Chitosan-amidated lignin aerogel beads efficiently loaded with lanthanum hydroxide for phosphate removal from aqueous solutions.

Developing phosphorus removal adsorbents with high adsorption performance and excellent structural stability remains a challenge. Herein, a chitosan (CS) - amidated lignin (AL) gel-bead adsorbent with high efficiency in immobilizing lanthanum hydroxide (La(OH)) was fabricated via an in situ precipitation and freeze-drying strategy (abbreviated as La@ALCS). The abundant hydroxyl and amino groups in CS promoted excellent loading of La(OH) on the surface and inside of the adsorbent. The introduction of lignin enhanced the structural stability of the beads along with the mass transfer efficiency. Owing to the porous structure and high La utilization, the adsorption capacity of La@ALCS reached 130.52 mg P g. Intra-sphere complexation of La(OH) with phosphate resulted in high adsorption selectivity of La@ALCS. Moreover, the millimeter-sized of La@ALCS has favourable recoverability and maintains high adsorption performance after five adsorption-desorption cycles. Characterization analysis indicated that electrostatic attraction and ligand exchange were the main adsorption mechanisms. The excellent phosphorus removal efficiency, separation efficiency and recyclability of La@ALCS provide a viable solution for the remediation of phosphate contaminated waters.