Study on the expansion behavior of Halloysite during in-situ leaching ionic rare earth ore

Magnesium sulfate is commonly used as the leaching agent in the in-situ leaching of ionic rare earth ore. However, the mining process often suffers from landslides caused by hydration expansion of clay minerals. Although various inhibitors about calcium salts, magnesium salts, and organic surfactants have been studied, there is still limited understanding of how potassium salts interact with different clay minerals. Potassium salts are selected due to the low hydration energy and suitable ionic radius of potassium ions. Results show that a magnesium sulfate–potassium salt compound solution at specific concentrations exhibits a significant inhibition effect during long-term contact with halloysite. The best suppression rates are 35.37 % for potassium benzoate and 23.37 % for potassium propionate. From XRD, FTIR, Zeta and TG analysis, potassium ions can neutralize the negative charges on clay surfaces, reduce the repulsive force between electrical double layers, and occupy the adsorption sites of water molecules. Furthermore, hydrophobic groups in the organic agents can form a barrier on the clay surface, preventing water molecules from entering.