Efficient extraction of the structural lithium from cookeite through a combined approach of roasting-leaching, co-precipitation, and elution

Clay-type lithium (Li) resources, as a new type of Li resources, have great commercial development value. In this study, the occurrence state of Li in a clay-type Li ore was systematically determined, and the results indicated that Li was dominantly accommodated in the interlayer hydroxide sheets of di-trioctahedral chlorite (i.e., cookeite), as a structural state. The efficient selective extraction of structural Li from cookeite was achieved using a combined approach of roasting-leaching, co-precipitation, and elution. Firstly, after simple sedimentation-purification, the resulting sample was treated with the roasting‑sulfuric acid (H ₂SO ₄ ) leaching method to obtain a lixivium containing Li and Al and to efficiently exclude Si. During this process, the cookeite completely dissolved and the structural Li was efficiently released into lixivium. Under the optimal conditions, the leaching efficiencies of Li and Al were up to 83.2% and 86.1%, respectively. Subsequently, sodium hydroxide (NaOH) solution was added into the lixivium to obtain a mixed precipitate of Li/Al-layered double hydroxide (Li/Al-LDH) and Al(OH) ₃, with a maximum precipitate efficiency of Li of 95.4%. Finally, the resulting Li/Al-LDH was roasted and then eluted with water. The maximum elution efficiency of Li was 95.3% under optimal conditions. In this procedure, the Li/Al-LDH transformed into Al ₂O ₃ to separate Li after roasting, and the released Li was easily eluted with water. The findings of this study contribute to the understanding of the occurrence state of Li in clay minerals, and the proposed approach can not only provide a promising strategy for the efficient industrial extraction of Li from clay-type Li resources but also achieve the co-recovery of Al.