Monodispersed and Organic Amine Modified La(OH)₃ Nanocrystals for Superior Advanced Phosphate Removal

Advanced phosphate removal is critical for alleviating the serious and widespread aquatic eutrophication, strongly depending on the development of superior adsorption materials to overcome low chemical affinity and sluggish mass transfer at low phosphate concentrations. Herein, the first synthesis of monodispersed and organic amine modified lanthanum hydroxide nanocrystals (OA-La(OH)₃) for advanced phosphate removal by modulating inner Helmholtz plane (IHP), is reported. These OA-La(OH)₃ nanocrystals with positively charged surfaces and abundant exposed La sites exhibit specific affinity toward phosphate, delivering a maximum adsorption capacity of 168 mg P g⁻¹ and a wide pH adaptability from 3.0 to 11.0, as well as a robust anti-interference performance, far surpassing those of documented phosphate removal materials. The superior phosphate removal performance of OA-La(OH)₃ is attributed to its protonated organic amine in IHP, which enhances the electrostatic attraction around the adsorbent-solution interface. Impressively, OA-La(OH)₃ can treat ≈5 000 and ≈3 200 bed volumes of simulated and real phosphate-containing wastewater to below extremely strict standard (0.1 mg L⁻¹) in a fixed-bed adsorption mode, exhibiting great potential for advanced phosphate removal. This study offers a facile modification strategy to improve phosphate removal performance of nanoscale adsorbents, and sheds light on the structure-reactivity relationship of La-based materials.