Study on the controllable synthesis of SH-MCM-41 mesoporous materials and their adsorption properties of the La3+, Gd3+ and Yb3+

Sulfhydryl MCM-41 (SH-MCM-41) mesoporous materials were prepared via a hydrothermal method, and -SH was successfully imported by a post-grafting method. The structure and surface properties of the materials were characterized using Fourier Transform infrared spectroscopy, X-ray diffraction and Transmission Electron Microscopy analysis. The low concentrations of La³⁺, Gd³⁺ and Yb³⁺ adsorption on the material were investigated. This paper discusses the effects of system factors, such as pH and the solid-liquid ratio, on the performance of the adsorption process. The adsorption thermodynamics and kinetics were also explored. Experimental results indicated that the materials were in good order and had high specific surface area (956 m²/g) with an average pore diameter of 2.1 nm; the mercapto groups were successfully grafted onto a molecular sieve, and the best grafted amount was 1.46 ×10^-3 mol/g. The materials showed preferable adsorption of La³⁺, Gd³⁺ and Yb³⁺ with maximum adsorption capacities of 560.56 mg/g, 467.60 mg/g and 540.68 mg/g, respectively. The adsorption process can be described by the Freundlich isotherm model, and the adsorption data fits pseudo-second-order kinetics. After repeating the elution-regeneration cycle four times, the adsorption capacity of rare earth ions was mostly maintained, indicating that the adsorbent can be regenerated well and recycled to save costs. It has potential in practical application.