Study on the preparation of La2(CO3)3·4H2O by ultrasonic-assisted dehydration and its phosphate binding effect

Lanthanum carbonate tetrahydrate (La₂(CO₃)₃·4H₂O), as the most clinically effective drug for treating hyperphosphatemia, faces challenges in production such as complex preparation processes and low phase purity. To address these shortcomings, an efficient and straightforward method was developed for preparing La₂(CO₃)₃·4H₂O in the form of flake-shaped, characterized by its high phase purity, crystallinity, and dispersibility. In this study, sodium bicarbonate and lanthanum chloride were used as starting materials to synthesize lanthanum carbonate octahydrate (La₂(CO₃)₃·8H₂O) under weakly acidic conditions, and ultrasonic technology was employed for its dehydration to prepare the target product, La₂(CO₃)₃·4H₂O, followed by an investigation of its phosphate binding capacity. The results show that subjecting La₂(CO₃)₃·8H₂O to ultrasonic dehydration treatment with an intensity of 60 W/m² in an ethanol solvent can effectively prevent the formation of basic lanthanum carbonate impurities, successfully preparing La₂(CO₃)₃·4H₂O with high phase purity and good crystallinity. In addition, the obtained sample exhibits excellent dispersibility, featuring a lamellar morphology with a particle size of approximately 5 μm. Phosphate binding experiments further demonstrate that the La₂(CO₃)₃·4H₂O prepared by ultrasound possesses superior phosphate binding capacity, able to bind 90 % of phosphate within 120 min. It was clear that the trivalent lanthanum ion combined with phosphate to form lanthanum phosphate and attached to the surface of the La₂(CO₃)₃·4H₂O sheets. The aforementioned research results indicate that the ultrasonic-assisted dehydration method can prepare La₂(CO₃)₃·4H₂O with excellent performance, and La₂(CO₃)₃·4H₂O exhibits outstanding phosphate binding capacity, showing good potential for clinical applications.