Composites beads based on Fe3O4@MCM-41 and calcium alginate for enhanced catalytic reduction of organic dyes

This work concerns the preparation of composite beads based on calcium alginate and Fe3O4@MCM-41. In the first step, the material Fe3O4@MCM-41 was prepared mechanically using several Fe3O4 contents, then was encapsulated by calcium alginate as a cross-linking matrix to give the composites MC@CA(x). The composite beads were used as catalysts for the reduction of MB and OG dyes in a simple system. Several parameters affecting the reduction reaction were investigated such as effect of the shape of composite beads, concentration of NaBH4, Fe3O4 content, catalyst mass and initial concentration of dye. The obtained results showed a higher immobilization of Fe3O4@MCM-41 in the alginate matrix leading to a high porous structure. The results showed that these catalysts have interesting catalytic activities towards the reduction of MB dye in which the reaction was more efficient with the catalyst containing a higher content of Fe3O4. The MC@CA(1) aerogel catalyst was the best in terms of stability compared to its MC@CA(1) hydrogel counterpart. Finally, the MC@CA(1) aerogel composite was reused in five successive cycles, with a slight loss of its activity during the fifth cycle due to the slight leaching of iron in the reaction medium. (C) 2020 Elsevier B.V. All rights reserved.