Hydrometallurgical recycling of lithium from waste saggar: Studies on influential role of acid/alkaline additives, leaching kinetics and mechanism

Waste recycling has become crucial with the increasing attention paid to environmental rules and the fast-depleting resources of critical elements. Soaring demands for lithium in cathode materials of rechargeable batteries result in a surge in waste saggar after being used in the calcination of cathode precursor. The recycling of lithium from waste saggar is therefore imperative due to the high supply-risk of lithium. Herein, waste saggar composed of various mineral phases (26.26 % LiAlSi4O10 approximately equal to 0.6 % Li; 6.34 % Li4SiO4 approximately equal to 1.47 % Li; 0.79 % LiOH & BULL;H2O approximately equal to 0.13 % Li; 0.03 % Li2CO3 approximately equal to 0.01 % Li) was leached in water for lithium extraction; while the effects of NaOH, Ca(OH)2, and H2SO4 as potential additives were examined under a wide temperature range of 5-80 degrees C. Interestingly, the observed order of leaching efficiency at lower temperature (20 degrees C) H2SO4 > NaOH > Ca(OH)2 was in variance with that at 80 degrees C (NaOH > H2SO4 Ca(OH)2). The apparent activation energy for lithium extraction was determined to be 29.8 kJ/mol using NaOH, 33.8 kJ/mol using Ca(OH)2, and 14.1 kJ/mol using H2SO4, indicating that the overall leaching process follows a mixed-controlled mechanism. The maximum effi-ciency of 94 % Li-extraction was achieved with NaOH which was used for the precipitation recovery of Li2CO3 of purity above 99 %.

Automated summary

Waste recycling is important due to environmental regulations and the depletion of critical resources. The recycling of lithium from waste saggar is crucial because of the high supply-risk of lithium. In this study, different additives and temperatures were examined for the leaching of lithium from waste saggar, and NaOH was found to be the most efficient for extraction and recovery.