Cerium oxide nanoparticle functionalized lignin as a nano-biosorbent for efficient phosphate removal

Abstract

Removing excess phosphorus is a highly effective method to prevent eutrophication in contaminated water. However, the design and preparation of an efficient biosorbent for phosphate capture is still a great challenge. We fabricated a novel, and inexpensive nano-biosorbent, L-NH₂@Ce, by loading cerium oxide nanoparticles (nano-CeO₂) within the aminated lignin using a facile <i>in situ</i> precipitation approach for efficient phosphate removal. The as-designed nano-biosorbent L-NH₂@Ce exhibited a BET surface area (<i>S</i> _BET) of 89.8 m² g^-1, 3 times that of lignin, and a pore volume (<i>V</i> _p) of 0.23 cm³ g^-1. Owing to these results, the adsorption capacity of L-NH₂@Ce increased by 14-fold to 27.86 mg g^-1 compared with lignin (1.92 mg g^-1). Moreover, the L-NH₂@Ce can quickly reduce a high phosphate concentration of 10 ppm to well below the discharge standard of 0.5 ppm recommended by the World Health Organization (WHO) for drinking water. Importantly, a study of leaching tests indicated the negligible risk of Ce ion leakage during phosphate adsorption over the wide pH range of 4-9. Moreover, L-NH₂@Ce exhibits good reusability and retains 90% of removal efficiency after two adsorption-desorption cycles. The environmentally benignity of the raw material, the simple preparation process, and the high stability and reusability makes L-NH₂@Ce a promising nano-biosorbent for phosphate removal.