Ion-adsorbed rare earth minerals have rare earth ions adsorbed on the surfaces of clay minerals such as kaolinite and have high contents of medium and heavy rare earth elements. They are important resources supporting the development of high-tech industries. In this study, the CASTEP module in Materials Studio was used to study the adsorption of the rare earth ion Y(III) on the interface of (Al-OH)-H₂O and (Si-O)-H₂O with density functional theory. The monitoring and calculation of the chemical bond of the adsorption structure showed that Y(III) on the (Al-OH)-H₂O interface has a bond with O32, O34, and water molecules in the interface. In the (Si-O)-H₂O interface, Y(III) interacts with O3, O4, and O10 to form new chemical bonds. The Mulliken population and density of states analysis showed that Y(III) bonds with surface oxygen atoms and water molecules in the kaolinite-H₂O interface, and finally adsorbs on the surface of kaolinite in the form of metal ion hydrate.

It is important to recover La³⁺ from metallurgical solutions or wastewater. However, the recovery rate of La³⁺ is usually less than 1% and the recovery methods are not environmentally friendly or user-friendly. Therefore, a straightforward, efficient, clean, and economically friendly method is needed. In this investigation, a modified adsorbent, COSAC-Na₂EDTA-15, which was made from the Camellia oleifera shell (COS) and disodium ethylenediaminetetraacetic acid (Na₂EDTA), was invented. In addition, characterization of the COSAC-Na₂EDTA-15 adsorbent was conducted using SEM and XPS, and the principle of adsorption was revealed. The adsorption kinetics followed P-S-O KM, while the isotherm of COS-activated carbon (COSAC) aligned more closely with the Langmuir model. Compared to COSAC, the maximum La³⁺ adsorption capacity of COSAC-Na₂EDTA-15 increased from 50 to 162.43 mg/g, and the content of O and N changed from 7.31% and 1.48% to 12.64% and 4.15%, respectively. The surface of the COSAC-Na₂EDTA-15 exhibited abundant C, N, and O elements, and La³⁺ was detected on the sample surface after adsorption. The test and analysis results fully indicate that La³⁺ can be successfully adsorbed on the surface of COSAC-Na₂EDTA-15. Because of its easy preparation, low cost, and superior performance, activated carbon made from COS finds extensive applications in the adsorption and recovery of rare earth elements.

The selective precipitation method was adopted to remove Ca(II), Pb(II), Zn(II), Mg(II) from the evaporative crystallization mother liquor of ammonia-conta