Leaching pH on the column: 300 g of ore samples below 20 mesh were uniformly packed into a Φ×H=60 mm×400 mm sand-core quartz column and 300 ml of 2 wt% (NH4)2SO4 solution was added at a solid-liquid ratio of 1:1. Each 10 ml of leachate was collected and the pH value of each leachate was measured. Experimental plots are shown in Figure 1 The clay samples were accurately weighed and mixed with 250 ml of deionized water, equilibrated in a constant temperature shaker at 25 ℃ for 30 min, and the Zeta potential during the leaching process was measured on an A80045-Zeta Probe at an adjusted speed of 200 rpm, using a certain concentration of leaching agent added drop by drop to the samples, and the Zeta potential, pH and conductivity were measured every 0.5 ml. The Zeta potential, pH and conductivity were measured every 0.5 ml, and for every 2 ml of leaching agent, 2 ml of sample was taken to determine the rare earth content, where the amount of leaching agent added drop by drop and the volume change were known, and the leaching agent concentration corresponding to the recorded data could be clearly calculated. When the drip addition of leaching agent was stopped, the tailings were filtered and leached with 250 ml of deionized water to determine their zeta potential during water leaching. During the determination of Zeta potential, the corresponding leaching and water leaching pH values were measured, and the equilibrium leaching filtrate pH was determined. Abrasion pH measures the pH of clay minerals in pure water, which reflects the hydration characteristics of the clay particles. The clay particles are negatively charged, and the cations inside the slip surface can only partially counteract the negative charge, and cations that maintain electrical neutrality will be present in the diffuse layer of the clay minerals. In pure water, the whole clay minerals resemble the hydrolysis of strong acid and weak base salts, the cations in the diffusion layer enter the solution, and the overall equivalent of a negatively charged group inside the slip surface, the group can combine with H + in the water, and the OH -in the solution increases, making the abrasion pH generally larger. Exchange pH measures the pH of clay minerals in the leaching and exchange process. The change of exchange pH is influenced by the hydration of ions and groups in the exchange process, but is mainly determined by the anion and cation of the leaching agent.