Abstract: The in-situ leaching process for weathered crust elution-deposited rare earth ores (WCE-DREO) is an important technology for mining medium-heavy rare earths. During the leachate injection process,the hydration swelling of clay minerals such as montmorillonite in the ore body could induce landslides and waste resources. In this work,poly-(dimethyl diallyl ammonium chloride) (PDDA) was selected as a swelling inhibitor. Its swelling inhibition performance and mechanism on the mineral particles of montmorillonite and rare earth were investigated. Linear swelling experiments indicated that 0. 5% PDDA solution is sufficient to produce good swelling inhibition effect for the mineral particles of montmorillonite and rare earth. Laser particle size,SEM and sedimentation analyses showed that PDDA could agglomerate fine mineral particles,reduce the pore space on the mineral surface,increase the settling efficiency and prevent its hydrological dispersion. FTIR,Zeta potential and XRD analyses demonstrated that the organic cationic groups of PDDA could be adsorbed on the surface of mineral particles to neutralize the negative surface charge of clay minerals,and inhibit the hydrological expansion of their crystal interlayer spacing. In addition,ammonium sulfate solution which commonly used as the rare earth leaching agent,did not significantly interfere with the swelling inhibition effect of PDDA. The result of this study could provide a reference for the selection and application of swelling inhibitors in the in-situ leaching process of rare earth mines.

Key words: rare earth,montmorillonite,swelling inhibitor,PDDA,in-situ leaching