Synthesis and application of alginate@ <scp> CuFe ₂ O ₄ </scp> polymeric spheres in 17‐ <i>β</i> ‐estradiol adsorption processes in Amazonian rivers

Abstract The presence of endocrine‐disrupting compounds, such as 17‐ β ‐estradiol, in aquatic ecosystems poses a significant threat to environmental health, necessitating the development of efficient remediation technologies. This study reports the synthesis and application of hybrid magnetic spheres composed of calcium alginate and copper ferrite (Alg@CuFe 2 O 4 ) for the removal of 17‐ β ‐estradiol from aqueous solutions. To optimize the adsorbent performance, the magnetic CuFe 2 O 4 nanoparticles were synthesized and calcined at 600, 800, and 1000 °C before encapsulation. Characterization techniques revealed that raising the calcination temperature to 1000 °C promoted phase purity, eliminating secondary hematite phases, reducing lattice microstrain, and significantly enhancing saturation magnetization, which facilitates magnetic recovery. The composite synthesized with ferrite at 1000 °C exhibited the highest structural stability, characterized by high crosslinking density (1.6 mol cm −3 ) and controlled swelling. Adsorption kinetic data were best described by the pseudo‐first‐order model, suggesting that the process is rate‐limited by physical diffusion through the polymer matrix. Isotherm modeling indicated a cooperative physisorption mechanism, best fitted by the Dubinin–Radushkevich model ( E &lt; 8 kJ mol −1 ), with a theoretical maximum adsorption capacity of 238.65 μg g −1 . Furthermore, the material demonstrated exceptional chemical stability in acidic media and maintained high efficiency over seven regeneration cycles. These results position the Alg@CuFe 2 O 4 composite as a robust, eco‐friendly, and reusable adsorbent for the treatment of hormone‐contaminated waters. © 2026 The Author(s). Polymer International published by John Wiley &amp; Sons Ltd on behalf of Society of Chemical Industry.