Nano?La (OH)3 particles were synthesized using a precipitation method in deep eutectic solvents (DES). These materials were analyzed and characterized by X?ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption (BET). The effects of different reaction conditions on the morphology of lanthanum hydroxide were explored. In addition, an adsorption test was performed with KH2PO4 simulated wastewater. The results show that the La(OH)3 particles synthesized with water and urea?choline chloride have a granular morphology, and the diameter is between 0.02 μm and 3.00 μm. When ethylene glycol?choline chloride is used as solvents, La(OH)3 have a rod morphology with particle length between 80 nm and 180 nm. The maximum adsorption capacity is between 58 mg/g and 86 mg/g and the adsorption isotherm of KH2PO4 is best fitted with Langmuir model.
