Ion-adsorption-type rare earth ores (IREOs) are an indispensable strategic resource. Rare earths can be extracted from IREOs by means of in situ leaching, which is strongly influenced by the migration of clay components. In order to clarify the effect of the interaction between mineral particles on the rare earth leaching process, the aggregation of IREO colloids was investigated in suspension after NaCl concentration and pH value were disturbed based on a light scattering method. The results show that IREO colloids are prone to unstable aggregation, which can be affected by salinity and pH in suspension. Combined with the analysis of the surface acid–base properties and the zeta potential of the IREO colloids, the long-range electrostatic attraction between mineral heterogeneous charge surfaces plays a leading role in the interaction between mineral particles. In suspension, electrolyte concentration and pH can adjust the strength of the electrostatic force and the force field overlapping between the surface double electric layers to influence the aggregation of the IREO colloids. The above conclusion can enrich and supplement the rare earth extraction theory, which has a certain guiding significance for green exploitation of IREOs.

Rare earths dissolved in carbonate solutions exhibit a metastable state. During the period of metastability, rare earths dissolve stably without precipitation. In this paper, neodymium was chosen as a representative rare earth element. The effects of additional NaCl and CO₂ on the metastable state were investigated. The metastable state can be controlled by adding NaCl to the Na₂CO₃ solution. Molecular dynamics studies indicated that the Cl⁻ provided by the additional NaCl partially occupied the coordination layer of Nd³⁺, causing the delayed formation of neodymium carbonate precipitation. In addition, the additional NaCl decreased the concentration of free carbonate in the solution, thereby reducing the behavior of free contact between carbonate and Nd, as well as resulting in the delay of Nd precipitate formation. Consequently, the period of the metastable state was prolonged in the case of introduction of NaCl. However, changing the solution environment by introducing CO₂ can destroy the metastable state rapidly. Introduction of CO₂ gas significantly decreased the CO₃²⁻ content in the solution and increased its activity, resulting in an increase of the free CO₃²⁻ concentration of the solution in the opposite direction. As a result, the precipitation process was accelerated and the metastable state was destroyed. It was possible to obtain a large amount of rare earth carbonate precipitation in a short term by introducing CO₂ into the solution with dissolved rare earths in the metastable state to achieve rapid separation of rare earths without introducing other precipitants during the process.

Ion-adsorption-type rare earth ores (IRE-ores) are a vital source of rare earth elements globally. The percolation properties of the ore body significantly determine the ease of rare earth extraction using in situ leaching processes. This paper investigates the interactions among clay particles in ion-adsorption-type rare earth ores within aqueous solutions, utilizing methods such as mineral particle aggregation and settling and acid–base adsorption on mineral surfaces. Based on these analyses, this paper elucidates the influence of solution properties on the percolation process of ion-type rare earth ores during leaching. The results indicate that the electrostatic attraction between minerals in aqueous solutions is pronounced, enhancing the interaction and resulting in a notable instability of the aggregates. The aggregation of minerals impacts the viscous effect of water bound to the mineral surface on the solution, thereby affecting the percolation rate. Extremely low concentrations of SO₄²⁻ and CH₃COO⁻ can act as surface modifiers, reducing the electrostatic attraction between particles and consequently increasing the leaching percolation rate.