Fabrication of CuCo-Layered Double Hydroxide-Functionalized Sodium Alginate Beads and Their Application for Efficient Phosphate and Chromate Removal

Advanced phosphate removal is crucial for mitigating eutrophication. Adsorption stands out for phosphate removal, yet, a weak affinity and slow mass transfer at low concentrations often hinder it. Herein, hierarchical CuCo-LDH@SA-10 hydrogel beads prepared by ZIF-67 conversion and alginate immobilization were fabricated with freeze-drying, which yielded a nanosheet-coated mesoporous architecture accelerating transport. The adsorbent removed phosphate from 50 to 0.05 mg L^-1 in real wastewater within three cycles, achieving an adsorption capacity of 140.65 mg g^-1 under batch conditions. Equilibrium data followed the Langmuir isotherm, while the pseudo-second-order model provided the best description of uptake kinetics. High removal persisted over a pH range of 3-6, with good tolerance to coexisting anions (chloride being the most suppressive). Beyond phosphate, the material effectively removed chromate, achieving an uptake of 86.75 mg g^-1. The beads were regenerable, retaining ≥90% capacity over three cycles and 87% after five cycles. Overall, the integration of hierarchical porosity, strong performance at low concentrations, and demonstrated dual-pollutant removal underscores CuCo-LDH@SA-10 as a promising adsorbent for advanced phosphate and chromate polishing in wastewater.