Rare earth elements (REEs) recovery and porous silica preparation from kaolinite

A kaolinite containing 245 ppm of REEs was used as a feedstock for REE recovery. Acid leaching test results showed that less than 20% of the REEs were leached using 1.2 mol/L HCl. However, after thermal treatment at 600 degrees C, a recovery of over 80% was obtained with a much lower acid concentration (0.01 mol/L). Meanwhile, only 3.91% Al, 2.34% Fe, 8.63% K, 9.32% Mg, 0.08% Ti, and 5.34% Ca were simultaneously extracted. Therefore, high-purity rare earth products are likely produced from the kaolinite. To achieve a more comprehensive utilization of the kaolinite, the residual solid after REE recovery was subjected to a selective leaching process to prepare porous silica. Comparisons among three different types of mineral acids showed that H2SO4 provided the best performance. The effects of different factors were investigated using the response surface methodology. A porous silica with as high as 336.95 m(2)/g specific surface area was ultimately produced. (C) 2021 Published by Elsevier B.V.

Automated summary

The experiment on rare earth recovery and preparation of porous silica from kaolinite containing rare earth elements shows that thermal treatment and selective leaching are effective methods. In addition, the application of analytical methods and response surface methodology in the process is important for improving product quality and yield.