An eggshell/Fe3O4 nanocomposite was synthesized simply via an economic and novel method, using recycled eggshell biowaste as a starting material and an aqueous solution of FeSO4 as a coating agent without any additional alkali or a protective atmosphere. Furthermore, the catalytic activity of the magnetic nanocomposite was investigated in the synthesis of 1,8-dioxo-octahydroxanthenes under solvent-free conditions. The reaction proceeds to completion in a short reaction time with an excellent yield. The suggested strategy for synthesizing 1,8-dioxo-octahydroxanthenes is of great interest because a novel, green, and low-cost magnetic nanocomposite is used as a heterogeneous catalyst, on account of its convenient preparation and high reusability.
