Rapid and selective adsorption of Li+ from concentrated seawater using repulsive force of Al3+–crosslinked alginate composite incorporated with hydrogen manganese oxide

The increasing demand of lithium (Li) receives great attention to the development of efficient Li recovery techniques. In this study, a novel strategy is proposed to separate Li+ ions from concentrated seawater by using the synergetic effect of Al3+–crosslinked alginate (Alg) and hydrogen manganese oxide (HMnO). The crosslinked Al3+ in the Alg network structure generates a strong repulsive force to salt cations. This environment probably increases the contact opportunity for Li+ ions with a low adsorption affinity to HMnO by rejecting other salt cations with a high adsorption affinity. Adsorption capability and selectivity of the fabricated HMnO-incorporated Alg (HMnO/Alg(Al)) composite greatly increase compared with those of normal Alg composites. As a proof of concept application, the selectivity separation factors αMeLi of HMnO/Alg(Al) composite from concentrated seawater are evaluated as 36.36 and 40.08 for αNaLi and αKLi, respectively, at the first repetition. However, these factors decrease after the second repetition because of structural instability. The proposed Li recovery technique would be utilized as an efficient alternative to state-of-the-art Li separation methods based on the ion-intercalation mechanism and would pave the way for the efficient recovery of Li from concentrated seawater. •HMnO powders are immobilized in Al3+–crosslinked alginate composite.•Strong repulsive force of Al3+–Alg network allows selective infiltration of Li+.•The incorporation of HMnO in Al3+–Alg networks enhances Li adsorption efficiency.