Swelling of clay minerals in ammonium leaching of weathered crust elution-deposited rare earth ores

The effect of hydrated radius, cation valence, pH and solution concentration on the zeta potential of clay minerals was investigated, and the relation between zeta potential of clay minerals and swelling was discussed in different leaching agents as well. The results show that the zeta potential of clay minerals decreases with the hydrated ionic radius increasing. It could be seen that the zeta potential of the clay minerals in AlCl3 solution is positive, whereas that in NH4Cl, KCl and MgCl2 solution is negative. And the zeta potential of clay minerals increases with the cation valence increasing. Moreover, the zeta potential of clay minerals decreases with the solution pH increasing, whereas that increases with the solution concentration increasing in different ammonium solutions. In addition, the swelling of clay minerals decreases while the zeta potential of clay minerals increasing in different ammonium solutions. The ability of compound ammonium to inhibit the swelling of clay minerals is lower than that of single ammonium solution.