Inhibition effect on swelling and permeability enhancement of potassium benzoate in ion adsorption rare earth ore elution

Contrast to the general rare earth ores from Jiangxi province, rare earth ores from Hunan province exhibit unique clay compositions, such as higher halloysite and kaolinite content, leading to the stronger swelling and different leaching behavior compared to Jiangxi ores. To promote the green and efficient exploitation of ion-adsorption rare earth ores, potassium benzoate (C 6 H 5 COOK) was chosen as a novel swelling inhibitor adding to MgSO 4 leaching solution to investigate its dual role in suppressing clay swelling and enhancing permeability in this study. Swelling tests, mud ball disintegration, sedimentation, and column leaching experiments were conducted to evaluate its effects on the structural stability and permeability of kaolinite, halloysite and rare earth ores, respectively. Experimental results showed that potassium benzoate significantly inhibited clay swelling during 72 h tested time and improved solution percolation between particles. The swelling rate decreased from 6.401% to 2.251%, corresponding to an inhibition rate of 64.83%, and a rare earth leaching recovery of 97.60% were achieved, demonstrating well performance in both structural stabilization and extraction efficiency. From fourier transform infrared spectroscopy (FTIR) and thermogravimetric (TG) mechanism analysis, potassium ions from potassium benzoate replaced interlayer cations via ion exchange, weakening the hydration film and suppressing interlayer expansion. Meanwhile, benzoate anions adsorbed onto mineral surfaces, forming a hydrophobic layer that stabilized the structure and promoted infiltration.