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.