Swelling suppression mechanism on the weathered crust elution-deposited rare earth ores leaching process with cetyltrimethylammonium bromide

Weathered crust elution-deposited rare earth ore (WREOs), a national strategic resource, is usually in-situ leached by (NH₄)₂SO₄ solutions to recover the rare earth in industry. However, a large number of (NH₄)₂SO₄ solutions are required in the leaching process to ensure the high recovery efficiency of rare earth, which will cause the hydration swelling of WREOs, leading to the occurrence of landslides. To ensure the mine safety, it is necessary to inhibit the swelling efficiency of WREOs in the leaching process. In this study, the swelling performance of WREOs leached by (NH₄)₂SO₄ was investigated. The effects of the presence of concentrations and leaching temperatures on inhibition of WREOs swelling and further the suppression mechanism was investigated. The results showed that the swelling efficiency of WREOs in 0.1 mol/L (NH₄)₂SO₄ was 0.884 %. With the addition of 0.04 % cetyltrimethylammonium bromide (CTAB), the swelling efficiency was reduced to 0.265 %. The lower temperature effectively inhibits the swelling efficiency of WREOs, while the pH of the leaching solution showed little to no effect. Zeta potential results showed that a small amount of cationic surfactant could balance the surface charge of WREOs, thus inhibiting its swelling efficiency. XRD and SEM results revealed that the swelling in WREOs was mainly due to surface hydration. This study can assist to solve the shortcomings of low leaching rate and lower the risk of the landslides in the mining process.