A one-step regeneration method in-situ for deactivated aluminum-based lithium adsorbent used in high Mg2+/Li+ brines

Abstract

Excessive Li+ deintercalation from the difficulty of precisely controlling desorption would lead to the deactivation of lithium/aluminum layered double hydroxide (Li/Al-LDH) as the aluminum-based lithium adsorbent in brines. In this study, a novel one-step regeneration method was established to in-suit recover the deactivated Li/Al-LDH and was verified to be universally applicable for Li/Al-LDH with different forms and deactivation degrees. It was witnessed the powdery and granulated Li/Al-LDH could be regenerated in less than 5 min and 2 h, respectively. The in-situ regeneration of deactivated granules was achieved in the fixed bed. Besides, high temperature, high Li+ concentration, alkalinity, and high ionic strength were conductive to the structural transformation of deactivated adsorbents from gibbsite (γ-Al(OH)3) to active Li/Al-LDH and restore to normal Li+ adsorption capacity on account of the intercalation reaction of Li+ in gibbsite. Moreover, the regeneration mechanism was further illustrated in detail that Cl− and water molecules entered the interlayer as Li+ was inserted into the vacancies of deactivated adsorbent laminates to reconstruct Li/Al-LDH structure. This efficient regeneration method resolves the deactivation of Li/Al-LDH adsorbents, and is expected to be applied in the industrial lithium extraction to completely solve the insufficient long-term cycle stability caused by excessive desorption.