Rationally Designed Recyclable Alginate Composite Hydrogel Beads to Remove Cationic and Anionic Dyes From Synthetic Wastewater

ABSTRACT Rapid industrialization has resulted in the discharge of significant amounts of dye‐contaminated wastewater, raising serious environmental concerns. Addressing this, the current study focuses on developing eco‐friendly, rationally designed alginate‐based composite hydrogel beads (ACHBs) for the efficient removal of both cationic (methylene blue, MB) and anionic (Congo red, CR) dyes from aqueous solutions. The ACHBs were synthesized and thoroughly characterized using FTIR, XRD, SEM–EDX, BET, TGA, and XPS analyses to confirm their structure and composition. Batch adsorption experiments were conducted to evaluate the dye removal efficiency under varying conditions including adsorbent dosage, dye concentration, contact time, pH, and temperature. Optimal adsorption capacities reached 47.8 mg g −1 for MB at pH 7.0 and 32.5 mg g −1 for CR at pH 4.5 with 50 mg of adsorbent and 90 min contact time. The incorporation and crosslinking of the composite components with Zr 4+ ions provided the ACHBs with mechanical integrity and enhanced performance. Distinct mechanisms facilitated the simultaneous removal: MB was primarily adsorbed by electrostatic attraction, while CR was captured via host–guest inclusion within beta‐cyclodextrin. The adsorption process was endothermic and spontaneous, and the Langmuir isotherm and pseudo‐second‐order models fit the data well. Regeneration studies confirmed the material's reusability for multiple cycles, demonstrating promise for sustainable water treatment.