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

Abstract

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.

Keywords: Alginate; Catalyst; Dye reduction; Fe3O4; MCM-41.