An in situ column leaching technique for extracting lithium ions from clay-type lithium ores under normal temperatures

The clay-type lithium ores, a significant lithium resource in China, contain lithium and other elements such as aluminum and silicon. Their molecular formulas are expressed as LiAl SinO_2n+2 and Li AlSinO_2n+2 in this study. The latter formula represents the ion-absorbed lithium ores, from which lithium ions can be readily extracted in leaching experiments. This study explores an environment-friendly, economical, normal-temperature in situ leaching technique for clay-type lithium ores, which requires that the chemical properties of lithium ores remain unchanged before leaching experiments. The contents of various elements, loss on ignition, and porosity (massive ores) of clay-type lithium ores were analyzed through the column leaching experiments. Three leaching reagents were used: 10% sulfuric acid solution, 10% ammonium sulfate solution, and a mixture of 5% sulfuric acid solution and 5% ammonium sulfate solution. The total leaching process lasted for 190 d. The concentrations of lithium and aluminum were determined at regular intervals. The experimental results show that the porosities of the clay-type lithium ores ranged from 0.38% to 6.20%. The first and third reagents demonstrated higher leaching efficiency, achieving a Li₂O leaching rate of up to 0.56% without refilling fresh reagents, whereas the leaching efficiency of the second reagent was not satisfactory. Notably, in the case of a reduced ore size, the third mixed leaching solution yielded the same leaching efficiency as the first high-concentration sulfuric acid solution. Overall, this study provides a practical in situ leaching technique for clay-type lithium ores in mines.