Phosphorus removal from wastewater is vital to mitigate the eutrophication of receiving waters. In this work, acidified diatomite (AD) was loaded with lanthanum carbonate (La₂O₂CO₃) by a solvothermal method to prepare a series of composites, La₂O₂CO₃@AD, which were used to adsorb phosphate. The La₂O₂CO₃@AD materials have ordered structures and rich functional groups as verified by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, energy spectrum analysis (EDS), and scanning electron microscopy (SEM). Then, all La₂O₂CO₃@AD were used as adsorbents for fast and efficient removal of phosphate from aqueous solution by batch equilibrium experiments. The experimental results demonstrate that the phosphate adsorption of La₂O₂CO₃@AD is pH dependent, and completed within 360 min. The adsorption kinetics and isotherm data follow the pseudo-second-order equation and the Freundlich model, respectively. The adsorption mechanisms of phosphate are ascribed to the chemical bond force and ligand exchange.