adsorption performances

A surge of interest has been attracted by Li 1.6 Mn 1.6 O 4 -type adsorbent for collecting lithium resources from salt-lake brines due to its excellent selectivity, high theorical adsorption capacity up to 72. 3 mg g −1 and low cost. However, its large-scale practical application is limited because of its bone element Mn dissolution during the cycled desorption process. Herein, F and Al co-modifying technique, an efficient method for stabilizing its spinel structure or forming protective coating, was employed to improve the application performances of Li 1.6 Mn 1.6 O 4 -type adsorbent prepared by sol–gel method. Based on the various characterization results, the co-modification not only leads to the formation of fluoride-rich coating and the substitution of Mn 3+ by Al 3+ , but also generates the active adsorbents with abundant nano-islands. DFT calculations revealed that the coating layer is indeed AlF 3 rather than LiF. In addition, in-situ high-temperature XRD tests demonstrates that the co-modification can significantly enhance the heat resistance and structural stability of the material. As-prepared adsorbent exhibits greatly improved Li adsorption capacity (increased from 28.5 to 33.7 mg g −1 ), lower Mn loss rate (decreased from 2.1 to 1.8%), enhanced cycling stability and good adsorption selectivity in the Qarhan brine containing Na + , K + , Ca 2+ , Mg 2+ , which is very significant and important for effectively removing lithium from low-grade brines.