Synthesis of three-dimensional porous lanthanum modified attapulgite chitosan hydrogel bead for phosphate removal: Performance, mechanism, cost-benefit analysis

The removal of phosphorus from eutrophication water by adsorption has been widely concerned, and the development of an efficient, cost-effective, and convenient recycling adsorbent is essential. Herein, a novel lanthanum-modified attapulgite chitosan hydrogel bead (LaATP/CS-0.1) was prepared by a green cross-linking method, which has the three-dimensional porous structure confirmed by SEM, BET. Batch experiments revealed that the adsorption capacity of LaATP/CS-0.1 was 114.1 mg/g and approximately 90% phosphate removal achieved within 400 min. Additionally, LaATP/CS-0.1 beads exhibited an excellent adsorption capacity with minimal lanthanum leaching at pH 3–9, and phosphate could be effectively removed from domestic wastewater at low concentrations. After five successive cycles, the adsorption capacity of LaATP/CS-0.1 was maintained at over 60%. The adsorption mechanism of phosphate onto LaATP/CS-0.1 mainly included surface precipitation, ligand exchange, electrostatic attraction, and inner-sphere complexation. Therefore, LaATP/CS-0.1 has great potential as an economic and reusable adsorbent for removing phosphate.