Synergistic leaching of lithium from clay-type lithium ore using sulfuric acid and oxalic acid

With the escalating market demand for lithium, the development and efficient utilization of lithium resources have become crucial. This study introduced a method for leaching lithium from raw clay-type lithium ores using a composite sulfuric acid oxalic acid system. The experimental results revealed that the optimal conditions for the leaching process included roasting temperature of 600 degrees C, sulfuric acid concentration of 0.8 mol/L, liquid- solid ratio of 5 mL/g, leaching temperature of 90 degrees C, leaching duration of 90 min, and oxalic acid dosage of 2 g. Under these conditions, the leaching efficiency of lithium reached 93.45 %. The structural changes during the lithium leaching process and leaching mechanism were analyzed by XRD, SEM, TOF-SIMS. It was found that the minerals after mixed-acid leaching showed a loose morphology, a decrease in the average particle size, and a significant increase in the specific surface area as well as the pore volume, leading to improved lithium leaching efficiency. Furthermore, the mechanism underlying the mixed-acid leaching of lithium from clay-type lithium ores was explored. According to this mechanism, sulfuric acid first dissociated H+, which disrupted the mineral structure, allowing further destruction by oxalic acid. During this process, Li+ was continuously replaced by H+ and reacted with C 2 O 4 2- dissociated from oxalic acid to form water-soluble Li2C2O4.