Sustainable β-cyclodextrin/polyethylenimine-encapsulated activated algae hydrogel beads for high-capacity Cd( ii ) removal: adsorption performance, mechanism, thermodynamics, and Box–Behnken optimization

Key Points

• The aim is to create an effective bio-adsorbent from algae for cadmium ion removal and to understand its mechanisms.
• Formation of hydrogel beads using β-cyclodextrin and polyethylenimine.
• Activation of algae with hyaluronic acid and functionalization with glutamic acid.
• Optimization of adsorption conditions using Box–Behnken design.
• The new bio-adsorbent demonstrated high capacity for Cd(II) removal.
• Adsorption performance was optimized for maximum efficiency.
• Thermodynamic analysis indicated favorable adsorption conditions.