Methylene blue removal by alginate–clay quasi-cryogel beads

Nowadays, dyes constitute a large part of pollutants and have long been used in dyeing, paper and pulp, textiles, plastics, leather, cosmetics, and food industries. Among the conventional dye removal techniques, adsorption is prominent. Research challenges are on developing low-cost, biodegradable and efficient adsorbents. This study investigates polysaccharide–clay composite beads for the removal of methylene blue dye. Alginate–montmorillonite composite beads were prepared and then a novel cryogelation-like strategy was developed by deep-freezing the alginate beads at − 21 °C. This process changed the morphology of beads and improved surface area and adsorption capacity. The results of the batch adsorption experiments were modeled using isothermal, kinetic, and thermodynamic models. It is found that the adsorption is favorable and follows physical mechanism, with an endothermic process up to 40 °C. The prepared composite beads are candidates for effective adsorbents for the dye removal.