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

Abstract

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 %.