The adsorption characteristics of rare earth elements on different rock weathering products are related to the enrichment of ion-absorbed type rare earth. To provide enlightenment for the study of rare earth mineralization mechanism, the adsorption characteristics of La3+ by two kinds of ion-absorbed type rare earth ores were analyzed. Through correlating the adsorption amount of La3+ with partition characteristics, specific surface area of particles and surface charge properties of ores, the enrichment mechanism of rare earth ore was discussed. Firstly, the adsorption experiment of La3+ on kaolin was carried out. Lanthanum chloride solutions with concentration of 0.025, 0.05, 0.075, 0.1, 0.15, 0.2, 0.25, 0.3, 0.4, 0.45, 0.5, 0.6, 0.8, 1 g·L-1 were prepared. Kaolin and lanthanum chloride solutions were added according tosolid-liquid ratio of 1:5, and then placed on a magnetic stirrer(300 r·min-1, 30 ℃) for 4 h. Concentration of La3+ in the supernatant was determined by Arsenazo III spectrophotometry. Relationship between the initial concentration of lanthanum chloride and the adsorption capacity of La3+ was analyzed. Secondly, the initial concentrations of lanthanum chloride were determinedby referring to the concentration corresponding to adsorption amount of La3+ rising, steady and re-rising on Kaolin. According to the solid-liquid ratio of 1:5, lanthanum chloride solutionand dry ore samples which from Xunwu (volcanics weathering products) and Anyuan (migmatite weathering products) were added respectively. The particle size of ore samples was -0.1 mm. Adsorption and test process as before. When ores were not saturated, separated supernatant and added lanthanum chloride with the same initial concentration, repeated the above operation. Adsorption capacities of La3+ on these two ores were compared, and partition, specific surface area and surface potential of ores were tested. Finally, the adsorption form and content of La3+ adsorbed on these two ores were analyzed through desorption test. Adsorption of La3+ on kaolin can be divided into three stages: rising stage, stable stage and re-rising stage. As initial concentration of lanthanum chloride ＜0.3 g·L-1, adsorption amount of La3+ increased with concentration of lanthanum chloride, while lanthanum chloride from 0.3 to 0.5 g·L-1, adsorption amount of La3+ remained stable, but as lanthanum chloride＞0.5 g·L-1, adsorption amount of La3+ increased again with concentration of lanthanum chloride. Lanthanum chloride concentrations of 0.1, 0.4 and 0.8 g·L-1 were determined as the initial concentration in the adsorption test of Xunwu ore and Anyuan ore. As lanthanum chlorideinitial concentration of 0.1 g·L-1, amounts of La3+ adsorption on these two ores were stable first, then decreased, and then stable again with the increase of adding times of lanthanum chloride solution. However, as lanthanum chlorideinitial concentration of 0.4 or 0.8 g·L-1, amounts of La3+ adsorption on these two ores were decreased rapidly first and then stable. The decrease rate of La3+ adsorption capacity with the addition of solution showed that Anyuanore was far greater than Xunwu ore in the early stage, and the later Xunwu ore was slightly greater. The final adsorption amount of La3+ was QXunwu＞QAnyuan, and QXunwu≈2QAnyuan. Adsorption amount of La3+ was not proportional to the initial concentration of lanthanum chloride, and there was a maximum adsorption with initial concentration c0=0.4 g·L-1. The specific surface area: Anyuan ore＞Xunwu ore; Absolute value of surface potential: Xunwu ore＞Anyuan ore. Desorption test showed that the amount of water-soluble La3+＜ion-exchangeable La3+＜fixed La3+ adsorbed on Xunwu ore with lanthanum chloride initial concentration of 0.1 or 0.8 g·L-1; while for lanthanum chloride initial concentration of 0.4 g·L-1, amount of water-soluble La3+＜fixed La3+＜ion-exchangeable La3+ adsorbed on Xunwu ore; but for Anyuan ore, with any of the three lanthanum chloride initial concentrations, La3+ adsorption capacity: water-soluble＜fixed＜ion-exchangeable. Forms of La3+ adsorbed on these two ores were mainly ion-exchangeable and fixed. Several conclusions were listed as following: (1) Adsorption amount of La3+ on these two ores were not directly proportional to the lanthanum chloride concentration, amaximum adsorption amount of La3+ was expected at lanthanum chloride concentration of 0.4 g·L-1. The reason why La3+ adsorbed on kaolin "step by step" might be due to the unsaturated adsorption on the kaolin surface, instead of forming colloidal phase La as the lanthanum chlorideincreases to a certain extent. (2) Adsorption capacity of La3+ on different rare earth ores were different, which was dominated by surface potential of particles. The greater the surface potential, the greater the adsorption capacity of La3+. There was no direct relationship between the specific surface area and the adsorption amount of La3+, not that the larger the specific surface area, the adsorption amount of La3+. (3) Forms of La3+ adsorption on these two ores were mainly ion-exchangeable. In comparison, adsorption capacity of La3+ on Xunwu ore was stronger than Anyuan ore, and more ion-exchangeable La3+ and fixed La3+ were formed on Xunwu ore. According to the electric double layer theory, the fixed La3+ are closer to the surface of the particles than the ion-exchangeable La3+, more affected by the electric field on the surface of the particles. Therefore, the affinity of Xunwu to La3+ was greater than that of Anyuan, which made it easier to form specific adsorption than Anyuan ore. This specific adsorption was related to the enrichment pattern of different rare earth minerals, that was, different enrichment pattern of rareearth minerals might be caused by different adsorption capacity of RE3+ on different rock weathering products. © 2022, Youke Publishing Co., Ltd. All right reserved.
