ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Hybrid alginate-industrial waste spheres for the adsorption and reuse of methylene blue

Paulo H. S. Lopes, Joyce M. G. da Costa, and Alexandre S. V. da Costa

Universidade Federal Dos Vales Do Jequitinhonha E Mucuri, Postgraduate Program in Biofuels, Diamantina, Brazil

E-mail: paulo.lopes@ufvjm.edu.br

Abstract:

This study investigates the design and application of hybrid alginate beads (F3) integrated with industrial primary sludge fibers (PF) and aluminum silicate (AS) for methylene blue (MB) removal via adsorption. Adsorbents were characterized for functional groups, microstructure, thermal stability, and point of zero charge (pH_pzc = 5.44). Using a Rotatable Central Composite Design (RCCD), the optimal formulation was identified as 0.40% PF, 0.20% AS, and 0.40% calcium chloride (CaCl₂). Non-linear modeling showed that the Freundlich isotherm provided the best fit (R² = 0.998, RMSE = 0.099), indicating a heterogeneous surface, while the Langmuir model yielded a maximum adsorption capacity of 77.76 mg g^–1 at 292 K. Kinetic data followed non-linear pseudo-second-order (R² = 0.986) and Avrami (R² = 0.998) models, suggesting a multiphase chemisorption mechanism. The beads exhibited high efficiency across a pH range of 3–11, with removal rates reaching 89.7% at higher pH levels. Reusability tests using ethanol regeneration demonstrated that the beads remain effective for at least four cycles; a ~ 1.45-fold capacity enhancement was observed from the first to the fourth cycle. These results confirm that the ternary hybrid beads are effective, sustainable, high-performance adsorbents for cationic dye removal, aligning with circular economy principles.

Graphical abstract

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-05073-0

Chemical Papers 80 (9) 11179–11208 (2026)